src/whereexpr.c

   1 /*
   2 ** 2015-06-08
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 ** This module contains C code that generates VDBE code used to process
  13 ** the WHERE clause of SQL statements.
  14 **
  15 ** This file was originally part of where.c but was split out to improve
  16 ** readability and editabiliity.  This file contains utility routines for
  17 ** analyzing Expr objects in the WHERE clause.
  18 */
  19 #include "sqliteInt.h"
  20 #include "whereInt.h"
  21
  22 /* Forward declarations */
  23 static void exprAnalyze(SrcList*, WhereClause*, int);
  24
  25 /*
  26 ** Deallocate all memory associated with a WhereOrInfo object.
  27 */
  28 static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
  29   sqlite3WhereClauseClear(&p->wc);
  30   sqlite3DbFree(db, p);
  31 }
  32
  33 /*
  34 ** Deallocate all memory associated with a WhereAndInfo object.
  35 */
  36 static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
  37   sqlite3WhereClauseClear(&p->wc);
  38   sqlite3DbFree(db, p);
  39 }
  40
  41 /*
  42 ** Add a single new WhereTerm entry to the WhereClause object pWC.
  43 ** The new WhereTerm object is constructed from Expr p and with wtFlags.
  44 ** The index in pWC->a[] of the new WhereTerm is returned on success.
  45 ** 0 is returned if the new WhereTerm could not be added due to a memory
  46 ** allocation error.  The memory allocation failure will be recorded in
  47 ** the db->mallocFailed flag so that higher-level functions can detect it.
  48 **
  49 ** This routine will increase the size of the pWC->a[] array as necessary.
  50 **
  51 ** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
  52 ** for freeing the expression p is assumed by the WhereClause object pWC.
  53 ** This is true even if this routine fails to allocate a new WhereTerm.
  54 **
  55 ** WARNING:  This routine might reallocate the space used to store
  56 ** WhereTerms.  All pointers to WhereTerms should be invalidated after
  57 ** calling this routine.  Such pointers may be reinitialized by referencing
  58 ** the pWC->a[] array.
  59 */
  60 static int whereClauseInsert(WhereClause *pWC, Expr *p, u16 wtFlags){
  61   WhereTerm *pTerm;
  62   int idx;
  63   testcase( wtFlags & TERM_VIRTUAL );
  64   if( pWC->nTerm>=pWC->nSlot ){
  65     WhereTerm *pOld = pWC->a;
  66     sqlite3 *db = pWC->pWInfo->pParse->db;
  67     pWC->a = sqlite3DbMallocRawNN(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
  68     if( pWC->a==0 ){
  69       if( wtFlags & TERM_DYNAMIC ){
  70         sqlite3ExprDelete(db, p);
  71       }
  72       pWC->a = pOld;
  73       return 0;
  74     }
  75     memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
  76     if( pOld!=pWC->aStatic ){
  77       sqlite3DbFree(db, pOld);
  78     }
  79     pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
  80   }
  81   pTerm = &pWC->a[idx = pWC->nTerm++];
  82   if( p && ExprHasProperty(p, EP_Unlikely) ){
  83     pTerm->truthProb = sqlite3LogEst(p->iTable) - 270;
  84   }else{
  85     pTerm->truthProb = 1;
  86   }
  87   pTerm->pExpr = sqlite3ExprSkipCollateAndLikely(p);
  88   pTerm->wtFlags = wtFlags;
  89   pTerm->pWC = pWC;
  90   pTerm->iParent = -1;
  91   memset(&pTerm->eOperator, 0,
  92          sizeof(WhereTerm) - offsetof(WhereTerm,eOperator));
  93   return idx;
  94 }
  95
  96 /*
  97 ** Return TRUE if the given operator is one of the operators that is
  98 ** allowed for an indexable WHERE clause term.  The allowed operators are
  99 ** "=", "<", ">", "<=", ">=", "IN", "IS", and "IS NULL"
 100 */
 101 static int allowedOp(int op){
 102   assert( TK_GT>TK_EQ && TK_GT<TK_GE );
 103   assert( TK_LT>TK_EQ && TK_LT<TK_GE );
 104   assert( TK_LE>TK_EQ && TK_LE<TK_GE );
 105   assert( TK_GE==TK_EQ+4 );
 106   return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL || op==TK_IS;
 107 }
 108
 109 /*
 110 ** Commute a comparison operator.  Expressions of the form "X op Y"
 111 ** are converted into "Y op X".
 112 */
 113 static u16 exprCommute(Parse *pParse, Expr *pExpr){
 114   if( pExpr->pLeft->op==TK_VECTOR
 115    || pExpr->pRight->op==TK_VECTOR
 116    || sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft, pExpr->pRight) !=
 117       sqlite3BinaryCompareCollSeq(pParse, pExpr->pRight, pExpr->pLeft)
 118   ){
 119     pExpr->flags ^= EP_Commuted;
 120   }
 121   SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
 122   if( pExpr->op>=TK_GT ){
 123     assert( TK_LT==TK_GT+2 );
 124     assert( TK_GE==TK_LE+2 );
 125     assert( TK_GT>TK_EQ );
 126     assert( TK_GT<TK_LE );
 127     assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
 128     pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
 129   }
 130   return 0;
 131 }
 132
 133 /*
 134 ** Translate from TK_xx operator to WO_xx bitmask.
 135 */
 136 static u16 operatorMask(int op){
 137   u16 c;
 138   assert( allowedOp(op) );
 139   if( op==TK_IN ){
 140     c = WO_IN;
 141   }else if( op==TK_ISNULL ){
 142     c = WO_ISNULL;
 143   }else if( op==TK_IS ){
 144     c = WO_IS;
 145   }else{
 146     assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
 147     c = (u16)(WO_EQ<<(op-TK_EQ));
 148   }
 149   assert( op!=TK_ISNULL || c==WO_ISNULL );
 150   assert( op!=TK_IN || c==WO_IN );
 151   assert( op!=TK_EQ || c==WO_EQ );
 152   assert( op!=TK_LT || c==WO_LT );
 153   assert( op!=TK_LE || c==WO_LE );
 154   assert( op!=TK_GT || c==WO_GT );
 155   assert( op!=TK_GE || c==WO_GE );
 156   assert( op!=TK_IS || c==WO_IS );
 157   return c;
 158 }
 159
 160
 161 #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
 162 /*
 163 ** Check to see if the given expression is a LIKE or GLOB operator that
 164 ** can be optimized using inequality constraints.  Return TRUE if it is
 165 ** so and false if not.
 166 **
 167 ** In order for the operator to be optimizible, the RHS must be a string
 168 ** literal that does not begin with a wildcard.  The LHS must be a column
 169 ** that may only be NULL, a string, or a BLOB, never a number. (This means
 170 ** that virtual tables cannot participate in the LIKE optimization.)  The
 171 ** collating sequence for the column on the LHS must be appropriate for
 172 ** the operator.
 173 */
 174 static int isLikeOrGlob(
 175   Parse *pParse,    /* Parsing and code generating context */
 176   Expr *pExpr,      /* Test this expression */
 177   Expr **ppPrefix,  /* Pointer to TK_STRING expression with pattern prefix */
 178   int *pisComplete, /* True if the only wildcard is % in the last character */
 179   int *pnoCase      /* True if uppercase is equivalent to lowercase */
 180 ){
 181   const u8 *z = 0;           /* String on RHS of LIKE operator */
 182   Expr *pRight, *pLeft;      /* Right and left size of LIKE operator */
 183   ExprList *pList;           /* List of operands to the LIKE operator */
 184   u8 c;                      /* One character in z[] */
 185   int cnt;                   /* Number of non-wildcard prefix characters */
 186   u8 wc[4];                  /* Wildcard characters */
 187   sqlite3 *db = pParse->db;  /* Database connection */
 188   sqlite3_value *pVal = 0;
 189   int op;                    /* Opcode of pRight */
 190   int rc;                    /* Result code to return */
 191
 192   if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, (char*)wc) ){
 193     return 0;
 194   }
 195 #ifdef SQLITE_EBCDIC
 196   if( *pnoCase ) return 0;
 197 #endif
 198   assert( ExprUseXList(pExpr) );
 199   pList = pExpr->x.pList;
 200   pLeft = pList->a[1].pExpr;
 201
 202   pRight = sqlite3ExprSkipCollate(pList->a[0].pExpr);
 203   op = pRight->op;
 204   if( op==TK_VARIABLE && (db->flags & SQLITE_EnableQPSG)==0 ){
 205     Vdbe *pReprepare = pParse->pReprepare;
 206     int iCol = pRight->iColumn;
 207     pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_BLOB);
 208     if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
 209       z = sqlite3_value_text(pVal);
 210     }
 211     sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
 212     assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
 213   }else if( op==TK_STRING ){
 214     assert( !ExprHasProperty(pRight, EP_IntValue) );
 215      z = (u8*)pRight->u.zToken;
 216   }
 217   if( z ){
 218
 219     /* Count the number of prefix characters prior to the first wildcard */
 220     cnt = 0;
 221     while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
 222       cnt++;
 223       if( c==wc[3] && z[cnt]!=0 ) cnt++;
 224     }
 225
 226     /* The optimization is possible only if (1) the pattern does not begin
 227     ** with a wildcard and if (2) the non-wildcard prefix does not end with
 228     ** an (illegal 0xff) character, or (3) the pattern does not consist of
 229     ** a single escape character. The second condition is necessary so
 230     ** that we can increment the prefix key to find an upper bound for the
 231     ** range search. The third is because the caller assumes that the pattern
 232     ** consists of at least one character after all escapes have been
 233     ** removed.  */
 234     if( cnt!=0 && 255!=(u8)z[cnt-1] && (cnt>1 || z[0]!=wc[3]) ){
 235       Expr *pPrefix;
 236
 237       /* A "complete" match if the pattern ends with "*" or "%" */
 238       *pisComplete = c==wc[0] && z[cnt+1]==0;
 239
 240       /* Get the pattern prefix.  Remove all escapes from the prefix. */
 241       pPrefix = sqlite3Expr(db, TK_STRING, (char*)z);
 242       if( pPrefix ){
 243         int iFrom, iTo;
 244         char *zNew;
 245         assert( !ExprHasProperty(pPrefix, EP_IntValue) );
 246         zNew = pPrefix->u.zToken;
 247         zNew[cnt] = 0;
 248         for(iFrom=iTo=0; iFrom<cnt; iFrom++){
 249           if( zNew[iFrom]==wc[3] ) iFrom++;
 250           zNew[iTo++] = zNew[iFrom];
 251         }
 252         zNew[iTo] = 0;
 253         assert( iTo>0 );
 254
 255         /* If the LHS is not an ordinary column with TEXT affinity, then the
 256         ** pattern prefix boundaries (both the start and end boundaries) must
 257         ** not look like a number.  Otherwise the pattern might be treated as
 258         ** a number, which will invalidate the LIKE optimization.
