/*
** 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 responsible 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.c,v 1.319 2008/08/01 17:37:41 danielk1977 Exp $
*/
#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 sqlite3WhereTrace = 0;
#endif
#if 0
# define WHERETRACE(X) if(sqlite3WhereTrace) 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(db, 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;
sqlite3 *db = pWC->pParse->db;
for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
if( a->flags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, a->pExpr);
}
}
if( pWC->a!=pWC->aStatic ){
sqlite3DbFree(db, 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 invalidated 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;
sqlite3 *db = pWC->pParse->db;
pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
if( pWC->a==0 ){
if( flags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, p);
}
pWC->a = pOld;
return 0;
}
memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
if( pOld!=pWC->aStatic ){
sqlite3DbFree(db, 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 comparison 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;
assert( iCur>=0 );
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( 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; pIdx->aiColumn[j]!=iColumn; j++){
if( NEVER(j>=pIdx->nColumn) ) return 0;
}
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 */
int *pnoCase /* True if uppercase is equivalent to lowercase */
){
const char *z;
Expr *pRight, *pLeft;
ExprList *pList;
int c, cnt;
char wc[3];
CollSeq *pColl;
if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
return 0;
}
#ifdef SQLITE_EBCDIC
if( *pnoCase ) return 0;
#endif
pList = pExpr->pList;
pRight = pList->a[0].pExpr;
if( pRight->op!=TK_STRING
&& (pRight->op!=TK_REGISTER || pRight->iColumn!=TK_STRING) ){
return 0;
}
pLeft = pList->a[1].pExpr;
if( pLeft->op!=TK_COLUMN ){
return 0;
}
pColl = pLeft->pColl;
assert( pColl!=0 || pLeft->iColumn==-1 );
if( pColl==0 ){
/* No collation is defined for the ROWID. Use the default. */
pColl = db->pDfltColl;
}
if( (pColl->type!=SQLITE_COLL_BINARY || *pnoCase) &&
(pColl->type!=SQLITE_COLL_NOCASE || !*pnoCase) ){
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 candidate 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 disqualified, 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;
Bitmask extraRight = 0;
int nPattern;
int isComplete;
int noCase;
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) ){
Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
prereqAll |= x;
extraRight = x-1; /* ON clause terms may not be used with an index
** on left table of a LEFT JOIN. Ticket #3015 */
}
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(db, 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;
if( db->mallocFailed ) goto or_not_possible;
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; 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(db, 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.
**
** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
**
** x>='abc' AND x<'abd' AND x LIKE 'abc%'
**
** The last character of the prefix "abc" is incremented to form the
** termination condition "abd".
*/
if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete, &noCase) ){
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 ){
u8 c, *pC;
assert( pStr2->token.dyn );
pC = (u8*)&pStr2->token.z[nPattern-1];
c = *pC;
if( noCase ){
if( c=='@' ) isComplete = 0;
c = sqlite3UpperToLower[c];
}
*pC = c + 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 */
/* Prevent ON clause terms of a LEFT JOIN from being used to drive
** an index for tables to the left of the join.
*/
pTerm->prereqRight |= extraRight;
}
/*
** 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 */
struct 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( i==pIdx->nColumn ){
/* Index column i is the rowid. All other terms match. */
break;
}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 operations 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( !sqlite3WhereTrace ) 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( !sqlite3WhereTrace ) 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 */
struct 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_vtab *pVtab = pTab->pVtab;
sqlite3_index_info *pIdxInfo;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_orderby *pIdxOrderBy;
struct 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&(pTerm->eOperator-1))==0 );
testcase( pTerm->eOperator==WO_IN );
testcase( pTerm->eOperator==WO_ISNULL );
if( pTerm->eOperator & (WO_IN|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 = 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 = (struct sqlite3_index_constraint*)&pIdxInfo[1];
pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
*(int*)&pIdxInfo->nConstraint = nTerm;
*(int*)&pIdxInfo->nOrderBy = nOrderBy;
*(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
*(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
*(struct 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&(pTerm->eOperator-1))==0 );
testcase( pTerm->eOperator==WO_IN );
testcase( pTerm->eOperator==WO_ISNULL );
if( pTerm->eOperator & (WO_IN|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( 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 = *(struct 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;
}
(void)sqlite3SafetyOff(pParse->db);
WHERETRACE(("xBestIndex for %s\n", pTab->zName));
TRACE_IDX_INPUTS(pIdxInfo);
rc = pVtab->pModule->xBestIndex(pVtab, pIdxInfo);
TRACE_IDX_OUTPUTS(pIdxInfo);
(void)sqlite3SafetyOn(pParse->db);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ){
pParse->db->mallocFailed = 1;
}else if( !pVtab->zErrMsg ){
sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
}else{
sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
}
}
sqlite3DbFree(pParse->db, pVtab->zErrMsg);
pVtab->zErrMsg = 0;
for(i=0; i<pIdxInfo->nConstraint; i++){
if( !pIdxInfo->aConstraint[i].usable && pUsage[i].argvIndex>0 ){
sqlite3ErrorMsg(pParse,
"table %s: xBestIndex returned an invalid plan", pTab->zName);
return 0.0;
}
}
*(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 */
struct 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=%llx\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( ALWAYS(pExpr->pList) ){
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
&& ALWAYS((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);
