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Overview
Comment:Change the way SQLite invokes the xBestIndex method of virtual tables so that N-way joins involving virtual tables work as expected.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | xbestindex-fix
Files: files | file ages | folders
SHA1: ffc65968ede2c402e616147e6e3d737e6f9de21d
User & Date: dan 2016-03-05 17:29:08
Context
2016-03-05
20:28
Adjust the cost estimates for RTREE such that the expected number of rows and expected cost is halved for each additional constraint. Closed-Leaf check-in: fd7cd060 user: drh tags: xbestindex-fix
17:29
Change the way SQLite invokes the xBestIndex method of virtual tables so that N-way joins involving virtual tables work as expected. check-in: ffc65968 user: dan tags: xbestindex-fix
15:35
Remove the unused journal.c source file (its function have been subsumed into memjournal.c). Refactor some of the names in memjournal.c. No functional changes. check-in: 5f2a262d user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/test_bestindex.c.

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};

/* A tcl cursor object */
struct tcl_cursor {
  sqlite3_vtab_cursor base;
  sqlite3_stmt *pStmt;            /* Read data from here */
};



































/*
** This function is the implementation of both the xConnect and xCreate
** methods of the fs virtual table.
**
** The argv[] array contains the following:
**
................................................................................
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  Tcl_Interp *interp = (Tcl_Interp*)pAux;
  tcl_vtab *pTab;
  const char *zCmd;
  Tcl_Obj *pScript = 0;
  int rc;

  if( argc!=4 ){
    *pzErr = sqlite3_mprintf("wrong number of arguments");
    return SQLITE_ERROR;
  }
  zCmd = argv[3];


  pTab = (tcl_vtab*)sqlite3_malloc(sizeof(tcl_vtab));
  if( pTab==0 ) return SQLITE_NOMEM;


  memset(pTab, 0, sizeof(tcl_vtab));

  pTab->pCmd = Tcl_NewStringObj(zCmd, -1);
  pTab->interp = interp;
  pTab->db = db;
  Tcl_IncrRefCount(pTab->pCmd);

  pScript = Tcl_DuplicateObj(pTab->pCmd);
  Tcl_IncrRefCount(pScript);
  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xConnect", -1));

  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
  if( rc!=TCL_OK ){
    *pzErr = sqlite3_mprintf("%s", Tcl_GetStringResult(interp));
    rc = SQLITE_ERROR;
  }else{
    rc = sqlite3_declare_vtab(db, Tcl_GetStringResult(interp));
  }

  if( rc!=SQLITE_OK ){
    sqlite3_free(pTab);
    pTab = 0;
  }





  *ppVtab = &pTab->base;
  return rc;
}

/* The xDisconnect and xDestroy methods are also the same */
static int tclDisconnect(sqlite3_vtab *pVtab){
  tcl_vtab *pTab = (tcl_vtab*)pVtab;







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};

/* A tcl cursor object */
struct tcl_cursor {
  sqlite3_vtab_cursor base;
  sqlite3_stmt *pStmt;            /* Read data from here */
};

/*
** Dequote string z in place.
*/
static void tclDequote(char *z){
  char q = z[0];

  /* Set stack variable q to the close-quote character */
  if( q=='[' || q=='\'' || q=='"' || q=='`' ){
    int iIn = 1;
    int iOut = 0;
    if( q=='[' ) q = ']';  

    while( ALWAYS(z[iIn]) ){
      if( z[iIn]==q ){
        if( z[iIn+1]!=q ){
          /* Character iIn was the close quote. */
          iIn++;
          break;
        }else{
          /* Character iIn and iIn+1 form an escaped quote character. Skip
          ** the input cursor past both and copy a single quote character 
          ** to the output buffer. */
          iIn += 2;
          z[iOut++] = q;
        }
      }else{
        z[iOut++] = z[iIn++];
      }
    }

    z[iOut] = '\0';
  }
}

/*
** This function is the implementation of both the xConnect and xCreate
** methods of the fs virtual table.
**
** The argv[] array contains the following:
**
................................................................................
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  Tcl_Interp *interp = (Tcl_Interp*)pAux;
  tcl_vtab *pTab = 0;
  char *zCmd = 0;
  Tcl_Obj *pScript = 0;
  int rc = SQLITE_OK;