 259         **
 260         ** Getting this right has been a persistent source of bugs in the
 261         ** LIKE optimization.  See, for example:
 262         **    2018-09-10 https://sqlite.org/src/info/c94369cae9b561b1
 263         **    2019-05-02 https://sqlite.org/src/info/b043a54c3de54b28
 264         **    2019-06-10 https://sqlite.org/src/info/fd76310a5e843e07
 265         **    2019-06-14 https://sqlite.org/src/info/ce8717f0885af975
 266         **    2019-09-03 https://sqlite.org/src/info/0f0428096f17252a
 267         */
 268         if( pLeft->op!=TK_COLUMN
 269          || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT
 270          || (ALWAYS( ExprUseYTab(pLeft) )
 271              && pLeft->y.pTab
 272              && IsVirtual(pLeft->y.pTab))  /* Might be numeric */
 273         ){
 274           int isNum;
 275           double rDummy;
 276           isNum = sqlite3AtoF(zNew, &rDummy, iTo, SQLITE_UTF8);
 277           if( isNum<=0 ){
 278             if( iTo==1 && zNew[0]=='-' ){
 279               isNum = +1;
 280             }else{
 281               zNew[iTo-1]++;
 282               isNum = sqlite3AtoF(zNew, &rDummy, iTo, SQLITE_UTF8);
 283               zNew[iTo-1]--;
 284             }
 285           }
 286           if( isNum>0 ){
 287             sqlite3ExprDelete(db, pPrefix);
 288             sqlite3ValueFree(pVal);
 289             return 0;
 290           }
 291         }
 292       }
 293       *ppPrefix = pPrefix;
 294
 295       /* If the RHS pattern is a bound parameter, make arrangements to
 296       ** reprepare the statement when that parameter is rebound */
 297       if( op==TK_VARIABLE ){
 298         Vdbe *v = pParse->pVdbe;
 299         sqlite3VdbeSetVarmask(v, pRight->iColumn);
 300         assert( !ExprHasProperty(pRight, EP_IntValue) );
 301         if( *pisComplete && pRight->u.zToken[1] ){
 302           /* If the rhs of the LIKE expression is a variable, and the current
 303           ** value of the variable means there is no need to invoke the LIKE
 304           ** function, then no OP_Variable will be added to the program.
 305           ** This causes problems for the sqlite3_bind_parameter_name()
 306           ** API. To work around them, add a dummy OP_Variable here.
 307           */
 308           int r1 = sqlite3GetTempReg(pParse);
 309           sqlite3ExprCodeTarget(pParse, pRight, r1);
 310           sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
 311           sqlite3ReleaseTempReg(pParse, r1);
 312         }
 313       }
 314     }else{
 315       z = 0;
 316     }
 317   }
 318
 319   rc = (z!=0);
 320   sqlite3ValueFree(pVal);
 321   return rc;
 322 }
 323 #endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
 324
 325
 326 #ifndef SQLITE_OMIT_VIRTUALTABLE
 327 /*
 328 ** Check to see if the pExpr expression is a form that needs to be passed
 329 ** to the xBestIndex method of virtual tables.  Forms of interest include:
 330 **
 331 **          Expression                   Virtual Table Operator
 332 **          -----------------------      ---------------------------------
 333 **      1.  column MATCH expr            SQLITE_INDEX_CONSTRAINT_MATCH
 334 **      2.  column GLOB expr             SQLITE_INDEX_CONSTRAINT_GLOB
 335 **      3.  column LIKE expr             SQLITE_INDEX_CONSTRAINT_LIKE
 336 **      4.  column REGEXP expr           SQLITE_INDEX_CONSTRAINT_REGEXP
 337 **      5.  column != expr               SQLITE_INDEX_CONSTRAINT_NE
 338 **      6.  expr != column               SQLITE_INDEX_CONSTRAINT_NE
 339 **      7.  column IS NOT expr           SQLITE_INDEX_CONSTRAINT_ISNOT
 340 **      8.  expr IS NOT column           SQLITE_INDEX_CONSTRAINT_ISNOT
 341 **      9.  column IS NOT NULL           SQLITE_INDEX_CONSTRAINT_ISNOTNULL
 342 **
 343 ** In every case, "column" must be a column of a virtual table.  If there
 344 ** is a match, set *ppLeft to the "column" expression, set *ppRight to the
 345 ** "expr" expression (even though in forms (6) and (8) the column is on the
 346 ** right and the expression is on the left).  Also set *peOp2 to the
 347 ** appropriate virtual table operator.  The return value is 1 or 2 if there
 348 ** is a match.  The usual return is 1, but if the RHS is also a column
 349 ** of virtual table in forms (5) or (7) then return 2.
 350 **
 351 ** If the expression matches none of the patterns above, return 0.
 352 */
 353 static int isAuxiliaryVtabOperator(
 354   sqlite3 *db,                    /* Parsing context */
 355   Expr *pExpr,                    /* Test this expression */
 356   unsigned char *peOp2,           /* OUT: 0 for MATCH, or else an op2 value */
 357   Expr **ppLeft,                  /* Column expression to left of MATCH/op2 */
 358   Expr **ppRight                  /* Expression to left of MATCH/op2 */
 359 ){
 360   if( pExpr->op==TK_FUNCTION ){
 361     static const struct Op2 {
 362       const char *zOp;
 363       unsigned char eOp2;
 364     } aOp[] = {
 365       { "match",  SQLITE_INDEX_CONSTRAINT_MATCH },
 366       { "glob",   SQLITE_INDEX_CONSTRAINT_GLOB },
 367       { "like",   SQLITE_INDEX_CONSTRAINT_LIKE },
 368       { "regexp", SQLITE_INDEX_CONSTRAINT_REGEXP }
 369     };
 370     ExprList *pList;
 371     Expr *pCol;                     /* Column reference */
 372     int i;
 373
 374     assert( ExprUseXList(pExpr) );
 375     pList = pExpr->x.pList;
 376     if( pList==0 || pList->nExpr!=2 ){
 377       return 0;
 378     }
 379
 380     /* Built-in operators MATCH, GLOB, LIKE, and REGEXP attach to a
 381     ** virtual table on their second argument, which is the same as
 382     ** the left-hand side operand in their in-fix form.
 383     **
 384     **       vtab_column MATCH expression
 385     **       MATCH(expression,vtab_column)
 386     */
 387     pCol = pList->a[1].pExpr;
 388     assert( pCol->op!=TK_COLUMN || ExprUseYTab(pCol) );
 389     testcase( pCol->op==TK_COLUMN && pCol->y.pTab==0 );
 390     if( ExprIsVtab(pCol) ){
 391       for(i=0; i<ArraySize(aOp); i++){
 392         assert( !ExprHasProperty(pExpr, EP_IntValue) );
 393         if( sqlite3StrICmp(pExpr->u.zToken, aOp[i].zOp)==0 ){
 394           *peOp2 = aOp[i].eOp2;
 395           *ppRight = pList->a[0].pExpr;
 396           *ppLeft = pCol;
 397           return 1;
 398         }
 399       }
 400     }
 401
 402     /* We can also match against the first column of overloaded
 403     ** functions where xFindFunction returns a value of at least
 404     ** SQLITE_INDEX_CONSTRAINT_FUNCTION.
 405     **
 406     **      OVERLOADED(vtab_column,expression)
 407     **
 408     ** Historically, xFindFunction expected to see lower-case function
 409     ** names.  But for this use case, xFindFunction is expected to deal
 410     ** with function names in an arbitrary case.
