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Comment:If a binary operator in a WHERE clause that should be performed with no affinity conversions applied to its operands (see http://www.sqlite.org/datatype3.html) is optimized by index lookup, do not apply any conversions to the key value before looking it up in the index. Fix for [93fb9f89d6].
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SHA1: e72186f2d68d28c2e0c32894f9adb28c155b5f63
User & Date: dan 2009-08-13 19:21:17
Original Comment: If a binary operator in a WHERE clause that should be performed with no affinity conversions applied to its operands (see http://www.sqlite.org/datatype3.html) is optimized by index lookup, do not apply any conversions to the key value before looking it up in the index. Fix for 93fb9f89d6.
References
2016-09-03
15:24 Ticket [199df416] Different answer with and without index on IN operator with type mismatch status still Open with 6 other changes artifact: 6a413497 user: drh
2009-08-19
15:21 Fixed ticket [93fb9f89]: Index causes incorrect WHERE clause evaluation plus 3 other changes artifact: 10bc6825 user: drh
Context
2009-08-13
19:54
Tweak to the new whereB.test file to make it more consistent. check-in: 06098505 user: drh tags: trunk
19:21
If a binary operator in a WHERE clause that should be performed with no affinity conversions applied to its operands (see http://www.sqlite.org/datatype3.html) is optimized by index lookup, do not apply any conversions to the key value before looking it up in the index. Fix for [93fb9f89d6]. check-in: e72186f2 user: dan tags: trunk
18:14
Enhancements to the whereB.test to check more affinity corner cases. check-in: 10484598 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/delete.c.

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    }else{
      sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);
      sqlite3ColumnDefault(v, pTab, idx, -1);
    }
  }
  if( doMakeRec ){
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);
    sqlite3IndexAffinityStr(v, pIdx);
    sqlite3ExprCacheAffinityChange(pParse, regBase, nCol+1);
  }
  sqlite3ReleaseTempRange(pParse, regBase, nCol+1);
  return regBase;
}

/* Make sure "isView" gets undefined in case this file becomes part of
** the amalgamation - so that subsequent files do not see isView as a
** macro. */
#undef isView







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    }else{
      sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);
      sqlite3ColumnDefault(v, pTab, idx, -1);
    }
  }
  if( doMakeRec ){
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);
    sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v, pIdx), 0);
    sqlite3ExprCacheAffinityChange(pParse, regBase, nCol+1);
  }
  sqlite3ReleaseTempRange(pParse, regBase, nCol+1);
  return regBase;
}

/* Make sure "isView" gets undefined in case this file becomes part of
** the amalgamation - so that subsequent files do not see isView as a
** macro. */
#undef isView

Changes to src/insert.c.

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  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite)?1:0, pTab->zName);
  sqlite3VdbeAddOp3(v, opcode, iCur, pTab->tnum, iDb);
  sqlite3VdbeChangeP4(v, -1, SQLITE_INT_TO_PTR(pTab->nCol), P4_INT32);
  VdbeComment((v, "%s", pTab->zName));
}

/*
** Set P4 of the most recently inserted opcode to a column affinity
** string for index pIdx. A column affinity string has one character
** for each column in the table, according to the affinity of the column:
**
**  Character      Column affinity
**  ------------------------------
**  'a'            TEXT
**  'b'            NONE
**  'c'            NUMERIC
**  'd'            INTEGER
**  'e'            REAL
**
** An extra 'b' is appended to the end of the string to cover the
** rowid that appears as the last column in every index.