}
}
}
}
/*
** Apply the affinities associated with the first n columns of index
** pIdx to the values in the n registers starting at base.
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, Index *pIdx){
if( n>0 ){
Vdbe *v = pParse->pVdbe;
assert( v!=0 );
sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
sqlite3IndexAffinityStr(v, pIdx);
sqlite3ExprCacheAffinityChange(pParse, base, n);
}
}
/*
** 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 in register iReg.
**
** 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 int 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 */
int iTarget /* Attempt to leave results in this register */
){
Expr *pX = pTerm->pExpr;
Vdbe *v = pParse->pVdbe;
int iReg; /* Register holding results */
if( iTarget<=0 ){
iReg = iTarget = sqlite3GetTempReg(pParse);
}
if( pX->op==TK_EQ ){
iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
}else if( pX->op==TK_ISNULL ){
iReg = iTarget;
sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
}else{
int eType;
int iTab;
struct InLoop *pIn;
assert( pX->op==TK_IN );
iReg = iTarget;
eType = sqlite3FindInIndex(pParse, pX, 0);
iTab = pX->iTable;
sqlite3VdbeAddOp2(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 = sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
sizeof(pLevel->aInLoop[0])*pLevel->nIn);
pIn = pLevel->aInLoop;
if( pIn ){
pIn += pLevel->nIn - 1;
pIn->iCur = iTab;
if( eType==IN_INDEX_ROWID ){
pIn->topAddr = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
}else{
pIn->topAddr = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
}
sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
}else{
pLevel->nIn = 0;
}
#endif
}
disableTerm(pLevel, pTerm);
return iReg;
}
/*
** 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 int 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 nExtraReg /* Number of extra registers to allocate */
){
int nEq = pLevel->nEq; /* The number of == or IN constraints to code */
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 */
int regBase; /* Base register */
/* 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 + 1;
regBase = pParse->nMem + 2;
pParse->nMem += pLevel->nEq + 2 + nExtraReg;
/* Evaluate the equality constraints
*/
assert( pIdx->nColumn>=nEq );
for(j=0; j<nEq; j++){
int r1;
int k = pIdx->aiColumn[j];
pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
if( NEVER(pTerm==0) ) break;
assert( (pTerm->flags & TERM_CODED)==0 );
r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
if( r1!=regBase+j ){
sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
}
testcase( pTerm->eOperator & WO_ISNULL );
testcase( pTerm->eOperator & WO_IN );
if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->brk);
}
}
return regBase;
}
#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;
sqlite3 *db = pWInfo->pParse->db;
for(i=0; i<pWInfo->nLevel; i++){
sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
if( pInfo ){
assert( pInfo->needToFreeIdxStr==0 );
sqlite3DbFree(db, pInfo);
}
}
sqlite3DbFree(db, 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 */
u8 wflags /* One of the WHERE_* flags defined in sqliteInt.h */
){
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 */
struct 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 */
ExprList *pOrderBy = 0;
/* 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;
}
if( ppOrderBy ){
pOrderBy = *ppOrderBy;
}
/* Split the WHERE clause into separate subexpressions where each
** subexpression is separated by an AND operator.
*/
initMaskSet(&maskSet);
whereClauseInit(&wc, pParse, &maskSet);
sqlite3ExprCodeConstants(pParse, pWhere);
whereSplit(&wc, pWhere, TK_AND);
/* Allocate and initialize the WhereInfo structure that will become the
** return value.
*/
db = pParse->db;
pWInfo = 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, SQLITE_JUMPIFNULL);
pWhere = 0;
}
/* Assign a bit from the bitmask to every term in the FROM clause.
