engine/sqlite/src/where.cpp
changeset 71 fbd95db6a4e1
parent 69 4a65cc85c4f3
child 72 2e267e7da513
--- a/engine/sqlite/src/where.cpp	Wed Apr 28 13:20:05 2010 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,2789 +0,0 @@
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This module contains C code that generates VDBE code used to process
-** the WHERE clause of SQL statements.  This module is reponsible for
-** generating the code that loops through a table looking for applicable
-** rows.  Indices are selected and used to speed the search when doing
-** so is applicable.  Because this module is responsible for selecting
-** indices, you might also think of this module as the "query optimizer".
-**
-** $Id: where.cpp 1282 2008-11-13 09:31:33Z LarsPson $
-*/
-#include "sqliteInt.h"
-
-/*
-** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
-*/
-#define BMS  (sizeof(Bitmask)*8)
-
-/*
-** Trace output macros
-*/
-#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
-int sqlite3_where_trace = 0;
-# define WHERETRACE(X)  if(sqlite3_where_trace) sqlite3DebugPrintf X
-#else
-# define WHERETRACE(X)
-#endif
-
-/* Forward reference
-*/
-typedef struct WhereClause WhereClause;
-typedef struct ExprMaskSet ExprMaskSet;
-
-/*
-** The query generator uses an array of instances of this structure to
-** help it analyze the subexpressions of the WHERE clause.  Each WHERE
-** clause subexpression is separated from the others by an AND operator.
-**
-** All WhereTerms are collected into a single WhereClause structure.  
-** The following identity holds:
-**
-**        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
-**
-** When a term is of the form:
-**
-**              X <op> <expr>
-**
-** where X is a column name and <op> is one of certain operators,
-** then WhereTerm.leftCursor and WhereTerm.leftColumn record the
-** cursor number and column number for X.  WhereTerm.operator records
-** the <op> using a bitmask encoding defined by WO_xxx below.  The
-** use of a bitmask encoding for the operator allows us to search
-** quickly for terms that match any of several different operators.
-**
-** prereqRight and prereqAll record sets of cursor numbers,
-** but they do so indirectly.  A single ExprMaskSet structure translates
-** cursor number into bits and the translated bit is stored in the prereq
-** fields.  The translation is used in order to maximize the number of
-** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
-** spread out over the non-negative integers.  For example, the cursor
-** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The ExprMaskSet
-** translates these sparse cursor numbers into consecutive integers
-** beginning with 0 in order to make the best possible use of the available
-** bits in the Bitmask.  So, in the example above, the cursor numbers
-** would be mapped into integers 0 through 7.
-*/
-typedef struct WhereTerm WhereTerm;
-struct WhereTerm {
-  Expr *pExpr;            /* Pointer to the subexpression */
-  i16 iParent;            /* Disable pWC->a[iParent] when this term disabled */
-  i16 leftCursor;         /* Cursor number of X in "X <op> <expr>" */
-  i16 leftColumn;         /* Column number of X in "X <op> <expr>" */
-  u16 eOperator;          /* A WO_xx value describing <op> */
-  u8 flags;               /* Bit flags.  See below */
-  u8 nChild;              /* Number of children that must disable us */
-  WhereClause *pWC;       /* The clause this term is part of */
-  Bitmask prereqRight;    /* Bitmask of tables used by pRight */
-  Bitmask prereqAll;      /* Bitmask of tables referenced by p */
-};
-
-/*
-** Allowed values of WhereTerm.flags
-*/
-#define TERM_DYNAMIC    0x01   /* Need to call sqlite3ExprDelete(pExpr) */
-#define TERM_VIRTUAL    0x02   /* Added by the optimizer.  Do not code */
-#define TERM_CODED      0x04   /* This term is already coded */
-#define TERM_COPIED     0x08   /* Has a child */
-#define TERM_OR_OK      0x10   /* Used during OR-clause processing */
-
-/*
-** An instance of the following structure holds all information about a
-** WHERE clause.  Mostly this is a container for one or more WhereTerms.
-*/
-struct WhereClause {
-  Parse *pParse;           /* The parser context */
-  ExprMaskSet *pMaskSet;   /* Mapping of table indices to bitmasks */
-  int nTerm;               /* Number of terms */
-  int nSlot;               /* Number of entries in a[] */
-  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
-  WhereTerm aStatic[10];   /* Initial static space for a[] */
-};
-
-/*
-** An instance of the following structure keeps track of a mapping
-** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
-**
-** The VDBE cursor numbers are small integers contained in 
-** SrcList_item.iCursor and Expr.iTable fields.  For any given WHERE 
-** clause, the cursor numbers might not begin with 0 and they might
-** contain gaps in the numbering sequence.  But we want to make maximum
-** use of the bits in our bitmasks.  This structure provides a mapping
-** from the sparse cursor numbers into consecutive integers beginning
-** with 0.
-**
-** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
-** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
-**
-** For example, if the WHERE clause expression used these VDBE
-** cursors:  4, 5, 8, 29, 57, 73.  Then the  ExprMaskSet structure
-** would map those cursor numbers into bits 0 through 5.
-**
-** Note that the mapping is not necessarily ordered.  In the example
-** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
-** 57->5, 73->4.  Or one of 719 other combinations might be used. It
-** does not really matter.  What is important is that sparse cursor
-** numbers all get mapped into bit numbers that begin with 0 and contain
-** no gaps.
-*/
-struct ExprMaskSet {
-  int n;                        /* Number of assigned cursor values */
-  int ix[sizeof(Bitmask)*8];    /* Cursor assigned to each bit */
-};
-
-
-/*
-** Bitmasks for the operators that indices are able to exploit.  An
-** OR-ed combination of these values can be used when searching for
-** terms in the where clause.
-*/
-#define WO_IN     1
-#define WO_EQ     2
-#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
-#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
-#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
-#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
-#define WO_MATCH  64
-#define WO_ISNULL 128
-
-/*
-** Value for flags returned by bestIndex().  
-**
-** The least significant byte is reserved as a mask for WO_ values above.
-** The WhereLevel.flags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
-** But if the table is the right table of a left join, WhereLevel.flags
-** is set to WO_IN|WO_EQ.  The WhereLevel.flags field can then be used as
-** the "op" parameter to findTerm when we are resolving equality constraints.
-** ISNULL constraints will then not be used on the right table of a left
-** join.  Tickets #2177 and #2189.
-*/
-#define WHERE_ROWID_EQ     0x000100   /* rowid=EXPR or rowid IN (...) */
-#define WHERE_ROWID_RANGE  0x000200   /* rowid<EXPR and/or rowid>EXPR */
-#define WHERE_COLUMN_EQ    0x001000   /* x=EXPR or x IN (...) */
-#define WHERE_COLUMN_RANGE 0x002000   /* x<EXPR and/or x>EXPR */
-#define WHERE_COLUMN_IN    0x004000   /* x IN (...) */
-#define WHERE_TOP_LIMIT    0x010000   /* x<EXPR or x<=EXPR constraint */
-#define WHERE_BTM_LIMIT    0x020000   /* x>EXPR or x>=EXPR constraint */
-#define WHERE_IDX_ONLY     0x080000   /* Use index only - omit table */
-#define WHERE_ORDERBY      0x100000   /* Output will appear in correct order */
-#define WHERE_REVERSE      0x200000   /* Scan in reverse order */
-#define WHERE_UNIQUE       0x400000   /* Selects no more than one row */
-#define WHERE_VIRTUALTABLE 0x800000   /* Use virtual-table processing */
-
-/*
-** Initialize a preallocated WhereClause structure.
-*/
-static void whereClauseInit(
-  WhereClause *pWC,        /* The WhereClause to be initialized */
-  Parse *pParse,           /* The parsing context */
-  ExprMaskSet *pMaskSet    /* Mapping from table indices to bitmasks */
-){
-  pWC->pParse = pParse;
-  pWC->pMaskSet = pMaskSet;
-  pWC->nTerm = 0;
-  pWC->nSlot = ArraySize(pWC->aStatic);
-  pWC->a = pWC->aStatic;
-}
-
-/*
-** Deallocate a WhereClause structure.  The WhereClause structure
-** itself is not freed.  This routine is the inverse of whereClauseInit().
-*/
-static void whereClauseClear(WhereClause *pWC){
-  int i;
-  WhereTerm *a;
-  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
-    if( a->flags & TERM_DYNAMIC ){
-      sqlite3ExprDelete(a->pExpr);
-    }
-  }
-  if( pWC->a!=pWC->aStatic ){
-    sqlite3_free(pWC->a);
-  }
-}
-
-/*
-** Add a new entries to the WhereClause structure.  Increase the allocated
-** space as necessary.
-**
-** If the flags argument includes TERM_DYNAMIC, then responsibility
-** for freeing the expression p is assumed by the WhereClause object.
-**
-** WARNING:  This routine might reallocate the space used to store
-** WhereTerms.  All pointers to WhereTerms should be invalided after
-** calling this routine.  Such pointers may be reinitialized by referencing
-** the pWC->a[] array.
-*/
-static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){
-  WhereTerm *pTerm;
-  int idx;
-  if( pWC->nTerm>=pWC->nSlot ){
-    WhereTerm *pOld = pWC->a;
-    pWC->a = (WhereTerm*)sqlite3_malloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
-    if( pWC->a==0 ){
-      pWC->pParse->db->mallocFailed = 1;
-      if( flags & TERM_DYNAMIC ){
-        sqlite3ExprDelete(p);
-      }
-      pWC->a = pOld;
-      return 0;
-    }
-    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
-    if( pOld!=pWC->aStatic ){
-      sqlite3_free(pOld);
-    }
-    pWC->nSlot *= 2;
-  }
-  pTerm = &pWC->a[idx = pWC->nTerm];
-  pWC->nTerm++;
-  pTerm->pExpr = p;
-  pTerm->flags = flags;
-  pTerm->pWC = pWC;
-  pTerm->iParent = -1;
-  return idx;
-}
-
-/*
-** This routine identifies subexpressions in the WHERE clause where
-** each subexpression is separated by the AND operator or some other
-** operator specified in the op parameter.  The WhereClause structure
-** is filled with pointers to subexpressions.  For example:
-**
-**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
-**           \________/     \_______________/     \________________/
-**            slot[0]            slot[1]               slot[2]
-**
-** The original WHERE clause in pExpr is unaltered.  All this routine
-** does is make slot[] entries point to substructure within pExpr.
-**
-** In the previous sentence and in the diagram, "slot[]" refers to
-** the WhereClause.a[] array.  This array grows as needed to contain
-** all terms of the WHERE clause.
-*/
-static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
-  if( pExpr==0 ) return;
-  if( pExpr->op!=op ){
-    whereClauseInsert(pWC, pExpr, 0);
-  }else{
-    whereSplit(pWC, pExpr->pLeft, op);
-    whereSplit(pWC, pExpr->pRight, op);
-  }
-}
-
-/*
-** Initialize an expression mask set
-*/
-#define initMaskSet(P)  memset(P, 0, sizeof(*P))
-
-/*
-** Return the bitmask for the given cursor number.  Return 0 if
-** iCursor is not in the set.
-*/
-static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
-  int i;
-  for(i=0; i<pMaskSet->n; i++){
-    if( pMaskSet->ix[i]==iCursor ){
-      return ((Bitmask)1)<<i;
-    }
-  }
-  return 0;
-}
-
-/*
-** Create a new mask for cursor iCursor.
-**
-** There is one cursor per table in the FROM clause.  The number of
-** tables in the FROM clause is limited by a test early in the
-** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
-** array will never overflow.
-*/
-static void createMask(ExprMaskSet *pMaskSet, int iCursor){
-  assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
-  pMaskSet->ix[pMaskSet->n++] = iCursor;
-}
-
-/*
-** This routine walks (recursively) an expression tree and generates
-** a bitmask indicating which tables are used in that expression
-** tree.
-**
-** In order for this routine to work, the calling function must have
-** previously invoked sqlite3ExprResolveNames() on the expression.  See
-** the header comment on that routine for additional information.
-** The sqlite3ExprResolveNames() routines looks for column names and
-** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
-** the VDBE cursor number of the table.  This routine just has to
-** translate the cursor numbers into bitmask values and OR all
-** the bitmasks together.