  if( argc!=4 ){
    *pzErr = sqlite3_mprintf("wrong number of arguments");
    return SQLITE_ERROR;
  }


  zCmd = sqlite3_malloc(strlen(argv[3])+1);
  pTab = (tcl_vtab*)sqlite3_malloc(sizeof(tcl_vtab));
  if( zCmd && pTab ){
    memcpy(zCmd, argv[3], strlen(argv[3])+1);
    tclDequote(zCmd);
    memset(pTab, 0, sizeof(tcl_vtab));

    pTab->pCmd = Tcl_NewStringObj(zCmd, -1);
    pTab->interp = interp;
    pTab->db = db;
    Tcl_IncrRefCount(pTab->pCmd);

    pScript = Tcl_DuplicateObj(pTab->pCmd);
    Tcl_IncrRefCount(pScript);
    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xConnect", -1));

    rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
    if( rc!=TCL_OK ){
      *pzErr = sqlite3_mprintf("%s", Tcl_GetStringResult(interp));
      rc = SQLITE_ERROR;
    }else{
      rc = sqlite3_declare_vtab(db, Tcl_GetStringResult(interp));
    }

    if( rc!=SQLITE_OK ){
      sqlite3_free(pTab);
      pTab = 0;
    }
  }else{
    rc = SQLITE_NOMEM;
  }

  sqlite3_free(zCmd);
  *ppVtab = &pTab->base;
  return rc;
}

/* The xDisconnect and xDestroy methods are also the same */
static int tclDisconnect(sqlite3_vtab *pVtab){
  tcl_vtab *pTab = (tcl_vtab*)pVtab;

Changes to src/where.c.

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    ** considered. */
    if( pSrc->pIBIndex ) break;
  }
  return rc;
}

#ifndef SQLITE_OMIT_VIRTUALTABLE

















































































































































/*
** Add all WhereLoop objects for a table of the join identified by
** pBuilder->pNew->iTab.  That table is guaranteed to be a virtual table.
**
** If there are no LEFT or CROSS JOIN joins in the query, both mExtra and
** mUnusable are set to 0. Otherwise, mExtra is a mask of all FROM clause
** entries that occur before the virtual table in the FROM clause and are
................................................................................
** mUnusable should always be configured as "not-usable" for xBestIndex.
*/
static int whereLoopAddVirtual(
  WhereLoopBuilder *pBuilder,  /* WHERE clause information */
  Bitmask mExtra,              /* Tables that must be scanned before this one */
  Bitmask mUnusable            /* Tables that must be scanned after this one */
){

  WhereInfo *pWInfo;           /* WHERE analysis context */
  Parse *pParse;               /* The parsing context */
  WhereClause *pWC;            /* The WHERE clause */
  struct SrcList_item *pSrc;   /* The FROM clause term to search */
  Table *pTab;
  sqlite3 *db;
  sqlite3_index_info *pIdxInfo;
  struct sqlite3_index_constraint *pIdxCons;
  struct sqlite3_index_constraint_usage *pUsage;
  WhereTerm *pTerm;
  int i, j;
  int iTerm, mxTerm;
  int nConstraint;
  int seenIn = 0;              /* True if an IN operator is seen */
  int seenVar = 0;             /* True if a non-constant constraint is seen */
  int iPhase;                  /* 0: const w/o IN, 1: const, 2: no IN,  2: IN */

  WhereLoop *pNew;
  int rc = SQLITE_OK;


