SQLite

typedef struct WhereAndInfo WhereAndInfo;
typedef struct WhereLevel WhereLevel;
typedef struct WhereLoop WhereLoop;
typedef struct WherePath WherePath;
typedef struct WhereTerm WhereTerm;
typedef struct WhereLoopBuilder WhereLoopBuilder;
typedef struct WhereScan WhereScan;
typedef struct WhereOrCost WhereOrCost;
typedef struct WhereOrSet WhereOrSet;

/*
** Cost X is tracked as 10*log2(X) stored in a 16-bit integer.  The
** maximum cost for ordinary tables is 64*(2**63) which becomes 6900.
** (Virtual tables can return a larger cost, but let's assume they do not.)
** So all costs can be stored in a 16-bit unsigned integer without risk
** of overflow.

  /**** whereLoopXfer() copies fields above ***********************/
# define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
  u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
  WhereTerm **aLTerm;   /* WhereTerms used */
  WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
  WhereTerm *aLTermSpace[4];  /* Initial aLTerm[] space */
};

/* This object holds the prerequisites and the cost of running a
** subquery on one operand of an OR operator in the WHERE clause.
** See WhereOrSet for additional information 
*/
struct WhereOrCost {
  Bitmask prereq;     /* Prerequisites */
  WhereCost rRun;     /* Cost of running this subquery */
  WhereCost nOut;     /* Number of outputs for this subquery */
};

/* The WhereOrSet object holds a set of possible WhereOrCosts that
** correspond to the subquery(s) of OR-clause processing.  At most
** favorable N_OR_COST elements are retained.
*/
#define N_OR_COST 3
struct WhereOrSet {
  u16 n;                      /* Number of valid a[] entries */
  WhereOrCost a[N_OR_COST];   /* Set of best costs */
};


/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);

/*
** Each instance of this object holds a sequence of WhereLoop objects
** that implement some or all of a query plan.

** to construct WhereLoop objects for a particular query.
*/
struct WhereLoopBuilder {
  WhereInfo *pWInfo;        /* Information about this WHERE */
  WhereClause *pWC;         /* WHERE clause terms */
  ExprList *pOrderBy;       /* ORDER BY clause */
  WhereLoop *pNew;          /* Template WhereLoop */
  WhereOrSet *pOrSet;       /* Record best loops here, if not NULL */
};

/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed

** Return TRUE if an UPDATE or DELETE statement can operate directly on
** the rowids returned by a WHERE clause.  Return FALSE if doing an
** UPDATE or DELETE might change subsequent WHERE clause results.
*/
int sqlite3WhereOkOnePass(WhereInfo *pWInfo){
  return pWInfo->okOnePass;
}

/*
** Move the content of pSrc into pDest
*/
static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
  pDest->n = pSrc->n;
  memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
}

/*
** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
**
** The new entry might overwrite an existing entry, or it might be
** appended, or it might be discarded.  Do whatever is the right thing
** so that pSet keeps the N_OR_COST best entries seen so far.
*/
static int whereOrInsert(
  WhereOrSet *pSet,      /* The WhereOrSet to be updated */
  Bitmask prereq,        /* Prerequisites of the new entry */
  WhereCost rRun,        /* Run-cost of the new entry */
  WhereCost nOut         /* Number of outputs for the new entry */
){
  u16 i;
  WhereOrCost *p;
  for(i=pSet->n, p=pSet->a; i>0; i--, p++){
    if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
      goto whereOrInsert_done;
    }
    if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
      return 0;
    }
  }
  if( pSet->n<N_OR_COST ){
    p = &pSet->a[pSet->n++];
    p->nOut = nOut;
  }else{
    p = pSet->a;
    for(i=1; i<pSet->n; i++){
      if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
    }
    if( p->rRun<=rRun ) return 0;
  }
whereOrInsert_done:
  p->prereq = prereq;
  p->rRun = rRun;
  if( p->nOut>nOut ) p->nOut = nOut;
  return 1;
}

/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(
  WhereClause *pWC,        /* The WhereClause to be initialized */
  WhereInfo *pWInfo        /* The WHERE processing context */

    ** is not contained in the ON clause of a LEFT JOIN.
    ** See ticket http://www.sqlite.org/src/info/f2369304e4
    */
    if( pWC->nTerm>1 ){
      int iTerm;
      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
        Expr *pExpr = pWC->a[iTerm].pExpr;
        if( &pWC->a[iTerm] == pTerm ) continue;
        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
        if( pWC->a[iTerm].wtFlags & (TERM_ORINFO) ) continue;
        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
        pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
        pAndExpr = sqlite3ExprAnd(pParse->db, pAndExpr, pExpr);
      }
      if( pAndExpr ){
        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
      }