*/
void sqlite3IndexAffinityStr(Vdbe *v, Index *pIdx){
  if( !pIdx->zColAff ){
    /* The first time a column affinity string for a particular index is
    ** required, it is allocated and populated here. It is then stored as
    ** a member of the Index structure for subsequent use.
    **
    ** The column affinity string will eventually be deleted by
    ** sqliteDeleteIndex() when the Index structure itself is cleaned
................................................................................
    */
    int n;
    Table *pTab = pIdx->pTable;
    sqlite3 *db = sqlite3VdbeDb(v);
    pIdx->zColAff = (char *)sqlite3Malloc(pIdx->nColumn+2);
    if( !pIdx->zColAff ){
      db->mallocFailed = 1;
      return;
    }
    for(n=0; n<pIdx->nColumn; n++){
      pIdx->zColAff[n] = pTab->aCol[pIdx->aiColumn[n]].affinity;
    }
    pIdx->zColAff[n++] = SQLITE_AFF_NONE;
    pIdx->zColAff[n] = 0;
  }
 
  sqlite3VdbeChangeP4(v, -1, pIdx->zColAff, 0);
}

/*
** Set P4 of the most recently inserted opcode to a column affinity
** string for table pTab. A column affinity string has one character
** for each column indexed by the index, according to the affinity of the
** column:
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
      }else{
        sqlite3VdbeAddOp2(v, OP_SCopy, regData+idx, regIdx+i);
      }
    }
    sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regIdx, pIdx->nColumn+1, aRegIdx[iCur]);
    sqlite3IndexAffinityStr(v, pIdx);
    sqlite3ExprCacheAffinityChange(pParse, regIdx, pIdx->nColumn+1);

    /* Find out what action to take in case there is an indexing conflict */
    onError = pIdx->onError;
    if( onError==OE_None ){ 
      sqlite3ReleaseTempRange(pParse, regIdx, pIdx->nColumn+1);
      continue;  /* pIdx is not a UNIQUE index */







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  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite)?1:0, pTab->zName);
  sqlite3VdbeAddOp3(v, opcode, iCur, pTab->tnum, iDb);
  sqlite3VdbeChangeP4(v, -1, SQLITE_INT_TO_PTR(pTab->nCol), P4_INT32);
  VdbeComment((v, "%s", pTab->zName));
}

/*
** Return a pointer to the column affinity string associated with index
** pIdx. A column affinity string has one character for each column in 
** the table, according to the affinity of the column:
**
**  Character      Column affinity
**  ------------------------------
**  'a'            TEXT
**  'b'            NONE
**  'c'            NUMERIC
**  'd'            INTEGER
**  'e'            REAL
**
** An extra 'b' is appended to the end of the string to cover the
** rowid that appears as the last column in every index.
**
** Memory for the buffer containing the column index affinity string
** is managed along with the rest of the Index structure. It will be
** released when sqlite3DeleteIndex() is called.
*/
const char *sqlite3IndexAffinityStr(Vdbe *v, Index *pIdx){
  if( !pIdx->zColAff ){
    /* The first time a column affinity string for a particular index is
    ** required, it is allocated and populated here. It is then stored as
    ** a member of the Index structure for subsequent use.
    **
    ** The column affinity string will eventually be deleted by
    ** sqliteDeleteIndex() when the Index structure itself is cleaned
................................................................................
    */
    int n;
    Table *pTab = pIdx->pTable;
    sqlite3 *db = sqlite3VdbeDb(v);
    pIdx->zColAff = (char *)sqlite3Malloc(pIdx->nColumn+2);
    if( !pIdx->zColAff ){
      db->mallocFailed = 1;
      return 0;
    }
    for(n=0; n<pIdx->nColumn; n++){
      pIdx->zColAff[n] = pTab->aCol[pIdx->aiColumn[n]].affinity;
    }
    pIdx->zColAff[n++] = SQLITE_AFF_NONE;
    pIdx->zColAff[n] = 0;
  }
 
  return pIdx->zColAff;
}

/*
** Set P4 of the most recently inserted opcode to a column affinity
** string for table pTab. A column affinity string has one character
** for each column indexed by the index, according to the affinity of the
** column:
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
      }else{
        sqlite3VdbeAddOp2(v, OP_SCopy, regData+idx, regIdx+i);
      }
    }
    sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regIdx, pIdx->nColumn+1, aRegIdx[iCur]);
    sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v, pIdx), 0);
    sqlite3ExprCacheAffinityChange(pParse, regIdx, pIdx->nColumn+1);

    /* Find out what action to take in case there is an indexing conflict */
    onError = pIdx->onError;
    if( onError==OE_None ){ 
      sqlite3ReleaseTempRange(pParse, regIdx, pIdx->nColumn+1);
      continue;  /* pIdx is not a UNIQUE index */

Changes to src/sqliteInt.h.