**
** When assigning bitmask values to FROM clause cursors, it must be
** the case that if X is the bitmask for the N-th FROM clause term then
** the bitmask for all FROM clause terms to the left of the N-th term
** is (X-1). An expression from the ON clause of a LEFT JOIN can use
** its Expr.iRightJoinTable value to find the bitmask of the right table
** of the join. Subtracting one from the right table bitmask gives a
** bitmask for all tables to the left of the join. Knowing the bitmask
** for all tables to the left of a left join is important. Ticket #3015.
*/
for(i=0; i<pTabList->nSrc; i++){
createMask(&maskSet, pTabList->a[i].iCursor);
}
#ifndef NDEBUG
{
Bitmask toTheLeft = 0;
for(i=0; i<pTabList->nSrc; i++){
Bitmask m = getMask(&maskSet, pTabList->a[i].iCursor);
assert( (m-1)==toTheLeft );
toTheLeft |= m;
}
}
#endif
/* 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.
*/
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 selects 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;
}
/* If the caller is an UPDATE or DELETE statement that is requesting
** to use a one-pass algorithm, determine if this is appropriate.
** The one-pass algorithm only works if the WHERE clause constraints
** the statement to update a single row.
*/
assert( (wflags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
if( (wflags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
pWInfo->okOnePass = 1;
pWInfo->a[0].flags &= ~WHERE_IDX_ONLY;
}
/* 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;
struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
if( pItem->zAlias ){
zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
}
if( (pIx = pLevel->pIdx)!=0 ){
zMsg = sqlite3MAppendf(db, zMsg, "%s WITH INDEX %s", zMsg, pIx->zName);
}else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
zMsg = sqlite3MAppendf(db, zMsg, "%s USING PRIMARY KEY", zMsg);
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
else if( pLevel->pBestIdx ){
sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
pBestIdx->idxNum, pBestIdx->idxStr);
}
#endif
if( pLevel->flags & WHERE_ORDERBY ){
zMsg = sqlite3MAppendf(db, zMsg, "%s ORDER BY", zMsg);
}
sqlite3VdbeAddOp4(v, OP_Explain, i, pLevel->iFrom, 0, zMsg, P4_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;
sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0,
(const char*)pTab->pVtab, P4_VTAB);
}else
#endif
if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
if( !pWInfo->okOnePass && pTab->nCol<(sizeof(Bitmask)*8) ){
Bitmask b = pTabItem->colUsed;
int n = 0;
for(; b; b=b>>1, n++){}
sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-2, 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 );
sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pIx->nColumn+1);
sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
(char*)pKey, P4_KEYINFO_HANDOFF);
VdbeComment((v, "%s", pIx->zName));
}
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 ){
pLevel->iLeftJoin = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Integer, 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;
int iReg; /* P3 Value for OP_VFilter */
sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
int nConstraint = pBestIdx->nConstraint;
struct sqlite3_index_constraint_usage *aUsage =
pBestIdx->aConstraintUsage;
const struct sqlite3_index_constraint *aConstraint =
pBestIdx->aConstraint;
iReg = sqlite3GetTempRange(pParse, nConstraint+2);
pParse->disableColCache++;
for(j=1; j<=nConstraint; j++){
int k;
for(k=0; k<nConstraint; k++){
if( aUsage[k].argvIndex==j ){
int iTerm = aConstraint[k].iTermOffset;
assert( pParse->disableColCache );
sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight, iReg+j+1);
break;
}
}
if( k==nConstraint ) break;
}
assert( pParse->disableColCache );
pParse->disableColCache--;
sqlite3VdbeAddOp2(v, OP_Integer, pBestIdx->idxNum, iReg);
sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
sqlite3VdbeAddOp4(v, OP_VFilter, iCur, brk, iReg, pBestIdx->idxStr,
pBestIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
pBestIdx->needToFreeIdxStr = 0;
for(j=0; j<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.
