diff -r 5f8e5adbbed9 -r 29cda98b007e engine/sqlite/src/where.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/engine/sqlite/src/where.cpp Thu Feb 25 14:29:19 2010 +0000 @@ -0,0 +1,2789 @@ +/* +** 2001 September 15 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This module contains C code that generates VDBE code used to process +** the WHERE clause of SQL statements. This module is reponsible for +** generating the code that loops through a table looking for applicable +** rows. Indices are selected and used to speed the search when doing +** so is applicable. Because this module is responsible for selecting +** indices, you might also think of this module as the "query optimizer". +** +** $Id: where.cpp 1282 2008-11-13 09:31:33Z LarsPson $ +*/ +#include "sqliteInt.h" + +/* +** The number of bits in a Bitmask. "BMS" means "BitMask Size". +*/ +#define BMS (sizeof(Bitmask)*8) + +/* +** Trace output macros +*/ +#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG) +int sqlite3_where_trace = 0; +# define WHERETRACE(X) if(sqlite3_where_trace) sqlite3DebugPrintf X +#else +# define WHERETRACE(X) +#endif + +/* Forward reference +*/ +typedef struct WhereClause WhereClause; +typedef struct ExprMaskSet ExprMaskSet; + +/* +** The query generator uses an array of instances of this structure to +** help it analyze the subexpressions of the WHERE clause. Each WHERE +** clause subexpression is separated from the others by an AND operator. +** +** All WhereTerms are collected into a single WhereClause structure. +** The following identity holds: +** +** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm +** +** When a term is of the form: +** +** X +** +** where X is a column name and is one of certain operators, +** then WhereTerm.leftCursor and WhereTerm.leftColumn record the +** cursor number and column number for X. WhereTerm.operator records +** the 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 " */ + i16 leftColumn; /* Column number of X in "X " */ + u16 eOperator; /* A WO_xx value describing */ + u8 flags; /* Bit flags. See below */ + u8 nChild; /* Number of children that must disable us */ + WhereClause *pWC; /* The clause this term is part of */ + Bitmask prereqRight; /* Bitmask of tables used by pRight */ + Bitmask prereqAll; /* Bitmask of tables referenced by p */ +}; + +/* +** Allowed values of WhereTerm.flags +*/ +#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(pExpr) */ +#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */ +#define TERM_CODED 0x04 /* This term is already coded */ +#define TERM_COPIED 0x08 /* Has a child */ +#define TERM_OR_OK 0x10 /* Used during OR-clause processing */ + +/* +** An instance of the following structure holds all information about a +** WHERE clause. Mostly this is a container for one or more WhereTerms. +*/ +struct WhereClause { + Parse *pParse; /* The parser context */ + ExprMaskSet *pMaskSet; /* Mapping of table indices to bitmasks */ + int nTerm; /* Number of terms */ + int nSlot; /* Number of entries in a[] */ + WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */ + WhereTerm aStatic[10]; /* Initial static space for a[] */ +}; + +/* +** An instance of the following structure keeps track of a mapping +** between VDBE cursor numbers and bits of the bitmasks in WhereTerm. +** +** The VDBE cursor numbers are small integers contained in +** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE +** clause, the cursor numbers might not begin with 0 and they might +** contain gaps in the numbering sequence. But we want to make maximum +** use of the bits in our bitmasks. This structure provides a mapping +** from the sparse cursor numbers into consecutive integers beginning +** with 0. +** +** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask +** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<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 /* rowidEXPR */ +#define WHERE_COLUMN_EQ 0x001000 /* x=EXPR or x IN (...) */ +#define WHERE_COLUMN_RANGE 0x002000 /* xEXPR */ +#define WHERE_COLUMN_IN 0x004000 /* x IN (...) */ +#define WHERE_TOP_LIMIT 0x010000 /* xEXPR or x>=EXPR constraint */ +#define WHERE_IDX_ONLY 0x080000 /* Use index only - omit table */ +#define WHERE_ORDERBY 0x100000 /* Output will appear in correct order */ +#define WHERE_REVERSE 0x200000 /* Scan in reverse order */ +#define WHERE_UNIQUE 0x400000 /* Selects no more than one row */ +#define WHERE_VIRTUALTABLE 0x800000 /* Use virtual-table processing */ + +/* +** Initialize a preallocated WhereClause structure. +*/ +static void whereClauseInit( + WhereClause *pWC, /* The WhereClause to be initialized */ + Parse *pParse, /* The parsing context */ + ExprMaskSet *pMaskSet /* Mapping from table indices to bitmasks */ +){ + pWC->pParse = pParse; + pWC->pMaskSet = pMaskSet; + pWC->nTerm = 0; + pWC->nSlot = ArraySize(pWC->aStatic); + pWC->a = pWC->aStatic; +} + +/* +** Deallocate a WhereClause structure. The WhereClause structure +** itself is not freed. This routine is the inverse of whereClauseInit(). +*/ +static void whereClauseClear(WhereClause *pWC){ + int i; + WhereTerm *a; + for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){ + if( a->flags & TERM_DYNAMIC ){ + sqlite3ExprDelete(a->pExpr); + } + } + if( pWC->a!=pWC->aStatic ){ + sqlite3_free(pWC->a); + } +} + +/* +** Add a new entries to the WhereClause structure. Increase the allocated +** space as necessary. +** +** If the flags argument includes TERM_DYNAMIC, then responsibility +** for freeing the expression p is assumed by the WhereClause object. +** +** WARNING: This routine might reallocate the space used to store +** WhereTerms. All pointers to WhereTerms should be invalided after +** calling this routine. Such pointers may be reinitialized by referencing +** the pWC->a[] array. +*/ +static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){ + WhereTerm *pTerm; + int idx; + if( pWC->nTerm>=pWC->nSlot ){ + WhereTerm *pOld = pWC->a; + pWC->a = (WhereTerm*)sqlite3_malloc( sizeof(pWC->a[0])*pWC->nSlot*2 ); + if( pWC->a==0 ){ + pWC->pParse->db->mallocFailed = 1; + if( flags & TERM_DYNAMIC ){ + sqlite3ExprDelete(p); + } + pWC->a = pOld; + return 0; + } + memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm); + if( pOld!=pWC->aStatic ){ + sqlite3_free(pOld); + } + pWC->nSlot *= 2; + } + pTerm = &pWC->a[idx = pWC->nTerm]; + pWC->nTerm++; + pTerm->pExpr = p; + pTerm->flags = flags; + pTerm->pWC = pWC; + pTerm->iParent = -1; + return idx; +} + +/* +** This routine identifies subexpressions in the WHERE clause where +** each subexpression is separated by the AND operator or some other +** operator specified in the op parameter. The WhereClause structure +** is filled with pointers to subexpressions. For example: +** +** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22) +** \________/ \_______________/ \________________/ +** slot[0] slot[1] slot[2] +** +** The original WHERE clause in pExpr is unaltered. All this routine +** does is make slot[] entries point to substructure within pExpr. +** +** In the previous sentence and in the diagram, "slot[]" refers to +** the WhereClause.a[] array. This array grows as needed to contain +** all terms of the WHERE clause. +*/ +static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){ + if( pExpr==0 ) return; + if( pExpr->op!=op ){ + whereClauseInsert(pWC, pExpr, 0); + }else{ + whereSplit(pWC, pExpr->pLeft, op); + whereSplit(pWC, pExpr->pRight, op); + } +} + +/* +** Initialize an expression mask set +*/ +#define initMaskSet(P) memset(P, 0, sizeof(*P)) + +/* +** Return the bitmask for the given cursor number. Return 0 if +** iCursor is not in the set. +*/ +static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){ + int i; + for(i=0; in; i++){ + if( pMaskSet->ix[i]==iCursor ){ + return ((Bitmask)1)<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; inExpr; 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_GTTK_EQ && TK_LTTK_EQ && TK_LE=TK_EQ && op<=TK_GE) || op==TK_ISNULL; +} + +/* +** Swap two objects of type T. +*/ +#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;} + +/* +** Commute a comparision operator. Expressions of the form "X op Y" +** are converted into "Y op X". +** +** If a collation sequence is associated with either the left or right +** side of the comparison, it remains associated with the same side after +** the commutation. So "Y collate NOCASE op X" becomes +** "X collate NOCASE op Y". This is because any collation sequence on +** the left hand side of a comparison overrides any collation sequence +** attached to the right. For the same reason the EP_ExpCollate flag +** is not commuted. +*/ +static void exprCommute(Expr *pExpr){ + u16 expRight = (pExpr->pRight->flags & EP_ExpCollate); + u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate); + assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN ); + SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl); + pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft; + pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight; + SWAP(Expr*,pExpr->pRight,pExpr->pLeft); + if( pExpr->op>=TK_GT ){ + assert( TK_LT==TK_GT+2 ); + assert( TK_GE==TK_LE+2 ); + assert( TK_GT>TK_EQ ); + assert( TK_GTop>=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 " +** where X is a reference to the iColumn of table iCur and is one of +** the WO_xx operator codes specified by the op parameter. +** Return a pointer to the term. Return 0 if not found. +*/ +static WhereTerm *findTerm( + WhereClause *pWC, /* The WHERE clause to be searched */ + int iCur, /* Cursor number of LHS */ + int iColumn, /* Column number of LHS */ + Bitmask notReady, /* RHS must not overlap with this mask */ + u16 op, /* Mask of WO_xx values describing operator */ + Index *pIdx /* Must be compatible with this index, if not NULL */ +){ + WhereTerm *pTerm; + int k; + for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){ + if( pTerm->leftCursor==iCur + && (pTerm->prereqRight & notReady)==0 + && pTerm->leftColumn==iColumn + && (pTerm->eOperator & op)!