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*/
#define getVarint32(A,B)  (u8)((*(A)<(u8)0x80) ? ((B) = (u32)*(A)),1 : sqlite3GetVarint32((A), (u32 *)&(B)))
#define putVarint32(A,B)  (u8)(((u32)(B)<(u32)0x80) ? (*(A) = (unsigned char)(B)),1 : sqlite3PutVarint32((A), (B)))
#define getVarint    sqlite3GetVarint
#define putVarint    sqlite3PutVarint


void sqlite3IndexAffinityStr(Vdbe *, Index *);
void sqlite3TableAffinityStr(Vdbe *, Table *);
char sqlite3CompareAffinity(Expr *pExpr, char aff2);
int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity);
char sqlite3ExprAffinity(Expr *pExpr);
int sqlite3Atoi64(const char*, i64*);
void sqlite3Error(sqlite3*, int, const char*,...);
void *sqlite3HexToBlob(sqlite3*, const char *z, int n);







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*/
#define getVarint32(A,B)  (u8)((*(A)<(u8)0x80) ? ((B) = (u32)*(A)),1 : sqlite3GetVarint32((A), (u32 *)&(B)))
#define putVarint32(A,B)  (u8)(((u32)(B)<(u32)0x80) ? (*(A) = (unsigned char)(B)),1 : sqlite3PutVarint32((A), (B)))
#define getVarint    sqlite3GetVarint
#define putVarint    sqlite3PutVarint


const char *sqlite3IndexAffinityStr(Vdbe *, Index *);
void sqlite3TableAffinityStr(Vdbe *, Table *);
char sqlite3CompareAffinity(Expr *pExpr, char aff2);
int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity);
char sqlite3ExprAffinity(Expr *pExpr);
int sqlite3Atoi64(const char*, i64*);
void sqlite3Error(sqlite3*, int, const char*,...);
void *sqlite3HexToBlob(sqlite3*, const char *z, int n);

Changes to src/where.c.

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        disableTerm(pLevel, pOther);
      }
    }
  }
}

/*
** Apply the affinities associated with the first n columns of index
** pIdx to the values in the n registers starting at base.




*/
static void codeApplyAffinity(Parse *pParse, int base, int n, Index *pIdx){
  if( n>0 ){
    Vdbe *v = pParse->pVdbe;
    assert( v!=0 );
    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
    sqlite3IndexAffinityStr(v, pIdx);

    sqlite3ExprCacheAffinityChange(pParse, base, n);
  }
}


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
................................................................................
**
** This routine always allocates at least one memory cell and returns
** the index of that memory cell. The code that
** calls this routine will use that memory cell to store the termination
** key value of the loop.  If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.















*/
static int codeAllEqualityTerms(
  Parse *pParse,        /* Parsing context */
  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
  WhereClause *pWC,     /* The WHERE clause */
  Bitmask notReady,     /* Which parts of FROM have not yet been coded */
  int nExtraReg         /* Number of extra registers to allocate */

){
  int nEq = pLevel->plan.nEq;   /* The number of == or IN constraints to code */
  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
  Index *pIdx;                  /* The index being used for this loop */
  int iCur = pLevel->iTabCur;   /* The cursor of the table */
  WhereTerm *pTerm;             /* A single constraint term */
  int j;                        /* Loop counter */
  int regBase;                  /* Base register */
  int nReg;                     /* Number of registers to allocate */


  /* This module is only called on query plans that use an index. */
  assert( pLevel->plan.wsFlags & WHERE_INDEXED );
  pIdx = pLevel->plan.u.pIdx;