 411     */
 412     pCol = pList->a[0].pExpr;
 413     assert( pCol->op!=TK_COLUMN || ExprUseYTab(pCol) );
 414     testcase( pCol->op==TK_COLUMN && pCol->y.pTab==0 );
 415     if( ExprIsVtab(pCol) ){
 416       sqlite3_vtab *pVtab;
 417       sqlite3_module *pMod;
 418       void (*xNotUsed)(sqlite3_context*,int,sqlite3_value**);
 419       void *pNotUsed;
 420       pVtab = sqlite3GetVTable(db, pCol->y.pTab)->pVtab;
 421       assert( pVtab!=0 );
 422       assert( pVtab->pModule!=0 );
 423       assert( !ExprHasProperty(pExpr, EP_IntValue) );
 424        pMod = (sqlite3_module *)pVtab->pModule;
 425       if( pMod->xFindFunction!=0 ){
 426         i = pMod->xFindFunction(pVtab,2, pExpr->u.zToken, &xNotUsed, &pNotUsed);
 427         if( i>=SQLITE_INDEX_CONSTRAINT_FUNCTION ){
 428           *peOp2 = i;
 429           *ppRight = pList->a[1].pExpr;
 430           *ppLeft = pCol;
 431           return 1;
 432         }
 433       }
 434     }
 435   }else if( pExpr->op==TK_NE || pExpr->op==TK_ISNOT || pExpr->op==TK_NOTNULL ){
 436     int res = 0;
 437     Expr *pLeft = pExpr->pLeft;
 438     Expr *pRight = pExpr->pRight;
 439     assert( pLeft->op!=TK_COLUMN || ExprUseYTab(pLeft) );
 440     testcase( pLeft->op==TK_COLUMN && pLeft->y.pTab==0 );
 441     if( ExprIsVtab(pLeft) ){
 442       res++;
 443     }
 444     assert( pRight==0 || pRight->op!=TK_COLUMN || ExprUseYTab(pRight) );
 445     testcase( pRight && pRight->op==TK_COLUMN && pRight->y.pTab==0 );
 446     if( pRight && ExprIsVtab(pRight) ){
 447       res++;
 448       SWAP(Expr*, pLeft, pRight);
 449     }
 450     *ppLeft = pLeft;
 451     *ppRight = pRight;
 452     if( pExpr->op==TK_NE ) *peOp2 = SQLITE_INDEX_CONSTRAINT_NE;
 453     if( pExpr->op==TK_ISNOT ) *peOp2 = SQLITE_INDEX_CONSTRAINT_ISNOT;
 454     if( pExpr->op==TK_NOTNULL ) *peOp2 = SQLITE_INDEX_CONSTRAINT_ISNOTNULL;
 455     return res;
 456   }
 457   return 0;
 458 }
 459 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 460
 461 /*
 462 ** If the pBase expression originated in the ON or USING clause of
 463 ** a join, then transfer the appropriate markings over to derived.
 464 */
 465 static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
 466   if( pDerived ){
 467     pDerived->flags |= pBase->flags & EP_FromJoin;
 468     pDerived->iRightJoinTable = pBase->iRightJoinTable;
 469   }
 470 }
 471
 472 /*
 473 ** Mark term iChild as being a child of term iParent
 474 */
 475 static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){
 476   pWC->a[iChild].iParent = iParent;
 477   pWC->a[iChild].truthProb = pWC->a[iParent].truthProb;
 478   pWC->a[iParent].nChild++;
 479 }
 480
 481 /*
 482 ** Return the N-th AND-connected subterm of pTerm.  Or if pTerm is not
 483 ** a conjunction, then return just pTerm when N==0.  If N is exceeds
 484 ** the number of available subterms, return NULL.
 485 */
 486 static WhereTerm *whereNthSubterm(WhereTerm *pTerm, int N){
 487   if( pTerm->eOperator!=WO_AND ){
 488     return N==0 ? pTerm : 0;
 489   }
 490   if( N<pTerm->u.pAndInfo->wc.nTerm ){
 491     return &pTerm->u.pAndInfo->wc.a[N];
 492   }
 493   return 0;
 494 }
 495
 496 /*
 497 ** Subterms pOne and pTwo are contained within WHERE clause pWC.  The
 498 ** two subterms are in disjunction - they are OR-ed together.
 499 **
 500 ** If these two terms are both of the form:  "A op B" with the same
 501 ** A and B values but different operators and if the operators are
 502 ** compatible (if one is = and the other is <, for example) then
 503 ** add a new virtual AND term to pWC that is the combination of the
 504 ** two.
 505 **
 506 ** Some examples:
 507 **
 508 **    x<y OR x=y    -->     x<=y
 509 **    x=y OR x=y    -->     x=y
 510 **    x<=y OR x<y   -->     x<=y
 511 **
 512 ** The following is NOT generated:
 513 **
 514 **    x<y OR x>y    -->     x!=y
 515 */
 516 static void whereCombineDisjuncts(
 517   SrcList *pSrc,         /* the FROM clause */
 518   WhereClause *pWC,      /* The complete WHERE clause */
 519   WhereTerm *pOne,       /* First disjunct */
 520   WhereTerm *pTwo        /* Second disjunct */
 521 ){
 522   u16 eOp = pOne->eOperator | pTwo->eOperator;
 523   sqlite3 *db;           /* Database connection (for malloc) */
 524   Expr *pNew;            /* New virtual expression */
 525   int op;                /* Operator for the combined expression */
 526   int idxNew;            /* Index in pWC of the next virtual term */
 527
 528   if( (pOne->wtFlags | pTwo->wtFlags) & TERM_VNULL ) return;
 529   if( (pOne->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
 530   if( (pTwo->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
 531   if( (eOp & (WO_EQ|WO_LT|WO_LE))!=eOp
 532    && (eOp & (WO_EQ|WO_GT|WO_GE))!=eOp ) return;
 533   assert( pOne->pExpr->pLeft!=0 && pOne->pExpr->pRight!=0 );
 534   assert( pTwo->pExpr->pLeft!=0 && pTwo->pExpr->pRight!=0 );
 535   if( sqlite3ExprCompare(0,pOne->pExpr->pLeft, pTwo->pExpr->pLeft, -1) ) return;
 536   if( sqlite3ExprCompare(0,pOne->pExpr->pRight, pTwo->pExpr->pRight,-1) )return;
 537   /* If we reach this point, it means the two subterms can be combined */
 538   if( (eOp & (eOp-1))!=0 ){
 539     if( eOp & (WO_LT|WO_LE) ){
 540       eOp = WO_LE;
 541     }else{
 542       assert( eOp & (WO_GT|WO_GE) );
 543       eOp = WO_GE;
 544     }
 545   }
 546   db = pWC->pWInfo->pParse->db;
 547   pNew = sqlite3ExprDup(db, pOne->pExpr, 0);
 548   if( pNew==0 ) return;
 549   for(op=TK_EQ; eOp!=(WO_EQ<<(op-TK_EQ)); op++){ assert( op<TK_GE ); }
 550   pNew->op = op;
 551   idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
 552   exprAnalyze(pSrc, pWC, idxNew);
 553 }
 554
 555 #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
 556 /*
 557 ** Analyze a term that consists of two or more OR-connected
 558 ** subterms.  So in:
 559 **
 560 **     ... WHERE  (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
 561 **                          ^^^^^^^^^^^^^^^^^^^^
 562 **
 563 ** This routine analyzes terms such as the middle term in the above example.
 564 ** A WhereOrTerm object is computed and attached to the term under
 565 ** analysis, regardless of the outcome of the analysis.  Hence:
 566 **
 567 **     WhereTerm.wtFlags   |=  TERM_ORINFO
 568 **     WhereTerm.u.pOrInfo  =  a dynamically allocated WhereOrTerm object
 569 **
 570 ** The term being analyzed must have two or more of OR-connected subterms.
 571 ** A single subterm might be a set of AND-connected sub-subterms.
 572 ** Examples of terms under analysis:
 573 **
 574 **     (A)     t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
 575 **     (B)     x=expr1 OR expr2=x OR x=expr3
 576 **     (C)     t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
 577 **     (D)     x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
 578 **     (E)     (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
 579 **     (F)     x>A OR (x=A AND y>=B)
 580 **
 581 ** CASE 1:
 582 **
 583 ** If all subterms are of the form T.C=expr for some single column of C and
 584 ** a single table T (as shown in example B above) then create a new virtual
 585 ** term that is an equivalent IN expression.  In other words, if the term
 586 ** being analyzed is:
 587 **
 588 **      x = expr1  OR  expr2 = x  OR  x = expr3
 589 **
 590 ** then create a new virtual term like this:
 591 **
 592 **      x IN (expr1,expr2,expr3)
 593 **
 594 ** CASE 2:
 595 **
 596 ** If there are exactly two disjuncts and one side has x>A and the other side
 597 ** has x=A (for the same x and A) then add a new virtual conjunct term to the
 598 ** WHERE clause of the form "x>=A".  Example:
 599 **
 600 **      x>A OR (x=A AND y>B)    adds:    x>=A
 601 **
 602 ** The added conjunct can sometimes be helpful in query planning.
 603 **
 604 ** CASE 3:
 605 **
 606 ** If all subterms are indexable by a single table T, then set
 607 **
 608 **     WhereTerm.eOperator              =  WO_OR
 609 **     WhereTerm.u.pOrInfo->indexable  |=  the cursor number for table T
 610 **
 611 ** A subterm is "indexable" if it is of the form
 612 ** "T.C <op> <expr>" where C is any column of table T and
 613 ** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
 614 ** A subterm is also indexable if it is an AND of two or more
 615 ** subsubterms at least one of which is indexable.  Indexable AND
 616 ** subterms have their eOperator set to WO_AND and they have
 617 ** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
 618 **
 619 ** From another point of view, "indexable" means that the subterm could
 620 ** potentially be used with an index if an appropriate index exists.
 621 ** This analysis does not consider whether or not the index exists; that
 622 ** is decided elsewhere.  This analysis only looks at whether subterms
 623 ** appropriate for indexing exist.
 624 **
 625 ** All examples A through E above satisfy case 3.  But if a term
 626 ** also satisfies case 1 (such as B) we know that the optimizer will
 627 ** always prefer case 1, so in that case we pretend that case 3 is not
 628 ** satisfied.
 629 **
 630 ** It might be the case that multiple tables are indexable.  For example,
 631 ** (E) above is indexable on tables P, Q, and R.