  assert( (mExtra & mUnusable)==0 );
  pWInfo = pBuilder->pWInfo;
  pParse = pWInfo->pParse;
  db = pParse->db;
  pWC = pBuilder->pWC;
  pNew = pBuilder->pNew;
  pSrc = &pWInfo->pTabList->a[pNew->iTab];
  pTab = pSrc->pTab;
  assert( IsVirtual(pTab) );
  pIdxInfo = allocateIndexInfo(pParse, pWC, mUnusable, pSrc,pBuilder->pOrderBy);
  if( pIdxInfo==0 ) return SQLITE_NOMEM_BKPT;
  pNew->prereq = 0;
  pNew->rSetup = 0;
  pNew->wsFlags = WHERE_VIRTUALTABLE;
  pNew->nLTerm = 0;
  pNew->u.vtab.needFree = 0;
  pUsage = pIdxInfo->aConstraintUsage;
  nConstraint = pIdxInfo->nConstraint;
  if( whereLoopResize(db, pNew, nConstraint) ){
    sqlite3DbFree(db, pIdxInfo);
    return SQLITE_NOMEM_BKPT;
  }

  for(iPhase=0; iPhase<=3; iPhase++){
    if( !seenIn && (iPhase&1)!=0 ){
      iPhase++;
      if( iPhase>3 ) break;
    }
    if( !seenVar && iPhase>1 ) break;
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      j = pIdxCons->iTermOffset;
      pTerm = &pWC->a[j];
      switch( iPhase ){
        case 0:    /* Constants without IN operator */
          pIdxCons->usable = 0;
          if( (pTerm->eOperator & WO_IN)!=0 ){
            seenIn = 1;
          }
          if( (pTerm->prereqRight & ~mExtra)!=0 ){
            seenVar = 1;
          }else if( (pTerm->eOperator & WO_IN)==0 ){
            pIdxCons->usable = 1;
          }
          break;
        case 1:    /* Constants with IN operators */
          assert( seenIn );
          pIdxCons->usable = (pTerm->prereqRight & ~mExtra)==0;
          break;
        case 2:    /* Variables without IN */
          assert( seenVar );
          pIdxCons->usable = (pTerm->eOperator & WO_IN)==0;
          break;
        default:   /* Variables with IN */
          assert( seenVar && seenIn );
          pIdxCons->usable = 1;
          break;
      }
    }
    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 / (double)2;
    pIdxInfo->estimatedRows = 25;
    pIdxInfo->idxFlags = 0;
    pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;
    rc = vtabBestIndex(pParse, pTab, pIdxInfo);
    if( rc ) goto whereLoopAddVtab_exit;
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    pNew->prereq = mExtra;
    mxTerm = -1;
    assert( pNew->nLSlot>=nConstraint );
    for(i=0; i<nConstraint; i++) pNew->aLTerm[i] = 0;
    pNew->u.vtab.omitMask = 0;
    for(i=0; i<nConstraint; i++, pIdxCons++){
      if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
        j = pIdxCons->iTermOffset;
        if( iTerm>=nConstraint
         || j<0
         || j>=pWC->nTerm
         || pNew->aLTerm[iTerm]!=0
        ){
          rc = SQLITE_ERROR;
          sqlite3ErrorMsg(pParse, "%s.xBestIndex() malfunction", pTab->zName);
          goto whereLoopAddVtab_exit;
        }
        testcase( iTerm==nConstraint-1 );
        testcase( j==0 );
        testcase( j==pWC->nTerm-1 );
        pTerm = &pWC->a[j];
        pNew->prereq |= pTerm->prereqRight;
        assert( iTerm<pNew->nLSlot );
        pNew->aLTerm[iTerm] = pTerm;
        if( iTerm>mxTerm ) mxTerm = iTerm;
        testcase( iTerm==15 );
        testcase( iTerm==16 );
        if( iTerm<16 && pUsage[i].omit ) pNew->u.vtab.omitMask |= 1<<iTerm;
        if( (pTerm->eOperator & WO_IN)!=0 ){
          /* A virtual table that is constrained by an IN clause may not
          ** consume the ORDER BY clause because (1) the order of IN terms
          ** is not necessarily related to the order of output terms and
          ** (2) Multiple outputs from a single IN value will not merge
          ** together.  */
          pIdxInfo->orderByConsumed = 0;
          pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
        }
      }
    }
    if( i>=nConstraint ){
      pNew->nLTerm = mxTerm+1;
      assert( pNew->nLTerm<=pNew->nLSlot );
      pNew->u.vtab.idxNum = pIdxInfo->idxNum;
      pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
      pIdxInfo->needToFreeIdxStr = 0;
      pNew->u.vtab.idxStr = pIdxInfo->idxStr;
      pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
                                      pIdxInfo->nOrderBy : 0);
      pNew->rSetup = 0;
      pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
      pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);