=0 + ){ + if( iCur>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){ + Expr *pX = pTerm->pExpr; + CollSeq *pColl; + char idxaff; + int j; + Parse *pParse = pWC->pParse; + + idxaff = pIdx->pTable->aCol[iColumn].affinity; + if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue; + + /* Figure out the collation sequence required from an index for + ** it to be useful for optimising expression pX. Store this + ** value in variable pColl. + */ + assert(pX->pLeft); + pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight); + if( !pColl ){ + pColl = pParse->db->pDfltColl; + } + + for(j=0; jnColumn && pIdx->aiColumn[j]!=iColumn; j++){} + assert( jnColumn ); + if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue; + } + return pTerm; + } + } + return 0; +} + +/* Forward reference */ +static void exprAnalyze(SrcList*, WhereClause*, int); + +/* +** Call exprAnalyze on all terms in a WHERE clause. +** +** +*/ +static void exprAnalyzeAll( + SrcList *pTabList, /* the FROM clause */ + WhereClause *pWC /* the WHERE clause to be analyzed */ +){ + int i; + for(i=pWC->nTerm-1; i>=0; i--){ + exprAnalyze(pTabList, pWC, i); + } +} + +#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION +/* +** Check to see if the given expression is a LIKE or GLOB operator that +** can be optimized using inequality constraints. Return TRUE if it is +** so and false if not. +** +** In order for the operator to be optimizible, the RHS must be a string +** literal that does not begin with a wildcard. +*/ +static int isLikeOrGlob( + sqlite3 *db, /* The database */ + Expr *pExpr, /* Test this expression */ + int *pnPattern, /* Number of non-wildcard prefix characters */ + int *pisComplete /* True if the only wildcard is % in the last character */ +){ + const char *z; + Expr *pRight, *pLeft; + ExprList *pList; + int c, cnt; + int noCase; + char wc[3]; + CollSeq *pColl; + + if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){ + return 0; + } + pList = pExpr->pList; + pRight = pList->a[0].pExpr; + if( pRight->op!=TK_STRING ){ + return 0; + } + pLeft = pList->a[1].pExpr; + if( pLeft->op!=TK_COLUMN ){ + return 0; + } + pColl = pLeft->pColl; + if( pColl==0 ){ + /* TODO: Coverage testing doesn't get this case. Is it actually possible + ** for an expression of type TK_COLUMN to not have an assigned collation + ** sequence at this point? + */ + pColl = db->pDfltColl; + } + if( (pColl->type!=SQLITE_COLL_BINARY || noCase) && + (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){ + return 0; + } + sqlite3DequoteExpr(db, pRight); + z = (char *)pRight->token.z; + cnt = 0; + if( z ){ + while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){ cnt++; } + } + if( cnt==0 || 255==(u8)z[cnt] ){ + return 0; + } + *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0; + *pnPattern = cnt; + return 1; +} +#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */ + + +#ifndef SQLITE_OMIT_VIRTUALTABLE +/* +** Check to see if the given expression is of the form +** +** column MATCH expr +** +** If it is then return TRUE. If not, return FALSE. +*/ +static int isMatchOfColumn( + Expr *pExpr /* Test this expression */ +){ + ExprList *pList; + + if( pExpr->op!=TK_FUNCTION ){ + return 0; + } + if( pExpr->token.n!=5 || + sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){ + return 0; + } + pList = pExpr->pList; + if( pList->nExpr!=2 ){ + return 0; + } + if( pList->a[1].pExpr->op != TK_COLUMN ){ + return 0; + } + return 1; +} +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + +/* +** If the pBase expression originated in the ON or USING clause of +** a join, then transfer the appropriate markings over to derived. +*/ +static void transferJoinMarkings(Expr *pDerived, Expr *pBase){ + pDerived->flags |= pBase->flags & EP_FromJoin; + pDerived->iRightJoinTable = pBase->iRightJoinTable; +} + +#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY) +/* +** Return TRUE if the given term of an OR clause can be converted +** into an IN clause. The iCursor and iColumn define the left-hand +** side of the IN clause. +** +** The context is that we have multiple OR-connected equality terms +** like this: +** +** a= OR a= OR b= OR ... +** +** The pOrTerm input to this routine corresponds to a single term of +** this OR clause. In order for the term to be a condidate for +** conversion to an IN operator, the following must be true: +** +** * The left-hand side of the term must be the column which +** is identified by iCursor and iColumn. +** +** * If the right-hand side is also a column, then the affinities +** of both right and left sides must be such that no type +** conversions are required on the right. (Ticket #2249) +** +** If both of these conditions are true, then return true. Otherwise +** return false. +*/ +static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){ + int affLeft, affRight; + assert( pOrTerm->eOperator==WO_EQ ); + if( pOrTerm->leftCursor!=iCursor ){ + return 0; + } + if( pOrTerm->leftColumn!=iColumn ){ + return 0; + } + affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight); + if( affRight==0 ){ + return 1; + } + affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft); + if( affRight!=affLeft ){ + return 0; + } + return 1; +} + +/* +** Return true if the given term of an OR clause can be ignored during +** a check to make sure all OR terms are candidates for optimization. +** In other words, return true if a call to the orTermIsOptCandidate() +** above returned false but it is not necessary to disqualify the +** optimization. +** +** Suppose the original OR phrase was this: +** +** a=4 OR a=11 OR a=b +** +** During analysis, the third term gets flipped around and duplicate +** so that we are left with this: +** +** a=4 OR a=11 OR a=b OR b=a +** +** Since the last two terms are duplicates, only one of them +** has to qualify in order for the whole phrase to qualify. When +** this routine is called, we know that pOrTerm did not qualify. +** This routine merely checks to see if pOrTerm has a duplicate that +** might qualify. If there is a duplicate that has not yet been +** disqualified, then return true. If there are no duplicates, or +** the duplicate has also been disqualifed, return false. +*/ +static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){ + if( pOrTerm->flags & TERM_COPIED ){ + /* This is the original term. The duplicate is to the left had + ** has not yet been analyzed and thus has not yet been disqualified. */ + return 1; + } + if( (pOrTerm->flags & TERM_VIRTUAL)!=0 + && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){ + /* This is a duplicate term. The original qualified so this one + ** does not have to. */ + return 1; + } + /* This is either a singleton term or else it is a duplicate for + ** which the original did not qualify. Either way we are done for. */ + return 0; +} +#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */ + +/* +** The input to this routine is an WhereTerm structure with only the +** "pExpr" field filled in. The job of this routine is to analyze the +** subexpression and populate all the other fields of the WhereTerm +** structure. +** +** If the expression is of the form " X" it gets commuted +** to the standard form of "X ". If the expression is of +** the form "X Y" where both X and Y are columns, then the original +** expression is unchanged and a new virtual expression of the form +** "Y X" is added to the WHERE clause and analyzed separately. +*/ +static void exprAnalyze( + SrcList *pSrc, /* the FROM clause */ + WhereClause *pWC, /* the WHERE clause */ + int idxTerm /* Index of the term to be analyzed */ +){ + WhereTerm *pTerm; + ExprMaskSet *pMaskSet; + Expr *pExpr; + Bitmask prereqLeft; + Bitmask prereqAll; + int nPattern; + int isComplete; + int op; + Parse *pParse = pWC->pParse; + sqlite3 *db = pParse->db; + + if( db->mallocFailed ){ + return; + } + pTerm = &pWC->a[idxTerm]; + pMaskSet = pWC->pMaskSet; + pExpr = pTerm->pExpr; + prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft); + op = pExpr->op; + if( op==TK_IN ){ + assert( pExpr->pRight==0 ); + pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList) + | exprSelectTableUsage(pMaskSet, pExpr->pSelect); + }else if( op==TK_ISNULL ){ + pTerm->prereqRight = 0; + }else{ + pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight); + } + prereqAll = exprTableUsage(pMaskSet, pExpr); + if( ExprHasProperty(pExpr, EP_FromJoin) ){ + prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable); + } + pTerm->prereqAll = prereqAll; + pTerm->leftCursor = -1; + pTerm->iParent = -1; + pTerm->eOperator = 0; + if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){ + Expr *pLeft = pExpr->pLeft; + Expr *pRight = pExpr->pRight; + if( pLeft->op==TK_COLUMN ){ + pTerm->leftCursor = pLeft->iTable; + pTerm->leftColumn = pLeft->iColumn; + pTerm->eOperator = operatorMask(op); + } + if( pRight && pRight->op==TK_COLUMN ){ + WhereTerm *pNew; + Expr *pDup; + if( pTerm->leftCursor>=0 ){ + int idxNew; + pDup = sqlite3ExprDup(db, pExpr); + if( db->mallocFailed ){ + sqlite3ExprDelete(pDup); + return; + } + idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC); + if( idxNew==0 ) return; + pNew = &pWC->a[idxNew]; + pNew->iParent = idxTerm; + pTerm = &pWC->a[idxTerm]; + pTerm->nChild = 1; + pTerm->flags |= TERM_COPIED; + }else{ + pDup = pExpr; + pNew = pTerm; + } + exprCommute(pDup); + pLeft = pDup->pLeft; + pNew->leftCursor = pLeft->iTable; + pNew->leftColumn = pLeft->iColumn; + pNew->prereqRight = prereqLeft; + pNew->prereqAll = prereqAll; + pNew->eOperator = operatorMask(pDup->op); + } + } + +#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION + /* If a term is the BETWEEN operator, create two new virtual terms + ** that define the range that the BETWEEN implements. + */ + else if( pExpr->op==TK_BETWEEN ){ + ExprList *pList = pExpr->pList; + int i; + static const u8 ops[] = {TK_GE, TK_LE}; + assert( pList!