  /* Figure out how many memory cells we will need then allocate them.
  */
  regBase = pParse->nMem + 1;
  nReg = pLevel->plan.nEq + nExtraReg;
  pParse->nMem += nReg;






  /* Evaluate the equality constraints
  */
  assert( pIdx->nColumn>=nEq );
  for(j=0; j<nEq; j++){
    int r1;
    int k = pIdx->aiColumn[j];
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);




    }
  }


  return regBase;
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
................................................................................
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */
    Index *pIdx;         /* The index we will be using */
    int iIdxCur;         /* The VDBE cursor for the index */
    int nExtraReg = 0;   /* Number of extra registers needed */
    int op;              /* Instruction opcode */


    pIdx = pLevel->plan.u.pIdx;
    iIdxCur = pLevel->iIdxCur;
    k = pIdx->aiColumn[nEq];     /* Column for inequality constraints */

    /* If this loop satisfies a sort order (pOrderBy) request that 
    ** was passed to this function to implement a "SELECT min(x) ..." 
................................................................................
      nExtraReg = 1;
    }

    /* Generate code to evaluate all constraint terms using == or IN
    ** and store the values of those terms in an array of registers
    ** starting at regBase.
    */

    regBase = codeAllEqualityTerms(pParse, pLevel, pWC, notReady, nExtraReg);

    addrNxt = pLevel->addrNxt;


    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
................................................................................
    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){

      sqlite3ExprCode(pParse, pRangeStart->pExpr->pRight, regBase+nEq);
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);








      nConstraint++;
    }else if( isMinQuery ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint, pIdx);
    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
    assert( op!=0 );
    testcase( op==OP_Rewind );
    testcase( op==OP_Last );
    testcase( op==OP_SeekGt );
    testcase( op==OP_SeekGe );
    testcase( op==OP_SeekLe );
................................................................................
                      SQLITE_INT_TO_PTR(nConstraint), P4_INT32);

    /* Load the value for the inequality constraint at the end of the
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){

      sqlite3ExprCacheRemove(pParse, regBase+nEq);
      sqlite3ExprCode(pParse, pRangeEnd->pExpr->pRight, regBase+nEq);
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);









      codeApplyAffinity(pParse, regBase, nEq+1, pIdx);
      nConstraint++;
    }

    /* Top of the loop body */
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);

    /* Check if the index cursor is past the end of the range. */







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        disableTerm(pLevel, pOther);
      }
    }
  }
}

/*
** Code an OP_Affinity opcode to apply the column affinity string zAff
** to the n registers starting at base. 
**
** Buffer zAff was allocated using sqlite3DbMalloc(). It is the 
** responsibility of this function to arrange for it to be eventually
** freed using sqlite3DbFree().
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){

  Vdbe *v = pParse->pVdbe;
  assert( v!=0 );
  sqlite3VdbeAddOp2(v, OP_Affinity, base, n);

  sqlite3VdbeChangeP4(v, -1, zAff, P4_DYNAMIC);
  sqlite3ExprCacheAffinityChange(pParse, base, n);

}


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
................................................................................
**
** This routine always allocates at least one memory cell and returns
** the index of that memory cell. The code that
** calls this routine will use that memory cell to store the termination
** key value of the loop.  If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
**
** Before returning, *pzAff is set to point to a buffer containing a
** copy of the column affinity string of the index allocated using
** sqlite3DbMalloc(). Except, entries in the copy of the string associated
** with equality constraints that use NONE affinity are set to
** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
**
**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
**
** In the example above, the index on t1(a) has TEXT affinity. But since
** the right hand side of the equality constraint (t2.b) has NONE affinity,
** no conversion should be attempted before using a t2.b value as part of
** a key to search the index. Hence the first byte in the returned affinity
** string in this example would be set to SQLITE_AFF_NONE.
*/
static int codeAllEqualityTerms(
  Parse *pParse,        /* Parsing context */
  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
  WhereClause *pWC,     /* The WHERE clause */
  Bitmask notReady,     /* Which parts of FROM have not yet been coded */
  int nExtraReg,        /* Number of extra registers to allocate */
  char **pzAff          /* OUT: Set to point to affinity string */
){
  int nEq = pLevel->plan.nEq;   /* The number of == or IN constraints to code */
  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
  Index *pIdx;                  /* The index being used for this loop */
  int iCur = pLevel->iTabCur;   /* The cursor of the table */
  WhereTerm *pTerm;             /* A single constraint term */
  int j;                        /* Loop counter */
  int regBase;                  /* Base register */
  int nReg;                     /* Number of registers to allocate */
  char *zAff;                   /* Affinity string to return */