      /* Set the WHERE_ONEROW flag if the xBestIndex() method indicated
      ** that the scan will visit at most one row. Clear it otherwise. */
      if( pIdxInfo->idxFlags & SQLITE_INDEX_SCAN_UNIQUE ){
        pNew->wsFlags |= WHERE_ONEROW;
      }else{
        pNew->wsFlags &= ~WHERE_ONEROW;
      }
      whereLoopInsert(pBuilder, pNew);
      if( pNew->u.vtab.needFree ){
        sqlite3_free(pNew->u.vtab.idxStr);
        pNew->u.vtab.needFree = 0;
      }
    }
  }  

whereLoopAddVtab_exit:
  if( pIdxInfo->needToFreeIdxStr ) sqlite3_free(pIdxInfo->idxStr);
  sqlite3DbFree(db, pIdxInfo);
  return rc;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

/*
** Add WhereLoop entries to handle OR terms.  This works for either
** btrees or virtual tables.







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    ** considered. */
    if( pSrc->pIBIndex ) break;
  }
  return rc;
}

#ifndef SQLITE_OMIT_VIRTUALTABLE

/*
** Argument pIdxInfo is already populated with all constraints that may
** be used by the virtual table identified by pBuilder->pNew->iTab. This
** function marks a subset of those constraints usable, invokes the
** xBestIndex method and adds the returned plan to pBuilder.
**
** A constraint is marked usable if:
**
**   * Argument mUsable indicates that its prerequisites are available, and
**
**   * It is not one of the operators specified in the mExclude mask passed
**     as the fourth argument (which in practice is either WO_IN or 0).
**
** Argument mExtra is a mask of tables that must be scanned before the
** virtual table in question. These are added to the plans prerequisites
** before it is added to pBuilder.
**
** Output parameter *pbIn is set to true if the plan added to pBuilder
** uses one or more WO_IN terms, or false otherwise.
*/
static int whereLoopAddVirtualOne(
  WhereLoopBuilder *pBuilder,
  Bitmask mExtra,                 /* Mask of tables that must be used. */
  Bitmask mUsable,                /* Mask of usable prereqs */
  u16 mExclude,                   /* Exclude terms for this operator */
  sqlite3_index_info *pIdxInfo,   /* Populated object for xBestIndex */
  int *pbIn                       /* OUT: True if plan uses an IN(...) op */
){
  WhereClause *pWC = pBuilder->pWC;
  struct sqlite3_index_constraint *pIdxCons;
  struct sqlite3_index_constraint_usage *pUsage = pIdxInfo->aConstraintUsage;
  int i;
  int mxTerm;
  int rc = SQLITE_OK;
  WhereLoop *pNew = pBuilder->pNew;
  Parse *pParse = pBuilder->pWInfo->pParse;
  struct SrcList_item *pSrc = &pBuilder->pWInfo->pTabList->a[pNew->iTab];
  int nConstraint = pIdxInfo->nConstraint;

  assert( (mUsable & mExtra)==mExtra );
  *pbIn = 0;
  pNew->prereq = mExtra;

  /* Set the usable flag on the subset of constraints identified by 
  ** arguments mUsable and mExclude. */
  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
  for(i=0; i<nConstraint; i++, pIdxCons++){
    WhereTerm *pTerm = &pWC->a[pIdxCons->iTermOffset];
    pIdxCons->usable = 0;
    if( (pTerm->prereqRight & mUsable)==pTerm->prereqRight 
     && (pTerm->eOperator & mExclude)==0
    ){
      pIdxCons->usable = 1;
    }
  }

  /* Initialize the output fields of the sqlite3_index_info structure */
  memset(pUsage, 0, sizeof(pUsage[0])*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 / (double)2;
  pIdxInfo->estimatedRows = 25;
  pIdxInfo->idxFlags = 0;
  pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;