-*/
-static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
-static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
-static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
-  Bitmask mask = 0;
-  if( p==0 ) return 0;
-  if( p->op==TK_COLUMN ){
-    mask = getMask(pMaskSet, p->iTable);
-    return mask;
-  }
-  mask = exprTableUsage(pMaskSet, p->pRight);
-  mask |= exprTableUsage(pMaskSet, p->pLeft);
-  mask |= exprListTableUsage(pMaskSet, p->pList);
-  mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
-  return mask;
-}
-static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
-  int i;
-  Bitmask mask = 0;
-  if( pList ){
-    for(i=0; i<pList->nExpr; i++){
-      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
-    }
-  }
-  return mask;
-}
-static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
-  Bitmask mask = 0;
-  while( pS ){
-    mask |= exprListTableUsage(pMaskSet, pS->pEList);
-    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
-    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
-    mask |= exprTableUsage(pMaskSet, pS->pWhere);
-    mask |= exprTableUsage(pMaskSet, pS->pHaving);
-    pS = pS->pPrior;
-  }
-  return mask;
-}
-
-/*
-** Return TRUE if the given operator is one of the operators that is
-** allowed for an indexable WHERE clause term.  The allowed operators are
-** "=", "<", ">", "<=", ">=", and "IN".
-*/
-static int allowedOp(int op){
-  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
-  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
-  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
-  assert( TK_GE==TK_EQ+4 );
-  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
-}
-
-/*
-** Swap two objects of type T.
-*/
-#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
-
-/*
-** Commute a comparision operator.  Expressions of the form "X op Y"
-** are converted into "Y op X".
-**
-** If a collation sequence is associated with either the left or right
-** side of the comparison, it remains associated with the same side after
-** the commutation. So "Y collate NOCASE op X" becomes 
-** "X collate NOCASE op Y". This is because any collation sequence on
-** the left hand side of a comparison overrides any collation sequence 
-** attached to the right. For the same reason the EP_ExpCollate flag
-** is not commuted.
-*/
-static void exprCommute(Expr *pExpr){
-  u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
-  u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
-  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
-  SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
-  pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
-  pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
-  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
-  if( pExpr->op>=TK_GT ){
-    assert( TK_LT==TK_GT+2 );
-    assert( TK_GE==TK_LE+2 );
-    assert( TK_GT>TK_EQ );
-    assert( TK_GT<TK_LE );
-    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
-    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
-  }
-}
-
-/*
-** Translate from TK_xx operator to WO_xx bitmask.
-*/
-static int operatorMask(int op){
-  int c;
-  assert( allowedOp(op) );
-  if( op==TK_IN ){
-    c = WO_IN;
-  }else if( op==TK_ISNULL ){
-    c = WO_ISNULL;
-  }else{
-    c = WO_EQ<<(op-TK_EQ);
-  }
-  assert( op!=TK_ISNULL || c==WO_ISNULL );
-  assert( op!=TK_IN || c==WO_IN );
-  assert( op!=TK_EQ || c==WO_EQ );
-  assert( op!=TK_LT || c==WO_LT );
-  assert( op!=TK_LE || c==WO_LE );
-  assert( op!=TK_GT || c==WO_GT );
-  assert( op!=TK_GE || c==WO_GE );
-  return c;
-}
-
-/*
-** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
-** where X is a reference to the iColumn of table iCur and <op> is one of
-** the WO_xx operator codes specified by the op parameter.
-** Return a pointer to the term.  Return 0 if not found.
-*/
-static WhereTerm *findTerm(
-  WhereClause *pWC,     /* The WHERE clause to be searched */
-  int iCur,             /* Cursor number of LHS */
-  int iColumn,          /* Column number of LHS */
-  Bitmask notReady,     /* RHS must not overlap with this mask */
-  u16 op,               /* Mask of WO_xx values describing operator */
-  Index *pIdx           /* Must be compatible with this index, if not NULL */
-){
-  WhereTerm *pTerm;
-  int k;
-  for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
-    if( pTerm->leftCursor==iCur
-       && (pTerm->prereqRight & notReady)==0
-       && pTerm->leftColumn==iColumn
-       && (pTerm->eOperator & op)!=0
-    ){
-      if( iCur>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){
-        Expr *pX = pTerm->pExpr;
-        CollSeq *pColl;
-        char idxaff;
-        int j;
-        Parse *pParse = pWC->pParse;
-
-        idxaff = pIdx->pTable->aCol[iColumn].affinity;
-        if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
-
-        /* Figure out the collation sequence required from an index for
-        ** it to be useful for optimising expression pX. Store this
-        ** value in variable pColl.
-        */
-        assert(pX->pLeft);
-        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
-        if( !pColl ){
-          pColl = pParse->db->pDfltColl;
-        }
-
-        for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
-        assert( j<pIdx->nColumn );
-        if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
-      }
-      return pTerm;
-    }
-  }
-  return 0;
-}
-
-/* Forward reference */
-static void exprAnalyze(SrcList*, WhereClause*, int);
-
-/*
-** Call exprAnalyze on all terms in a WHERE clause.  
-**
-**
-*/
-static void exprAnalyzeAll(
-  SrcList *pTabList,       /* the FROM clause */
-  WhereClause *pWC         /* the WHERE clause to be analyzed */
-){
-  int i;
-  for(i=pWC->nTerm-1; i>=0; i--){
-    exprAnalyze(pTabList, pWC, i);
-  }
-}
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
-/*
-** Check to see if the given expression is a LIKE or GLOB operator that
-** can be optimized using inequality constraints.  Return TRUE if it is
-** so and false if not.
-**
-** In order for the operator to be optimizible, the RHS must be a string
-** literal that does not begin with a wildcard.  
-*/
-static int isLikeOrGlob(
-  sqlite3 *db,      /* The database */
-  Expr *pExpr,      /* Test this expression */
-  int *pnPattern,   /* Number of non-wildcard prefix characters */
-  int *pisComplete  /* True if the only wildcard is % in the last character */
-){
-  const char *z;
-  Expr *pRight, *pLeft;
-  ExprList *pList;
-  int c, cnt;
-  int noCase;
-  char wc[3];
-  CollSeq *pColl;
-
-  if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
-    return 0;
-  }
-  pList = pExpr->pList;
-  pRight = pList->a[0].pExpr;
-  if( pRight->op!=TK_STRING ){
-    return 0;
-  }
-  pLeft = pList->a[1].pExpr;
-  if( pLeft->op!=TK_COLUMN ){
-    return 0;
-  }
-  pColl = pLeft->pColl;
-  if( pColl==0 ){
-    /* TODO: Coverage testing doesn't get this case. Is it actually possible
-    ** for an expression of type TK_COLUMN to not have an assigned collation 
-    ** sequence at this point?
-    */
-    pColl = db->pDfltColl;
-  }
-  if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
-      (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
-    return 0;
-  }
-  sqlite3DequoteExpr(db, pRight);
-  z = (char *)pRight->token.z;
-  cnt = 0;
-  if( z ){
-    while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){ cnt++; }
-  }
-  if( cnt==0 || 255==(u8)z[cnt] ){
-    return 0;
-  }
-  *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
-  *pnPattern = cnt;
-  return 1;
-}
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Check to see if the given expression is of the form
-**
-**         column MATCH expr
-**
-** If it is then return TRUE.  If not, return FALSE.
-*/
-static int isMatchOfColumn(
-  Expr *pExpr      /* Test this expression */
-){
-  ExprList *pList;
-
-  if( pExpr->op!=TK_FUNCTION ){
-    return 0;
-  }
-  if( pExpr->token.n!=5 ||
-       sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){
-    return 0;
-  }
-  pList = pExpr->pList;
-  if( pList->nExpr!=2 ){
-    return 0;
-  }
-  if( pList->a[1].pExpr->op != TK_COLUMN ){
-    return 0;
-  }
-  return 1;
-}
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-/*
-** If the pBase expression originated in the ON or USING clause of
-** a join, then transfer the appropriate markings over to derived.
-*/
-static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
-  pDerived->flags |= pBase->flags & EP_FromJoin;
-  pDerived->iRightJoinTable = pBase->iRightJoinTable;
-}
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
-/*
-** Return TRUE if the given term of an OR clause can be converted
-** into an IN clause.  The iCursor and iColumn define the left-hand
-** side of the IN clause.
-**
-** The context is that we have multiple OR-connected equality terms
-** like this:
-**
-**           a=<expr1> OR  a=<expr2> OR b=<expr3>  OR ...
-**
-** The pOrTerm input to this routine corresponds to a single term of
-** this OR clause.  In order for the term to be a condidate for
-** conversion to an IN operator, the following must be true:
-**
-**     *  The left-hand side of the term must be the column which
-**        is identified by iCursor and iColumn.
-**
-**     *  If the right-hand side is also a column, then the affinities
-**        of both right and left sides must be such that no type
-**        conversions are required on the right.  (Ticket #2249)
-**
-** If both of these conditions are true, then return true.  Otherwise
-** return false.
-*/
-static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){
-  int affLeft, affRight;
-  assert( pOrTerm->eOperator==WO_EQ );
-  if( pOrTerm->leftCursor!=iCursor ){
-    return 0;
-  }
-  if( pOrTerm->leftColumn!=iColumn ){
-    return 0;
-  }
-  affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
-  if( affRight==0 ){
-    return 1;
-  }
-  affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
-  if( affRight!=affLeft ){
-    return 0;
-  }
-  return 1;
-}
-
-/*
-** Return true if the given term of an OR clause can be ignored during
-** a check to make sure all OR terms are candidates for optimization.
-** In other words, return true if a call to the orTermIsOptCandidate()
-** above returned false but it is not necessary to disqualify the
-** optimization.
-**
-** Suppose the original OR phrase was this:
-**
-**           a=4  OR  a=11  OR  a=b
-**
-** During analysis, the third term gets flipped around and duplicate
-** so that we are left with this:
-**
-**           a=4  OR  a=11  OR  a=b  OR  b=a
-**
-** Since the last two terms are duplicates, only one of them
-** has to qualify in order for the whole phrase to qualify.  When
-** this routine is called, we know that pOrTerm did not qualify.
-** This routine merely checks to see if pOrTerm has a duplicate that
-** might qualify.  If there is a duplicate that has not yet been
-** disqualified, then return true.  If there are no duplicates, or
-** the duplicate has also been disqualifed, return false.
-*/
-static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){
-  if( pOrTerm->flags & TERM_COPIED ){
-    /* This is the original term.  The duplicate is to the left had
-    ** has not yet been analyzed and thus has not yet been disqualified. */
-    return 1;
-  }
-  if( (pOrTerm->flags & TERM_VIRTUAL)!=0
-     && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){
-    /* This is a duplicate term.  The original qualified so this one
-    ** does not have to. */
-    return 1;
-  }
-  /* This is either a singleton term or else it is a duplicate for
-  ** which the original did not qualify.  Either way we are done for. */
-  return 0;
-}
-#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
-
-/*
-** The input to this routine is an WhereTerm structure with only the
-** "pExpr" field filled in.  The job of this routine is to analyze the
-** subexpression and populate all the other fields of the WhereTerm
-** structure.
-**
-** If the expression is of the form "<expr> <op> X" it gets commuted
-** to the standard form of "X <op> <expr>".  If the expression is of
-** the form "X <op> Y" where both X and Y are columns, then the original
-** expression is unchanged and a new virtual expression of the form
-** "Y <op> X" is added to the WHERE clause and analyzed separately.
