SQLite

#define WHERE_ROWID_RANGE  0x00002000  /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ    0x00010000  /* x=EXPR or x IN (...) or x IS NULL */
#define WHERE_COLUMN_RANGE 0x00020000  /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN    0x00040000  /* x IN (...) */
#define WHERE_COLUMN_NULL  0x00080000  /* x IS NULL */
#define WHERE_INDEXED      0x000f0000  /* Anything that uses an index */
#define WHERE_NOT_FULLSCAN 0x100f3000  /* Does not do a full table scan */
#define WHERE_IN_ABLE      0x080f1000  /* Able to support an IN operator */
#define WHERE_TOP_LIMIT    0x00100000  /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT    0x00200000  /* x>EXPR or x>=EXPR constraint */
#define WHERE_BOTH_LIMIT   0x00300000  /* Both x>EXPR and x<EXPR */
#define WHERE_IDX_ONLY     0x00400000  /* Use index only - omit table */
#define WHERE_ORDERED      0x00800000  /* Output will appear in correct order */
#define WHERE_REVERSE      0x01000000  /* Scan in reverse order */
#define WHERE_UNIQUE       0x02000000  /* Selects no more than one row */

  /* Count the number of possible WHERE clause constraints referring
  ** to this virtual table */
  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    if( pTerm->leftCursor != pSrc->iCursor ) continue;
    assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
    testcase( pTerm->eOperator==WO_IN );
    testcase( pTerm->eOperator==WO_ISNULL );
    if( pTerm->eOperator & (WO_ISNULL) ) continue;
    if( pTerm->wtFlags & TERM_VNULL ) continue;
    nTerm++;
  }

  /* If the ORDER BY clause contains only columns in the current 
  ** virtual table then allocate space for the aOrderBy part of
  ** the sqlite3_index_info structure.

  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
  *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
  *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
  *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
                                                                   pUsage;

  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    u8 op;
    if( pTerm->leftCursor != pSrc->iCursor ) continue;
    assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
    testcase( pTerm->eOperator==WO_IN );
    testcase( pTerm->eOperator==WO_ISNULL );
    if( pTerm->eOperator & (WO_ISNULL) ) continue;
    if( pTerm->wtFlags & TERM_VNULL ) continue;
    pIdxCons[j].iColumn = pTerm->u.leftColumn;
    pIdxCons[j].iTermOffset = i;
    op = (u8)pTerm->eOperator;
    if( op==WO_IN ) op = WO_EQ;
    pIdxCons[j].op = op;
    /* The direct assignment in the previous line is possible only because
    ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
    ** following asserts verify this fact. */
    assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
    assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
    assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
    assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
    assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
    assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
    assert( pTerm->eOperator & (WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
    j++;
  }
  for(i=0; i<nOrderBy; i++){
    Expr *pExpr = pOrderBy->a[i].pExpr;
    pIdxOrderBy[i].iColumn = pExpr->iColumn;
    pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
  }

  Table *pTab = pSrc->pTab;
  sqlite3_index_info *pIdxInfo;
  struct sqlite3_index_constraint *pIdxCons;
  struct sqlite3_index_constraint_usage *pUsage;
  WhereTerm *pTerm;
  int i, j;
  int nOrderBy;
  int bAllowIN;                   /* Allow IN optimizations */
  double rCost;

  /* Make sure wsFlags is initialized to some sane value. Otherwise, if the 
  ** malloc in allocateIndexInfo() fails and this function returns leaving
  ** wsFlags in an uninitialized state, the caller may behave unpredictably.
  */
  memset(&p->cost, 0, sizeof(p->cost));

  /* The module name must be defined. Also, by this point there must
  ** be a pointer to an sqlite3_vtab structure. Otherwise
  ** sqlite3ViewGetColumnNames() would have picked up the error. 
  */
  assert( pTab->azModuleArg && pTab->azModuleArg[0] );
  assert( sqlite3GetVTable(pParse->db, pTab) );

  /* Try once or twice.  On the first attempt, allow IN optimizations.
  ** If an IN optimization is accepted by the virtual table xBestIndex
  ** method, but the  pInfo->aConstrainUsage.omit flag is not set, then
  ** the query will not work because it might allow duplicate rows in
  ** output.  In that case, run the xBestIndex method a second time