  /* Invoke the virtual table xBestIndex() method */
  rc = vtabBestIndex(pParse, pSrc->pTab, pIdxInfo);
  if( rc ) return rc;

  mxTerm = -1;
  assert( pNew->nLSlot>=nConstraint );
  for(i=0; i<nConstraint; i++) pNew->aLTerm[i] = 0;
  pNew->u.vtab.omitMask = 0;
  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
  for(i=0; i<nConstraint; i++, pIdxCons++){
    int iTerm;
    if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
      WhereTerm *pTerm;
      int j = pIdxCons->iTermOffset;
      if( iTerm>=nConstraint
       || j<0
       || j>=pWC->nTerm
       || pNew->aLTerm[iTerm]!=0
      ){
        rc = SQLITE_ERROR;
        sqlite3ErrorMsg(pParse,"%s.xBestIndex() malfunction",pSrc->pTab->zName);
        return rc;
      }
      testcase( iTerm==nConstraint-1 );
      testcase( j==0 );
      testcase( j==pWC->nTerm-1 );
      pTerm = &pWC->a[j];
      pNew->prereq |= pTerm->prereqRight;
      assert( iTerm<pNew->nLSlot );
      pNew->aLTerm[iTerm] = pTerm;
      if( iTerm>mxTerm ) mxTerm = iTerm;
      testcase( iTerm==15 );
      testcase( iTerm==16 );
      if( iTerm<16 && pUsage[i].omit ) pNew->u.vtab.omitMask |= 1<<iTerm;
      if( (pTerm->eOperator & WO_IN)!=0 ){
        /* A virtual table that is constrained by an IN clause may not
        ** consume the ORDER BY clause because (1) the order of IN terms
        ** is not necessarily related to the order of output terms and
        ** (2) Multiple outputs from a single IN value will not merge
        ** together.  */
        pIdxInfo->orderByConsumed = 0;
        pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
        *pbIn = 1;
      }
    }
  }

  pNew->nLTerm = mxTerm+1;
  assert( pNew->nLTerm<=pNew->nLSlot );
  pNew->u.vtab.idxNum = pIdxInfo->idxNum;
  pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
  pIdxInfo->needToFreeIdxStr = 0;
  pNew->u.vtab.idxStr = pIdxInfo->idxStr;
  pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
      pIdxInfo->nOrderBy : 0);
  pNew->rSetup = 0;
  pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
  pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);

  /* Set the WHERE_ONEROW flag if the xBestIndex() method indicated
  ** that the scan will visit at most one row. Clear it otherwise. */
  if( pIdxInfo->idxFlags & SQLITE_INDEX_SCAN_UNIQUE ){
    pNew->wsFlags |= WHERE_ONEROW;
  }else{
    pNew->wsFlags &= ~WHERE_ONEROW;
  }
  whereLoopInsert(pBuilder, pNew);
  if( pNew->u.vtab.needFree ){
    sqlite3_free(pNew->u.vtab.idxStr);
    pNew->u.vtab.needFree = 0;
  }

  return SQLITE_OK;
}


/*
** Add all WhereLoop objects for a table of the join identified by
** pBuilder->pNew->iTab.  That table is guaranteed to be a virtual table.
**
** If there are no LEFT or CROSS JOIN joins in the query, both mExtra and
** mUnusable are set to 0. Otherwise, mExtra is a mask of all FROM clause
** entries that occur before the virtual table in the FROM clause and are
................................................................................
** mUnusable should always be configured as "not-usable" for xBestIndex.
*/
static int whereLoopAddVirtual(
  WhereLoopBuilder *pBuilder,  /* WHERE clause information */
  Bitmask mExtra,              /* Tables that must be scanned before this one */
  Bitmask mUnusable            /* Tables that must be scanned after this one */
){
  int rc = SQLITE_OK;          /* Return code */
  WhereInfo *pWInfo;           /* WHERE analysis context */
  Parse *pParse;               /* The parsing context */
  WhereClause *pWC;            /* The WHERE clause */
  struct SrcList_item *pSrc;   /* The FROM clause term to search */


  sqlite3_index_info *p;       /* Object to pass to xBestIndex() */





  int nConstraint;             /* Number of constraints in p */



  int bIn;                     /* True if plan uses IN(...) operator */
  WhereLoop *pNew;