-*/
-static void exprAnalyze(
-  SrcList *pSrc,            /* the FROM clause */
-  WhereClause *pWC,         /* the WHERE clause */
-  int idxTerm               /* Index of the term to be analyzed */
-){
-  WhereTerm *pTerm;
-  ExprMaskSet *pMaskSet;
-  Expr *pExpr;
-  Bitmask prereqLeft;
-  Bitmask prereqAll;
-  int nPattern;
-  int isComplete;
-  int op;
-  Parse *pParse = pWC->pParse;
-  sqlite3 *db = pParse->db;
-
-  if( db->mallocFailed ){
-    return;
-  }
-  pTerm = &pWC->a[idxTerm];
-  pMaskSet = pWC->pMaskSet;
-  pExpr = pTerm->pExpr;
-  prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
-  op = pExpr->op;
-  if( op==TK_IN ){
-    assert( pExpr->pRight==0 );
-    pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
-                          | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
-  }else if( op==TK_ISNULL ){
-    pTerm->prereqRight = 0;
-  }else{
-    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
-  }
-  prereqAll = exprTableUsage(pMaskSet, pExpr);
-  if( ExprHasProperty(pExpr, EP_FromJoin) ){
-    prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
-  }
-  pTerm->prereqAll = prereqAll;
-  pTerm->leftCursor = -1;
-  pTerm->iParent = -1;
-  pTerm->eOperator = 0;
-  if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
-    Expr *pLeft = pExpr->pLeft;
-    Expr *pRight = pExpr->pRight;
-    if( pLeft->op==TK_COLUMN ){
-      pTerm->leftCursor = pLeft->iTable;
-      pTerm->leftColumn = pLeft->iColumn;
-      pTerm->eOperator = operatorMask(op);
-    }
-    if( pRight && pRight->op==TK_COLUMN ){
-      WhereTerm *pNew;
-      Expr *pDup;
-      if( pTerm->leftCursor>=0 ){
-        int idxNew;
-        pDup = sqlite3ExprDup(db, pExpr);
-        if( db->mallocFailed ){
-          sqlite3ExprDelete(pDup);
-          return;
-        }
-        idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
-        if( idxNew==0 ) return;
-        pNew = &pWC->a[idxNew];
-        pNew->iParent = idxTerm;
-        pTerm = &pWC->a[idxTerm];
-        pTerm->nChild = 1;
-        pTerm->flags |= TERM_COPIED;
-      }else{
-        pDup = pExpr;
-        pNew = pTerm;
-      }
-      exprCommute(pDup);
-      pLeft = pDup->pLeft;
-      pNew->leftCursor = pLeft->iTable;
-      pNew->leftColumn = pLeft->iColumn;
-      pNew->prereqRight = prereqLeft;
-      pNew->prereqAll = prereqAll;
-      pNew->eOperator = operatorMask(pDup->op);
-    }
-  }
-
-#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
-  /* If a term is the BETWEEN operator, create two new virtual terms
-  ** that define the range that the BETWEEN implements.
-  */
-  else if( pExpr->op==TK_BETWEEN ){
-    ExprList *pList = pExpr->pList;
-    int i;
-    static const u8 ops[] = {TK_GE, TK_LE};
-    assert( pList!=0 );
-    assert( pList->nExpr==2 );
-    for(i=0; i<2; i++){
-      Expr *pNewExpr;
-      int idxNew;
-      pNewExpr = sqlite3Expr(db, ops[i], sqlite3ExprDup(db, pExpr->pLeft),
-                             sqlite3ExprDup(db, pList->a[i].pExpr), 0);
-      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
-      exprAnalyze(pSrc, pWC, idxNew);
-      pTerm = &pWC->a[idxTerm];
-      pWC->a[idxNew].iParent = idxTerm;
-    }
-    pTerm->nChild = 2;
-  }
-#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
-  /* Attempt to convert OR-connected terms into an IN operator so that
-  ** they can make use of indices.  Example:
-  **
-  **      x = expr1  OR  expr2 = x  OR  x = expr3
-  **
-  ** is converted into
-  **
-  **      x IN (expr1,expr2,expr3)
-  **
-  ** This optimization must be omitted if OMIT_SUBQUERY is defined because
-  ** the compiler for the the IN operator is part of sub-queries.
-  */
-  else if( pExpr->op==TK_OR ){
-    int ok;
-    int i, j;
-    int iColumn, iCursor;
-    WhereClause sOr;
-    WhereTerm *pOrTerm;
-
-    assert( (pTerm->flags & TERM_DYNAMIC)==0 );
-    whereClauseInit(&sOr, pWC->pParse, pMaskSet);
-    whereSplit(&sOr, pExpr, TK_OR);
-    exprAnalyzeAll(pSrc, &sOr);
-    assert( sOr.nTerm>=2 );
-    j = 0;
-    do{
-      assert( j<sOr.nTerm );
-      iColumn = sOr.a[j].leftColumn;
-      iCursor = sOr.a[j].leftCursor;
-      ok = iCursor>=0;
-      for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
-        if( pOrTerm->eOperator!=WO_EQ ){
-          goto or_not_possible;
-        }
-        if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){
-          pOrTerm->flags |= TERM_OR_OK;
-        }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){
-          pOrTerm->flags &= ~TERM_OR_OK;
-        }else{
-          ok = 0;
-        }
-      }
-    }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 );
-    if( ok ){
-      ExprList *pList = 0;
-      Expr *pNew, *pDup;
-      Expr *pLeft = 0;
-      for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
-        if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
-        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight);
-        pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup, 0);
-        pLeft = pOrTerm->pExpr->pLeft;
-      }
-      assert( pLeft!=0 );
-      pDup = sqlite3ExprDup(db, pLeft);
-      pNew = sqlite3Expr(db, TK_IN, pDup, 0, 0);
-      if( pNew ){
-        int idxNew;
-        transferJoinMarkings(pNew, pExpr);
-        pNew->pList = pList;
-        idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
-        exprAnalyze(pSrc, pWC, idxNew);
-        pTerm = &pWC->a[idxTerm];
-        pWC->a[idxNew].iParent = idxTerm;
-        pTerm->nChild = 1;
-      }else{
-        sqlite3ExprListDelete(pList);
-      }
-    }
-or_not_possible:
-    whereClauseClear(&sOr);
-  }
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
-  /* Add constraints to reduce the search space on a LIKE or GLOB
-  ** operator.
-  */
-  if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete) ){
-    Expr *pLeft, *pRight;
-    Expr *pStr1, *pStr2;
-    Expr *pNewExpr1, *pNewExpr2;
-    int idxNew1, idxNew2;
-
-    pLeft = pExpr->pList->a[1].pExpr;
-    pRight = pExpr->pList->a[0].pExpr;
-    pStr1 = sqlite3PExpr(pParse, TK_STRING, 0, 0, 0);
-    if( pStr1 ){
-      sqlite3TokenCopy(db, &pStr1->token, &pRight->token);
-      pStr1->token.n = nPattern;
-      pStr1->flags = EP_Dequoted;
-    }
-    pStr2 = sqlite3ExprDup(db, pStr1);
-    if( !db->mallocFailed ){
-      assert( pStr2->token.dyn );
-      ++*(u8*)&pStr2->token.z[nPattern-1];
-    }
-    pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft), pStr1, 0);
-    idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
-    exprAnalyze(pSrc, pWC, idxNew1);
-    pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft), pStr2, 0);
-    idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
-    exprAnalyze(pSrc, pWC, idxNew2);
-    pTerm = &pWC->a[idxTerm];
-    if( isComplete ){
-      pWC->a[idxNew1].iParent = idxTerm;
-      pWC->a[idxNew2].iParent = idxTerm;
-      pTerm->nChild = 2;
-    }
-  }
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-  /* Add a WO_MATCH auxiliary term to the constraint set if the
-  ** current expression is of the form:  column MATCH expr.
-  ** This information is used by the xBestIndex methods of
-  ** virtual tables.  The native query optimizer does not attempt
-  ** to do anything with MATCH functions.
-  */
-  if( isMatchOfColumn(pExpr) ){
-    int idxNew;
-    Expr *pRight, *pLeft;
-    WhereTerm *pNewTerm;
-    Bitmask prereqColumn, prereqExpr;
-
-    pRight = pExpr->pList->a[0].pExpr;
-    pLeft = pExpr->pList->a[1].pExpr;
-    prereqExpr = exprTableUsage(pMaskSet, pRight);
-    prereqColumn = exprTableUsage(pMaskSet, pLeft);
-    if( (prereqExpr & prereqColumn)==0 ){
-      Expr *pNewExpr;
-      pNewExpr = sqlite3Expr(db, TK_MATCH, 0, sqlite3ExprDup(db, pRight), 0);
-      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
-      pNewTerm = &pWC->a[idxNew];
-      pNewTerm->prereqRight = prereqExpr;
-      pNewTerm->leftCursor = pLeft->iTable;
-      pNewTerm->leftColumn = pLeft->iColumn;
-      pNewTerm->eOperator = WO_MATCH;
-      pNewTerm->iParent = idxTerm;
-      pTerm = &pWC->a[idxTerm];
-      pTerm->nChild = 1;
-      pTerm->flags |= TERM_COPIED;
-      pNewTerm->prereqAll = pTerm->prereqAll;
-    }
-  }
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-}
-
-/*
-** Return TRUE if any of the expressions in pList->a[iFirst...] contain
-** a reference to any table other than the iBase table.
-*/
-static int referencesOtherTables(
-  ExprList *pList,          /* Search expressions in ths list */
-  ExprMaskSet *pMaskSet,    /* Mapping from tables to bitmaps */
-  int iFirst,               /* Be searching with the iFirst-th expression */
-  int iBase                 /* Ignore references to this table */
-){
-  Bitmask allowed = ~getMask(pMaskSet, iBase);
-  while( iFirst<pList->nExpr ){
-    if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
-      return 1;
-    }
-  }
-  return 0;
-}
-
-
-/*
-** This routine decides if pIdx can be used to satisfy the ORDER BY
-** clause.  If it can, it returns 1.  If pIdx cannot satisfy the
-** ORDER BY clause, this routine returns 0.
-**
-** pOrderBy is an ORDER BY clause from a SELECT statement.  pTab is the
-** left-most table in the FROM clause of that same SELECT statement and
-** the table has a cursor number of "base".  pIdx is an index on pTab.
-**
-** nEqCol is the number of columns of pIdx that are used as equality
-** constraints.  Any of these columns may be missing from the ORDER BY
-** clause and the match can still be a success.
-**
-** All terms of the ORDER BY that match against the index must be either
-** ASC or DESC.  (Terms of the ORDER BY clause past the end of a UNIQUE
-** index do not need to satisfy this constraint.)  The *pbRev value is
-** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
-** the ORDER BY clause is all ASC.
-*/
-static int isSortingIndex(
-  Parse *pParse,          /* Parsing context */
-  ExprMaskSet *pMaskSet,  /* Mapping from table indices to bitmaps */
-  Index *pIdx,            /* The index we are testing */
-  int base,               /* Cursor number for the table to be sorted */
-  ExprList *pOrderBy,     /* The ORDER BY clause */
-  int nEqCol,             /* Number of index columns with == constraints */
-  int *pbRev              /* Set to 1 if ORDER BY is DESC */
-){
-  int i, j;                       /* Loop counters */
-  int sortOrder = 0;              /* XOR of index and ORDER BY sort direction */
-  int nTerm;                      /* Number of ORDER BY terms */
-  ExprList::ExprList_item *pTerm;    /* A term of the ORDER BY clause */
-  sqlite3 *db = pParse->db;
-
-  assert( pOrderBy!=0 );
-  nTerm = pOrderBy->nExpr;
-  assert( nTerm>0 );
-
-  /* Match terms of the ORDER BY clause against columns of
-  ** the index.
-  **
-  ** Note that indices have pIdx->nColumn regular columns plus
-  ** one additional column containing the rowid.  The rowid column
-  ** of the index is also allowed to match against the ORDER BY
-  ** clause.
-  */
-  for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
-    Expr *pExpr;       /* The expression of the ORDER BY pTerm */
-    CollSeq *pColl;    /* The collating sequence of pExpr */
-    int termSortOrder; /* Sort order for this term */
-    int iColumn;       /* The i-th column of the index.  -1 for rowid */
-    int iSortOrder;    /* 1 for DESC, 0 for ASC on the i-th index term */
-    const char *zColl; /* Name of the collating sequence for i-th index term */
-
-    pExpr = pTerm->pExpr;
-    if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
-      /* Can not use an index sort on anything that is not a column in the
-      ** left-most table of the FROM clause */
-      break;
-    }
-    pColl = sqlite3ExprCollSeq(pParse, pExpr);
-    if( !pColl ){
-      pColl = db->pDfltColl;
-    }
-    if( i<pIdx->nColumn ){
-      iColumn = pIdx->aiColumn[i];
-      if( iColumn==pIdx->pTable->iPKey ){
-        iColumn = -1;
-      }
-      iSortOrder = pIdx->aSortOrder[i];
-      zColl = pIdx->azColl[i];
-    }else{
-      iColumn = -1;
-      iSortOrder = 0;
-      zColl = pColl->zName;
-    }
-    if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
-      /* Term j of the ORDER BY clause does not match column i of the index */
-      if( i<nEqCol ){
-        /* If an index column that is constrained by == fails to match an
-        ** ORDER BY term, that is OK.  Just ignore that column of the index
-        */
-        continue;
-      }else{
-        /* If an index column fails to match and is not constrained by ==
-        ** then the index cannot satisfy the ORDER BY constraint.