  ** without the IN constraints.  Usually this loop only runs once.









  ** The loop will exit using a "break" statement.





  */
  for(bAllowIN=1; 1; bAllowIN--){
    assert( bAllowIN==0 || bAllowIN==1 );

    /* Set the aConstraint[].usable fields and initialize all 
    ** output variables to zero.
    **
    ** aConstraint[].usable is true for constraints where the right-hand
    ** side contains only references to tables to the left of the current
    ** table.  In other words, if the constraint is of the form:
    **
    **           column = expr
    **
    ** and we are evaluating a join, then the constraint on column is 
    ** only valid if all tables referenced in expr occur to the left
    ** of the table containing column.
    **
    ** The aConstraints[] array contains entries for all constraints
    ** on the current table.  That way we only have to compute it once
    ** even though we might try to pick the best index multiple times.
    ** For each attempt at picking an index, the order of tables in the
    ** join might be different so we have to recompute the usable flag
    ** each time.
    */
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    pUsage = pIdxInfo->aConstraintUsage;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      j = pIdxCons->iTermOffset;
      pTerm = &pWC->a[j];
      if( (pTerm->prereqRight&p->notReady)==0
       && (bAllowIN || pTerm->eOperator!=WO_IN)
      ){
        pIdxCons->usable = 1;
      }else{
        pIdxCons->usable = 0;
      }
    }
    memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
    if( pIdxInfo->needToFreeIdxStr ){
      sqlite3_free(pIdxInfo->idxStr);
    }
    pIdxInfo->idxStr = 0;
    pIdxInfo->idxNum = 0;
    pIdxInfo->needToFreeIdxStr = 0;
    pIdxInfo->orderByConsumed = 0;
    /* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
    pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
    nOrderBy = pIdxInfo->nOrderBy;
    if( !p->pOrderBy ){
      pIdxInfo->nOrderBy = 0;
    }
  
    if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
      return;
    }
  
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      if( pUsage[i].argvIndex>0 ){
        j = pIdxCons->iTermOffset;
        pTerm = &pWC->a[j];
        p->cost.used |= pTerm->prereqRight;
        if( pTerm->eOperator==WO_IN && pUsage[i].omit==0 ){
          /* Do not attempt to use an IN constraint if the virtual table
          ** says that the equivalent EQ constraint cannot be safely omitted.
          ** If we do attempt to use such a constraint, some rows might be
          ** repeated in the output. */
          break;
        }
      }
    }
    if( i>=pIdxInfo->nConstraint ) break;
  }
  
  /* If there is an ORDER BY clause, and the selected virtual table index
  ** does not satisfy it, increase the cost of the scan accordingly. This
  ** matches the processing for non-virtual tables in bestBtreeIndex().
  */
  rCost = pIdxInfo->estimatedCost;
  if( p->pOrderBy && pIdxInfo->orderByConsumed==0 ){
    rCost += estLog(rCost)*rCost;

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if(  (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
    /* Case 0:  The table is a virtual-table.  Use the VFilter and VNext
    **          to access the data.
    */
    int iReg;   /* P3 Value for OP_VFilter */
    int addrNotFound;
    sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
    int nConstraint = pVtabIdx->nConstraint;
    struct sqlite3_index_constraint_usage *aUsage =
                                                pVtabIdx->aConstraintUsage;
    const struct sqlite3_index_constraint *aConstraint =
                                                pVtabIdx->aConstraint;

    sqlite3ExprCachePush(pParse);
    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
    addrNotFound = pLevel->addrBrk;
    for(j=1; j<=nConstraint; j++){
      for(k=0; k<nConstraint; k++){
        if( aUsage[k].argvIndex==j ){
          WhereTerm *pTerm = &pWC->a[aConstraint[k].iTermOffset];
          int iTarget = iReg+j+1;
          if( pTerm->eOperator & WO_IN ){
            codeEqualityTerm(pParse, pTerm, pLevel, iTarget);
            addrNotFound = pLevel->addrNxt;
          }else{
            sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
          }
          break;
        }
      }
      if( k==nConstraint ) break;
    }
    sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg, pVtabIdx->idxStr,
                      pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
    pVtabIdx->needToFreeIdxStr = 0;
    for(j=0; j<nConstraint; j++){
      if( aUsage[j].omit ){
        int iTerm = aConstraint[j].iTermOffset;
        disableTerm(pLevel, &pWC->a[iTerm]);
      }