=0 ); + assert( pList->nExpr==2 ); + for(i=0; i<2; i++){ + Expr *pNewExpr; + int idxNew; + pNewExpr = sqlite3Expr(db, ops[i], sqlite3ExprDup(db, pExpr->pLeft), + sqlite3ExprDup(db, pList->a[i].pExpr), 0); + idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC); + exprAnalyze(pSrc, pWC, idxNew); + pTerm = &pWC->a[idxTerm]; + pWC->a[idxNew].iParent = idxTerm; + } + pTerm->nChild = 2; + } +#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */ + +#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY) + /* Attempt to convert OR-connected terms into an IN operator so that + ** they can make use of indices. Example: + ** + ** x = expr1 OR expr2 = x OR x = expr3 + ** + ** is converted into + ** + ** x IN (expr1,expr2,expr3) + ** + ** This optimization must be omitted if OMIT_SUBQUERY is defined because + ** the compiler for the the IN operator is part of sub-queries. + */ + else if( pExpr->op==TK_OR ){ + int ok; + int i, j; + int iColumn, iCursor; + WhereClause sOr; + WhereTerm *pOrTerm; + + assert( (pTerm->flags & TERM_DYNAMIC)==0 ); + whereClauseInit(&sOr, pWC->pParse, pMaskSet); + whereSplit(&sOr, pExpr, TK_OR); + exprAnalyzeAll(pSrc, &sOr); + assert( sOr.nTerm>=2 ); + j = 0; + do{ + assert( j=0; + for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){ + if( pOrTerm->eOperator!=WO_EQ ){ + goto or_not_possible; + } + if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){ + pOrTerm->flags |= TERM_OR_OK; + }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){ + pOrTerm->flags &= ~TERM_OR_OK; + }else{ + ok = 0; + } + } + }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 ); + if( ok ){ + ExprList *pList = 0; + Expr *pNew, *pDup; + Expr *pLeft = 0; + for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){ + if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue; + pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight); + pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup, 0); + pLeft = pOrTerm->pExpr->pLeft; + } + assert( pLeft!=0 ); + pDup = sqlite3ExprDup(db, pLeft); + pNew = sqlite3Expr(db, TK_IN, pDup, 0, 0); + if( pNew ){ + int idxNew; + transferJoinMarkings(pNew, pExpr); + pNew->pList = pList; + idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC); + exprAnalyze(pSrc, pWC, idxNew); + pTerm = &pWC->a[idxTerm]; + pWC->a[idxNew].iParent = idxTerm; + pTerm->nChild = 1; + }else{ + sqlite3ExprListDelete(pList); + } + } +or_not_possible: + whereClauseClear(&sOr); + } +#endif /* SQLITE_OMIT_OR_OPTIMIZATION */ + +#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION + /* Add constraints to reduce the search space on a LIKE or GLOB + ** operator. + */ + if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete) ){ + Expr *pLeft, *pRight; + Expr *pStr1, *pStr2; + Expr *pNewExpr1, *pNewExpr2; + int idxNew1, idxNew2; + + pLeft = pExpr->pList->a[1].pExpr; + pRight = pExpr->pList->a[0].pExpr; + pStr1 = sqlite3PExpr(pParse, TK_STRING, 0, 0, 0); + if( pStr1 ){ + sqlite3TokenCopy(db, &pStr1->token, &pRight->token); + pStr1->token.n = nPattern; + pStr1->flags = EP_Dequoted; + } + pStr2 = sqlite3ExprDup(db, pStr1); + if( !db->mallocFailed ){ + assert( pStr2->token.dyn ); + ++*(u8*)&pStr2->token.z[nPattern-1]; + } + pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft), pStr1, 0); + idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC); + exprAnalyze(pSrc, pWC, idxNew1); + pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft), pStr2, 0); + idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC); + exprAnalyze(pSrc, pWC, idxNew2); + pTerm = &pWC->a[idxTerm]; + if( isComplete ){ + pWC->a[idxNew1].iParent = idxTerm; + pWC->a[idxNew2].iParent = idxTerm; + pTerm->nChild = 2; + } + } +#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */ + +#ifndef SQLITE_OMIT_VIRTUALTABLE + /* Add a WO_MATCH auxiliary term to the constraint set if the + ** current expression is of the form: column MATCH expr. + ** This information is used by the xBestIndex methods of + ** virtual tables. The native query optimizer does not attempt + ** to do anything with MATCH functions. + */ + if( isMatchOfColumn(pExpr) ){ + int idxNew; + Expr *pRight, *pLeft; + WhereTerm *pNewTerm; + Bitmask prereqColumn, prereqExpr; + + pRight = pExpr->pList->a[0].pExpr; + pLeft = pExpr->pList->a[1].pExpr; + prereqExpr = exprTableUsage(pMaskSet, pRight); + prereqColumn = exprTableUsage(pMaskSet, pLeft); + if( (prereqExpr & prereqColumn)==0 ){ + Expr *pNewExpr; + pNewExpr = sqlite3Expr(db, TK_MATCH, 0, sqlite3ExprDup(db, pRight), 0); + idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC); + pNewTerm = &pWC->a[idxNew]; + pNewTerm->prereqRight = prereqExpr; + pNewTerm->leftCursor = pLeft->iTable; + pNewTerm->leftColumn = pLeft->iColumn; + pNewTerm->eOperator = WO_MATCH; + pNewTerm->iParent = idxTerm; + pTerm = &pWC->a[idxTerm]; + pTerm->nChild = 1; + pTerm->flags |= TERM_COPIED; + pNewTerm->prereqAll = pTerm->prereqAll; + } + } +#endif /* SQLITE_OMIT_VIRTUALTABLE */ +} + +/* +** Return TRUE if any of the expressions in pList->a[iFirst...] contain +** a reference to any table other than the iBase table. +*/ +static int referencesOtherTables( + ExprList *pList, /* Search expressions in ths list */ + ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */ + int iFirst, /* Be searching with the iFirst-th expression */ + int iBase /* Ignore references to this table */ +){ + Bitmask allowed = ~getMask(pMaskSet, iBase); + while( iFirstnExpr ){ + if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){ + return 1; + } + } + return 0; +} + + +/* +** This routine decides if pIdx can be used to satisfy the ORDER BY +** clause. If it can, it returns 1. If pIdx cannot satisfy the +** ORDER BY clause, this routine returns 0. +** +** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the +** left-most table in the FROM clause of that same SELECT statement and +** the table has a cursor number of "base". pIdx is an index on pTab. +** +** nEqCol is the number of columns of pIdx that are used as equality +** constraints. Any of these columns may be missing from the ORDER BY +** clause and the match can still be a success. +** +** All terms of the ORDER BY that match against the index must be either +** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE +** index do not need to satisfy this constraint.) The *pbRev value is +** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if +** the ORDER BY clause is all ASC. +*/ +static int isSortingIndex( + Parse *pParse, /* Parsing context */ + ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */ + Index *pIdx, /* The index we are testing */ + int base, /* Cursor number for the table to be sorted */ + ExprList *pOrderBy, /* The ORDER BY clause */ + int nEqCol, /* Number of index columns with == constraints */ + int *pbRev /* Set to 1 if ORDER BY is DESC */ +){ + int i, j; /* Loop counters */ + int sortOrder = 0; /* XOR of index and ORDER BY sort direction */ + int nTerm; /* Number of ORDER BY terms */ + ExprList::ExprList_item *pTerm; /* A term of the ORDER BY clause */ + sqlite3 *db = pParse->db; + + assert( pOrderBy!=0 ); + nTerm = pOrderBy->nExpr; + assert( nTerm>0 ); + + /* Match terms of the ORDER BY clause against columns of + ** the index. + ** + ** Note that indices have pIdx->nColumn regular columns plus + ** one additional column containing the rowid. The rowid column + ** of the index is also allowed to match against the ORDER BY + ** clause. + */ + for(i=j=0, pTerm=pOrderBy->a; jnColumn; 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( inColumn ){ + 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( iaSortOrder!=0 ); + assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 ); + assert( iSortOrder==0 || iSortOrder==1 ); + termSortOrder = iSortOrder ^ pTerm->sortOrder; + if( i>nEqCol ){ + if( termSortOrder!=sortOrder ){ + /* Indices can only be used if all ORDER BY terms past the + ** equality constraints are all either DESC or ASC. */ + return 0; + } + }else{ + sortOrder = termSortOrder; + } + j++; + pTerm++; + if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){ + /* If the indexed column is the primary key and everything matches + ** so far and none of the ORDER BY terms to the right reference other + ** tables in the join, then we are assured that the index can be used + ** to sort because the primary key is unique and so none of the other + ** columns will make any difference + */ + j = nTerm; + } + } + + *pbRev = sortOrder!=0; + if( j>=nTerm ){ + /* All terms of the ORDER BY clause are covered by this index so + ** this index can be used for sorting. */ + return 1; + } + if( pIdx->onError!=OE_None && i==pIdx->nColumn + && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){ + /* All terms of this index match some prefix of the ORDER BY clause + ** and the index is UNIQUE and no terms on the tail of the ORDER BY + ** clause reference other tables in a join. If this is all true then + ** the order by clause is superfluous. */ + return 1; + } + return 0; +} + +/* +** Check table to see if the ORDER BY clause in pOrderBy can be satisfied +** by sorting in order of ROWID. Return true if so and set *pbRev to be +** true for reverse ROWID and false for forward ROWID order. +*/ +static int sortableByRowid( + int base, /* Cursor number for table to be sorted */ + ExprList *pOrderBy, /* The ORDER BY clause */ + ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */ + int *pbRev /* Set to 1 if ORDER BY is DESC */ +){ + Expr *p; + + assert( pOrderBy!