-        */
-        return 0;
-      }
-    }
-    assert( pIdx->aSortOrder!=0 );
-    assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
-    assert( iSortOrder==0 || iSortOrder==1 );
-    termSortOrder = iSortOrder ^ pTerm->sortOrder;
-    if( i>nEqCol ){
-      if( termSortOrder!=sortOrder ){
-        /* Indices can only be used if all ORDER BY terms past the
-        ** equality constraints are all either DESC or ASC. */
-        return 0;
-      }
-    }else{
-      sortOrder = termSortOrder;
-    }
-    j++;
-    pTerm++;
-    if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
-      /* If the indexed column is the primary key and everything matches
-      ** so far and none of the ORDER BY terms to the right reference other
-      ** tables in the join, then we are assured that the index can be used 
-      ** to sort because the primary key is unique and so none of the other
-      ** columns will make any difference
-      */
-      j = nTerm;
-    }
-  }
-
-  *pbRev = sortOrder!=0;
-  if( j>=nTerm ){
-    /* All terms of the ORDER BY clause are covered by this index so
-    ** this index can be used for sorting. */
-    return 1;
-  }
-  if( pIdx->onError!=OE_None && i==pIdx->nColumn
-      && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
-    /* All terms of this index match some prefix of the ORDER BY clause
-    ** and the index is UNIQUE and no terms on the tail of the ORDER BY
-    ** clause reference other tables in a join.  If this is all true then
-    ** the order by clause is superfluous. */
-    return 1;
-  }
-  return 0;
-}
-
-/*
-** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
-** by sorting in order of ROWID.  Return true if so and set *pbRev to be
-** true for reverse ROWID and false for forward ROWID order.
-*/
-static int sortableByRowid(
-  int base,               /* Cursor number for table to be sorted */
-  ExprList *pOrderBy,     /* The ORDER BY clause */
-  ExprMaskSet *pMaskSet,  /* Mapping from tables to bitmaps */
-  int *pbRev              /* Set to 1 if ORDER BY is DESC */
-){
-  Expr *p;
-
-  assert( pOrderBy!=0 );
-  assert( pOrderBy->nExpr>0 );
-  p = pOrderBy->a[0].pExpr;
-  if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
-    && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
-    *pbRev = pOrderBy->a[0].sortOrder;
-    return 1;
-  }
-  return 0;
-}
-
-/*
-** Prepare a crude estimate of the logarithm of the input value.
-** The results need not be exact.  This is only used for estimating
-** the total cost of performing operatings with O(logN) or O(NlogN)
-** complexity.  Because N is just a guess, it is no great tragedy if
-** logN is a little off.
-*/
-static double estLog(double N){
-  double logN = 1;
-  double x = 10;
-  while( N>x ){
-    logN += 1;
-    x *= 10;
-  }
-  return logN;
-}
-
-/*
-** Two routines for printing the content of an sqlite3_index_info
-** structure.  Used for testing and debugging only.  If neither
-** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
-** are no-ops.
-*/
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
-static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
-  int i;
-  if( !sqlite3_where_trace ) return;
-  for(i=0; i<p->nConstraint; i++){
-    sqlite3DebugPrintf("  constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
-       i,
-       p->aConstraint[i].iColumn,
-       p->aConstraint[i].iTermOffset,
-       p->aConstraint[i].op,
-       p->aConstraint[i].usable);
-  }
-  for(i=0; i<p->nOrderBy; i++){
-    sqlite3DebugPrintf("  orderby[%d]: col=%d desc=%d\n",
-       i,
-       p->aOrderBy[i].iColumn,
-       p->aOrderBy[i].desc);
-  }
-}
-static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
-  int i;
-  if( !sqlite3_where_trace ) return;
-  for(i=0; i<p->nConstraint; i++){
-    sqlite3DebugPrintf("  usage[%d]: argvIdx=%d omit=%d\n",
-       i,
-       p->aConstraintUsage[i].argvIndex,
-       p->aConstraintUsage[i].omit);
-  }
-  sqlite3DebugPrintf("  idxNum=%d\n", p->idxNum);
-  sqlite3DebugPrintf("  idxStr=%s\n", p->idxStr);
-  sqlite3DebugPrintf("  orderByConsumed=%d\n", p->orderByConsumed);
-  sqlite3DebugPrintf("  estimatedCost=%g\n", p->estimatedCost);
-}
-#else
-#define TRACE_IDX_INPUTS(A)
-#define TRACE_IDX_OUTPUTS(A)
-#endif
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Compute the best index for a virtual table.
-**
-** The best index is computed by the xBestIndex method of the virtual
-** table module.  This routine is really just a wrapper that sets up
-** the sqlite3_index_info structure that is used to communicate with
-** xBestIndex.
-**
-** In a join, this routine might be called multiple times for the
-** same virtual table.  The sqlite3_index_info structure is created
-** and initialized on the first invocation and reused on all subsequent
-** invocations.  The sqlite3_index_info structure is also used when
-** code is generated to access the virtual table.  The whereInfoDelete() 
-** routine takes care of freeing the sqlite3_index_info structure after
-** everybody has finished with it.
-*/
-static double bestVirtualIndex(
-  Parse *pParse,                 /* The parsing context */
-  WhereClause *pWC,              /* The WHERE clause */
-  SrcList::SrcList_item *pSrc,     /* The FROM clause term to search */
-  Bitmask notReady,              /* Mask of cursors that are not available */
-  ExprList *pOrderBy,            /* The order by clause */
-  int orderByUsable,             /* True if we can potential sort */
-  sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
-){
-  Table *pTab = pSrc->pTab;
-  sqlite3_index_info *pIdxInfo;
-  sqlite3_index_info::sqlite3_index_constraint *pIdxCons;
-  sqlite3_index_info::sqlite3_index_orderby *pIdxOrderBy;
-  sqlite3_index_info::sqlite3_index_constraint_usage *pUsage;
-  WhereTerm *pTerm;
-  int i, j;
-  int nOrderBy;
-  int rc;
-
-  /* If the sqlite3_index_info structure has not been previously
-  ** allocated and initialized for this virtual table, then allocate
-  ** and initialize it now
-  */
-  pIdxInfo = *ppIdxInfo;
-  if( pIdxInfo==0 ){
-    WhereTerm *pTerm;
-    int nTerm;
-    WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));
-
-    /* Count the number of possible WHERE clause constraints referring
-    ** to this virtual table */
-    for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
-      if( pTerm->leftCursor != pSrc->iCursor ) continue;
-      if( pTerm->eOperator==WO_IN ) continue;
-      if( pTerm->eOperator==WO_ISNULL ) continue;
-      nTerm++;
-    }
-
-    /* If the ORDER BY clause contains only columns in the current 
-    ** virtual table then allocate space for the aOrderBy part of
-    ** the sqlite3_index_info structure.
-    */
-    nOrderBy = 0;
-    if( pOrderBy ){
-      for(i=0; i<pOrderBy->nExpr; i++){
-        Expr *pExpr = pOrderBy->a[i].pExpr;
-        if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
-      }
-      if( i==pOrderBy->nExpr ){
-        nOrderBy = pOrderBy->nExpr;
-      }
-    }
-
-    /* Allocate the sqlite3_index_info structure
-    */
-    pIdxInfo = (sqlite3_index_info*)sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
-                             + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
-                             + sizeof(*pIdxOrderBy)*nOrderBy );
-    if( pIdxInfo==0 ){
-      sqlite3ErrorMsg(pParse, "out of memory");
-      return 0.0;
-    }
-    *ppIdxInfo = pIdxInfo;
-
-    /* Initialize the structure.  The sqlite3_index_info structure contains
-    ** many fields that are declared "const" to prevent xBestIndex from
-    ** changing them.  We have to do some funky casting in order to
-    ** initialize those fields.
-    */
-	pIdxCons = (sqlite3_index_info::sqlite3_index_constraint*)&pIdxInfo[1];
-	pIdxOrderBy = (sqlite3_index_info::sqlite3_index_orderby*)&pIdxCons[nTerm];
-	pUsage = (sqlite3_index_info::sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
-    *(int*)&pIdxInfo->nConstraint = nTerm;
-    *(int*)&pIdxInfo->nOrderBy = nOrderBy;
-	*(sqlite3_index_info::sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
-	*(sqlite3_index_info::sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
-	*(sqlite3_index_info::sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
-                                                                     pUsage;
-
-    for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
-      if( pTerm->leftCursor != pSrc->iCursor ) continue;
-      if( pTerm->eOperator==WO_IN ) continue;
-      if( pTerm->eOperator==WO_ISNULL ) continue;
-      pIdxCons[j].iColumn = pTerm->leftColumn;
-      pIdxCons[j].iTermOffset = i;
-      pIdxCons[j].op = pTerm->eOperator;
-      /* The direct assignment in the previous line is possible only because
-      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
-      ** following asserts verify this fact. */
-      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
-      assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
-      assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
-      assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
-      assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
-      assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
-      assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
-      j++;
-    }
-    for(i=0; i<nOrderBy; i++){
-      Expr *pExpr = pOrderBy->a[i].pExpr;
-      pIdxOrderBy[i].iColumn = pExpr->iColumn;
-      pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
-    }
-  }
-
-  /* At this point, the sqlite3_index_info structure that pIdxInfo points
-  ** to will have been initialized, either during the current invocation or
-  ** during some prior invocation.  Now we just have to customize the
-  ** details of pIdxInfo for the current invocation and pass it to
-  ** xBestIndex.
-  */
-
-  /* The module name must be defined. Also, by this point there must
-  ** be a pointer to an sqlite3_vtab structure. Otherwise
-  ** sqlite3ViewGetColumnNames() would have picked up the error. 
-  */
-  assert( pTab->azModuleArg && pTab->azModuleArg[0] );
-  assert( pTab->pVtab );
-#if 0
-  if( pTab->pVtab==0 ){
-    sqlite3ErrorMsg(pParse, "undefined module %s for table %s",
-        pTab->azModuleArg[0], pTab->zName);
-    return 0.0;
-  }
-#endif
-
-  /* Set the aConstraint[].usable fields and initialize all 
-  ** output variables to zero.
-  **
-  ** aConstraint[].usable is true for constraints where the right-hand
-  ** side contains only references to tables to the left of the current
-  ** table.  In other words, if the constraint is of the form:
-  **
-  **           column = expr
-  **
-  ** and we are evaluating a join, then the constraint on column is 
-  ** only valid if all tables referenced in expr occur to the left
-  ** of the table containing column.
-  **
-  ** The aConstraints[] array contains entries for all constraints
-  ** on the current table.  That way we only have to compute it once
-  ** even though we might try to pick the best index multiple times.
-  ** For each attempt at picking an index, the order of tables in the
-  ** join might be different so we have to recompute the usable flag
-  ** each time.
-  */
-  pIdxCons = *(sqlite3_index_info::sqlite3_index_constraint**)&pIdxInfo->aConstraint;
-  pUsage = pIdxInfo->aConstraintUsage;
-  for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
-    j = pIdxCons->iTermOffset;
-    pTerm = &pWC->a[j];
-    pIdxCons->usable =  (pTerm->prereqRight & notReady)==0;
-  }
-  memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
-  if( pIdxInfo->needToFreeIdxStr ){
-    sqlite3_free(pIdxInfo->idxStr);
-  }
-  pIdxInfo->idxStr = 0;
-  pIdxInfo->idxNum = 0;
-  pIdxInfo->needToFreeIdxStr = 0;
-  pIdxInfo->orderByConsumed = 0;
-  pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0;
-  nOrderBy = pIdxInfo->nOrderBy;
-  if( pIdxInfo->nOrderBy && !orderByUsable ){
-    *(int*)&pIdxInfo->nOrderBy = 0;
-  }
-
-  sqlite3SafetyOff(pParse->db);
-  WHERETRACE(("xBestIndex for %s\n", pTab->zName));
-  TRACE_IDX_INPUTS(pIdxInfo);
-  rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
-  TRACE_IDX_OUTPUTS(pIdxInfo);
-  if( rc!=SQLITE_OK ){
-    if( rc==SQLITE_NOMEM ){
-      pParse->db->mallocFailed = 1;
-    }else {
-      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
-    }
-    sqlite3SafetyOn(pParse->db);
-  }else{
-    rc = sqlite3SafetyOn(pParse->db);
-  }
-  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
-
-  return pIdxInfo->estimatedCost;
-}
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-/*
-** Find the best index for accessing a particular table.  Return a pointer
-** to the index, flags that describe how the index should be used, the
-** number of equality constraints, and the "cost" for this index.