} {15 {} 16}
do_test vtab1.13-3 {
  execsql { 
    SELECT * FROM echo_c WHERE b IS NULL AND a = 15;
  }
} {15 {} 16}


do_test vtab1-14.001 {
  execsql {SELECT rowid, * FROM echo_c WHERE +rowid IN (1,2,3)}
} {1 3 G H 2 {} 15 16 3 15 {} 16}
do_test vtab1-14.002 {
  execsql {SELECT rowid, * FROM echo_c WHERE rowid IN (1,2,3)}
} {1 3 G H 2 {} 15 16 3 15 {} 16}
do_test vtab1-14.003 {
  execsql {SELECT rowid, * FROM echo_c WHERE +rowid IN (0,1,5,2,'a',3,NULL)}
} {1 3 G H 2 {} 15 16 3 15 {} 16}
do_test vtab1-14.004 {
  execsql {SELECT rowid, * FROM echo_c WHERE rowid IN (0,1,5,'a',2,3,NULL)}
} {1 3 G H 2 {} 15 16 3 15 {} 16}
do_test vtab1-14.005 {
  execsql {SELECT rowid, * FROM echo_c WHERE rowid NOT IN (0,1,5,'a',2,3)}
} {}
do_test vtab1-14.006 {
  execsql {SELECT rowid, * FROM echo_c WHERE rowid NOT IN (0,5,'a',2,3)}
} {1 3 G H}
do_test vtab1-14.007 {
  execsql {SELECT rowid, * FROM echo_c WHERE +rowid NOT IN (0,5,'a',2,3,NULL)}
} {}
do_test vtab1-14.008 {
  execsql {SELECT rowid, * FROM echo_c WHERE rowid NOT IN (0,5,'a',2,3,NULL)}
} {}
do_test vtab1-14.011 {
  execsql {SELECT * FROM echo_c WHERE +a IN (1,3,8,'x',NULL,15,24)}
} {3 G H 15 {} 16}
do_test vtab1-14.012 {
  execsql {SELECT * FROM echo_c WHERE a IN (1,3,8,'x',NULL,15,24)}
} {3 G H 15 {} 16}
do_test vtab1-14.013 {
  execsql {SELECT * FROM echo_c WHERE a NOT IN (1,8,'x',15,24)}
} {3 G H}
do_test vtab1-14.014 {
  execsql {SELECT * FROM echo_c WHERE a NOT IN (1,8,'x',NULL,15,24)}
} {}
do_test vtab1-14.015 {
  execsql {SELECT * FROM echo_c WHERE +a NOT IN (1,8,'x',NULL,15,24)}
} {}



do_test vtab1-14.1 {
  execsql { DELETE FROM c }
  set echo_module ""
  execsql { SELECT * FROM echo_c WHERE rowid IN (1, 2, 3) }
  set echo_module
} {/xBestIndex {SELECT rowid, . FROM 'c' WHERE rowid = .} xFilter {SELECT rowid, . FROM 'c' WHERE rowid = .} 1/}

do_test vtab1-14.2 {
  set echo_module ""
  execsql { SELECT * FROM echo_c WHERE rowid = 1 }
  set echo_module
} [list xBestIndex {SELECT rowid, * FROM 'c' WHERE rowid = ?} xFilter {SELECT rowid, * FROM 'c' WHERE rowid = ?} 1]

do_test vtab1-14.3 {
  set echo_module ""
  execsql { SELECT * FROM echo_c WHERE a = 1 }
  set echo_module
} [list xBestIndex {SELECT rowid, * FROM 'c' WHERE a = ?} xFilter {SELECT rowid, * FROM 'c' WHERE a = ?} 1]

do_test vtab1-14.4 {
  set echo_module ""
  execsql { SELECT * FROM echo_c WHERE a IN (1, 2) }
  set echo_module
} {/xBestIndex {SELECT rowid, . FROM 'c' WHERE a = .} xFilter {SELECT rowid, . FROM 'c' WHERE a = .} 1/}

do_test vtab1-15.1 {
  execsql {
    CREATE TABLE t1(a, b, c);
    CREATE VIRTUAL TABLE echo_t1 USING echo(t1);
  }
} {}