=0 ); + assert( pOrderBy->nExpr>0 ); + p = pOrderBy->a[0].pExpr; + if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1 + && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){ + *pbRev = pOrderBy->a[0].sortOrder; + return 1; + } + return 0; +} + +/* +** Prepare a crude estimate of the logarithm of the input value. +** The results need not be exact. This is only used for estimating +** the total cost of performing operatings with O(logN) or O(NlogN) +** complexity. Because N is just a guess, it is no great tragedy if +** logN is a little off. +*/ +static double estLog(double N){ + double logN = 1; + double x = 10; + while( N>x ){ + logN += 1; + x *= 10; + } + return logN; +} + +/* +** Two routines for printing the content of an sqlite3_index_info +** structure. Used for testing and debugging only. If neither +** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines +** are no-ops. +*/ +#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG) +static void TRACE_IDX_INPUTS(sqlite3_index_info *p){ + int i; + if( !sqlite3_where_trace ) return; + for(i=0; inConstraint; 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; inOrderBy; i++){ + sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n", + i, + p->aOrderBy[i].iColumn, + p->aOrderBy[i].desc); + } +} +static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){ + int i; + if( !sqlite3_where_trace ) return; + for(i=0; inConstraint; i++){ + sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n", + i, + p->aConstraintUsage[i].argvIndex, + p->aConstraintUsage[i].omit); + } + sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum); + sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr); + sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed); + sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost); +} +#else +#define TRACE_IDX_INPUTS(A) +#define TRACE_IDX_OUTPUTS(A) +#endif + +#ifndef SQLITE_OMIT_VIRTUALTABLE +/* +** Compute the best index for a virtual table. +** +** The best index is computed by the xBestIndex method of the virtual +** table module. This routine is really just a wrapper that sets up +** the sqlite3_index_info structure that is used to communicate with +** xBestIndex. +** +** In a join, this routine might be called multiple times for the +** same virtual table. The sqlite3_index_info structure is created +** and initialized on the first invocation and reused on all subsequent +** invocations. The sqlite3_index_info structure is also used when +** code is generated to access the virtual table. The whereInfoDelete() +** routine takes care of freeing the sqlite3_index_info structure after +** everybody has finished with it. +*/ +static double bestVirtualIndex( + Parse *pParse, /* The parsing context */ + WhereClause *pWC, /* The WHERE clause */ + SrcList::SrcList_item *pSrc, /* The FROM clause term to search */ + Bitmask notReady, /* Mask of cursors that are not available */ + ExprList *pOrderBy, /* The order by clause */ + int orderByUsable, /* True if we can potential sort */ + sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */ +){ + Table *pTab = pSrc->pTab; + sqlite3_index_info *pIdxInfo; + sqlite3_index_info::sqlite3_index_constraint *pIdxCons; + sqlite3_index_info::sqlite3_index_orderby *pIdxOrderBy; + sqlite3_index_info::sqlite3_index_constraint_usage *pUsage; + WhereTerm *pTerm; + int i, j; + int nOrderBy; + int rc; + + /* If the sqlite3_index_info structure has not been previously + ** allocated and initialized for this virtual table, then allocate + ** and initialize it now + */ + pIdxInfo = *ppIdxInfo; + if( pIdxInfo==0 ){ + WhereTerm *pTerm; + int nTerm; + WHERETRACE(("Recomputing index info for %s...\n", pTab->zName)); + + /* Count the number of possible WHERE clause constraints referring + ** to this virtual table */ + for(i=nTerm=0, pTerm=pWC->a; inTerm; i++, pTerm++){ + if( pTerm->leftCursor != pSrc->iCursor ) continue; + if( pTerm->eOperator==WO_IN ) continue; + if( pTerm->eOperator==WO_ISNULL ) continue; + nTerm++; + } + + /* If the ORDER BY clause contains only columns in the current + ** virtual table then allocate space for the aOrderBy part of + ** the sqlite3_index_info structure. + */ + nOrderBy = 0; + if( pOrderBy ){ + for(i=0; inExpr; i++){ + Expr *pExpr = pOrderBy->a[i].pExpr; + if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break; + } + if( i==pOrderBy->nExpr ){ + nOrderBy = pOrderBy->nExpr; + } + } + + /* Allocate the sqlite3_index_info structure + */ + pIdxInfo = (sqlite3_index_info*)sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo) + + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm + + sizeof(*pIdxOrderBy)*nOrderBy ); + if( pIdxInfo==0 ){ + sqlite3ErrorMsg(pParse, "out of memory"); + return 0.0; + } + *ppIdxInfo = pIdxInfo; + + /* Initialize the structure. The sqlite3_index_info structure contains + ** many fields that are declared "const" to prevent xBestIndex from + ** changing them. We have to do some funky casting in order to + ** initialize those fields. + */ + pIdxCons = (sqlite3_index_info::sqlite3_index_constraint*)&pIdxInfo[1]; + pIdxOrderBy = (sqlite3_index_info::sqlite3_index_orderby*)&pIdxCons[nTerm]; + pUsage = (sqlite3_index_info::sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy]; + *(int*)&pIdxInfo->nConstraint = nTerm; + *(int*)&pIdxInfo->nOrderBy = nOrderBy; + *(sqlite3_index_info::sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons; + *(sqlite3_index_info::sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy; + *(sqlite3_index_info::sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage = + pUsage; + + for(i=j=0, pTerm=pWC->a; inTerm; i++, pTerm++){ + if( pTerm->leftCursor != pSrc->iCursor ) continue; + if( pTerm->eOperator==WO_IN ) continue; + if( pTerm->eOperator==WO_ISNULL ) continue; + pIdxCons[j].iColumn = pTerm->leftColumn; + pIdxCons[j].iTermOffset = i; + pIdxCons[j].op = pTerm->eOperator; + /* The direct assignment in the previous line is possible only because + ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The + ** following asserts verify this fact. */ + assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ ); + assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT ); + assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE ); + assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT ); + assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE ); + assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH ); + assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) ); + j++; + } + for(i=0; ia[i].pExpr; + pIdxOrderBy[i].iColumn = pExpr->iColumn; + pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder; + } + } + + /* At this point, the sqlite3_index_info structure that pIdxInfo points + ** to will have been initialized, either during the current invocation or + ** during some prior invocation. Now we just have to customize the + ** details of pIdxInfo for the current invocation and pass it to + ** xBestIndex. + */ + + /* The module name must be defined. Also, by this point there must + ** be a pointer to an sqlite3_vtab structure. Otherwise + ** sqlite3ViewGetColumnNames() would have picked up the error. + */ + assert( pTab->azModuleArg && pTab->azModuleArg[0] ); + assert( pTab->pVtab ); +#if 0 + if( pTab->pVtab==0 ){ + sqlite3ErrorMsg(pParse, "undefined module %s for table %s", + pTab->azModuleArg[0], pTab->zName); + return 0.0; + } +#endif + + /* Set the aConstraint[].usable fields and initialize all + ** output variables to zero. + ** + ** aConstraint[].usable is true for constraints where the right-hand + ** side contains only references to tables to the left of the current + ** table. In other words, if the constraint is of the form: + ** + ** column = expr + ** + ** and we are evaluating a join, then the constraint on column is + ** only valid if all tables referenced in expr occur to the left + ** of the table containing column. + ** + ** The aConstraints[] array contains entries for all constraints + ** on the current table. That way we only have to compute it once + ** even though we might try to pick the best index multiple times. + ** For each attempt at picking an index, the order of tables in the + ** join might be different so we have to recompute the usable flag + ** each time. + */ + pIdxCons = *(sqlite3_index_info::sqlite3_index_constraint**)&pIdxInfo->aConstraint; + pUsage = pIdxInfo->aConstraintUsage; + for(i=0; inConstraint; i++, pIdxCons++){ + j = pIdxCons->iTermOffset; + pTerm = &pWC->a[j]; + pIdxCons->usable = (pTerm->prereqRight & notReady)==0; + } + memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint); + if( pIdxInfo->needToFreeIdxStr ){ + sqlite3_free(pIdxInfo->idxStr); + } + pIdxInfo->idxStr = 0; + pIdxInfo->idxNum = 0; + pIdxInfo->needToFreeIdxStr = 0; + pIdxInfo->orderByConsumed = 0; + pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0; + nOrderBy = pIdxInfo->nOrderBy; + if( pIdxInfo->nOrderBy && !orderByUsable ){ + *(int*)&pIdxInfo->nOrderBy = 0; + } + + sqlite3SafetyOff(pParse->db); + WHERETRACE(("xBestIndex for %s\n", pTab->zName)); + TRACE_IDX_INPUTS(pIdxInfo); + rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo); + TRACE_IDX_OUTPUTS(pIdxInfo); + if( rc!