-**
-** The lowest cost index wins.  The cost is an estimate of the amount of
-** CPU and disk I/O need to process the request using the selected index.
-** Factors that influence cost include:
-**
-**    *  The estimated number of rows that will be retrieved.  (The
-**       fewer the better.)
-**
-**    *  Whether or not sorting must occur.
-**
-**    *  Whether or not there must be separate lookups in the
-**       index and in the main table.
-**
-*/
-static double bestIndex(
-  Parse *pParse,              /* The parsing context */
-  WhereClause *pWC,           /* The WHERE clause */
-  SrcList::SrcList_item *pSrc,  /* The FROM clause term to search */
-  Bitmask notReady,           /* Mask of cursors that are not available */
-  ExprList *pOrderBy,         /* The order by clause */
-  Index **ppIndex,            /* Make *ppIndex point to the best index */
-  int *pFlags,                /* Put flags describing this choice in *pFlags */
-  int *pnEq                   /* Put the number of == or IN constraints here */
-){
-  WhereTerm *pTerm;
-  Index *bestIdx = 0;         /* Index that gives the lowest cost */
-  double lowestCost;          /* The cost of using bestIdx */
-  int bestFlags = 0;          /* Flags associated with bestIdx */
-  int bestNEq = 0;            /* Best value for nEq */
-  int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
-  Index *pProbe;              /* An index we are evaluating */
-  int rev;                    /* True to scan in reverse order */
-  int flags;                  /* Flags associated with pProbe */
-  int nEq;                    /* Number of == or IN constraints */
-  int eqTermMask;             /* Mask of valid equality operators */
-  double cost;                /* Cost of using pProbe */
-
-  WHERETRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady));
-  lowestCost = SQLITE_BIG_DBL;
-  pProbe = pSrc->pTab->pIndex;
-
-  /* If the table has no indices and there are no terms in the where
-  ** clause that refer to the ROWID, then we will never be able to do
-  ** anything other than a full table scan on this table.  We might as
-  ** well put it first in the join order.  That way, perhaps it can be
-  ** referenced by other tables in the join.
-  */
-  if( pProbe==0 &&
-     findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
-     (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
-    *pFlags = 0;
-    *ppIndex = 0;
-    *pnEq = 0;
-    return 0.0;
-  }
-
-  /* Check for a rowid=EXPR or rowid IN (...) constraints
-  */
-  pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
-  if( pTerm ){
-    Expr *pExpr;
-    *ppIndex = 0;
-    bestFlags = WHERE_ROWID_EQ;
-    if( pTerm->eOperator & WO_EQ ){
-      /* Rowid== is always the best pick.  Look no further.  Because only
-      ** a single row is generated, output is always in sorted order */
-      *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
-      *pnEq = 1;
-      WHERETRACE(("... best is rowid\n"));
-      return 0.0;
-    }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
-      /* Rowid IN (LIST): cost is NlogN where N is the number of list
-      ** elements.  */
-      lowestCost = pExpr->pList->nExpr;
-      lowestCost *= estLog(lowestCost);
-    }else{
-      /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
-      ** in the result of the inner select.  We have no way to estimate
-      ** that value so make a wild guess. */
-      lowestCost = 200;
-    }
-    WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost));
-  }
-
-  /* Estimate the cost of a table scan.  If we do not know how many
-  ** entries are in the table, use 1 million as a guess.
-  */
-  cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
-  WHERETRACE(("... table scan base cost: %.9g\n", cost));
-  flags = WHERE_ROWID_RANGE;
-
-  /* Check for constraints on a range of rowids in a table scan.
-  */
-  pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
-  if( pTerm ){
-    if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
-      flags |= WHERE_TOP_LIMIT;
-      cost /= 3;  /* Guess that rowid<EXPR eliminates two-thirds or rows */
-    }
-    if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
-      flags |= WHERE_BTM_LIMIT;
-      cost /= 3;  /* Guess that rowid>EXPR eliminates two-thirds of rows */
-    }
-    WHERETRACE(("... rowid range reduces cost to %.9g\n", cost));
-  }else{
-    flags = 0;
-  }
-
-  /* If the table scan does not satisfy the ORDER BY clause, increase
-  ** the cost by NlogN to cover the expense of sorting. */
-  if( pOrderBy ){
-    if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
-      flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
-      if( rev ){
-        flags |= WHERE_REVERSE;
-      }
-    }else{
-      cost += cost*estLog(cost);
-      WHERETRACE(("... sorting increases cost to %.9g\n", cost));
-    }
-  }
-  if( cost<lowestCost ){
-    lowestCost = cost;
-    bestFlags = flags;
-  }
-
-  /* If the pSrc table is the right table of a LEFT JOIN then we may not
-  ** use an index to satisfy IS NULL constraints on that table.  This is
-  ** because columns might end up being NULL if the table does not match -
-  ** a circumstance which the index cannot help us discover.  Ticket #2177.
-  */
-  if( (pSrc->jointype & JT_LEFT)!=0 ){
-    eqTermMask = WO_EQ|WO_IN;
-  }else{
-    eqTermMask = WO_EQ|WO_IN|WO_ISNULL;
-  }
-
-  /* Look at each index.
-  */
-  for(; pProbe; pProbe=pProbe->pNext){
-    int i;                       /* Loop counter */
-    double inMultiplier = 1;
-
-    WHERETRACE(("... index %s:\n", pProbe->zName));
-
-    /* Count the number of columns in the index that are satisfied
-    ** by x=EXPR constraints or x IN (...) constraints.
-    */
-    flags = 0;
-    for(i=0; i<pProbe->nColumn; i++){
-      int j = pProbe->aiColumn[i];
-      pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe);
-      if( pTerm==0 ) break;
-      flags |= WHERE_COLUMN_EQ;
-      if( pTerm->eOperator & WO_IN ){
-        Expr *pExpr = pTerm->pExpr;
-        flags |= WHERE_COLUMN_IN;
-        if( pExpr->pSelect!=0 ){
-          inMultiplier *= 25;
-        }else if( pExpr->pList!=0 ){
-          inMultiplier *= pExpr->pList->nExpr + 1;
-        }
-      }
-    }
-    cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
-    nEq = i;
-    if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
-         && nEq==pProbe->nColumn ){
-      flags |= WHERE_UNIQUE;
-    }
-    WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost));
-
-    /* Look for range constraints
-    */
-    if( nEq<pProbe->nColumn ){
-      int j = pProbe->aiColumn[nEq];
-      pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
-      if( pTerm ){
-        flags |= WHERE_COLUMN_RANGE;
-        if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
-          flags |= WHERE_TOP_LIMIT;
-          cost /= 3;
-        }
-        if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
-          flags |= WHERE_BTM_LIMIT;
-          cost /= 3;
-        }
-        WHERETRACE(("...... range reduces cost to %.9g\n", cost));
-      }
-    }
-
-    /* Add the additional cost of sorting if that is a factor.
-    */
-    if( pOrderBy ){
-      if( (flags & WHERE_COLUMN_IN)==0 &&
-           isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
-        if( flags==0 ){
-          flags = WHERE_COLUMN_RANGE;
-        }
-        flags |= WHERE_ORDERBY;
-        if( rev ){
-          flags |= WHERE_REVERSE;
-        }
-      }else{
-        cost += cost*estLog(cost);
-        WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
-      }
-    }
-
-    /* Check to see if we can get away with using just the index without
-    ** ever reading the table.  If that is the case, then halve the
-    ** cost of this index.
-    */
-    if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
-      Bitmask m = pSrc->colUsed;
-      int j;
-      for(j=0; j<pProbe->nColumn; j++){
-        int x = pProbe->aiColumn[j];
-        if( x<BMS-1 ){
-          m &= ~(((Bitmask)1)<<x);
-        }
-      }
-      if( m==0 ){
-        flags |= WHERE_IDX_ONLY;
-        cost /= 2;
-        WHERETRACE(("...... idx-only reduces cost to %.9g\n", cost));
-      }
-    }
-
-    /* If this index has achieved the lowest cost so far, then use it.
-    */
-    if( flags && cost < lowestCost ){
-      bestIdx = pProbe;
-      lowestCost = cost;
-      bestFlags = flags;
-      bestNEq = nEq;
-    }
-  }
-
-  /* Report the best result
-  */
-  *ppIndex = bestIdx;
-  WHERETRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
-        bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
-  *pFlags = bestFlags | eqTermMask;
-  *pnEq = bestNEq;
-  return lowestCost;
-}
-
-
-/*
-** Disable a term in the WHERE clause.  Except, do not disable the term
-** if it controls a LEFT OUTER JOIN and it did not originate in the ON
-** or USING clause of that join.
-**
-** Consider the term t2.z='ok' in the following queries:
-**
-**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
-**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
-**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
-**
-** The t2.z='ok' is disabled in the in (2) because it originates
-** in the ON clause.  The term is disabled in (3) because it is not part
-** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
-**
-** Disabling a term causes that term to not be tested in the inner loop
-** of the join.  Disabling is an optimization.  When terms are satisfied
-** by indices, we disable them to prevent redundant tests in the inner
-** loop.  We would get the correct results if nothing were ever disabled,
-** but joins might run a little slower.  The trick is to disable as much
-** as we can without disabling too much.  If we disabled in (1), we'd get
-** the wrong answer.  See ticket #813.
-*/
-static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
-  if( pTerm
-      && (pTerm->flags & TERM_CODED)==0
-      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
-  ){
-    pTerm->flags |= TERM_CODED;
-    if( pTerm->iParent>=0 ){
-      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
-      if( (--pOther->nChild)==0 ){
-        disableTerm(pLevel, pOther);
-      }
-    }
-  }
-}
-
-/*
-** Generate code that builds a probe for an index.
-**
-** There should be nColumn values on the stack.  The index
-** to be probed is pIdx.  Pop the values from the stack and
-** replace them all with a single record that is the index
-** problem.
-*/
-static void buildIndexProbe(
-  Vdbe *v,        /* Generate code into this VM */
-  int nColumn,    /* The number of columns to check for NULL */
-  Index *pIdx     /* Index that we will be searching */
-){
-  sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
-  sqlite3IndexAffinityStr(v, pIdx);
-}
-
-
-/*
-** Generate code for a single equality term of the WHERE clause.  An equality
-** term can be either X=expr or X IN (...).   pTerm is the term to be 
-** coded.
-**
-** The current value for the constraint is left on the top of the stack.
-**
-** For a constraint of the form X=expr, the expression is evaluated and its
-** result is left on the stack.  For constraints of the form X IN (...)
-** this routine sets up a loop that will iterate over all values of X.
-*/
-static void codeEqualityTerm(
-  Parse *pParse,      /* The parsing context */
-  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
-  WhereLevel *pLevel  /* When level of the FROM clause we are working on */
-){
-  Expr *pX = pTerm->pExpr;
-  Vdbe *v = pParse->pVdbe;
-  if( pX->op==TK_EQ ){
-    sqlite3ExprCode(pParse, pX->pRight);
-  }else if( pX->op==TK_ISNULL ){
-    sqlite3VdbeAddOp(v, OP_Null, 0, 0);
-#ifndef SQLITE_OMIT_SUBQUERY
-  }else{
-    int eType;
-    int iTab;
-	WhereLevel::InLoop *pIn;
-
-    assert( pX->op==TK_IN );
-    eType = sqlite3FindInIndex(pParse, pX, 1);
-    iTab = pX->iTable;
-    sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
-    VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
-    if( pLevel->nIn==0 ){
-      pLevel->nxt = sqlite3VdbeMakeLabel(v);
-    }
-    pLevel->nIn++;
-	pLevel->aInLoop = (WhereLevel::InLoop*)sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
-                                    sizeof(pLevel->aInLoop[0])*pLevel->nIn);
-	pIn = (WhereLevel::InLoop*)pLevel->aInLoop;
-    if( pIn ){
-      int op = ((eType==IN_INDEX_ROWID)?OP_Rowid:OP_Column);
-      pIn += pLevel->nIn - 1;
-      pIn->iCur = iTab;
-      pIn->topAddr = sqlite3VdbeAddOp(v, op, iTab, 0);
-      sqlite3VdbeAddOp(v, OP_IsNull, -1, 0);
-    }else{
-      pLevel->nIn = 0;
-    }
-#endif
-  }
-  disableTerm(pLevel, pTerm);
-}
-
-/*
-** Generate code that will evaluate all == and IN constraints for an
-** index.  The values for all constraints are left on the stack.