*/
int r1;
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 );
r1 = codeEqualityTerm(pParse, pTerm, pLevel, 0);
nxt = pLevel->nxt;
sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, nxt);
sqlite3VdbeAddOp3(v, OP_NotExists, iCur, nxt, r1);
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;
int r1, regFree1;
pX = pStart->pExpr;
assert( pX!=0 );
assert( pStart->leftCursor==iCur );
r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, ®Free1);
sqlite3VdbeAddOp3(v, OP_ForceInt, r1, brk,
pX->op==TK_LE || pX->op==TK_GT);
sqlite3VdbeAddOp3(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk, r1);
VdbeComment((v, "pk"));
sqlite3ReleaseTempReg(pParse, regFree1);
disableTerm(pLevel, pStart);
}else{
sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
}
if( pEnd ){
Expr *pX;
pX = pEnd->pExpr;
assert( pX!=0 );
assert( pEnd->leftCursor==iCur );
pLevel->iMem = ++pParse->nMem;
sqlite3ExprCode(pParse, pX->pRight, pLevel->iMem);
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 ){
int r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
/* sqlite3VdbeAddOp2(v, OP_SCopy, pLevel->iMem, 0); */
sqlite3VdbeAddOp3(v, testOp, pLevel->iMem, brk, r1);
sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
sqlite3ReleaseTempReg(pParse, r1);
}
}else if( pLevel->flags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
/* Case 3: A scan using an index.
**
** The WHERE clause may contain zero or more equality
** terms ("==" or "IN" operators) that refer to the N
** left-most columns of the index. It may also contain
** inequality constraints (>, <, >= or <=) on the indexed
** column that immediately follows the N equalities. Only
** the right-most column can be an inequality - the rest must
** use the "==" and "IN" operators. For example, if the
** index is on (x,y,z), then the following clauses are all
** optimized:
**
** x=5
** x=5 AND y=10
** x=5 AND y<10
** x=5 AND y>5 AND y<10
** x=5 AND y=5 AND z<=10
**
** The z<10 term of the following cannot be used, only
** the x=5 term:
**
** x=5 AND z<10
**
** N may be zero if there are inequality constraints.
** If there are no inequality constraints, then N is at
** least one.
**
** 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 aStartOp[] = {
0,
0,
OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
OP_Last, /* 3: (!start_constraints && startEq && bRev) */
OP_MoveGt, /* 4: (start_constraints && !startEq && !bRev) */
OP_MoveLt, /* 5: (start_constraints && !startEq && bRev) */
OP_MoveGe, /* 6: (start_constraints && startEq && !bRev) */
OP_MoveLe /* 7: (start_constraints && startEq && bRev) */
};
int aEndOp[] = {
OP_Noop, /* 0: (!end_constraints) */
OP_IdxGE, /* 1: (end_constraints && !bRev) */
OP_IdxLT /* 2: (end_constraints && bRev) */
};
int nEq = pLevel->nEq;
int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
int regBase; /* Base register holding constraint values */
int r1; /* Temp register */
WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
int startEq; /* True if range start uses ==, >= or <= */
int endEq; /* True if range end uses ==, >= or <= */
int start_constraints; /* Start of range is constrained */
int k = pIdx->aiColumn[nEq]; /* Column for inequality constraints */
int nConstraint; /* Number of constraint terms */
int op;
/* Generate code to evaluate all constraint terms using == or IN
** and store the values of those terms in an array of registers
** starting at regBase.
*/
regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 2);
nxt = pLevel->nxt;
/* If this loop satisfies a sort order (pOrderBy) request that
** was passed to this function to implement a "SELECT min(x) ..."
** query, then the caller will only allow the loop to run for
** a single iteration. This means that the first row returned
** should not have a NULL value stored in 'x'. If column 'x' is
** the first one after the nEq equality constraints in the index,
** this requires some special handling.
*/
if( (wflags&WHERE_ORDERBY_MIN)!=0
&& (pLevel->flags&WHERE_ORDERBY)
&& (pIdx->nColumn>nEq)
){
assert( pOrderBy->nExpr==1 );
assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] );
isMinQuery = 1;