=SQLITE_OK ){ + if( rc==SQLITE_NOMEM ){ + pParse->db->mallocFailed = 1; + }else { + sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc)); + } + sqlite3SafetyOn(pParse->db); + }else{ + rc = sqlite3SafetyOn(pParse->db); + } + *(int*)&pIdxInfo->nOrderBy = nOrderBy; + + return pIdxInfo->estimatedCost; +} +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + +/* +** Find the best index for accessing a particular table. Return a pointer +** to the index, flags that describe how the index should be used, the +** number of equality constraints, and the "cost" for this index. +** +** The lowest cost index wins. The cost is an estimate of the amount of +** CPU and disk I/O need to process the request using the selected index. +** Factors that influence cost include: +** +** * The estimated number of rows that will be retrieved. (The +** fewer the better.) +** +** * Whether or not sorting must occur. +** +** * Whether or not there must be separate lookups in the +** index and in the main table. +** +*/ +static double bestIndex( + Parse *pParse, /* The parsing context */ + WhereClause *pWC, /* The WHERE clause */ + SrcList::SrcList_item *pSrc, /* The FROM clause term to search */ + Bitmask notReady, /* Mask of cursors that are not available */ + ExprList *pOrderBy, /* The order by clause */ + Index **ppIndex, /* Make *ppIndex point to the best index */ + int *pFlags, /* Put flags describing this choice in *pFlags */ + int *pnEq /* Put the number of == or IN constraints here */ +){ + WhereTerm *pTerm; + Index *bestIdx = 0; /* Index that gives the lowest cost */ + double lowestCost; /* The cost of using bestIdx */ + int bestFlags = 0; /* Flags associated with bestIdx */ + int bestNEq = 0; /* Best value for nEq */ + int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */ + Index *pProbe; /* An index we are evaluating */ + int rev; /* True to scan in reverse order */ + int flags; /* Flags associated with pProbe */ + int nEq; /* Number of == or IN constraints */ + int eqTermMask; /* Mask of valid equality operators */ + double cost; /* Cost of using pProbe */ + + WHERETRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady)); + lowestCost = SQLITE_BIG_DBL; + pProbe = pSrc->pTab->pIndex; + + /* If the table has no indices and there are no terms in the where + ** clause that refer to the ROWID, then we will never be able to do + ** anything other than a full table scan on this table. We might as + ** well put it first in the join order. That way, perhaps it can be + ** referenced by other tables in the join. + */ + if( pProbe==0 && + findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 && + (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){ + *pFlags = 0; + *ppIndex = 0; + *pnEq = 0; + return 0.0; + } + + /* Check for a rowid=EXPR or rowid IN (...) constraints + */ + pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0); + if( pTerm ){ + Expr *pExpr; + *ppIndex = 0; + bestFlags = WHERE_ROWID_EQ; + if( pTerm->eOperator & WO_EQ ){ + /* Rowid== is always the best pick. Look no further. Because only + ** a single row is generated, output is always in sorted order */ + *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE; + *pnEq = 1; + WHERETRACE(("... best is rowid\n")); + return 0.0; + }else if( (pExpr = pTerm->pExpr)->pList!=0 ){ + /* Rowid IN (LIST): cost is NlogN where N is the number of list + ** elements. */ + lowestCost = pExpr->pList->nExpr; + lowestCost *= estLog(lowestCost); + }else{ + /* Rowid IN (SELECT): cost is NlogN where N is the number of rows + ** in the result of the inner select. We have no way to estimate + ** that value so make a wild guess. */ + lowestCost = 200; + } + WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost)); + } + + /* Estimate the cost of a table scan. If we do not know how many + ** entries are in the table, use 1 million as a guess. + */ + cost = pProbe ? pProbe->aiRowEst[0] : 1000000; + WHERETRACE(("... table scan base cost: %.9g\n", cost)); + flags = WHERE_ROWID_RANGE; + + /* Check for constraints on a range of rowids in a table scan. + */ + pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0); + if( pTerm ){ + if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){ + flags |= WHERE_TOP_LIMIT; + cost /= 3; /* Guess that rowidEXPR 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( costjointype & 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; inColumn; i++){ + int j = pProbe->aiColumn[i]; + pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe); + if( pTerm==0 ) break; + flags |= WHERE_COLUMN_EQ; + if( pTerm->eOperator & WO_IN ){ + Expr *pExpr = pTerm->pExpr; + flags |= WHERE_COLUMN_IN; + if( pExpr->pSelect!=0 ){ + inMultiplier *= 25; + }else if( pExpr->pList!=0 ){ + inMultiplier *= pExpr->pList->nExpr + 1; + } + } + } + cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier); + nEq = i; + if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0 + && nEq==pProbe->nColumn ){ + flags |= WHERE_UNIQUE; + } + WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost)); + + /* Look for range constraints + */ + if( nEqnColumn ){ + 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; jnColumn; j++){ + int x = pProbe->aiColumn[j]; + if( xzName : "(none)", lowestCost, bestFlags, bestNEq)); + *pFlags = bestFlags | eqTermMask; + *pnEq = bestNEq; + return lowestCost; +} + + +/* +** Disable a term in the WHERE clause. Except, do not disable the term +** if it controls a LEFT OUTER JOIN and it did not originate in the ON +** or USING clause of that join. +** +** Consider the term t2.z='ok' in the following queries: +** +** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok' +** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok' +** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok' +** +** The t2.z='ok' is disabled in the in (2) because it originates +** in the ON clause. The term is disabled in (3) because it is not part +** of a LEFT OUTER JOIN. In (1), the term is not disabled. +** +** Disabling a term causes that term to not be tested in the inner loop +** of the join. Disabling is an optimization. When terms are satisfied +** by indices, we disable them to prevent redundant tests in the inner +** loop. We would get the correct results if nothing were ever disabled, +** but joins might run a little slower. The trick is to disable as much +** as we can without disabling too much. If we disabled in (1), we'd get +** the wrong answer. See ticket #813. +*/ +static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){ + if( pTerm + && (pTerm->flags & TERM_CODED)==0 + && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin)) + ){ + pTerm->flags |= TERM_CODED; + if( pTerm->iParent>=0 ){ + WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent]; + if( (--pOther->nChild)==0 ){ + disableTerm(pLevel, pOther); + } + } + } +} + +/* +** Generate code that builds a probe for an index. +** +** There should be nColumn values on the stack. The index +** to be probed is pIdx. Pop the values from the stack and +** replace them all with a single record that is the index +** problem. +*/ +static void buildIndexProbe( + Vdbe *v, /* Generate code into this VM */ + int nColumn, /* The number of columns to check for NULL */ + Index *pIdx /* Index that we will be searching */ +){ + sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0); + sqlite3IndexAffinityStr(v, pIdx); +} + + +/* +** Generate code for a single equality term of the WHERE clause. An equality +** term can be either X=expr or X IN (...). pTerm is the term to be +** coded. +** +** The current value for the constraint is left on the top of the stack. +** +** For a constraint of the form X=expr, the expression is evaluated and its +** result is left on the stack. For constraints of the form X IN (...) +** this routine sets up a loop that will iterate over all values of X. +*/ +static void codeEqualityTerm( + Parse *pParse, /* The parsing context */ + WhereTerm *pTerm, /* The term of the WHERE clause to be coded */ + WhereLevel *pLevel /* When level of the FROM clause we are working on */ +){ + Expr *pX = pTerm->pExpr; + Vdbe *v = pParse->pVdbe; + if( pX->op==TK_EQ ){ + sqlite3ExprCode(pParse, pX->pRight); + }else if( pX->op==TK_ISNULL ){ + sqlite3VdbeAddOp(v, OP_Null, 0, 0); +#ifndef SQLITE_OMIT_SUBQUERY + }else{ + int eType; + int iTab; + WhereLevel::InLoop *pIn; + + assert( pX->op==TK_IN ); + eType = sqlite3FindInIndex(pParse, pX, 1); + iTab = pX->iTable; + sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0); + VdbeComment((v, "# %.*s", pX->span.n, pX->span.z)); + if( pLevel->nIn==0 ){ + pLevel->nxt = sqlite3VdbeMakeLabel(v); + } + pLevel->nIn++; + pLevel->aInLoop = (WhereLevel::InLoop*)sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop, + sizeof(pLevel->aInLoop[0])*pLevel->nIn); + pIn = (WhereLevel::InLoop*)pLevel->aInLoop; + if( pIn ){ + int op = ((eType==IN_INDEX_ROWID)?OP_Rowid:OP_Column); + pIn += pLevel->nIn - 1; + pIn->iCur = iTab; + pIn->topAddr = sqlite3VdbeAddOp(v, op, iTab, 0); + sqlite3VdbeAddOp(v, OP_IsNull, -1, 0); + }else{ + pLevel->nIn = 0; + } +#endif + } + disableTerm(pLevel, pTerm); +} + +/* +** Generate code that will evaluate all == and IN constraints for an +** index. The values for all constraints are left on the stack. +** +** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c). +** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10 +** The index has as many as three equality constraints, but in this +** example, the third "c" value is an inequality. So only two +** constraints are coded. This routine will generate code to evaluate +** a==5 and b IN (1,2,3). The current values for a and b will be left +** on the stack - a is the deepest and b the shallowest. +** +** In the example above nEq==2. But this subroutine works for any value +** of nEq including 0. If nEq==0, this routine is nearly a no-op. +** The only thing it does is allocate the pLevel->iMem memory cell. +** +** This routine always allocates at least one memory cell and puts +** the address of that memory cell in pLevel->iMem. The code that +** calls this routine will use pLevel->iMem to store the termination +** key value of the loop. If one or more IN operators appear, then +** this routine allocates an additional nEq memory cells for internal +** use. +*/ +static void codeAllEqualityTerms( + Parse *pParse, /* Parsing context */ + WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */ + WhereClause *pWC, /* The WHERE clause */ + Bitmask notReady /* Which parts of FROM have not yet been coded */ +){ + int nEq = pLevel->nEq; /* The number of == or IN constraints to code */ + int termsInMem = 0; /* If true, store value in mem[] cells */ + Vdbe *v = pParse->pVdbe; /* The virtual machine under construction */ + Index *pIdx = pLevel->pIdx; /* The index being used for this loop */ + int iCur = pLevel->iTabCur; /* The cursor of the table */ + WhereTerm *pTerm; /* A single constraint term */ + int j; /* Loop counter */ + + /* Figure out how many memory cells we will need then allocate them. + ** We always need at least one used to store the loop terminator + ** value. If there are IN operators we'll need one for each == or + ** IN constraint. + */ + pLevel->iMem = pParse->nMem++; + if( pLevel->flags & WHERE_COLUMN_IN ){ + pParse->nMem += pLevel->nEq; + termsInMem = 1; + } + + /* Evaluate the equality constraints + */ + assert( pIdx->nColumn>=nEq ); + for(j=0; jaiColumn[j]; + pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx); + if( pTerm==0 ) break; + assert( (pTerm->flags & TERM_CODED)==0 ); + codeEqualityTerm(pParse, pTerm, pLevel); + if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){ + sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk); + } + if( termsInMem ){ + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1); + } + } + + /* Make sure all the constraint values are on the top of the stack + */ + if( termsInMem ){ + for(j=0; jiMem+j+1, 0); + } + } +} + +#if defined(SQLITE_TEST) +/* +** The following variable holds a text description of query plan generated +** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin +** overwrites the previous. This information is used for testing and +** analysis only. +*/ +char sqlite3_query_plan[BMS*2*40]; /* Text of the join */ +static int nQPlan = 0; /* Next free slow in _query_plan[] */ + +#endif /* SQLITE_TEST */ + + +/* +** Free a WhereInfo structure +*/ +static void whereInfoFree(WhereInfo *pWInfo){ + if( pWInfo ){ + int i; + for(i=0; inLevel; i++){ + sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo; + if( pInfo ){ + if( pInfo->needToFreeIdxStr ){ + /* Coverage: Don't think this can be reached. By the time this + ** function is called, the index-strings have been passed + ** to the vdbe layer for deletion. + */ + sqlite3_free(pInfo->idxStr); + } + sqlite3_free(pInfo); + } + } + sqlite3_free(pWInfo); + } +} + + +/* +** Generate the beginning of the loop used for WHERE clause processing. +** The return value is a pointer to an opaque structure that contains +** information needed to terminate the loop. Later, the calling routine +** should invoke sqlite3WhereEnd() with the return value of this function +** in order to complete the WHERE clause processing. +** +** If an error occurs, this routine returns NULL. +** +** The basic idea is to do a nested loop, one loop for each table in +** the FROM clause of a select. (INSERT and UPDATE statements are the +** same as a SELECT with only a single table in the FROM clause.) For +** example, if the SQL is this: +** +** SELECT * FROM t1, t2, t3 WHERE ...; +** +** Then the code generated is conceptually like the following: +** +** foreach row1 in t1 do \ Code generated +** foreach row2 in t2 do |-- by sqlite3WhereBegin() +** foreach row3 in t3 do / +** ... +** end \ Code generated +** end |-- by sqlite3WhereEnd() +** end / +** +** Note that the loops might not be nested in the order in which they +** appear in the FROM clause if a different order is better able to make +** use of indices. Note also that when the IN operator appears in +** the WHERE clause, it might result in additional nested loops for +** scanning through all values on the right-hand side of the IN. +** +** There are Btree cursors associated with each table. t1 uses cursor +** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor. +** And so forth. This routine generates code to open those VDBE cursors +** and sqlite3WhereEnd() generates the code to close them. +** +** The code that sqlite3WhereBegin() generates leaves the cursors named +** in pTabList pointing at their appropriate entries. The [...] code +** can use OP_Column and OP_Rowid opcodes on these cursors to extract +** data from the various tables of the loop. +** +** If the WHERE clause is empty, the foreach loops must each scan their +** entire tables. Thus a three-way join is an O(N^3) operation. But if +** the tables have indices and there are terms in the WHERE clause that +** refer to those indices, a complete table scan can be avoided and the +** code will run much faster. Most of the work of this routine is checking +** to see if there are indices that can be used to speed up the loop. +** +** Terms of the WHERE clause are also used to limit which rows actually +** make it to the "..." in the middle of the loop. After each "foreach", +** terms of the WHERE clause that use only terms in that loop and outer +** loops are evaluated and if false a jump is made around all subsequent +** inner loops (or around the "..." if the test occurs within the inner- +** most loop) +** +** OUTER JOINS +** +** An outer join of tables t1 and t2 is conceptally coded as follows: +** +** foreach row1 in t1 do +** flag = 0 +** foreach row2 in t2 do +** start: +** ... +** flag = 1 +** end +** if flag==0 then +** move the row2 cursor to a null row +** goto start +** fi +** end +** +** ORDER BY CLAUSE PROCESSING +** +** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement, +** if there is one. If there is no ORDER BY clause or if this routine +** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL. +** +** If an index can be used so that the natural output order of the table +** scan is correct for the ORDER BY clause, then that index is used and +** *ppOrderBy is set to NULL. This is an optimization that prevents an +** unnecessary sort of the result set if an index appropriate for the +** ORDER BY clause already exists. +** +** If the where clause loops cannot be arranged to provide the correct +** output order, then the *ppOrderBy is unchanged. +*/ +WhereInfo *sqlite3WhereBegin( + Parse *pParse, /* The parser context */ + SrcList *pTabList, /* A list of all tables to be scanned */ + Expr *pWhere, /* The WHERE clause */ + ExprList **ppOrderBy /* An ORDER BY clause, or NULL */ +){ + int i; /* Loop counter */ + WhereInfo *pWInfo; /* Will become the return value of this function */ + Vdbe *v = pParse->pVdbe; /* The virtual database engine */ + int brk, cont = 0; /* Addresses used during code generation */ + Bitmask notReady; /* Cursors that are not yet positioned */ + WhereTerm *pTerm; /* A single term in the WHERE clause */ + ExprMaskSet maskSet; /* The expression mask set */ + WhereClause wc; /* The WHERE clause is divided into these terms */ + SrcList::SrcList_item *pTabItem; /* A single entry from pTabList */ + WhereLevel *pLevel; /* A single level in the pWInfo list */ + int iFrom; /* First unused FROM clause element */ + int andFlags; /* AND-ed combination of all wc.a[].flags */ + sqlite3 *db; /* Database connection */ + + /* The number of tables in the FROM clause is limited by the number of + ** bits in a Bitmask + */ + if( pTabList->nSrc>BMS ){ + sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS); + return 0; + } + + /* Split the WHERE clause into separate subexpressions where each + ** subexpression is separated by an AND operator. + */ + initMaskSet(&maskSet); + whereClauseInit(&wc, pParse, &maskSet); + whereSplit(&wc, pWhere, TK_AND); + + /* Allocate and initialize the WhereInfo structure that will become the + ** return value. + */ + db = pParse->db; + pWInfo = (WhereInfo*)sqlite3DbMallocZero(db, + sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel)); + if( db->mallocFailed ){ + goto whereBeginNoMem; + } + pWInfo->nLevel = pTabList->nSrc; + pWInfo->pParse = pParse; + pWInfo->pTabList = pTabList; + pWInfo->iBreak = sqlite3VdbeMakeLabel(v); + + /* Special case: a WHERE clause that is constant. Evaluate the + ** expression and either jump over all of the code or fall thru. + */ + if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){ + sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1); + pWhere = 0; + } + + /* Analyze all of the subexpressions. Note that exprAnalyze() might + ** add new virtual terms onto the end of the WHERE clause. We do not + ** want to analyze these virtual terms, so start analyzing at the end + ** and work forward so that the added virtual terms are never processed. + */ + for(i=0; inSrc; i++){ + createMask(&maskSet, pTabList->a[i].iCursor); + } + exprAnalyzeAll(pTabList, &wc); + if( db->mallocFailed ){ + goto whereBeginNoMem; + } + + /* Chose the best index to use for each table in the FROM clause. + ** + ** This loop fills in the following fields: + ** + ** pWInfo->a[].pIdx The index to use for this level of the loop. + ** pWInfo->a[].flags WHERE_xxx flags associated with pIdx + ** pWInfo->a[].nEq The number of == and IN constraints + ** pWInfo->a[].iFrom When term of the FROM clause is being coded + ** pWInfo->a[].iTabCur The VDBE cursor for the database table + ** pWInfo->a[].iIdxCur The VDBE cursor for the index + ** + ** This loop also figures out the nesting order of tables in the FROM + ** clause. + */ + notReady = ~(Bitmask)0; + pTabItem = pTabList->a; + pLevel = pWInfo->a; + andFlags = ~0; + WHERETRACE(("*** Optimizer Start ***\n")); + for(i=iFrom=0, pLevel=pWInfo->a; inSrc; 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]; jnSrc; 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)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( costpBestIdx = pIndex; + } + if( doNotReorder ) break; + } + WHERETRACE(("*** Optimizer choose table %d for loop %d\n", bestJ, + pLevel-pWInfo->a)); + if( (bestFlags & WHERE_ORDERBY)!=0 ){ + *ppOrderBy = 0; + } + andFlags &= bestFlags; + pLevel->flags = bestFlags; + pLevel->pIdx = pBest; + pLevel->nEq = bestNEq; + pLevel->aInLoop = 0; + pLevel->nIn = 0; + if( pBest ){ + pLevel->iIdxCur = pParse->nTab++; + }else{ + pLevel->iIdxCur = -1; + } + notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor); + pLevel->iFrom = bestJ; + } + WHERETRACE(("*** Optimizer Finished ***\n")); + + /* If the total query only selects a single row, then the ORDER BY + ** clause is irrelevant. + */ + if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){ + *ppOrderBy = 0; + } + + /* Open all tables in the pTabList and any indices selected for + ** searching those tables. + */ + sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */ + for(i=0, pLevel=pWInfo->a; inSrc; i++, pLevel++){ + Table *pTab; /* Table to open */ + Index *pIx; /* Index used to access pTab (if any) */ + int iDb; /* Index of database containing table/index */ + int iIdxCur = pLevel->iIdxCur; + +#ifndef SQLITE_OMIT_EXPLAIN + if( pParse->explain==2 ){ + char *zMsg; + SrcList::SrcList_item *pItem = &pTabList->a[pLevel->iFrom]; + zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName); + if( pItem->zAlias ){ + zMsg = sqlite3MPrintf(db, "%z AS %s", zMsg, pItem->zAlias); + } + if( (pIx = pLevel->pIdx)!