-**
-** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
-** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
-** The index has as many as three equality constraints, but in this
-** example, the third "c" value is an inequality.  So only two 
-** constraints are coded.  This routine will generate code to evaluate
-** a==5 and b IN (1,2,3).  The current values for a and b will be left
-** on the stack - a is the deepest and b the shallowest.
-**
-** In the example above nEq==2.  But this subroutine works for any value
-** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
-** The only thing it does is allocate the pLevel->iMem memory cell.
-**
-** This routine always allocates at least one memory cell and puts
-** the address of that memory cell in pLevel->iMem.  The code that
-** calls this routine will use pLevel->iMem to store the termination
-** key value of the loop.  If one or more IN operators appear, then
-** this routine allocates an additional nEq memory cells for internal
-** use.
-*/
-static void codeAllEqualityTerms(
-  Parse *pParse,        /* Parsing context */
-  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
-  WhereClause *pWC,     /* The WHERE clause */
-  Bitmask notReady      /* Which parts of FROM have not yet been coded */
-){
-  int nEq = pLevel->nEq;        /* The number of == or IN constraints to code */
-  int termsInMem = 0;           /* If true, store value in mem[] cells */
-  Vdbe *v = pParse->pVdbe;      /* The virtual machine under construction */
-  Index *pIdx = pLevel->pIdx;   /* The index being used for this loop */
-  int iCur = pLevel->iTabCur;   /* The cursor of the table */
-  WhereTerm *pTerm;             /* A single constraint term */
-  int j;                        /* Loop counter */
-
-  /* Figure out how many memory cells we will need then allocate them.
-  ** We always need at least one used to store the loop terminator
-  ** value.  If there are IN operators we'll need one for each == or
-  ** IN constraint.
-  */
-  pLevel->iMem = pParse->nMem++;
-  if( pLevel->flags & WHERE_COLUMN_IN ){
-    pParse->nMem += pLevel->nEq;
-    termsInMem = 1;
-  }
-
-  /* Evaluate the equality constraints
-  */
-  assert( pIdx->nColumn>=nEq );
-  for(j=0; j<nEq; j++){
-    int k = pIdx->aiColumn[j];
-    pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
-    if( pTerm==0 ) break;
-    assert( (pTerm->flags & TERM_CODED)==0 );
-    codeEqualityTerm(pParse, pTerm, pLevel);
-    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
-      sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk);
-    }
-    if( termsInMem ){
-      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
-    }
-  }
-
-  /* Make sure all the constraint values are on the top of the stack
-  */
-  if( termsInMem ){
-    for(j=0; j<nEq; j++){
-      sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
-    }
-  }
-}
-
-#if defined(SQLITE_TEST)
-/*
-** The following variable holds a text description of query plan generated
-** by the most recent call to sqlite3WhereBegin().  Each call to WhereBegin
-** overwrites the previous.  This information is used for testing and
-** analysis only.
-*/
-char sqlite3_query_plan[BMS*2*40];  /* Text of the join */
-static int nQPlan = 0;              /* Next free slow in _query_plan[] */
-
-#endif /* SQLITE_TEST */
-
-
-/*
-** Free a WhereInfo structure
-*/
-static void whereInfoFree(WhereInfo *pWInfo){
-  if( pWInfo ){
-    int i;
-    for(i=0; i<pWInfo->nLevel; i++){
-      sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
-      if( pInfo ){
-        if( pInfo->needToFreeIdxStr ){
-          /* Coverage: Don't think this can be reached. By the time this
-          ** function is called, the index-strings have been passed
-          ** to the vdbe layer for deletion.
-          */
-          sqlite3_free(pInfo->idxStr);
-        }
-        sqlite3_free(pInfo);
-      }
-    }
-    sqlite3_free(pWInfo);
-  }
-}
-
-
-/*
-** Generate the beginning of the loop used for WHERE clause processing.
-** The return value is a pointer to an opaque structure that contains
-** information needed to terminate the loop.  Later, the calling routine
-** should invoke sqlite3WhereEnd() with the return value of this function
-** in order to complete the WHERE clause processing.
-**
-** If an error occurs, this routine returns NULL.
-**
-** The basic idea is to do a nested loop, one loop for each table in
-** the FROM clause of a select.  (INSERT and UPDATE statements are the
-** same as a SELECT with only a single table in the FROM clause.)  For
-** example, if the SQL is this:
-**
-**       SELECT * FROM t1, t2, t3 WHERE ...;
-**
-** Then the code generated is conceptually like the following:
-**
-**      foreach row1 in t1 do       \    Code generated
-**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
-**          foreach row3 in t3 do   /
-**            ...
-**          end                     \    Code generated
-**        end                        |-- by sqlite3WhereEnd()
-**      end                         /
-**
-** Note that the loops might not be nested in the order in which they
-** appear in the FROM clause if a different order is better able to make
-** use of indices.  Note also that when the IN operator appears in
-** the WHERE clause, it might result in additional nested loops for
-** scanning through all values on the right-hand side of the IN.
-**
-** There are Btree cursors associated with each table.  t1 uses cursor
-** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
-** And so forth.  This routine generates code to open those VDBE cursors
-** and sqlite3WhereEnd() generates the code to close them.
-**
-** The code that sqlite3WhereBegin() generates leaves the cursors named
-** in pTabList pointing at their appropriate entries.  The [...] code
-** can use OP_Column and OP_Rowid opcodes on these cursors to extract
-** data from the various tables of the loop.
-**
-** If the WHERE clause is empty, the foreach loops must each scan their
-** entire tables.  Thus a three-way join is an O(N^3) operation.  But if
-** the tables have indices and there are terms in the WHERE clause that
-** refer to those indices, a complete table scan can be avoided and the
-** code will run much faster.  Most of the work of this routine is checking
-** to see if there are indices that can be used to speed up the loop.
-**
-** Terms of the WHERE clause are also used to limit which rows actually
-** make it to the "..." in the middle of the loop.  After each "foreach",
-** terms of the WHERE clause that use only terms in that loop and outer
-** loops are evaluated and if false a jump is made around all subsequent
-** inner loops (or around the "..." if the test occurs within the inner-
-** most loop)
-**
-** OUTER JOINS
-**
-** An outer join of tables t1 and t2 is conceptally coded as follows:
-**
-**    foreach row1 in t1 do
-**      flag = 0
-**      foreach row2 in t2 do
-**        start:
-**          ...
-**          flag = 1
-**      end
-**      if flag==0 then
-**        move the row2 cursor to a null row
-**        goto start
-**      fi
-**    end
-**
-** ORDER BY CLAUSE PROCESSING
-**
-** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
-** if there is one.  If there is no ORDER BY clause or if this routine
-** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
-**
-** If an index can be used so that the natural output order of the table
-** scan is correct for the ORDER BY clause, then that index is used and
-** *ppOrderBy is set to NULL.  This is an optimization that prevents an
-** unnecessary sort of the result set if an index appropriate for the
-** ORDER BY clause already exists.
-**
-** If the where clause loops cannot be arranged to provide the correct
-** output order, then the *ppOrderBy is unchanged.
-*/
-WhereInfo *sqlite3WhereBegin(
-  Parse *pParse,        /* The parser context */
-  SrcList *pTabList,    /* A list of all tables to be scanned */
-  Expr *pWhere,         /* The WHERE clause */
-  ExprList **ppOrderBy  /* An ORDER BY clause, or NULL */
-){
-  int i;                     /* Loop counter */
-  WhereInfo *pWInfo;         /* Will become the return value of this function */
-  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
-  int brk, cont = 0;         /* Addresses used during code generation */
-  Bitmask notReady;          /* Cursors that are not yet positioned */
-  WhereTerm *pTerm;          /* A single term in the WHERE clause */
-  ExprMaskSet maskSet;       /* The expression mask set */
-  WhereClause wc;            /* The WHERE clause is divided into these terms */
-  SrcList::SrcList_item *pTabItem;  /* A single entry from pTabList */
-  WhereLevel *pLevel;             /* A single level in the pWInfo list */
-  int iFrom;                      /* First unused FROM clause element */
-  int andFlags;              /* AND-ed combination of all wc.a[].flags */
-  sqlite3 *db;               /* Database connection */
-
-  /* The number of tables in the FROM clause is limited by the number of
-  ** bits in a Bitmask 
-  */
-  if( pTabList->nSrc>BMS ){
-    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
-    return 0;
-  }
-
-  /* Split the WHERE clause into separate subexpressions where each
-  ** subexpression is separated by an AND operator.
-  */
-  initMaskSet(&maskSet);
-  whereClauseInit(&wc, pParse, &maskSet);
-  whereSplit(&wc, pWhere, TK_AND);
-    
-  /* Allocate and initialize the WhereInfo structure that will become the
-  ** return value.
-  */
-  db = pParse->db;
-  pWInfo = (WhereInfo*)sqlite3DbMallocZero(db,  
-                      sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
-  if( db->mallocFailed ){
-    goto whereBeginNoMem;
-  }
-  pWInfo->nLevel = pTabList->nSrc;
-  pWInfo->pParse = pParse;
-  pWInfo->pTabList = pTabList;
-  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
-
-  /* Special case: a WHERE clause that is constant.  Evaluate the
-  ** expression and either jump over all of the code or fall thru.
-  */
-  if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
-    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
-    pWhere = 0;
-  }
-
-  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
-  ** add new virtual terms onto the end of the WHERE clause.  We do not
-  ** want to analyze these virtual terms, so start analyzing at the end
-  ** and work forward so that the added virtual terms are never processed.
-  */
-  for(i=0; i<pTabList->nSrc; i++){
-    createMask(&maskSet, pTabList->a[i].iCursor);
-  }
-  exprAnalyzeAll(pTabList, &wc);
-  if( db->mallocFailed ){
-    goto whereBeginNoMem;
-  }
-
-  /* Chose the best index to use for each table in the FROM clause.
-  **
-  ** This loop fills in the following fields:
-  **
-  **   pWInfo->a[].pIdx      The index to use for this level of the loop.
-  **   pWInfo->a[].flags     WHERE_xxx flags associated with pIdx
-  **   pWInfo->a[].nEq       The number of == and IN constraints
-  **   pWInfo->a[].iFrom     When term of the FROM clause is being coded
-  **   pWInfo->a[].iTabCur   The VDBE cursor for the database table
-  **   pWInfo->a[].iIdxCur   The VDBE cursor for the index
-  **
-  ** This loop also figures out the nesting order of tables in the FROM
-  ** clause.