  Bitmask mBest;               /* Tables used by best possible plan */

  assert( (mExtra & mUnusable)==0 );
  pWInfo = pBuilder->pWInfo;
  pParse = pWInfo->pParse;

  pWC = pBuilder->pWC;
  pNew = pBuilder->pNew;
  pSrc = &pWInfo->pTabList->a[pNew->iTab];

  assert( IsVirtual(pSrc->pTab) );
  p = allocateIndexInfo(pParse, pWC, mUnusable, pSrc,pBuilder->pOrderBy);
  if( p==0 ) return SQLITE_NOMEM_BKPT;

  pNew->rSetup = 0;
  pNew->wsFlags = WHERE_VIRTUALTABLE;
  pNew->nLTerm = 0;
  pNew->u.vtab.needFree = 0;
  nConstraint = p->nConstraint;
  if( whereLoopResize(pParse->db, pNew, nConstraint) ){
    sqlite3DbFree(pParse->db, p);
    return SQLITE_NOMEM_BKPT;
  }

  /* First call xBestIndex() with all constraints usable. */
  rc = whereLoopAddVirtualOne(pBuilder, mExtra, (Bitmask)(-1), 0, p, &bIn);
  mBest = pNew->prereq & ~mExtra;

  /* If the call to xBestIndex() with all terms enabled produced a plan
  ** that does not require any source tables, there is no point in making
  ** any further calls - if the xBestIndex() method is sane they will all
  ** return the same plan anyway.
  */
  if( mBest ){
    int seenZero = 0;             /* True if a plan with no prereqs seen */
    int seenZeroNoIN = 0;         /* Plan with no prereqs and no IN(...) seen */
    Bitmask mPrev = 0;
    Bitmask mBestNoIn = 0;

    /* If the plan produced by the earlier call uses an IN(...) term, call
    ** xBestIndex again, this time with IN(...) terms disabled. */
    if( rc==SQLITE_OK && bIn ){
      rc = whereLoopAddVirtualOne(pBuilder, mExtra, (Bitmask)-1, WO_IN, p,&bIn);
      mBestNoIn = pNew->prereq & ~mExtra;
      if( mBestNoIn==0 ){
        seenZero = 1;
        if( bIn==0 ) seenZeroNoIN = 1;
      }
    }

    /* Call xBestIndex once for each distinct value of (prereqRight & ~mExtra) 
    ** in the set of terms that apply to the current virtual table.  */
    while( rc==SQLITE_OK ){
      int i;
      Bitmask mNext = (Bitmask)(-1);
      assert( mNext>0 );
      for(i=0; i<nConstraint; i++){
        Bitmask mThis = (
            pWC->a[p->aConstraint[i].iTermOffset].prereqRight & ~mExtra
        );
        if( mThis>mPrev && mThis<mNext ) mNext = mThis;
      }
      mPrev = mNext;
      if( mNext==(Bitmask)(-1) ) break;
      if( mNext==mBest || mNext==mBestNoIn ) continue;
      rc = whereLoopAddVirtualOne(pBuilder, mExtra, mNext, 0, p, &bIn);
      if( pNew->prereq==mExtra ){
        seenZero = 1;
        if( bIn==0 ) seenZeroNoIN = 1;
      }
    }

    /* If the calls to xBestIndex() in the above loop did not find a plan
    ** that requires no source tables at all (i.e. one guaranteed to be
    ** usable), make a call here with all source tables disabled */
    if( rc==SQLITE_OK && seenZero==0 ){
      rc = whereLoopAddVirtualOne(pBuilder, mExtra, mExtra, 0, p, &bIn);
      if( bIn==0 ) seenZeroNoIN = 1;
    }

    /* If the calls to xBestIndex() have so far failed to find a plan
    ** that requires no source tables at all and does not use an IN(...)
    ** operator, make a final call to obtain one here.  */
    if( rc==SQLITE_OK && seenZeroNoIN==0 ){
      rc = whereLoopAddVirtualOne(pBuilder, mExtra, mExtra, WO_IN, p, &bIn);
    }
  }

  if( p->needToFreeIdxStr ) sqlite3_free(p->idxStr);
  sqlite3DbFree(pParse->db, p);






















































  return rc;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

/*
** Add WhereLoop entries to handle OR terms.  This works for either
** btrees or virtual tables.