=0 ){ + zMsg = sqlite3MPrintf(db, "%z WITH INDEX %s", zMsg, pIx->zName); + }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){ + zMsg = sqlite3MPrintf(db, "%z USING PRIMARY KEY", zMsg); + } +#ifndef SQLITE_OMIT_VIRTUALTABLE + else if( pLevel->pBestIdx ){ + sqlite3_index_info *pBestIdx = pLevel->pBestIdx; + zMsg = sqlite3MPrintf(db, "%z VIRTUAL TABLE INDEX %d:%s", zMsg, + pBestIdx->idxNum, pBestIdx->idxStr); + } +#endif + if( pLevel->flags & WHERE_ORDERBY ){ + zMsg = sqlite3MPrintf(db, "%z ORDER BY", zMsg); + } + sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC); + } +#endif /* SQLITE_OMIT_EXPLAIN */ + pTabItem = &pTabList->a[pLevel->iFrom]; + pTab = pTabItem->pTab; + iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema); + if( pTab->isEphem || pTab->pSelect ) continue; +#ifndef SQLITE_OMIT_VIRTUALTABLE + if( pLevel->pBestIdx ){ + int iCur = pTabItem->iCursor; + sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB); + }else +#endif + if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){ + sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead); + if( pTab->nCol<(sizeof(Bitmask)*8) ){ + Bitmask b = pTabItem->colUsed; + int n = 0; + for(; b; b=b>>1, n++){} + sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n); + assert( n<=pTab->nCol ); + } + }else{ + sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName); + } + pLevel->iTabCur = pTabItem->iCursor; + if( (pIx = pLevel->pIdx)!=0 ){ + KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx); + assert( pIx->pSchema==pTab->pSchema ); + sqlite3VdbeAddOp(v, OP_Integer, iDb, 0); + VdbeComment((v, "# %s", pIx->zName)); + sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum, + (char*)pKey, P3_KEYINFO_HANDOFF); + sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1); + } + sqlite3CodeVerifySchema(pParse, iDb); + } + pWInfo->iTop = sqlite3VdbeCurrentAddr(v); + + /* Generate the code to do the search. Each iteration of the for + ** loop below generates code for a single nested loop of the VM + ** program. + */ + notReady = ~(Bitmask)0; + for(i=0, pLevel=pWInfo->a; inSrc; i++, pLevel++){ + int j; + int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */ + Index *pIdx; /* The index we will be using */ + int nxt; /* Where to jump to continue with the next IN case */ + int iIdxCur; /* The VDBE cursor for the index */ + int omitTable; /* True if we use the index only */ + int bRev; /* True if we need to scan in reverse order */ + + pTabItem = &pTabList->a[pLevel->iFrom]; + iCur = pTabItem->iCursor; + pIdx = pLevel->pIdx; + iIdxCur = pLevel->iIdxCur; + bRev = (pLevel->flags & WHERE_REVERSE)!=0; + omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0; + + /* Create labels for the "break" and "continue" instructions + ** for the current loop. Jump to brk to break out of a loop. + ** Jump to cont to go immediately to the next iteration of the + ** loop. + ** + ** When there is an IN operator, we also have a "nxt" label that + ** means to continue with the next IN value combination. When + ** there are no IN operators in the constraints, the "nxt" label + ** is the same as "brk". + */ + brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v); + cont = pLevel->cont = sqlite3VdbeMakeLabel(v); + + /* If this is the right table of a LEFT OUTER JOIN, allocate and + ** initialize a memory cell that records if this table matches any + ** row of the left table of the join. + */ + if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){ + if( !pParse->nMem ) pParse->nMem++; + pLevel->iLeftJoin = pParse->nMem++; + sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin); + VdbeComment((v, "# init LEFT JOIN no-match flag")); + } + +#ifndef SQLITE_OMIT_VIRTUALTABLE + if( pLevel->pBestIdx ){ + /* Case 0: The table is a virtual-table. Use the VFilter and VNext + ** to access the data. + */ + int j; + sqlite3_index_info *pBestIdx = pLevel->pBestIdx; + int nConstraint = pBestIdx->nConstraint; + sqlite3_index_info::sqlite3_index_constraint_usage *aUsage = + pBestIdx->aConstraintUsage; + const sqlite3_index_info::sqlite3_index_constraint *aConstraint = + pBestIdx->aConstraint; + + for(j=1; j<=nConstraint; j++){ + int k; + for(k=0; kpRight); + break; + } + } + if( k==nConstraint ) break; + } + sqlite3VdbeAddOp(v, OP_Integer, j-1, 0); + sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0); + sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr, + pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC); + pBestIdx->needToFreeIdxStr = 0; + for(j=0; jnConstraint; j++){ + if( aUsage[j].omit ){ + int iTerm = aConstraint[j].iTermOffset; + disableTerm(pLevel, &wc.a[iTerm]); + } + } + pLevel->op = OP_VNext; + pLevel->p1 = iCur; + pLevel->p2 = sqlite3VdbeCurrentAddr(v); + }else +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + + if( pLevel->flags & WHERE_ROWID_EQ ){ + /* Case 1: We can directly reference a single row using an + ** equality comparison against the ROWID field. Or + ** we reference multiple rows using a "rowid IN (...)" + ** construct. + */ + pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0); + assert( pTerm!=0 ); + assert( pTerm->pExpr!=0 ); + assert( pTerm->leftCursor==iCur ); + assert( omitTable==0 ); + codeEqualityTerm(pParse, pTerm, pLevel); + nxt = pLevel->nxt; + sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt); + sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt); + VdbeComment((v, "pk")); + pLevel->op = OP_Noop; + }else if( pLevel->flags & WHERE_ROWID_RANGE ){ + /* Case 2: We have an inequality comparison against the ROWID field. + */ + int testOp = OP_Noop; + int start; + WhereTerm *pStart, *pEnd; + + assert( omitTable==0 ); + pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0); + pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0); + if( bRev ){ + pTerm = pStart; + pStart = pEnd; + pEnd = pTerm; + } + if( pStart ){ + Expr *pX; + pX = pStart->pExpr; + assert( pX!=0 ); + assert( pStart->leftCursor==iCur ); + sqlite3ExprCode(pParse, pX->pRight); + sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk); + sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk); + VdbeComment((v, "pk")); + disableTerm(pLevel, pStart); + }else{ + sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk); + } + if( pEnd ){ + Expr *pX; + pX = pEnd->pExpr; + assert( pX!=0 ); + assert( pEnd->leftCursor==iCur ); + sqlite3ExprCode(pParse, pX->pRight); + pLevel->iMem = pParse->nMem++; + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); + if( pX->op==TK_LT || pX->op==TK_GT ){ + testOp = bRev ? OP_Le : OP_Ge; + }else{ + testOp = bRev ? OP_Lt : OP_Gt; + } + disableTerm(pLevel, pEnd); + } + start = sqlite3VdbeCurrentAddr(v); + pLevel->op = bRev ? OP_Prev : OP_Next; + pLevel->p1 = iCur; + pLevel->p2 = start; + if( testOp!=OP_Noop ){ + sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0); + sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk); + } + }else if( pLevel->flags & WHERE_COLUMN_RANGE ){ + /* Case 3: The WHERE clause term that refers to the right-most + ** column of the index is an inequality. For example, if + ** the index is on (x,y,z) and the WHERE clause is of the + ** form "x=5 AND y<10" then this case is used. Only the + ** right-most column can be an inequality - the rest must + ** use the "==" and "IN" operators. + ** + ** This case is also used when there are no WHERE clause + ** constraints but an index is selected anyway, in order + ** to force the output order to conform to an ORDER BY. + */ + int start; + int nEq = pLevel->nEq; + int topEq=0; /* True if top limit uses ==. False is strictly < */ + int btmEq=0; /* True if btm limit uses ==. False if strictly > */ + int topOp, btmOp; /* Operators for the top and bottom search bounds */ + int testOp; + int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0; + int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0; + + /* Generate code to evaluate all constraint terms using == or IN + ** and level the values of those terms on the stack. + */ + codeAllEqualityTerms(pParse, pLevel, &wc, notReady); + + /* Duplicate the equality term values because they will all be + ** used twice: once to make the termination key and once to make the + ** start key. + */ + for(j=0; j or >= + ** operator and the top bound is a < or <= operator. For a descending + ** index the operators are reversed. + */ + if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){ + topOp = WO_LT|WO_LE; + btmOp = WO_GT|WO_GE; + }else{ + topOp = WO_GT|WO_GE; + btmOp = WO_LT|WO_LE; + SWAP(int, topLimit, btmLimit); + } + + /* Generate the termination key. This is the key value that + ** will end the search. There is no termination key if there + ** are no equality terms and no "X<..." term. + ** + ** 2002-Dec-04: On a reverse-order scan, the so-called "termination" + ** key computed here really ends up being the start key. + */ + nxt = pLevel->nxt; + if( topLimit ){ + Expr *pX; + int k = pIdx->aiColumn[j]; + pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx); + assert( pTerm!=0 ); + pX = pTerm->pExpr; + assert( (pTerm->flags & TERM_CODED)==0 ); + sqlite3ExprCode(pParse, pX->pRight); + sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt); + topEq = pTerm->eOperator & (WO_LE|WO_GE); + disableTerm(pLevel, pTerm); + testOp = OP_IdxGE; + }else{ + testOp = nEq>0 ? OP_IdxGE : OP_Noop; + topEq = 1; + } + if( testOp!