-  */
-  notReady = ~(Bitmask)0;
-  pTabItem = pTabList->a;
-  pLevel = pWInfo->a;
-  andFlags = ~0;
-  WHERETRACE(("*** Optimizer Start ***\n"));
-  for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
-    Index *pIdx;                /* Index for FROM table at pTabItem */
-    int flags;                  /* Flags asssociated with pIdx */
-    int nEq;                    /* Number of == or IN constraints */
-    double cost;                /* The cost for pIdx */
-    int j;                      /* For looping over FROM tables */
-    Index *pBest = 0;           /* The best index seen so far */
-    int bestFlags = 0;          /* Flags associated with pBest */
-    int bestNEq = 0;            /* nEq associated with pBest */
-    double lowestCost;          /* Cost of the pBest */
-    int bestJ = 0;              /* The value of j */
-    Bitmask m;                  /* Bitmask value for j or bestJ */
-    int once = 0;               /* True when first table is seen */
-    sqlite3_index_info *pIndex; /* Current virtual index */
-
-    lowestCost = SQLITE_BIG_DBL;
-    for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
-      int doNotReorder;  /* True if this table should not be reordered */
-
-      doNotReorder =  (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
-      if( once && doNotReorder ) break;
-      m = getMask(&maskSet, pTabItem->iCursor);
-      if( (m & notReady)==0 ){
-        if( j==iFrom ) iFrom++;
-        continue;
-      }
-      assert( pTabItem->pTab );
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-      if( IsVirtual(pTabItem->pTab) ){
-        sqlite3_index_info **ppIdxInfo = &pWInfo->a[j].pIdxInfo;
-        cost = bestVirtualIndex(pParse, &wc, pTabItem, notReady,
-                                ppOrderBy ? *ppOrderBy : 0, i==0,
-                                ppIdxInfo);
-        flags = WHERE_VIRTUALTABLE;
-        pIndex = *ppIdxInfo;
-        if( pIndex && pIndex->orderByConsumed ){
-          flags = WHERE_VIRTUALTABLE | WHERE_ORDERBY;
-        }
-        pIdx = 0;
-        nEq = 0;
-        if( (SQLITE_BIG_DBL/2.0)<cost ){
-          /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
-          ** inital value of lowestCost in this loop. If it is, then
-          ** the (cost<lowestCost) test below will never be true and
-          ** pLevel->pBestIdx never set.
-          */ 
-          cost = (SQLITE_BIG_DBL/2.0);
-        }
-      }else 
-#endif
-      {
-        cost = bestIndex(pParse, &wc, pTabItem, notReady,
-                         (i==0 && ppOrderBy) ? *ppOrderBy : 0,
-                         &pIdx, &flags, &nEq);
-        pIndex = 0;
-      }
-      if( cost<lowestCost ){
-        once = 1;
-        lowestCost = cost;
-        pBest = pIdx;
-        bestFlags = flags;
-        bestNEq = nEq;
-        bestJ = j;
-        pLevel->pBestIdx = pIndex;
-      }
-      if( doNotReorder ) break;
-    }
-    WHERETRACE(("*** Optimizer choose table %d for loop %d\n", bestJ,
-           pLevel-pWInfo->a));
-    if( (bestFlags & WHERE_ORDERBY)!=0 ){
-      *ppOrderBy = 0;
-    }
-    andFlags &= bestFlags;
-    pLevel->flags = bestFlags;
-    pLevel->pIdx = pBest;
-    pLevel->nEq = bestNEq;
-    pLevel->aInLoop = 0;
-    pLevel->nIn = 0;
-    if( pBest ){
-      pLevel->iIdxCur = pParse->nTab++;
-    }else{
-      pLevel->iIdxCur = -1;
-    }
-    notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
-    pLevel->iFrom = bestJ;
-  }
-  WHERETRACE(("*** Optimizer Finished ***\n"));
-
-  /* If the total query only selects a single row, then the ORDER BY
-  ** clause is irrelevant.
-  */
-  if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
-    *ppOrderBy = 0;
-  }
-
-  /* Open all tables in the pTabList and any indices selected for
-  ** searching those tables.
-  */
-  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
-  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
-    Table *pTab;     /* Table to open */
-    Index *pIx;      /* Index used to access pTab (if any) */
-    int iDb;         /* Index of database containing table/index */
-    int iIdxCur = pLevel->iIdxCur;
-
-#ifndef SQLITE_OMIT_EXPLAIN
-    if( pParse->explain==2 ){
-      char *zMsg;
-	  SrcList::SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
-      zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
-      if( pItem->zAlias ){
-        zMsg = sqlite3MPrintf(db, "%z AS %s", zMsg, pItem->zAlias);
-      }
-      if( (pIx = pLevel->pIdx)!=0 ){
-        zMsg = sqlite3MPrintf(db, "%z WITH INDEX %s", zMsg, pIx->zName);
-      }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
-        zMsg = sqlite3MPrintf(db, "%z USING PRIMARY KEY", zMsg);
-      }
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-      else if( pLevel->pBestIdx ){
-        sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
-        zMsg = sqlite3MPrintf(db, "%z VIRTUAL TABLE INDEX %d:%s", zMsg,
-                    pBestIdx->idxNum, pBestIdx->idxStr);
-      }
-#endif
-      if( pLevel->flags & WHERE_ORDERBY ){
-        zMsg = sqlite3MPrintf(db, "%z ORDER BY", zMsg);
-      }
-      sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC);
-    }
-#endif /* SQLITE_OMIT_EXPLAIN */
-    pTabItem = &pTabList->a[pLevel->iFrom];
-    pTab = pTabItem->pTab;
-    iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
-    if( pTab->isEphem || pTab->pSelect ) continue;
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-    if( pLevel->pBestIdx ){
-      int iCur = pTabItem->iCursor;
-      sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB);
-    }else
-#endif
-    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
-      sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
-      if( pTab->nCol<(sizeof(Bitmask)*8) ){
-        Bitmask b = pTabItem->colUsed;
-        int n = 0;
-        for(; b; b=b>>1, n++){}
-        sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n);
-        assert( n<=pTab->nCol );
-      }
-    }else{
-      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
-    }
-    pLevel->iTabCur = pTabItem->iCursor;
-    if( (pIx = pLevel->pIdx)!=0 ){
-      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
-      assert( pIx->pSchema==pTab->pSchema );
-      sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
-      VdbeComment((v, "# %s", pIx->zName));
-      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
-                     (char*)pKey, P3_KEYINFO_HANDOFF);
-      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
-    }
-    sqlite3CodeVerifySchema(pParse, iDb);
-  }
-  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
-
-  /* Generate the code to do the search.  Each iteration of the for
-  ** loop below generates code for a single nested loop of the VM
-  ** program.
-  */
-  notReady = ~(Bitmask)0;
-  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
-    int j;
-    int iCur = pTabItem->iCursor;  /* The VDBE cursor for the table */
-    Index *pIdx;       /* The index we will be using */
-    int nxt;           /* Where to jump to continue with the next IN case */
-    int iIdxCur;       /* The VDBE cursor for the index */
-    int omitTable;     /* True if we use the index only */
-    int bRev;          /* True if we need to scan in reverse order */
-
-    pTabItem = &pTabList->a[pLevel->iFrom];
-    iCur = pTabItem->iCursor;
-    pIdx = pLevel->pIdx;
-    iIdxCur = pLevel->iIdxCur;
-    bRev = (pLevel->flags & WHERE_REVERSE)!=0;
-    omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;
-
-    /* Create labels for the "break" and "continue" instructions
-    ** for the current loop.  Jump to brk to break out of a loop.
-    ** Jump to cont to go immediately to the next iteration of the
-    ** loop.
-    **
-    ** When there is an IN operator, we also have a "nxt" label that
-    ** means to continue with the next IN value combination.  When
-    ** there are no IN operators in the constraints, the "nxt" label
-    ** is the same as "brk".
-    */
-    brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v);
-    cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
-
-    /* If this is the right table of a LEFT OUTER JOIN, allocate and
-    ** initialize a memory cell that records if this table matches any
-    ** row of the left table of the join.
-    */
-    if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
-      if( !pParse->nMem ) pParse->nMem++;
-      pLevel->iLeftJoin = pParse->nMem++;
-      sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin);
-      VdbeComment((v, "# init LEFT JOIN no-match flag"));
-    }
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-    if( pLevel->pBestIdx ){
-      /* Case 0:  The table is a virtual-table.  Use the VFilter and VNext
-      **          to access the data.
-      */
-      int j;
-      sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
-      int nConstraint = pBestIdx->nConstraint;
-	  sqlite3_index_info::sqlite3_index_constraint_usage *aUsage =
-                                                  pBestIdx->aConstraintUsage;
-	  const sqlite3_index_info::sqlite3_index_constraint *aConstraint =
-                                                  pBestIdx->aConstraint;
-
-      for(j=1; j<=nConstraint; j++){
-        int k;
-        for(k=0; k<nConstraint; k++){
-          if( aUsage[k].argvIndex==j ){
-            int iTerm = aConstraint[k].iTermOffset;
-            sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight);
-            break;
-          }
-        }
-        if( k==nConstraint ) break;
-      }
-      sqlite3VdbeAddOp(v, OP_Integer, j-1, 0);
-      sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0);
-      sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr,
-                      pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC);
-      pBestIdx->needToFreeIdxStr = 0;
-      for(j=0; j<pBestIdx->nConstraint; j++){
-        if( aUsage[j].omit ){
-          int iTerm = aConstraint[j].iTermOffset;
-          disableTerm(pLevel, &wc.a[iTerm]);
-        }
-      }
-      pLevel->op = OP_VNext;
-      pLevel->p1 = iCur;
-      pLevel->p2 = sqlite3VdbeCurrentAddr(v);
-    }else
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-    if( pLevel->flags & WHERE_ROWID_EQ ){
-      /* Case 1:  We can directly reference a single row using an
-      **          equality comparison against the ROWID field.  Or
-      **          we reference multiple rows using a "rowid IN (...)"
-      **          construct.
-      */
-      pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
-      assert( pTerm!=0 );
-      assert( pTerm->pExpr!=0 );
-      assert( pTerm->leftCursor==iCur );
-      assert( omitTable==0 );
-      codeEqualityTerm(pParse, pTerm, pLevel);
-      nxt = pLevel->nxt;
-      sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt);
-      sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt);
-      VdbeComment((v, "pk"));
-      pLevel->op = OP_Noop;
-    }else if( pLevel->flags & WHERE_ROWID_RANGE ){
-      /* Case 2:  We have an inequality comparison against the ROWID field.
-      */
-      int testOp = OP_Noop;
-      int start;
-      WhereTerm *pStart, *pEnd;
-
-      assert( omitTable==0 );
-      pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
-      pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
-      if( bRev ){
-        pTerm = pStart;
-        pStart = pEnd;
-        pEnd = pTerm;
-      }
-      if( pStart ){
-        Expr *pX;
-        pX = pStart->pExpr;
-        assert( pX!=0 );
-        assert( pStart->leftCursor==iCur );
-        sqlite3ExprCode(pParse, pX->pRight);
-        sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
-        sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
-        VdbeComment((v, "pk"));
-        disableTerm(pLevel, pStart);
-      }else{
-        sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
-      }
-      if( pEnd ){
-        Expr *pX;
-        pX = pEnd->pExpr;
-        assert( pX!=0 );
-        assert( pEnd->leftCursor==iCur );
-        sqlite3ExprCode(pParse, pX->pRight);
-        pLevel->iMem = pParse->nMem++;
-        sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
-        if( pX->op==TK_LT || pX->op==TK_GT ){
-          testOp = bRev ? OP_Le : OP_Ge;
-        }else{
-          testOp = bRev ? OP_Lt : OP_Gt;
-        }
-        disableTerm(pLevel, pEnd);
-      }
-      start = sqlite3VdbeCurrentAddr(v);
-      pLevel->op = bRev ? OP_Prev : OP_Next;
-      pLevel->p1 = iCur;
-      pLevel->p2 = start;
-      if( testOp!=OP_Noop ){
-        sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
-        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
-        sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk);
-      }
-    }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
-      /* Case 3: The WHERE clause term that refers to the right-most
-      **         column of the index is an inequality.  For example, if
-      **         the index is on (x,y,z) and the WHERE clause is of the
-      **         form "x=5 AND y<10" then this case is used.  Only the
-      **         right-most column can be an inequality - the rest must
-      **         use the "==" and "IN" operators.
-      **
-      **         This case is also used when there are no WHERE clause
-      **         constraints but an index is selected anyway, in order
-      **         to force the output order to conform to an ORDER BY.
-      */
-      int start;
-      int nEq = pLevel->nEq;
-      int topEq=0;        /* True if top limit uses ==. False is strictly < */
-      int btmEq=0;        /* True if btm limit uses ==. False if strictly > */
-      int topOp, btmOp;   /* Operators for the top and bottom search bounds */
-      int testOp;
-      int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
-      int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
-
-      /* Generate code to evaluate all constraint terms using == or IN
-      ** and level the values of those terms on the stack.
-      */
-      codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
-
-      /* Duplicate the equality term values because they will all be
-      ** used twice: once to make the termination key and once to make the
-      ** start key.
-      */
-      for(j=0; j<nEq; j++){
-        sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
-      }
-
-      /* Figure out what comparison operators to use for top and bottom 
-      ** search bounds. For an ascending index, the bottom bound is a > or >=
-      ** operator and the top bound is a < or <= operator.  For a descending
-      ** index the operators are reversed.