}
/* Find any inequality constraint terms for the start and end
** of the range.
*/
if( pLevel->flags & WHERE_TOP_LIMIT ){
pRangeEnd = findTerm(&wc, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
}
if( pLevel->flags & WHERE_BTM_LIMIT ){
pRangeStart = findTerm(&wc, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
}
/* If we are doing a reverse order scan on an ascending index, or
** a forward order scan on a descending index, interchange the
** start and end terms (pRangeStart and pRangeEnd).
*/
if( bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
SWAP(WhereTerm *, pRangeEnd, pRangeStart);
}
testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
start_constraints = pRangeStart || nEq>0;
/* Seek the index cursor to the start of the range. */
nConstraint = nEq;
if( pRangeStart ){
int dcc = pParse->disableColCache;
if( pRangeEnd ){
pParse->disableColCache++;
}
sqlite3ExprCode(pParse, pRangeStart->pExpr->pRight, regBase+nEq);
pParse->disableColCache = dcc;
sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);
nConstraint++;
}else if( isMinQuery ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
nConstraint++;
startEq = 0;
start_constraints = 1;
}
codeApplyAffinity(pParse, regBase, nConstraint, pIdx);
op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
assert( op!=0 );
testcase( op==OP_Rewind );
testcase( op==OP_Last );
testcase( op==OP_MoveGt );
testcase( op==OP_MoveGe );
testcase( op==OP_MoveLe );
testcase( op==OP_MoveLt );
sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase,
SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
/* Load the value for the inequality constraint at the end of the
** range (if any).
*/
nConstraint = nEq;
if( pRangeEnd ){
sqlite3ExprCode(pParse, pRangeEnd->pExpr->pRight, regBase+nEq);
sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);
codeApplyAffinity(pParse, regBase, nEq+1, pIdx);
nConstraint++;
}
/* Top of the loop body */
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
/* Check if the index cursor is past the end of the range. */
op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
testcase( op==OP_Noop );
testcase( op==OP_IdxGE );
testcase( op==OP_IdxLT );
sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase,
SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
sqlite3VdbeChangeP5(v, endEq!=bRev);
/* If there are inequality constraints, check that the value
** of the table column that the inequality contrains is not NULL.
** If it is, jump to the next iteration of the loop.
*/
r1 = sqlite3GetTempReg(pParse);
testcase( pLevel->flags & WHERE_BTM_LIMIT );
testcase( pLevel->flags & WHERE_TOP_LIMIT );
if( pLevel->flags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT) ){
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
sqlite3VdbeAddOp2(v, OP_IsNull, r1, cont);
}
/* Seek the table cursor, if required */
if( !omitTable ){
sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, r1);
sqlite3VdbeAddOp3(v, OP_MoveGe, iCur, 0, r1); /* Deferred seek */
}
sqlite3ReleaseTempReg(pParse, r1);
/* Record the instruction used to terminate the loop. Disable
** WHERE clause terms made redundant by the index range scan.
*/
pLevel->op = bRev ? OP_Prev : OP_Next;
pLevel->p1 = iIdxCur;
disableTerm(pLevel, pRangeStart);
disableTerm(pLevel, pRangeEnd);
}else{
/* Case 4: 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 + sqlite3VdbeAddOp2(v, OP_Rewind, iCur, brk);
}
notReady &= ~getMask(&maskSet, iCur);
/* 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;
testcase( pTerm->flags & TERM_VIRTUAL );
testcase( pTerm->flags & TERM_CODED );
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, SQLITE_JUMPIFNULL);
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);
sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
VdbeComment((v, "record LEFT JOIN hit"));
sqlite3ExprClearColumnCache(pParse, pLevel->iTabCur);
sqlite3ExprClearColumnCache(pParse, pLevel->iIdxCur);
for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
testcase( pTerm->flags & TERM_VIRTUAL );
testcase( pTerm->flags & TERM_CODED );
if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( (pTerm->prereqAll & notReady)!=0 ) continue;
assert( pTerm->pExpr );
sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, SQLITE_JUMPIFNULL);
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++] = ' ';
}
testcase( pLevel->flags & WHERE_ROWID_EQ );
testcase( pLevel->flags & WHERE_ROWID_RANGE );
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){
Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
int i;
WhereLevel *pLevel;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
/* Generate loop termination code.
*/
sqlite3ExprClearColumnCache(pParse, -1);
for(i=pTabList->nSrc-1; i>=0; i--){
pLevel = &pWInfo->a[i];
sqlite3VdbeResolveLabel(v, pLevel->cont);
if( pLevel->op!=OP_Noop ){
sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
}
if( pLevel->nIn ){
struct 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);
sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->topAddr);
sqlite3VdbeJumpHere(v, pIn->topAddr-1);
}
sqlite3DbFree(db, pLevel->aInLoop);
}
sqlite3VdbeResolveLabel(v, pLevel->brk);
if( pLevel->iLeftJoin ){
int addr;
addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
if( pLevel->iIdxCur>=0 ){
sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
}
sqlite3VdbeAddOp2(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++){
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
if( pTab->isEphem || pTab->pSelect ) continue;
if( !pWInfo->okOnePass && (pLevel->flags & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
}
if( pLevel->pIdx!=0 ){
sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
}
/* 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;
}