**
** An existing WhereLoop entry might be overwritten if the new template
** is better and has fewer dependencies.  Or the template will be ignored
** and no insert will occur if an existing WhereLoop is faster and has
** fewer dependencies than the template.  Otherwise a new WhereLoop is
** added based on the template.
**
** If pBuilder->pOrSet is not NULL then we only care about only the
** prerequisites and rRun and nOut costs of the N best loops.  That
** information is gathered in the pBuilder->pOrSet object.  This special
** processing mode is used only for OR clause processing.
**
** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
** still might overwrite similar loops with the new template if the
** template is better.  Loops may be overwritten if the following 
** conditions are met:
**
**    (1)  They have the same iTab.
**    (2)  They have the same iSortIdx.
**    (3)  The template has same or fewer dependencies than the current loop
**    (4)  The template has the same or lower cost than the current loop
**    (5)  The template uses more terms of the same index but has no additional
**         dependencies          
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
  WhereLoop **ppPrev, *p, *pNext = 0;
  WhereInfo *pWInfo = pBuilder->pWInfo;
  sqlite3 *db = pWInfo->pParse->db;

  /* If pBuilder->pOrSet is defined, then only keep track of the costs

  ** and prereqs.

  */
  if( pBuilder->pOrSet!=0 ){
#if WHERETRACE_ENABLED
    u16 n = pBuilder->pOrSet->n;
    int x =
#endif

    whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
                                    pTemplate->nOut);







#if WHERETRACE_ENABLED
    if( sqlite3WhereTrace & 0x8 ){
      sqlite3DebugPrintf(x?"   or-%d:  ":"   or-X:  ", n);
      whereLoopPrint(pTemplate, pWInfo->pTabList);
    }
#endif

    return SQLITE_OK;
  }

  /* Search for an existing WhereLoop to overwrite, or which takes
  ** priority over pTemplate.
  */
  for(ppPrev=&pWInfo->pLoops, p=*ppPrev; p; ppPrev=&p->pNextLoop, p=*ppPrev){

  }
  return SQLITE_OK;

  /* Jump here if the insert is a no-op */
whereLoopInsert_noop:
#if WHERETRACE_ENABLED
  if( sqlite3WhereTrace & 0x8 ){
    sqlite3DebugPrintf("ins-noop: ");
    whereLoopPrint(pTemplate, pWInfo->pTabList);
  }
#endif
  return SQLITE_OK;  
}

/*

    }
    pProbe = &sPk;
  }
  rSize = whereCost(pSrc->pTab->nRowEst);
  rLogSize = estLog(rSize);

  /* Automatic indexes */
  if( !pBuilder->pOrSet
   && (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
   && pSrc->pIndex==0
   && !pSrc->viaCoroutine
   && !pSrc->notIndexed
   && !pSrc->isCorrelated
  ){
    /* Generate auto-index WhereLoops */

  WhereClause *pWC;
  WhereLoop *pNew;
  WhereTerm *pTerm, *pWCEnd;
  int rc = SQLITE_OK;
  int iCur;
  WhereClause tempWC;
  WhereLoopBuilder sSubBuild;
  WhereOrSet sSum, sCur, sPrev;
  struct SrcList_item *pItem;
  
  pWC = pBuilder->pWC;
  if( pWInfo->wctrlFlags & WHERE_AND_ONLY ) return SQLITE_OK;
  pWCEnd = pWC->a + pWC->nTerm;
  pNew = pBuilder->pNew;

  for(pTerm=pWC->a; pTerm<pWCEnd && rc==SQLITE_OK; pTerm++){
    if( (pTerm->eOperator & WO_OR)!=0
     && (pTerm->u.pOrInfo->indexable & pNew->maskSelf)!=0 
    ){
      WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
      WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
      WhereTerm *pOrTerm;
      int once = 1;
      int i, j;

    

      pItem = pWInfo->pTabList->a + pNew->iTab;
      iCur = pItem->iCursor;
      sSubBuild = *pBuilder;
      sSubBuild.pOrderBy = 0;
      sSubBuild.pOrSet = &sCur;