 632 **
 633 ** Terms that satisfy case 3 are candidates for lookup by using
 634 ** separate indices to find rowids for each subterm and composing
 635 ** the union of all rowids using a RowSet object.  This is similar
 636 ** to "bitmap indices" in other database engines.
 637 **
 638 ** OTHERWISE:
 639 **
 640 ** If none of cases 1, 2, or 3 apply, then leave the eOperator set to
 641 ** zero.  This term is not useful for search.
 642 */
 643 static void exprAnalyzeOrTerm(
 644   SrcList *pSrc,            /* the FROM clause */
 645   WhereClause *pWC,         /* the complete WHERE clause */
 646   int idxTerm               /* Index of the OR-term to be analyzed */
 647 ){
 648   WhereInfo *pWInfo = pWC->pWInfo;        /* WHERE clause processing context */
 649   Parse *pParse = pWInfo->pParse;         /* Parser context */
 650   sqlite3 *db = pParse->db;               /* Database connection */
 651   WhereTerm *pTerm = &pWC->a[idxTerm];    /* The term to be analyzed */
 652   Expr *pExpr = pTerm->pExpr;             /* The expression of the term */
 653   int i;                                  /* Loop counters */
 654   WhereClause *pOrWc;       /* Breakup of pTerm into subterms */
 655   WhereTerm *pOrTerm;       /* A Sub-term within the pOrWc */
 656   WhereOrInfo *pOrInfo;     /* Additional information associated with pTerm */
 657   Bitmask chngToIN;         /* Tables that might satisfy case 1 */
 658   Bitmask indexable;        /* Tables that are indexable, satisfying case 2 */
 659
 660   /*
 661   ** Break the OR clause into its separate subterms.  The subterms are
 662   ** stored in a WhereClause structure containing within the WhereOrInfo
 663   ** object that is attached to the original OR clause term.
 664   */
 665   assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
 666   assert( pExpr->op==TK_OR );
 667   pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
 668   if( pOrInfo==0 ) return;
 669   pTerm->wtFlags |= TERM_ORINFO;
 670   pOrWc = &pOrInfo->wc;
 671   memset(pOrWc->aStatic, 0, sizeof(pOrWc->aStatic));
 672   sqlite3WhereClauseInit(pOrWc, pWInfo);
 673   sqlite3WhereSplit(pOrWc, pExpr, TK_OR);
 674   sqlite3WhereExprAnalyze(pSrc, pOrWc);
 675   if( db->mallocFailed ) return;
 676   assert( pOrWc->nTerm>=2 );
 677
 678   /*
 679   ** Compute the set of tables that might satisfy cases 1 or 3.
 680   */
 681   indexable = ~(Bitmask)0;
 682   chngToIN = ~(Bitmask)0;
 683   for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
 684     if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
 685       WhereAndInfo *pAndInfo;
 686       assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
 687       chngToIN = 0;
 688       pAndInfo = sqlite3DbMallocRawNN(db, sizeof(*pAndInfo));
 689       if( pAndInfo ){
 690         WhereClause *pAndWC;
 691         WhereTerm *pAndTerm;
 692         int j;
 693         Bitmask b = 0;
 694         pOrTerm->u.pAndInfo = pAndInfo;
 695         pOrTerm->wtFlags |= TERM_ANDINFO;
 696         pOrTerm->eOperator = WO_AND;
 697         pOrTerm->leftCursor = -1;
 698         pAndWC = &pAndInfo->wc;
 699         memset(pAndWC->aStatic, 0, sizeof(pAndWC->aStatic));
 700         sqlite3WhereClauseInit(pAndWC, pWC->pWInfo);
 701         sqlite3WhereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
 702         sqlite3WhereExprAnalyze(pSrc, pAndWC);
 703         pAndWC->pOuter = pWC;
 704         if( !db->mallocFailed ){
 705           for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
 706             assert( pAndTerm->pExpr );
 707             if( allowedOp(pAndTerm->pExpr->op)
 708              || pAndTerm->eOperator==WO_AUX
 709             ){
 710               b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
 711             }
 712           }
 713         }
 714         indexable &= b;
 715       }
 716     }else if( pOrTerm->wtFlags & TERM_COPIED ){
 717       /* Skip this term for now.  We revisit it when we process the
 718       ** corresponding TERM_VIRTUAL term */
 719     }else{
 720       Bitmask b;
 721       b = sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
 722       if( pOrTerm->wtFlags & TERM_VIRTUAL ){
 723         WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
 724         b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pOther->leftCursor);
 725       }
 726       indexable &= b;
 727       if( (pOrTerm->eOperator & WO_EQ)==0 ){
 728         chngToIN = 0;
 729       }else{
 730         chngToIN &= b;
 731       }
 732     }
 733   }
 734
 735   /*
 736   ** Record the set of tables that satisfy case 3.  The set might be
 737   ** empty.
 738   */
 739   pOrInfo->indexable = indexable;
 740   pTerm->eOperator = WO_OR;
 741   pTerm->leftCursor = -1;
 742   if( indexable ){
 743     pWC->hasOr = 1;
 744   }
 745
 746   /* For a two-way OR, attempt to implementation case 2.
 747   */
 748   if( indexable && pOrWc->nTerm==2 ){
 749     int iOne = 0;
 750     WhereTerm *pOne;
 751     while( (pOne = whereNthSubterm(&pOrWc->a[0],iOne++))!=0 ){
 752       int iTwo = 0;
 753       WhereTerm *pTwo;
 754       while( (pTwo = whereNthSubterm(&pOrWc->a[1],iTwo++))!=0 ){
 755         whereCombineDisjuncts(pSrc, pWC, pOne, pTwo);
 756       }
 757     }
 758   }
 759
 760   /*
 761   ** chngToIN holds a set of tables that *might* satisfy case 1.  But
 762   ** we have to do some additional checking to see if case 1 really
 763   ** is satisfied.
 764   **
 765   ** chngToIN will hold either 0, 1, or 2 bits.  The 0-bit case means
 766   ** that there is no possibility of transforming the OR clause into an
 767   ** IN operator because one or more terms in the OR clause contain
 768   ** something other than == on a column in the single table.  The 1-bit
 769   ** case means that every term of the OR clause is of the form
 770   ** "table.column=expr" for some single table.  The one bit that is set
 771   ** will correspond to the common table.  We still need to check to make
 772   ** sure the same column is used on all terms.  The 2-bit case is when
 773   ** the all terms are of the form "table1.column=table2.column".  It
 774   ** might be possible to form an IN operator with either table1.column
 775   ** or table2.column as the LHS if either is common to every term of
 776   ** the OR clause.
 777   **
 778   ** Note that terms of the form "table.column1=table.column2" (the
 779   ** same table on both sizes of the ==) cannot be optimized.
 780   */
 781   if( chngToIN ){
 782     int okToChngToIN = 0;     /* True if the conversion to IN is valid */
 783     int iColumn = -1;         /* Column index on lhs of IN operator */
 784     int iCursor = -1;         /* Table cursor common to all terms */
 785     int j = 0;                /* Loop counter */
 786
 787     /* Search for a table and column that appears on one side or the
 788     ** other of the == operator in every subterm.  That table and column
 789     ** will be recorded in iCursor and iColumn.  There might not be any
 790     ** such table and column.  Set okToChngToIN if an appropriate table
 791     ** and column is found but leave okToChngToIN false if not found.
 792     */
 793     for(j=0; j<2 && !okToChngToIN; j++){
 794       Expr *pLeft = 0;
 795       pOrTerm = pOrWc->a;
 796       for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
 797         assert( pOrTerm->eOperator & WO_EQ );
 798         pOrTerm->wtFlags &= ~TERM_OR_OK;
 799         if( pOrTerm->leftCursor==iCursor ){
 800           /* This is the 2-bit case and we are on the second iteration and
 801           ** current term is from the first iteration.  So skip this term. */
 802           assert( j==1 );
 803           continue;
 804         }
 805         if( (chngToIN & sqlite3WhereGetMask(&pWInfo->sMaskSet,
 806                                             pOrTerm->leftCursor))==0 ){
 807           /* This term must be of the form t1.a==t2.b where t2 is in the
 808           ** chngToIN set but t1 is not.  This term will be either preceded
 809           ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term
 810           ** and use its inversion. */
 811           testcase( pOrTerm->wtFlags & TERM_COPIED );
 812           testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
 813           assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
 814           continue;
 815         }
 816         assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
 817         iColumn = pOrTerm->u.x.leftColumn;
 818         iCursor = pOrTerm->leftCursor;
 819         pLeft = pOrTerm->pExpr->pLeft;
 820         break;
 821       }
 822       if( i<0 ){
 823         /* No candidate table+column was found.  This can only occur
 824         ** on the second iteration */
 825         assert( j==1 );
 826         assert( IsPowerOfTwo(chngToIN) );
 827         assert( chngToIN==sqlite3WhereGetMask(&pWInfo->sMaskSet, iCursor) );
 828         break;
 829       }
 830       testcase( j==1 );
 831
 832       /* We have found a candidate table and column.  Check to see if that
 833       ** table and column is common to every term in the OR clause */
 834       okToChngToIN = 1;
 835       for(; i>=0 && okToChngToIN; i--, pOrTerm++){
 836         assert( pOrTerm->eOperator & WO_EQ );
 837         assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
 838         if( pOrTerm->leftCursor!=iCursor ){
 839           pOrTerm->wtFlags &= ~TERM_OR_OK;
 840         }else if( pOrTerm->u.x.leftColumn!=iColumn || (iColumn==XN_EXPR
 841                && sqlite3ExprCompare(pParse, pOrTerm->pExpr->pLeft, pLeft, -1)
 842         )){
 843           okToChngToIN = 0;
 844         }else{
 845           int affLeft, affRight;
 846           /* If the right-hand side is also a column, then the affinities
 847           ** of both right and left sides must be such that no type
 848           ** conversions are required on the right.  (Ticket #2249)
 849           */
 850           affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
 851           affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
 852           if( affRight!=0 && affRight!=affLeft ){
 853             okToChngToIN = 0;
 854           }else{
 855             pOrTerm->wtFlags |= TERM_OR_OK;
 856           }
 857         }
 858       }
 859     }
 860
 861     /* At this point, okToChngToIN is true if original pTerm satisfies
 862     ** case 1.  In that case, construct a new virtual term that is
 863     ** pTerm converted into an IN operator.