Added test/bestindex2.test.































































































































































































































































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# 2016 March 3
#
# 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.
#
#***********************************************************************

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix bestindex2


#-------------------------------------------------------------------------
# Virtual table callback for table named $tbl, with the columns specified
# by list argument $cols. e.g. if the function is invoked as:
#
#   vtab_cmd t1 {a b c} ...
#
# The table created is:
#
#      "CREATE TABLE t1 (a, b, c)"
#
# The tables xBestIndex method behaves as if all possible combinations of
# "=" constraints (but no others) may be optimized. The cost of a full table
# scan is:
#
#      "WHERE 1"                "cost 1000000 rows 1000000"
#
# If one or more "=" constraints are in use, the cost and estimated number
# of rows returned are both is (11 - nCons)*1000, where nCons is the number
# of constraints used. e.g.
#
#   "WHERE a=? AND b=?"    ->   "cost  900 rows  900"
#   "WHERE c=? AND b<?"    ->   "cost 1000 rows 1000"
#  
proc vtab_cmd {tbl cols method args} {
  switch -- $method {
    xConnect {
      return "CREATE TABLE $tbl ([join $cols ,])"
    }
    xBestIndex {
      foreach {clist orderby mask} $args {}

      set cons [list]
      set used [list]

      for {set i 0} {$i < [llength $clist]} {incr i} {
        array unset C
        array set C [lindex $clist $i]
        if {$C(op)=="eq" && $C(usable) && [lsearch $cons $C(column)]<0} {
          lappend used use $i
          lappend cons $C(column)
        }
      }

      set nCons [llength $cons]
      if {$nCons==0} {
        return "cost 1000000 rows 1000000"
      } else {
        set cost [expr (11-$nCons) * 1000]
        set ret [concat $used "cost $cost rows $cost"]

        set txt [list]
        foreach c $cons { lappend txt "[lindex $cols $c]=?" }
        lappend ret idxstr "indexed([join $txt { AND }])"

        return $ret
      }
    }
  }
  return ""
}

register_tcl_module db

do_execsql_test 1.0 {
  CREATE VIRTUAL TABLE t1 USING tcl("vtab_cmd t1 {a b}");
  CREATE VIRTUAL TABLE t2 USING tcl("vtab_cmd t2 {c d}");
  CREATE VIRTUAL TABLE t3 USING tcl("vtab_cmd t3 {e f}");
}

do_eqp_test 1.1 {
  SELECT * FROM t1 WHERE a='abc'
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:indexed(a=?)}
}
do_eqp_test 1.2 {
  SELECT * FROM t1 WHERE a='abc' AND b='def'
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:indexed(a=? AND b=?)}
}
do_eqp_test 1.3 {
  SELECT * FROM t1 WHERE a='abc' AND a='def'
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:indexed(a=?)}
}
do_eqp_test 1.4 {
  SELECT * FROM t1,t2 WHERE c=a
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:} 
  0 1 1 {SCAN TABLE t2 VIRTUAL TABLE INDEX 0:indexed(c=?)}
}

do_eqp_test 1.5 {
  SELECT * FROM t1, t2 CROSS JOIN t3 WHERE t2.c = +t1.b AND t3.e=t2.d
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:} 
  0 1 1 {SCAN TABLE t2 VIRTUAL TABLE INDEX 0:indexed(c=?)} 
  0 2 2 {SCAN TABLE t3 VIRTUAL TABLE INDEX 0:indexed(e=?)}
}

# This is the one that fails (as of 2016/3/3).
#
do_eqp_test 1.6 {
  SELECT * FROM t1, t2, t3 WHERE t2.c = +t1.b AND t3.e = t2.d
} {
  0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:} 
  0 1 1 {SCAN TABLE t2 VIRTUAL TABLE INDEX 0:indexed(c=?)} 
  0 2 2 {SCAN TABLE t3 VIRTUAL TABLE INDEX 0:indexed(e=?)}
}

finish_test