      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
        if( (pOrTerm->eOperator & WO_AND)!=0 ){
          sSubBuild.pWC = &pOrTerm->u.pAndInfo->wc;
        }else if( pOrTerm->leftCursor==iCur ){
          tempWC.pWInfo = pWC->pWInfo;
          tempWC.pOuter = pWC;
          tempWC.op = TK_AND;
          tempWC.nTerm = 1;
          tempWC.a = pOrTerm;
          sSubBuild.pWC = &tempWC;
        }else{
          continue;
        }


        sCur.n = 0;
#ifndef SQLITE_OMIT_VIRTUALTABLE
        if( IsVirtual(pItem->pTab) ){
          rc = whereLoopAddVirtual(&sSubBuild);
          for(i=0; i<sCur.n; i++) sCur.a[i].prereq |= mExtra;
        }else
#endif
        {
          rc = whereLoopAddBtree(&sSubBuild, mExtra);
        }

        assert( rc==SQLITE_OK || sCur.n==0 );
        if( sCur.n==0 ){
          sSum.n = 0;
          break;
        }else if( once ){
          whereOrMove(&sSum, &sCur);
          once = 0;
        }else{
          whereOrMove(&sPrev, &sSum);
          sSum.n = 0;
          for(i=0; i<sPrev.n; i++){
            for(j=0; j<sCur.n; j++){
              whereOrInsert(&sSum, sPrev.a[i].prereq | sCur.a[j].prereq,
                            whereCostAdd(sPrev.a[i].rRun, sCur.a[j].rRun),
                            whereCostAdd(sPrev.a[i].nOut, sCur.a[j].nOut));

            }


          }
        }
      }
      pNew->nLTerm = 1;
      pNew->aLTerm[0] = pTerm;
      pNew->wsFlags = WHERE_MULTI_OR;
      pNew->rSetup = 0;
      pNew->iSortIdx = 0;
      memset(&pNew->u, 0, sizeof(pNew->u));
      for(i=0; rc==SQLITE_OK && i<sSum.n; i++){
        /* TUNING: Multiple by 3.5 for the secondary table lookup */
        pNew->rRun = sSum.a[i].rRun + 18;
        pNew->nOut = sSum.a[i].nOut;
        pNew->prereq = sSum.a[i].prereq;

        rc = whereLoopInsert(pBuilder, pNew);
      }

    }
  }
  return rc;
}

/*
** Add all WhereLoop objects for all tables 

  }
} {4}
do_test where2-11.4 {
  execsql {
    SELECT d FROM t11 WHERE c=7 OR (a=1 AND b=2) ORDER BY d;
  }
} {4 8 10}

# Verify that the OR clause is used in an outer loop even when
# the OR clause scores slightly better on an inner loop.
do_execsql_test where2-12.1 {
  CREATE TABLE t12(x INTEGER PRIMARY KEY, y);
  CREATE INDEX t12y ON t12(y);
  EXPLAIN QUERY PLAN
    SELECT a.x, b.x
      FROM t12 AS a JOIN t12 AS b ON a.y=b.x
     WHERE (b.x=$abc OR b.y=$abc);
} {/.*SEARCH TABLE t12 AS b .*SEARCH TABLE t12 AS b .*/}


finish_test

    SELECT a, d FROM t1, t2 WHERE (a = 2 OR a = 3) AND d = a
  }
} {2 2 3 3 0 0}

do_test where8-3.5 {
  execsql_status {
    SELECT a, d FROM t1, t2 WHERE (a = 2 OR a = 3) AND (d = a OR e = 'sixteen')
     ORDER BY +a, +d;
  }
} {2 2 2 4 3 3 3 4 0 1}

do_test where8-3.6 {
  # The first part of the WHERE clause in this query, (a=2 OR a=3) is
  # transformed into "a IN (2, 3)". This is why the sort is required.
  #
  execsql_status {
    SELECT a, d 
    FROM t1, t2 
    WHERE (a = 2 OR a = 3) AND (d = a OR e = 'sixteen')
    ORDER BY t1.rowid
  }
} {2 2 2 4 3 3 3 4 0 1}
do_test where8-3.7 {
  execsql_status {
    SELECT a, d 
    FROM t1, t2 
    WHERE a = 2 AND (d = a OR e = 'sixteen')
    ORDER BY t1.rowid
  }
} {/2 2 2 4 0 [01]/}
do_test where8-3.8 {
  execsql_status {
    SELECT a, d 
    FROM t1, t2 
    WHERE (a = 2 OR b = 'three') AND (d = a OR e = 'sixteen')
    ORDER BY t1.rowid
  }