 864     */
 865     if( okToChngToIN ){
 866       Expr *pDup;            /* A transient duplicate expression */
 867       ExprList *pList = 0;   /* The RHS of the IN operator */
 868       Expr *pLeft = 0;       /* The LHS of the IN operator */
 869       Expr *pNew;            /* The complete IN operator */
 870
 871       for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
 872         if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
 873         assert( pOrTerm->eOperator & WO_EQ );
 874         assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
 875         assert( pOrTerm->leftCursor==iCursor );
 876         assert( pOrTerm->u.x.leftColumn==iColumn );
 877         pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
 878         pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
 879         pLeft = pOrTerm->pExpr->pLeft;
 880       }
 881       assert( pLeft!=0 );
 882       pDup = sqlite3ExprDup(db, pLeft, 0);
 883       pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0);
 884       if( pNew ){
 885         int idxNew;
 886         transferJoinMarkings(pNew, pExpr);
 887         assert( ExprUseXList(pNew) );
 888         pNew->x.pList = pList;
 889         idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
 890         testcase( idxNew==0 );
 891         exprAnalyze(pSrc, pWC, idxNew);
 892         /* pTerm = &pWC->a[idxTerm]; // would be needed if pTerm where reused */
 893         markTermAsChild(pWC, idxNew, idxTerm);
 894       }else{
 895         sqlite3ExprListDelete(db, pList);
 896       }
 897     }
 898   }
 899 }
 900 #endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
 901
 902 /*
 903 ** We already know that pExpr is a binary operator where both operands are
 904 ** column references.  This routine checks to see if pExpr is an equivalence
 905 ** relation:
 906 **   1.  The SQLITE_Transitive optimization must be enabled
 907 **   2.  Must be either an == or an IS operator
 908 **   3.  Not originating in the ON clause of an OUTER JOIN
 909 **   4.  The affinities of A and B must be compatible
 910 **   5a. Both operands use the same collating sequence OR
 911 **   5b. The overall collating sequence is BINARY
 912 ** If this routine returns TRUE, that means that the RHS can be substituted
 913 ** for the LHS anyplace else in the WHERE clause where the LHS column occurs.
 914 ** This is an optimization.  No harm comes from returning 0.  But if 1 is
 915 ** returned when it should not be, then incorrect answers might result.
 916 */
 917 static int termIsEquivalence(Parse *pParse, Expr *pExpr){
 918   char aff1, aff2;
 919   CollSeq *pColl;
 920   if( !OptimizationEnabled(pParse->db, SQLITE_Transitive) ) return 0;
 921   if( pExpr->op!=TK_EQ && pExpr->op!=TK_IS ) return 0;
 922   if( ExprHasProperty(pExpr, EP_FromJoin) ) return 0;
 923   aff1 = sqlite3ExprAffinity(pExpr->pLeft);
 924   aff2 = sqlite3ExprAffinity(pExpr->pRight);
 925   if( aff1!=aff2
 926    && (!sqlite3IsNumericAffinity(aff1) || !sqlite3IsNumericAffinity(aff2))
 927   ){
 928     return 0;
 929   }
 930   pColl = sqlite3ExprCompareCollSeq(pParse, pExpr);
 931   if( sqlite3IsBinary(pColl) ) return 1;
 932   return sqlite3ExprCollSeqMatch(pParse, pExpr->pLeft, pExpr->pRight);
 933 }
 934
 935 /*
 936 ** Recursively walk the expressions of a SELECT statement and generate
 937 ** a bitmask indicating which tables are used in that expression
 938 ** tree.
 939 */
 940 static Bitmask exprSelectUsage(WhereMaskSet *pMaskSet, Select *pS){
 941   Bitmask mask = 0;
 942   while( pS ){
 943     SrcList *pSrc = pS->pSrc;
 944     mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pEList);
 945     mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pGroupBy);
 946     mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pOrderBy);
 947     mask |= sqlite3WhereExprUsage(pMaskSet, pS->pWhere);
 948     mask |= sqlite3WhereExprUsage(pMaskSet, pS->pHaving);
 949     if( ALWAYS(pSrc!=0) ){
 950       int i;
 951       for(i=0; i<pSrc->nSrc; i++){
 952         mask |= exprSelectUsage(pMaskSet, pSrc->a[i].pSelect);
 953         mask |= sqlite3WhereExprUsage(pMaskSet, pSrc->a[i].pOn);
 954         if( pSrc->a[i].fg.isTabFunc ){
 955           mask |= sqlite3WhereExprListUsage(pMaskSet, pSrc->a[i].u1.pFuncArg);
 956         }
 957       }
 958     }
 959     pS = pS->pPrior;
 960   }
 961   return mask;
 962 }
 963
 964 /*
 965 ** Expression pExpr is one operand of a comparison operator that might
 966 ** be useful for indexing.  This routine checks to see if pExpr appears
 967 ** in any index.  Return TRUE (1) if pExpr is an indexed term and return
 968 ** FALSE (0) if not.  If TRUE is returned, also set aiCurCol[0] to the cursor
 969 ** number of the table that is indexed and aiCurCol[1] to the column number
 970 ** of the column that is indexed, or XN_EXPR (-2) if an expression is being
 971 ** indexed.
 972 **
 973 ** If pExpr is a TK_COLUMN column reference, then this routine always returns
 974 ** true even if that particular column is not indexed, because the column
 975 ** might be added to an automatic index later.
 976 */
 977 static SQLITE_NOINLINE int exprMightBeIndexed2(
 978   SrcList *pFrom,        /* The FROM clause */
 979   Bitmask mPrereq,       /* Bitmask of FROM clause terms referenced by pExpr */
 980   int *aiCurCol,         /* Write the referenced table cursor and column here */
 981   Expr *pExpr            /* An operand of a comparison operator */
 982 ){
 983   Index *pIdx;
 984   int i;
 985   int iCur;
 986   for(i=0; mPrereq>1; i++, mPrereq>>=1){}
 987   iCur = pFrom->a[i].iCursor;
 988   for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
 989     if( pIdx->aColExpr==0 ) continue;
 990     for(i=0; i<pIdx->nKeyCol; i++){
 991       if( pIdx->aiColumn[i]!=XN_EXPR ) continue;
 992       if( sqlite3ExprCompareSkip(pExpr, pIdx->aColExpr->a[i].pExpr, iCur)==0 ){
 993         aiCurCol[0] = iCur;
 994         aiCurCol[1] = XN_EXPR;
 995         return 1;
 996       }
 997     }
 998   }
 999   return 0;
1000 }
1001 static int exprMightBeIndexed(
1002   SrcList *pFrom,        /* The FROM clause */
1003   Bitmask mPrereq,       /* Bitmask of FROM clause terms referenced by pExpr */
1004   int *aiCurCol,         /* Write the referenced table cursor & column here */
1005   Expr *pExpr,           /* An operand of a comparison operator */
1006   int op                 /* The specific comparison operator */
1007 ){
1008   /* If this expression is a vector to the left or right of a
1009   ** inequality constraint (>, <, >= or <=), perform the processing
1010   ** on the first element of the vector.  */
1011   assert( TK_GT+1==TK_LE && TK_GT+2==TK_LT && TK_GT+3==TK_GE );
1012   assert( TK_IS<TK_GE && TK_ISNULL<TK_GE && TK_IN<TK_GE );
1013   assert( op<=TK_GE );
1014   if( pExpr->op==TK_VECTOR && (op>=TK_GT && ALWAYS(op<=TK_GE)) ){
1015     assert( ExprUseXList(pExpr) );
1016     pExpr = pExpr->x.pList->a[0].pExpr;
1017
1018   }
1019
1020   if( pExpr->op==TK_COLUMN ){
1021     aiCurCol[0] = pExpr->iTable;
1022     aiCurCol[1] = pExpr->iColumn;
1023     return 1;
1024   }
1025   if( mPrereq==0 ) return 0;                 /* No table references */
1026   if( (mPrereq&(mPrereq-1))!=0 ) return 0;   /* Refs more than one table */
1027   return exprMightBeIndexed2(pFrom,mPrereq,aiCurCol,pExpr);
1028 }
1029
1030
1031 /*
1032 ** The input to this routine is an WhereTerm structure with only the
1033 ** "pExpr" field filled in.  The job of this routine is to analyze the
1034 ** subexpression and populate all the other fields of the WhereTerm
1035 ** structure.
1036 **
1037 ** If the expression is of the form "<expr> <op> X" it gets commuted
1038 ** to the standard form of "X <op> <expr>".
1039 **
1040 ** If the expression is of the form "X <op> Y" where both X and Y are
1041 ** columns, then the original expression is unchanged and a new virtual
1042 ** term of the form "Y <op> X" is added to the WHERE clause and
1043 ** analyzed separately.  The original term is marked with TERM_COPIED
1044 ** and the new term is marked with TERM_DYNAMIC (because it's pExpr
1045 ** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
1046 ** is a commuted copy of a prior term.)  The original term has nChild=1
1047 ** and the copy has idxParent set to the index of the original term.