  /* This module is only called on query plans that use an index. */
  assert( pLevel->plan.wsFlags & WHERE_INDEXED );
  pIdx = pLevel->plan.u.pIdx;

  /* Figure out how many memory cells we will need then allocate them.
  */
  regBase = pParse->nMem + 1;
  nReg = pLevel->plan.nEq + nExtraReg;
  pParse->nMem += nReg;

  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
  if( !zAff ){
    pParse->db->mallocFailed = 1;
  }

  /* Evaluate the equality constraints
  */
  assert( pIdx->nColumn>=nEq );
  for(j=0; j<nEq; j++){
    int r1;
    int k = pIdx->aiColumn[j];
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
      if( zAff 
       && sqlite3CompareAffinity(pTerm->pExpr->pRight, zAff[j])==SQLITE_AFF_NONE
      ){
        zAff[j] = SQLITE_AFF_NONE;
      }
    }
  }
  *pzAff = zAff;
  return regBase;
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
................................................................................
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */
    Index *pIdx;         /* The index we will be using */
    int iIdxCur;         /* The VDBE cursor for the index */
    int nExtraReg = 0;   /* Number of extra registers needed */
    int op;              /* Instruction opcode */
    char *zAff;

    pIdx = pLevel->plan.u.pIdx;
    iIdxCur = pLevel->iIdxCur;
    k = pIdx->aiColumn[nEq];     /* Column for inequality constraints */

    /* If this loop satisfies a sort order (pOrderBy) request that 
    ** was passed to this function to implement a "SELECT min(x) ..." 
................................................................................
      nExtraReg = 1;
    }

    /* Generate code to evaluate all constraint terms using == or IN
    ** and store the values of those terms in an array of registers
    ** starting at regBase.
    */
    regBase = codeAllEqualityTerms(
        pParse, pLevel, pWC, notReady, nExtraReg, &zAff
    );
    addrNxt = pLevel->addrNxt;


    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
................................................................................
    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
      if( zAff 
       && sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE
      ){
        /* Since the comparison is to be performed with no conversions applied
        ** to the operands, set the affinity to apply to pRight to 
        ** SQLITE_AFF_NONE.  */
        zAff[nConstraint] = SQLITE_AFF_NONE;
      }
      nConstraint++;
    }else if( isMinQuery ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint, zAff);
    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
    assert( op!=0 );
    testcase( op==OP_Rewind );
    testcase( op==OP_Last );
    testcase( op==OP_SeekGt );
    testcase( op==OP_SeekGe );
    testcase( op==OP_SeekLe );
................................................................................
                      SQLITE_INT_TO_PTR(nConstraint), P4_INT32);

    /* Load the value for the inequality constraint at the end of the
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
      zAff = sqlite3DbStrDup(pParse->db, zAff);
      if( zAff 
       && sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE
      ){
        /* Since the comparison is to be performed with no conversions applied
        ** to the operands, set the affinity to apply to pRight to 
        ** SQLITE_AFF_NONE.  */
        zAff[nConstraint] = SQLITE_AFF_NONE;
      }
      codeApplyAffinity(pParse, regBase, nEq+1, zAff);
      nConstraint++;
    }

    /* Top of the loop body */
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);

    /* Check if the index cursor is past the end of the range. */