=OP_Noop ){ + int nCol = nEq + topLimit; + pLevel->iMem = pParse->nMem++; + buildIndexProbe(v, nCol, pIdx); + if( bRev ){ + int op = topEq ? OP_MoveLe : OP_MoveLt; + sqlite3VdbeAddOp(v, op, iIdxCur, nxt); + }else{ + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); + } + }else if( bRev ){ + sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk); + } + + /* Generate the start key. This is the key that defines the lower + ** bound on the search. There is no start key if there are no + ** equality terms and if there is no "X>..." term. In + ** that case, generate a "Rewind" instruction in place of the + ** start key search. + ** + ** 2002-Dec-04: In the case of a reverse-order search, the so-called + ** "start" key really ends up being used as the termination key. + */ + if( btmLimit ){ + Expr *pX; + int k = pIdx->aiColumn[j]; + pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx); + assert( pTerm!=0 ); + pX = pTerm->pExpr; + assert( (pTerm->flags & TERM_CODED)==0 ); + sqlite3ExprCode(pParse, pX->pRight); + sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt); + btmEq = pTerm->eOperator & (WO_LE|WO_GE); + disableTerm(pLevel, pTerm); + }else{ + btmEq = 1; + } + if( nEq>0 || btmLimit ){ + int nCol = nEq + btmLimit; + buildIndexProbe(v, nCol, pIdx); + if( bRev ){ + pLevel->iMem = pParse->nMem++; + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); + testOp = OP_IdxLT; + }else{ + int op = btmEq ? OP_MoveGe : OP_MoveGt; + sqlite3VdbeAddOp(v, op, iIdxCur, nxt); + } + }else if( bRev ){ + testOp = OP_Noop; + }else{ + sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk); + } + + /* Generate the the top of the loop. If there is a termination + ** key we have to test for that key and abort at the top of the + ** loop. + */ + start = sqlite3VdbeCurrentAddr(v); + if( testOp!=OP_Noop ){ + sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt); + if( (topEq && !bRev) || (!btmEq && bRev) ){ + sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC); + } + } + if( topLimit | btmLimit ){ + sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq); + sqlite3VdbeAddOp(v, OP_IsNull, 1, cont); + } + if( !omitTable ){ + sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); + } + + /* Record the instruction used to terminate the loop. + */ + pLevel->op = bRev ? OP_Prev : OP_Next; + pLevel->p1 = iIdxCur; + pLevel->p2 = start; + }else if( pLevel->flags & WHERE_COLUMN_EQ ){ + /* Case 4: There is an index and all terms of the WHERE clause that + ** refer to the index using the "==" or "IN" operators. + */ + int start; + int nEq = pLevel->nEq; + + /* Generate code to evaluate all constraint terms using == or IN + ** and leave the values of those terms on the stack. + */ + codeAllEqualityTerms(pParse, pLevel, &wc, notReady); + nxt = pLevel->nxt; + + /* Generate a single key that will be used to both start and terminate + ** the search + */ + buildIndexProbe(v, nEq, pIdx); + sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0); + + /* Generate code (1) to move to the first matching element of the table. + ** Then generate code (2) that jumps to "nxt" after the cursor is past + ** the last matching element of the table. The code (1) is executed + ** once to initialize the search, the code (2) is executed before each + ** iteration of the scan to see if the scan has finished. */ + if( bRev ){ + /* Scan in reverse order */ + sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt); + start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt); + pLevel->op = OP_Prev; + }else{ + /* Scan in the forward order */ + sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt); + start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); + sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC); + pLevel->op = OP_Next; + } + if( !omitTable ){ + sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); + sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); + } + pLevel->p1 = iIdxCur; + pLevel->p2 = start; + }else{ + /* Case 5: There is no usable index. We must do a complete + ** scan of the entire table. + */ + assert( omitTable==0 ); + assert( bRev==0 ); + pLevel->op = OP_Next; + pLevel->p1 = iCur; + pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk); + } + notReady &= ~getMask(&maskSet, iCur); + sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0); + + /* Insert code to test every subexpression that can be completely + ** computed using the current set of tables. + */ + for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){ + Expr *pE; + if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue; + if( (pTerm->prereqAll & notReady)!=0 ) continue; + pE = pTerm->pExpr; + assert( pE!=0 ); + if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){ + continue; + } + sqlite3ExprIfFalse(pParse, pE, cont, 1); + pTerm->flags |= TERM_CODED; + } + + /* For a LEFT OUTER JOIN, generate code that will record the fact that + ** at least one row of the right table has matched the left table. + */ + if( pLevel->iLeftJoin ){ + pLevel->top = sqlite3VdbeCurrentAddr(v); + sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin); + VdbeComment((v, "# record LEFT JOIN hit")); + for(pTerm=wc.a, j=0; jflags & (TERM_VIRTUAL|TERM_CODED) ) continue; + if( (pTerm->prereqAll & notReady)!=0 ) continue; + assert( pTerm->pExpr ); + sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1); + pTerm->flags |= TERM_CODED; + } + } + } + +#ifdef SQLITE_TEST /* For testing and debugging use only */ + /* Record in the query plan information about the current table + ** and the index used to access it (if any). If the table itself + ** is not used, its name is just '{}'. If no index is used + ** the index is listed as "{}". If the primary key is used the + ** index name is '*'. + */ + for(i=0; inSrc; i++){ + char *z; + int n; + pLevel = &pWInfo->a[i]; + pTabItem = &pTabList->a[pLevel->iFrom]; + z = pTabItem->zAlias; + if( z==0 ) z = pTabItem->pTab->zName; + n = strlen(z); + if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){ + if( pLevel->flags & WHERE_IDX_ONLY ){ + memcpy(&sqlite3_query_plan[nQPlan], "{}", 2); + nQPlan += 2; + }else{ + memcpy(&sqlite3_query_plan[nQPlan], z, n); + nQPlan += n; + } + sqlite3_query_plan[nQPlan++] = ' '; + } + if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){ + memcpy(&sqlite3_query_plan[nQPlan], "* ", 2); + nQPlan += 2; + }else if( pLevel->pIdx==0 ){ + memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3); + nQPlan += 3; + }else{ + n = strlen(pLevel->pIdx->zName); + if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){ + memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n); + nQPlan += n; + sqlite3_query_plan[nQPlan++] = ' '; + } + } + } + while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){ + sqlite3_query_plan[--nQPlan] = 0; + } + sqlite3_query_plan[nQPlan] = 0; + nQPlan = 0; +#endif /* SQLITE_TEST // Testing and debugging use only */ + + /* Record the continuation address in the WhereInfo structure. Then + ** clean up and return. + */ + pWInfo->iContinue = cont; + whereClauseClear(&wc); + return pWInfo; + + /* Jump here if malloc fails */ +whereBeginNoMem: + whereClauseClear(&wc); + whereInfoFree(pWInfo); + return 0; +} + +/* +** Generate the end of the WHERE loop. See comments on +** sqlite3WhereBegin() for additional information. +*/ +void sqlite3WhereEnd(WhereInfo *pWInfo){ + Vdbe *v = pWInfo->pParse->pVdbe; + int i; + WhereLevel *pLevel; + SrcList *pTabList = pWInfo->pTabList; + + /* Generate loop termination code. + */ + for(i=pTabList->nSrc-1; i>=0; i--){ + pLevel = &pWInfo->a[i]; + sqlite3VdbeResolveLabel(v, pLevel->cont); + if( pLevel->op!=OP_Noop ){ + sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2); + } + if( pLevel->nIn ){ + WhereLevel::InLoop *pIn; + int j; + sqlite3VdbeResolveLabel(v, pLevel->nxt); + for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){ + sqlite3VdbeJumpHere(v, pIn->topAddr+1); + sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr); + sqlite3VdbeJumpHere(v, pIn->topAddr-1); + } + sqlite3_free(pLevel->aInLoop); + } + sqlite3VdbeResolveLabel(v, pLevel->brk); + if( pLevel->iLeftJoin ){ + int addr; + addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0); + sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0); + if( pLevel->iIdxCur>=0 ){ + sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0); + } + sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top); + sqlite3VdbeJumpHere(v, addr); + } + } + + /* The "break" point is here, just past the end of the outer loop. + ** Set it. + */ + sqlite3VdbeResolveLabel(v, pWInfo->iBreak); + + /* Close all of the cursors that were opened by sqlite3WhereBegin. + */ + for(i=0, pLevel=pWInfo->a; inSrc; i++, pLevel++){ + SrcList::SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom]; + Table *pTab = pTabItem->pTab; + assert( pTab!=0 ); + if( pTab->isEphem || pTab->pSelect ) continue; + if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){ + sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0); + } + if( pLevel->pIdx!=0 ){ + sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0); + } + + /* If this scan uses an index, make code substitutions to read data + ** from the index in preference to the table. Sometimes, this means + ** the table need never be read from. This is a performance boost, + ** as the vdbe level waits until the table is read before actually + ** seeking the table cursor to the record corresponding to the current + ** position in the index. + ** + ** Calls to the code generator in between sqlite3WhereBegin and + ** sqlite3WhereEnd will have created code that references the table + ** directly. This loop scans all that code looking for opcodes + ** that reference the table and converts them into opcodes that + ** reference the index. + */ + if( pLevel->pIdx ){ + int k, j, last; + VdbeOp *pOp; + Index *pIdx = pLevel->pIdx; + int useIndexOnly = pLevel->flags & WHERE_IDX_ONLY; + + assert( pIdx!=0 ); + pOp = sqlite3VdbeGetOp(v, pWInfo->iTop); + last = sqlite3VdbeCurrentAddr(v); + for(k=pWInfo->iTop; kp1!=pLevel->iTabCur ) continue; + if( pOp->opcode==OP_Column ){ + for(j=0; jnColumn; j++){ + if( pOp->p2==pIdx->aiColumn[j] ){ + pOp->p2 = j; + pOp->p1 = pLevel->iIdxCur; + break; + } + } + assert(!useIndexOnly || jnColumn); + }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; +}