1048 */
1049 static void exprAnalyze(
1050   SrcList *pSrc,            /* the FROM clause */
1051   WhereClause *pWC,         /* the WHERE clause */
1052   int idxTerm               /* Index of the term to be analyzed */
1053 ){
1054   WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
1055   WhereTerm *pTerm;                /* The term to be analyzed */
1056   WhereMaskSet *pMaskSet;          /* Set of table index masks */
1057   Expr *pExpr;                     /* The expression to be analyzed */
1058   Bitmask prereqLeft;              /* Prerequesites of the pExpr->pLeft */
1059   Bitmask prereqAll;               /* Prerequesites of pExpr */
1060   Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
1061   Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
1062   int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
1063   int noCase = 0;                  /* uppercase equivalent to lowercase */
1064   int op;                          /* Top-level operator.  pExpr->op */
1065   Parse *pParse = pWInfo->pParse;  /* Parsing context */
1066   sqlite3 *db = pParse->db;        /* Database connection */
1067   unsigned char eOp2 = 0;          /* op2 value for LIKE/REGEXP/GLOB */
1068   int nLeft;                       /* Number of elements on left side vector */
1069
1070   if( db->mallocFailed ){
1071     return;
1072   }
1073   pTerm = &pWC->a[idxTerm];
1074   pMaskSet = &pWInfo->sMaskSet;
1075   pExpr = pTerm->pExpr;
1076   assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
1077   prereqLeft = sqlite3WhereExprUsage(pMaskSet, pExpr->pLeft);
1078   op = pExpr->op;
1079   if( op==TK_IN ){
1080     assert( pExpr->pRight==0 );
1081     if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
1082     if( ExprUseXSelect(pExpr) ){
1083       pTerm->prereqRight = exprSelectUsage(pMaskSet, pExpr->x.pSelect);
1084     }else{
1085       pTerm->prereqRight = sqlite3WhereExprListUsage(pMaskSet, pExpr->x.pList);
1086     }
1087   }else if( op==TK_ISNULL ){
1088     pTerm->prereqRight = 0;
1089   }else{
1090     pTerm->prereqRight = sqlite3WhereExprUsage(pMaskSet, pExpr->pRight);
1091   }
1092   pMaskSet->bVarSelect = 0;
1093   prereqAll = sqlite3WhereExprUsageNN(pMaskSet, pExpr);
1094   if( pMaskSet->bVarSelect ) pTerm->wtFlags |= TERM_VARSELECT;
1095   if( ExprHasProperty(pExpr, EP_FromJoin) ){
1096     Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->iRightJoinTable);
1097     prereqAll |= x;
1098     extraRight = x-1;  /* ON clause terms may not be used with an index
1099                        ** on left table of a LEFT JOIN.  Ticket #3015 */
1100     if( (prereqAll>>1)>=x ){
1101       sqlite3ErrorMsg(pParse, "ON clause references tables to its right");
1102       return;
1103     }
1104   }
1105   pTerm->prereqAll = prereqAll;
1106   pTerm->leftCursor = -1;
1107   pTerm->iParent = -1;
1108   pTerm->eOperator = 0;
1109   if( allowedOp(op) ){
1110     int aiCurCol[2];
1111     Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
1112     Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
1113     u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
1114
1115     if( pTerm->u.x.iField>0 ){
1116       assert( op==TK_IN );
1117       assert( pLeft->op==TK_VECTOR );
1118       assert( ExprUseXList(pLeft) );
1119       pLeft = pLeft->x.pList->a[pTerm->u.x.iField-1].pExpr;
1120     }
1121
1122     if( exprMightBeIndexed(pSrc, prereqLeft, aiCurCol, pLeft, op) ){
1123       pTerm->leftCursor = aiCurCol[0];
1124       assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
1125       pTerm->u.x.leftColumn = aiCurCol[1];
1126       pTerm->eOperator = operatorMask(op) & opMask;
1127     }
1128     if( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
1129     if( pRight
1130      && exprMightBeIndexed(pSrc, pTerm->prereqRight, aiCurCol, pRight, op)
1131      && !ExprHasProperty(pRight, EP_FixedCol)
1132     ){
1133       WhereTerm *pNew;
1134       Expr *pDup;
1135       u16 eExtraOp = 0;        /* Extra bits for pNew->eOperator */
1136       assert( pTerm->u.x.iField==0 );
1137       if( pTerm->leftCursor>=0 ){
1138         int idxNew;
1139         pDup = sqlite3ExprDup(db, pExpr, 0);
1140         if( db->mallocFailed ){
1141           sqlite3ExprDelete(db, pDup);
1142           return;
1143         }
1144         idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
1145         if( idxNew==0 ) return;
1146         pNew = &pWC->a[idxNew];
1147         markTermAsChild(pWC, idxNew, idxTerm);
1148         if( op==TK_IS ) pNew->wtFlags |= TERM_IS;
1149         pTerm = &pWC->a[idxTerm];
1150         pTerm->wtFlags |= TERM_COPIED;
1151
1152         if( termIsEquivalence(pParse, pDup) ){
1153           pTerm->eOperator |= WO_EQUIV;
1154           eExtraOp = WO_EQUIV;
1155         }
1156       }else{
1157         pDup = pExpr;
1158         pNew = pTerm;
1159       }
1160       pNew->wtFlags |= exprCommute(pParse, pDup);
1161       pNew->leftCursor = aiCurCol[0];
1162       assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
1163       pNew->u.x.leftColumn = aiCurCol[1];
1164       testcase( (prereqLeft | extraRight) != prereqLeft );
1165       pNew->prereqRight = prereqLeft | extraRight;
1166       pNew->prereqAll = prereqAll;
1167       pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
1168     }else
1169     if( op==TK_ISNULL
1170      && !ExprHasProperty(pExpr,EP_FromJoin)
1171      && 0==sqlite3ExprCanBeNull(pLeft)
1172     ){
1173       assert( !ExprHasProperty(pExpr, EP_IntValue) );
1174       pExpr->op = TK_TRUEFALSE;
1175       pExpr->u.zToken = "false";
1176       ExprSetProperty(pExpr, EP_IsFalse);
1177       pTerm->prereqAll = 0;
1178       pTerm->eOperator = 0;
1179     }
1180   }
1181
1182 #ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
1183   /* If a term is the BETWEEN operator, create two new virtual terms
1184   ** that define the range that the BETWEEN implements.  For example:
1185   **
1186   **      a BETWEEN b AND c
1187   **
1188   ** is converted into:
1189   **
1190   **      (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
1191   **
1192   ** The two new terms are added onto the end of the WhereClause object.
1193   ** The new terms are "dynamic" and are children of the original BETWEEN
1194   ** term.  That means that if the BETWEEN term is coded, the children are
1195   ** skipped.  Or, if the children are satisfied by an index, the original
1196   ** BETWEEN term is skipped.
1197   */
1198   else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
1199     ExprList *pList;
1200     int i;
1201     static const u8 ops[] = {TK_GE, TK_LE};
1202     assert( ExprUseXList(pExpr) );
1203     pList = pExpr->x.pList;
1204     assert( pList!=0 );
1205     assert( pList->nExpr==2 );
1206     for(i=0; i<2; i++){
1207       Expr *pNewExpr;
1208       int idxNew;
1209       pNewExpr = sqlite3PExpr(pParse, ops[i],
1210                              sqlite3ExprDup(db, pExpr->pLeft, 0),
1211                              sqlite3ExprDup(db, pList->a[i].pExpr, 0));
1212       transferJoinMarkings(pNewExpr, pExpr);
1213       idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1214       testcase( idxNew==0 );
1215       exprAnalyze(pSrc, pWC, idxNew);
1216       pTerm = &pWC->a[idxTerm];
1217       markTermAsChild(pWC, idxNew, idxTerm);
1218     }
1219   }
1220 #endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
1221
1222 #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
1223   /* Analyze a term that is composed of two or more subterms connected by
1224   ** an OR operator.
1225   */
1226   else if( pExpr->op==TK_OR ){
1227     assert( pWC->op==TK_AND );
1228     exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
1229     pTerm = &pWC->a[idxTerm];
1230   }
1231 #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
1232   /* The form "x IS NOT NULL" can sometimes be evaluated more efficiently
1233   ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
1234   ** virtual term of that form.
1235   **
1236   ** The virtual term must be tagged with TERM_VNULL.
1237   */
1238   else if( pExpr->op==TK_NOTNULL ){
1239     if( pExpr->pLeft->op==TK_COLUMN
1240      && pExpr->pLeft->iColumn>=0
1241      && !ExprHasProperty(pExpr, EP_FromJoin)
1242     ){
1243       Expr *pNewExpr;
1244       Expr *pLeft = pExpr->pLeft;
1245       int idxNew;
1246       WhereTerm *pNewTerm;
1247
1248       pNewExpr = sqlite3PExpr(pParse, TK_GT,
1249                               sqlite3ExprDup(db, pLeft, 0),
1250                               sqlite3ExprAlloc(db, TK_NULL, 0, 0));
1251
1252       idxNew = whereClauseInsert(pWC, pNewExpr,
1253                                 TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
1254       if( idxNew ){
1255         pNewTerm = &pWC->a[idxNew];
1256         pNewTerm->prereqRight = 0;
1257         pNewTerm->leftCursor = pLeft->iTable;
1258         pNewTerm->u.x.leftColumn = pLeft->iColumn;
1259         pNewTerm->eOperator = WO_GT;
1260         markTermAsChild(pWC, idxNew, idxTerm);
1261         pTerm = &pWC->a[idxTerm];
1262         pTerm->wtFlags |= TERM_COPIED;
1263         pNewTerm->prereqAll = pTerm->prereqAll;
1264       }
1265     }
1266   }
1267
1268
1269 #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
1270   /* Add constraints to reduce the search space on a LIKE or GLOB
1271   ** operator.