-      */
-      if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
-        topOp = WO_LT|WO_LE;
-        btmOp = WO_GT|WO_GE;
-      }else{
-        topOp = WO_GT|WO_GE;
-        btmOp = WO_LT|WO_LE;
-        SWAP(int, topLimit, btmLimit);
-      }
-
-      /* Generate the termination key.  This is the key value that
-      ** will end the search.  There is no termination key if there
-      ** are no equality terms and no "X<..." term.
-      **
-      ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
-      ** key computed here really ends up being the start key.
-      */
-      nxt = pLevel->nxt;
-      if( topLimit ){
-        Expr *pX;
-        int k = pIdx->aiColumn[j];
-        pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
-        assert( pTerm!=0 );
-        pX = pTerm->pExpr;
-        assert( (pTerm->flags & TERM_CODED)==0 );
-        sqlite3ExprCode(pParse, pX->pRight);
-        sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt);
-        topEq = pTerm->eOperator & (WO_LE|WO_GE);
-        disableTerm(pLevel, pTerm);
-        testOp = OP_IdxGE;
-      }else{
-        testOp = nEq>0 ? OP_IdxGE : OP_Noop;
-        topEq = 1;
-      }
-      if( testOp!=OP_Noop ){
-        int nCol = nEq + topLimit;
-        pLevel->iMem = pParse->nMem++;
-        buildIndexProbe(v, nCol, pIdx);
-        if( bRev ){
-          int op = topEq ? OP_MoveLe : OP_MoveLt;
-          sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
-        }else{
-          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
-        }
-      }else if( bRev ){
-        sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
-      }
-
-      /* Generate the start key.  This is the key that defines the lower
-      ** bound on the search.  There is no start key if there are no
-      ** equality terms and if there is no "X>..." term.  In
-      ** that case, generate a "Rewind" instruction in place of the
-      ** start key search.
-      **
-      ** 2002-Dec-04: In the case of a reverse-order search, the so-called
-      ** "start" key really ends up being used as the termination key.
-      */
-      if( btmLimit ){
-        Expr *pX;
-        int k = pIdx->aiColumn[j];
-        pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
-        assert( pTerm!=0 );
-        pX = pTerm->pExpr;
-        assert( (pTerm->flags & TERM_CODED)==0 );
-        sqlite3ExprCode(pParse, pX->pRight);
-        sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt);
-        btmEq = pTerm->eOperator & (WO_LE|WO_GE);
-        disableTerm(pLevel, pTerm);
-      }else{
-        btmEq = 1;
-      }
-      if( nEq>0 || btmLimit ){
-        int nCol = nEq + btmLimit;
-        buildIndexProbe(v, nCol, pIdx);
-        if( bRev ){
-          pLevel->iMem = pParse->nMem++;
-          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
-          testOp = OP_IdxLT;
-        }else{
-          int op = btmEq ? OP_MoveGe : OP_MoveGt;
-          sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
-        }
-      }else if( bRev ){
-        testOp = OP_Noop;
-      }else{
-        sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
-      }
-
-      /* Generate the the top of the loop.  If there is a termination
-      ** key we have to test for that key and abort at the top of the
-      ** loop.
-      */
-      start = sqlite3VdbeCurrentAddr(v);
-      if( testOp!=OP_Noop ){
-        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
-        sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt);
-        if( (topEq && !bRev) || (!btmEq && bRev) ){
-          sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
-        }
-      }
-      if( topLimit | btmLimit ){
-        sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq);
-        sqlite3VdbeAddOp(v, OP_IsNull, 1, cont);
-      }
-      if( !omitTable ){
-        sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
-        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
-      }
-
-      /* Record the instruction used to terminate the loop.
-      */
-      pLevel->op = bRev ? OP_Prev : OP_Next;
-      pLevel->p1 = iIdxCur;
-      pLevel->p2 = start;
-    }else if( pLevel->flags & WHERE_COLUMN_EQ ){
-      /* Case 4:  There is an index and all terms of the WHERE clause that
-      **          refer to the index using the "==" or "IN" operators.
-      */
-      int start;
-      int nEq = pLevel->nEq;
-
-      /* Generate code to evaluate all constraint terms using == or IN
-      ** and leave the values of those terms on the stack.
-      */
-      codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
-      nxt = pLevel->nxt;
-
-      /* Generate a single key that will be used to both start and terminate
-      ** the search
-      */
-      buildIndexProbe(v, nEq, pIdx);
-      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
-
-      /* Generate code (1) to move to the first matching element of the table.
-      ** Then generate code (2) that jumps to "nxt" after the cursor is past
-      ** the last matching element of the table.  The code (1) is executed
-      ** once to initialize the search, the code (2) is executed before each
-      ** iteration of the scan to see if the scan has finished. */
-      if( bRev ){
-        /* Scan in reverse order */
-        sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt);
-        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
-        sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt);
-        pLevel->op = OP_Prev;
-      }else{
-        /* Scan in the forward order */
-        sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt);
-        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
-        sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC);
-        pLevel->op = OP_Next;
-      }
-      if( !omitTable ){
-        sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
-        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
-      }
-      pLevel->p1 = iIdxCur;
-      pLevel->p2 = start;
-    }else{
-      /* Case 5:  There is no usable index.  We must do a complete
-      **          scan of the entire table.
-      */
-      assert( omitTable==0 );
-      assert( bRev==0 );
-      pLevel->op = OP_Next;
-      pLevel->p1 = iCur;
-      pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
-    }
-    notReady &= ~getMask(&maskSet, iCur);
-    sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0);
-
-    /* Insert code to test every subexpression that can be completely
-    ** computed using the current set of tables.
-    */
-    for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
-      Expr *pE;
-      if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-      if( (pTerm->prereqAll & notReady)!=0 ) continue;
-      pE = pTerm->pExpr;
-      assert( pE!=0 );
-      if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
-        continue;
-      }
-      sqlite3ExprIfFalse(pParse, pE, cont, 1);
-      pTerm->flags |= TERM_CODED;
-    }
-
-    /* For a LEFT OUTER JOIN, generate code that will record the fact that
-    ** at least one row of the right table has matched the left table.  
-    */
-    if( pLevel->iLeftJoin ){
-      pLevel->top = sqlite3VdbeCurrentAddr(v);
-      sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
-      VdbeComment((v, "# record LEFT JOIN hit"));
-      for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
-        if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-        if( (pTerm->prereqAll & notReady)!=0 ) continue;
-        assert( pTerm->pExpr );
-        sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
-        pTerm->flags |= TERM_CODED;
-      }
-    }
-  }
-
-#ifdef SQLITE_TEST  /* For testing and debugging use only */
-  /* Record in the query plan information about the current table
-  ** and the index used to access it (if any).  If the table itself
-  ** is not used, its name is just '{}'.  If no index is used
-  ** the index is listed as "{}".  If the primary key is used the
-  ** index name is '*'.
-  */
-  for(i=0; i<pTabList->nSrc; i++){
-    char *z;
-    int n;
-    pLevel = &pWInfo->a[i];
-    pTabItem = &pTabList->a[pLevel->iFrom];
-    z = pTabItem->zAlias;
-    if( z==0 ) z = pTabItem->pTab->zName;
-    n = strlen(z);
-    if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
-      if( pLevel->flags & WHERE_IDX_ONLY ){
-        memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
-        nQPlan += 2;
-      }else{
-        memcpy(&sqlite3_query_plan[nQPlan], z, n);
-        nQPlan += n;
-      }
-      sqlite3_query_plan[nQPlan++] = ' ';
-    }
-    if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
-      memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
-      nQPlan += 2;
-    }else if( pLevel->pIdx==0 ){
-      memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
-      nQPlan += 3;
-    }else{
-      n = strlen(pLevel->pIdx->zName);
-      if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
-        memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n);
-        nQPlan += n;
-        sqlite3_query_plan[nQPlan++] = ' ';
-      }
-    }
-  }
-  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
-    sqlite3_query_plan[--nQPlan] = 0;
-  }
-  sqlite3_query_plan[nQPlan] = 0;
-  nQPlan = 0;
-#endif /* SQLITE_TEST // Testing and debugging use only */
-
-  /* Record the continuation address in the WhereInfo structure.  Then
-  ** clean up and return.
-  */
-  pWInfo->iContinue = cont;
-  whereClauseClear(&wc);
-  return pWInfo;
-
-  /* Jump here if malloc fails */
-whereBeginNoMem:
-  whereClauseClear(&wc);
-  whereInfoFree(pWInfo);
-  return 0;
-}
-
-/*
-** Generate the end of the WHERE loop.  See comments on 
-** sqlite3WhereBegin() for additional information.
-*/
-void sqlite3WhereEnd(WhereInfo *pWInfo){
-  Vdbe *v = pWInfo->pParse->pVdbe;
-  int i;
-  WhereLevel *pLevel;
-  SrcList *pTabList = pWInfo->pTabList;
-
-  /* Generate loop termination code.
-  */
-  for(i=pTabList->nSrc-1; i>=0; i--){
-    pLevel = &pWInfo->a[i];
-    sqlite3VdbeResolveLabel(v, pLevel->cont);
-    if( pLevel->op!=OP_Noop ){
-      sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
-    }
-    if( pLevel->nIn ){
-		WhereLevel::InLoop *pIn;
-      int j;
-      sqlite3VdbeResolveLabel(v, pLevel->nxt);
-      for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){
-        sqlite3VdbeJumpHere(v, pIn->topAddr+1);
-        sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr);
-        sqlite3VdbeJumpHere(v, pIn->topAddr-1);
-      }
-      sqlite3_free(pLevel->aInLoop);
-    }
-    sqlite3VdbeResolveLabel(v, pLevel->brk);
-    if( pLevel->iLeftJoin ){
-      int addr;
-      addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
-      sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
-      if( pLevel->iIdxCur>=0 ){
-        sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
-      }
-      sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
-      sqlite3VdbeJumpHere(v, addr);
-    }
-  }
-
-  /* The "break" point is here, just past the end of the outer loop.
-  ** Set it.
-  */
-  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
-
-  /* Close all of the cursors that were opened by sqlite3WhereBegin.
-  */
-  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
-	  SrcList::SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
-    Table *pTab = pTabItem->pTab;
-    assert( pTab!=0 );
-    if( pTab->isEphem || pTab->pSelect ) continue;
-    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
-      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
-    }
-    if( pLevel->pIdx!=0 ){
-      sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
-    }
-
-    /* If this scan uses an index, make code substitutions to read data
-    ** from the index in preference to the table. Sometimes, this means
-    ** the table need never be read from. This is a performance boost,
-    ** as the vdbe level waits until the table is read before actually
-    ** seeking the table cursor to the record corresponding to the current
-    ** position in the index.
-    ** 
-    ** Calls to the code generator in between sqlite3WhereBegin and
-    ** sqlite3WhereEnd will have created code that references the table
-    ** directly.  This loop scans all that code looking for opcodes
-    ** that reference the table and converts them into opcodes that
-    ** reference the index.
-    */
-    if( pLevel->pIdx ){
-      int k, j, last;
-      VdbeOp *pOp;
-      Index *pIdx = pLevel->pIdx;
-      int useIndexOnly = pLevel->flags & WHERE_IDX_ONLY;
-
-      assert( pIdx!=0 );
-      pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
-      last = sqlite3VdbeCurrentAddr(v);
-      for(k=pWInfo->iTop; k<last; k++, pOp++){
-        if( pOp->p1!=pLevel->iTabCur ) continue;
-        if( pOp->opcode==OP_Column ){
-          for(j=0; j<pIdx->nColumn; j++){
-            if( pOp->p2==pIdx->aiColumn[j] ){
-              pOp->p2 = j;
-              pOp->p1 = pLevel->iIdxCur;
-              break;
-            }
-          }
-          assert(!useIndexOnly || j<pIdx->nColumn);
-        }else if( pOp->opcode==OP_Rowid ){
-          pOp->p1 = pLevel->iIdxCur;
-          pOp->opcode = OP_IdxRowid;
-        }else if( pOp->opcode==OP_NullRow && useIndexOnly ){
-          pOp->opcode = OP_Noop;
-        }
-      }
-    }
-  }
-
-  /* Final cleanup
-  */
-  whereInfoFree(pWInfo);
-  return;
-}