1272   **
1273   ** A like pattern of the form "x LIKE 'aBc%'" is changed into constraints
1274   **
1275   **          x>='ABC' AND x<'abd' AND x LIKE 'aBc%'
1276   **
1277   ** The last character of the prefix "abc" is incremented to form the
1278   ** termination condition "abd".  If case is not significant (the default
1279   ** for LIKE) then the lower-bound is made all uppercase and the upper-
1280   ** bound is made all lowercase so that the bounds also work when comparing
1281   ** BLOBs.
1282   */
1283   else if( pExpr->op==TK_FUNCTION
1284    && pWC->op==TK_AND
1285    && isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
1286   ){
1287     Expr *pLeft;       /* LHS of LIKE/GLOB operator */
1288     Expr *pStr2;       /* Copy of pStr1 - RHS of LIKE/GLOB operator */
1289     Expr *pNewExpr1;
1290     Expr *pNewExpr2;
1291     int idxNew1;
1292     int idxNew2;
1293     const char *zCollSeqName;     /* Name of collating sequence */
1294     const u16 wtFlags = TERM_LIKEOPT | TERM_VIRTUAL | TERM_DYNAMIC;
1295
1296     assert( ExprUseXList(pExpr) );
1297     pLeft = pExpr->x.pList->a[1].pExpr;
1298     pStr2 = sqlite3ExprDup(db, pStr1, 0);
1299     assert( pStr1==0 || !ExprHasProperty(pStr1, EP_IntValue) );
1300     assert( pStr2==0 || !ExprHasProperty(pStr2, EP_IntValue) );
1301
1302
1303     /* Convert the lower bound to upper-case and the upper bound to
1304     ** lower-case (upper-case is less than lower-case in ASCII) so that
1305     ** the range constraints also work for BLOBs
1306     */
1307     if( noCase && !pParse->db->mallocFailed ){
1308       int i;
1309       char c;
1310       pTerm->wtFlags |= TERM_LIKE;
1311       for(i=0; (c = pStr1->u.zToken[i])!=0; i++){
1312         pStr1->u.zToken[i] = sqlite3Toupper(c);
1313         pStr2->u.zToken[i] = sqlite3Tolower(c);
1314       }
1315     }
1316
1317     if( !db->mallocFailed ){
1318       u8 c, *pC;       /* Last character before the first wildcard */
1319       pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
1320       c = *pC;
1321       if( noCase ){
1322         /* The point is to increment the last character before the first
1323         ** wildcard.  But if we increment '@', that will push it into the
1324         ** alphabetic range where case conversions will mess up the
1325         ** inequality.  To avoid this, make sure to also run the full
1326         ** LIKE on all candidate expressions by clearing the isComplete flag
1327         */
1328         if( c=='A'-1 ) isComplete = 0;
1329         c = sqlite3UpperToLower[c];
1330       }
1331       *pC = c + 1;
1332     }
1333     zCollSeqName = noCase ? "NOCASE" : sqlite3StrBINARY;
1334     pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
1335     pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
1336            sqlite3ExprAddCollateString(pParse,pNewExpr1,zCollSeqName),
1337            pStr1);
1338     transferJoinMarkings(pNewExpr1, pExpr);
1339     idxNew1 = whereClauseInsert(pWC, pNewExpr1, wtFlags);
1340     testcase( idxNew1==0 );
1341     exprAnalyze(pSrc, pWC, idxNew1);
1342     pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
1343     pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
1344            sqlite3ExprAddCollateString(pParse,pNewExpr2,zCollSeqName),
1345            pStr2);
1346     transferJoinMarkings(pNewExpr2, pExpr);
1347     idxNew2 = whereClauseInsert(pWC, pNewExpr2, wtFlags);
1348     testcase( idxNew2==0 );
1349     exprAnalyze(pSrc, pWC, idxNew2);
1350     pTerm = &pWC->a[idxTerm];
1351     if( isComplete ){
1352       markTermAsChild(pWC, idxNew1, idxTerm);
1353       markTermAsChild(pWC, idxNew2, idxTerm);
1354     }
1355   }
1356 #endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
1357
1358   /* If there is a vector == or IS term - e.g. "(a, b) == (?, ?)" - create
1359   ** new terms for each component comparison - "a = ?" and "b = ?".  The
1360   ** new terms completely replace the original vector comparison, which is
1361   ** no longer used.
1362   **
1363   ** This is only required if at least one side of the comparison operation
1364   ** is not a sub-select.  */
1365   if( (pExpr->op==TK_EQ || pExpr->op==TK_IS)
1366    && (nLeft = sqlite3ExprVectorSize(pExpr->pLeft))>1
1367    && sqlite3ExprVectorSize(pExpr->pRight)==nLeft
1368    && ( (pExpr->pLeft->flags & EP_xIsSelect)==0
1369      || (pExpr->pRight->flags & EP_xIsSelect)==0)
1370    && pWC->op==TK_AND
1371   ){
1372     int i;
1373     for(i=0; i<nLeft; i++){
1374       int idxNew;
1375       Expr *pNew;
1376       Expr *pLeft = sqlite3ExprForVectorField(pParse, pExpr->pLeft, i, nLeft);
1377       Expr *pRight = sqlite3ExprForVectorField(pParse, pExpr->pRight, i, nLeft);
1378
1379       pNew = sqlite3PExpr(pParse, pExpr->op, pLeft, pRight);
1380       transferJoinMarkings(pNew, pExpr);
1381       idxNew = whereClauseInsert(pWC, pNew, TERM_DYNAMIC);
1382       exprAnalyze(pSrc, pWC, idxNew);
1383     }
1384     pTerm = &pWC->a[idxTerm];
1385     pTerm->wtFlags |= TERM_CODED|TERM_VIRTUAL;  /* Disable the original */
1386     pTerm->eOperator = 0;
1387   }
1388
1389   /* If there is a vector IN term - e.g. "(a, b) IN (SELECT ...)" - create
1390   ** a virtual term for each vector component. The expression object
1391   ** used by each such virtual term is pExpr (the full vector IN(...)
1392   ** expression). The WhereTerm.u.x.iField variable identifies the index within
1393   ** the vector on the LHS that the virtual term represents.
1394   **
1395   ** This only works if the RHS is a simple SELECT (not a compound) that does
1396   ** not use window functions.
1397   */
1398   else if( pExpr->op==TK_IN
1399    && pTerm->u.x.iField==0
1400    && pExpr->pLeft->op==TK_VECTOR
1401    && ALWAYS( ExprUseXSelect(pExpr) )
1402    && pExpr->x.pSelect->pPrior==0
1403 #ifndef SQLITE_OMIT_WINDOWFUNC
1404    && pExpr->x.pSelect->pWin==0
1405 #endif
1406    && pWC->op==TK_AND
1407   ){
1408     int i;
1409     for(i=0; i<sqlite3ExprVectorSize(pExpr->pLeft); i++){
1410       int idxNew;
1411       idxNew = whereClauseInsert(pWC, pExpr, TERM_VIRTUAL);
1412       pWC->a[idxNew].u.x.iField = i+1;
1413       exprAnalyze(pSrc, pWC, idxNew);
1414       markTermAsChild(pWC, idxNew, idxTerm);
1415     }
1416   }
1417
1418 #ifndef SQLITE_OMIT_VIRTUALTABLE
1419   /* Add a WO_AUX auxiliary term to the constraint set if the
1420   ** current expression is of the form "column OP expr" where OP
1421   ** is an operator that gets passed into virtual tables but which is
1422   ** not normally optimized for ordinary tables.  In other words, OP
1423   ** is one of MATCH, LIKE, GLOB, REGEXP, !=, IS, IS NOT, or NOT NULL.
1424   ** This information is used by the xBestIndex methods of
1425   ** virtual tables.  The native query optimizer does not attempt
1426   ** to do anything with MATCH functions.
1427   */
1428   else if( pWC->op==TK_AND ){
1429     Expr *pRight = 0, *pLeft = 0;
1430     int res = isAuxiliaryVtabOperator(db, pExpr, &eOp2, &pLeft, &pRight);
1431     while( res-- > 0 ){
1432       int idxNew;
1433       WhereTerm *pNewTerm;
1434       Bitmask prereqColumn, prereqExpr;
1435
1436       prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);
1437       prereqColumn = sqlite3WhereExprUsage(pMaskSet, pLeft);
1438       if( (prereqExpr & prereqColumn)==0 ){
1439         Expr *pNewExpr;
1440         pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
1441             0, sqlite3ExprDup(db, pRight, 0));
1442         if( ExprHasProperty(pExpr, EP_FromJoin) && pNewExpr ){
1443           ExprSetProperty(pNewExpr, EP_FromJoin);
1444           pNewExpr->iRightJoinTable = pExpr->iRightJoinTable;
1445         }
1446         idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1447         testcase( idxNew==0 );
1448         pNewTerm = &pWC->a[idxNew];
1449         pNewTerm->prereqRight = prereqExpr;
1450         pNewTerm->leftCursor = pLeft->iTable;
1451         pNewTerm->u.x.leftColumn = pLeft->iColumn;
1452         pNewTerm->eOperator = WO_AUX;
1453         pNewTerm->eMatchOp = eOp2;
1454         markTermAsChild(pWC, idxNew, idxTerm);
1455         pTerm = &pWC->a[idxTerm];
1456         pTerm->wtFlags |= TERM_COPIED;
1457         pNewTerm->prereqAll = pTerm->prereqAll;
1458       }
1459       SWAP(Expr*, pLeft, pRight);
1460     }
1461   }
1462 #endif /* SQLITE_OMIT_VIRTUALTABLE */
1463
1464   /* Prevent ON clause terms of a LEFT JOIN from being used to drive
1465   ** an index for tables to the left of the join.
1466   */
1467   testcase( pTerm!=&pWC->a[idxTerm] );
1468   pTerm = &pWC->a[idxTerm];
1469   pTerm->prereqRight |= extraRight;
1470 }
1471
1472 /***************************************************************************
1473 ** Routines with file scope above.  Interface to the rest of the where.c
1474 ** subsystem follows.
1475 ***************************************************************************/
1476
1477 /*
1478 ** This routine identifies subexpressions in the WHERE clause where
1479 ** each subexpression is separated by the AND operator or some other
1480 ** operator specified in the op parameter.  The WhereClause structure
1481 ** is filled with pointers to subexpressions.  For example:
1482 **
1483 **    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
1484 **           \________/     \_______________/     \________________/
1485 **            slot[0]            slot[1]               slot[2]
1486 **
1487 ** The original WHERE clause in pExpr is unaltered.  All this routine
1488 ** does is make slot[] entries point to substructure within pExpr.
1489 **
1490 ** In the previous sentence and in the diagram, "slot[]" refers to
1491 ** the WhereClause.a[] array.  The slot[] array grows as needed to contain
1492 ** all terms of the WHERE clause.
1493 */
1494 void sqlite3WhereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
1495   Expr *pE2 = sqlite3ExprSkipCollateAndLikely(pExpr);
1496   pWC->op = op;
1497   assert( pE2!=0 || pExpr==0 );
1498   if( pE2==0 ) return;
1499   if( pE2->op!=op ){
1500     whereClauseInsert(pWC, pExpr, 0);
1501   }else{
1502     sqlite3WhereSplit(pWC, pE2->pLeft, op);
1503     sqlite3WhereSplit(pWC, pE2->pRight, op);
1504   }
1505 }
1506
1507 /*
1508 ** Initialize a preallocated WhereClause structure.
1509 */
1510 void sqlite3WhereClauseInit(
1511   WhereClause *pWC,        /* The WhereClause to be initialized */
1512   WhereInfo *pWInfo        /* The WHERE processing context */
1513 ){
1514   pWC->pWInfo = pWInfo;
1515   pWC->hasOr = 0;
1516   pWC->pOuter = 0;
1517   pWC->nTerm = 0;
1518   pWC->nSlot = ArraySize(pWC->aStatic);
1519   pWC->a = pWC->aStatic;
1520 }
1521
1522 /*
1523 ** Deallocate a WhereClause structure.  The WhereClause structure
1524 ** itself is not freed.  This routine is the inverse of
1525 ** sqlite3WhereClauseInit().
1526 */
1527 void sqlite3WhereClauseClear(WhereClause *pWC){
1528   int i;
1529   WhereTerm *a;
1530   sqlite3 *db = pWC->pWInfo->pParse->db;
1531   for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
1532     if( a->wtFlags & TERM_DYNAMIC ){
1533       sqlite3ExprDelete(db, a->pExpr);
1534     }
1535     if( a->wtFlags & TERM_ORINFO ){
1536       whereOrInfoDelete(db, a->u.pOrInfo);
1537     }else if( a->wtFlags & TERM_ANDINFO ){
1538       whereAndInfoDelete(db, a->u.pAndInfo);
1539     }
1540   }
1541   if( pWC->a!=pWC->aStatic ){
1542     sqlite3DbFree(db, pWC->a);
1543   }
1544 }
1545
1546
1547 /*
1548 ** These routines walk (recursively) an expression tree and generate
1549 ** a bitmask indicating which tables are used in that expression
1550 ** tree.
1551 */
1552 Bitmask sqlite3WhereExprUsageNN(WhereMaskSet *pMaskSet, Expr *p){
1553   Bitmask mask;
1554   if( p->op==TK_COLUMN && !ExprHasProperty(p, EP_FixedCol) ){
1555     return sqlite3WhereGetMask(pMaskSet, p->iTable);
1556   }else if( ExprHasProperty(p, EP_TokenOnly|EP_Leaf) ){
1557     assert( p->op!=TK_IF_NULL_ROW );
1558     return 0;
1559   }
1560   mask = (p->op==TK_IF_NULL_ROW) ? sqlite3WhereGetMask(pMaskSet, p->iTable) : 0;
1561   if( p->pLeft ) mask |= sqlite3WhereExprUsageNN(pMaskSet, p->pLeft);
1562   if( p->pRight ){
1563     mask |= sqlite3WhereExprUsageNN(pMaskSet, p->pRight);
1564     assert( p->x.pList==0 );
1565   }else if( ExprUseXSelect(p) ){
1566     if( ExprHasProperty(p, EP_VarSelect) ) pMaskSet->bVarSelect = 1;
1567     mask |= exprSelectUsage(pMaskSet, p->x.pSelect);
1568   }else if( p->x.pList ){
1569     mask |= sqlite3WhereExprListUsage(pMaskSet, p->x.pList);
1570   }
1571 #ifndef SQLITE_OMIT_WINDOWFUNC
1572   if( (p->op==TK_FUNCTION || p->op==TK_AGG_FUNCTION) && ExprUseYWin(p) ){
1573     assert( p->y.pWin!=0 );
1574     mask |= sqlite3WhereExprListUsage(pMaskSet, p->y.pWin->pPartition);
1575     mask |= sqlite3WhereExprListUsage(pMaskSet, p->y.pWin->pOrderBy);
1576     mask |= sqlite3WhereExprUsage(pMaskSet, p->y.pWin->pFilter);
1577   }
1578 #endif
1579   return mask;
1580 }
1581 Bitmask sqlite3WhereExprUsage(WhereMaskSet *pMaskSet, Expr *p){
1582   return p ? sqlite3WhereExprUsageNN(pMaskSet,p) : 0;
1583 }
1584 Bitmask sqlite3WhereExprListUsage(WhereMaskSet *pMaskSet, ExprList *pList){
1585   int i;
1586   Bitmask mask = 0;
1587   if( pList ){
1588     for(i=0; i<pList->nExpr; i++){
1589       mask |= sqlite3WhereExprUsage(pMaskSet, pList->a[i].pExpr);
1590     }
1591   }
1592   return mask;
1593 }
1594
1595
1596 /*
1597 ** Call exprAnalyze on all terms in a WHERE clause.
1598 **
1599 ** Note that exprAnalyze() might add new virtual terms onto the
1600 ** end of the WHERE clause.  We do not want to analyze these new
1601 ** virtual terms, so start analyzing at the end and work forward
1602 ** so that the added virtual terms are never processed.
1603 */
1604 void sqlite3WhereExprAnalyze(
1605   SrcList *pTabList,       /* the FROM clause */
1606   WhereClause *pWC         /* the WHERE clause to be analyzed */
1607 ){
1608   int i;
1609   for(i=pWC->nTerm-1; i>=0; i--){
1610     exprAnalyze(pTabList, pWC, i);
1611   }
1612 }
1613
1614 /*
1615 ** For table-valued-functions, transform the function arguments into
1616 ** new WHERE clause terms.
1617 **
1618 ** Each function argument translates into an equality constraint against
1619 ** a HIDDEN column in the table.
1620 */
1621 void sqlite3WhereTabFuncArgs(
1622   Parse *pParse,                    /* Parsing context */
1623   SrcItem *pItem,                   /* The FROM clause term to process */
1624   WhereClause *pWC                  /* Xfer function arguments to here */
1625 ){
1626   Table *pTab;
1627   int j, k;
1628   ExprList *pArgs;
1629   Expr *pColRef;
1630   Expr *pTerm;
1631   if( pItem->fg.isTabFunc==0 ) return;
1632   pTab = pItem->pTab;
1633   assert( pTab!=0 );
1634   pArgs = pItem->u1.pFuncArg;
1635   if( pArgs==0 ) return;
1636   for(j=k=0; j<pArgs->nExpr; j++){
1637     Expr *pRhs;
1638     while( k<pTab->nCol && (pTab->aCol[k].colFlags & COLFLAG_HIDDEN)==0 ){k++;}
1639     if( k>=pTab->nCol ){
1640       sqlite3ErrorMsg(pParse, "too many arguments on %s() - max %d",
1641                       pTab->zName, j);
1642       return;
1643     }
1644     pColRef = sqlite3ExprAlloc(pParse->db, TK_COLUMN, 0, 0);
1645     if( pColRef==0 ) return;
1646     pColRef->iTable = pItem->iCursor;
1647     pColRef->iColumn = k++;
1648     assert( ExprUseYTab(pColRef) );
1649     pColRef->y.pTab = pTab;
1650     pRhs = sqlite3PExpr(pParse, TK_UPLUS,
1651         sqlite3ExprDup(pParse->db, pArgs->a[j].pExpr, 0), 0);
1652     pTerm = sqlite3PExpr(pParse, TK_EQ, pColRef, pRhs);
1653     if( pItem->fg.jointype & JT_LEFT ){
1654       sqlite3SetJoinExpr(pTerm, pItem->iCursor);
1655     }
1656     whereClauseInsert(pWC, pTerm, TERM_DYNAMIC);
1657   }
1658 }