SQLite

**
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** of the code in this file is, therefore, important.  See other comments
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** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.731 2008/04/18 09:01:16 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor

case OP_Affinity: {
  char *zAffinity = pOp->p4.z;
  Mem *pData0 = &p->aMem[pOp->p1];
  Mem *pLast = &pData0[pOp->p2-1];
  Mem *pRec;

  for(pRec=pData0; pRec<=pLast; pRec++){

    applyAffinity(pRec, zAffinity[pRec-pData0], encoding);
  }
  break;
}

/* Opcode: MakeRecord P1 P2 P3 P4 *
**

  int i = pOp->p1;
  assert( i>=0 && i<p->nCursor );
  sqlite3VdbeFreeCursor(p, p->apCsr[i]);
  p->apCsr[i] = 0;
  break;
}

/* Opcode: MoveGe P1 P2 P3 * *
**

** Use the value in register P3 as a key.  Reposition



** cursor P1 so that it points to the smallest entry that is greater
** than or equal to the key in register P3.
** If there are no records greater than or equal to the key and P2 
** is not zero, then jump to P2.
**
** A special feature of this opcode (and different from the
** related OP_MoveGt, OP_MoveLt, and OP_MoveLe) is that if P2 is
** zero and P1 is an SQL table (a b-tree with integer keys) then
** the seek is deferred until it is actually needed.  It might be
** the case that the cursor is never accessed.  By deferring the
** seek, we avoid unnecessary seeks.
**
** See also: Found, NotFound, Distinct, MoveLt, MoveGt, MoveLe
*/
/* Opcode: MoveGt P1 P2 P3 * *
**

** Use the value in register P3 as a key.  Reposition



** cursor P1 so that it points to the smallest entry that is greater
** than the key in register P3.
** If there are no records greater than the key 
** then jump to P2.
**
** See also: Found, NotFound, Distinct, MoveLt, MoveGe, MoveLe
*/
/* Opcode: MoveLt P1 P2 P3 * * 
**

** Use the value in register P3 as a key.  Reposition



** cursor P1 so that it points to the largest entry that is less
** than the key in register P3.
** If there are no records less than the key
** then jump to P2.
**
** See also: Found, NotFound, Distinct, MoveGt, MoveGe, MoveLe
*/
/* Opcode: MoveLe P1 P2 P3 P4 *
**
** P4 is always an integer value. If it is zero, then use the value in
** register P3 as a key. Reposition cursor P1 so that it points to the
** largest entry that is less than or equal to the key. If there are no 
** records less than or eqal to the key then jump to P2.
**
** If the integer value in operand P4 is non-zero, then P3 is the first
** of a contiguous array of P4 memory cells that form an unpacked index
** key. In this case the unpacked key is used instead of the value of
** register P3 in the procedure described above.
**
** See also: Found, NotFound, Distinct, MoveGt, MoveGe, MoveLt
*/
case OP_MoveLt:         /* jump, in3 */
case OP_MoveLe:         /* jump, in3 */
case OP_MoveGe:         /* jump, in3 */
case OP_MoveGt: {       /* jump, in3 */

      rc = sqlite3BtreeMoveto(pC->pCursor, 0, 0, (u64)iKey, 0, &res);
      if( rc!=SQLITE_OK ){
        goto abort_due_to_error;
      }
      pC->lastRowid = iKey;
      pC->rowidIsValid = res==0;
    }else{

      int nField = ((pOp->p4type==P4_INT32)?pOp->p4.i:0);
      assert( pIn3->flags&MEM_Blob || nField>0 );
      if( nField==0 ){
        ExpandBlob(pIn3);
        rc = sqlite3BtreeMoveto(pC->pCursor, pIn3->z, 0, pIn3->n, 0, &res);
      }else{
        UnpackedRecord r;
        r.pKeyInfo = pC->pKeyInfo;
        r.nField = nField;
        r.needFree = 0;
        r.needDestroy = 0;
        r.aMem = &p->aMem[pOp->p3];
        rc = sqlite3BtreeMoveto(pC->pCursor, 0, &r, 0, 0, &res);
      }
      if( rc!=SQLITE_OK ){
        goto abort_due_to_error;
      }
      pC->rowidIsValid = 0;
    }
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.300 2008/04/18 09:01:16 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

        disableTerm(pLevel, pOther);
      }
    }
  }
}

/*
** Generate code that builds a probe for an index.
**
** There should be nColumn values on the stack.  The index
** to be probed is pIdx.  Pop the values from the stack and
** replace them all with a single record that is the index
** problem.
*/
static void buildIndexProbe(
  Parse *pParse,  /* Parsing and code generation context */
  int nColumn,    /* The number of columns to check for NULL */
  Index *pIdx,    /* Index that we will be searching */
  int regSrc,     /* Take values from this register */
  int regDest     /* Write the result into this register */
){
  Vdbe *v = pParse->pVdbe;
  assert( regSrc>0 );
  assert( regDest>0 );
  assert( v!=0 );
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regSrc, nColumn, regDest);
  sqlite3IndexAffinityStr(v, pIdx);
  sqlite3ExprCacheAffinityChange(pParse, regSrc, nColumn);

}


/*
** 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.

        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
        /* sqlite3VdbeAddOp2(v, OP_SCopy, pLevel->iMem, 0); */
        sqlite3VdbeAddOp3(v, testOp, pLevel->iMem, brk, r1);
        sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
        sqlite3ReleaseTempReg(pParse, r1);
      }
    }else if( pLevel->flags & WHERE_COLUMN_RANGE ){


      /* Case 3: The WHERE clause term that refers to the right-most
      **         column of the index is an inequality.  For example, if
      **         the index is on (x,y,z) and the WHERE clause is of the
      **         form "x=5 AND y<10" then this case is used.  Only the

      **         right-most column can be an inequality - the rest must
      **         use the "==" and "IN" operators.












      **
      **         This case is also used when there are no WHERE clause
      **         constraints but an index is selected anyway, in order
      **         to force the output order to conform to an ORDER BY.
      */
      int aStartOp[] = {
        0,
        0,
        OP_Rewind,           /* 2: (!start_constraints && startEq && !bRev) */
        OP_Last,             /* 3: (!start_constraints && startEq && bRev)  */
        OP_MoveGt,           /* 4: (start_constraints  && !startEq && !bRev) */
        OP_MoveLt,           /* 5: (start_constraints  && !startEq && bRev) */
        OP_MoveGe,           /* 6: (start_constraints  &&  startEq && !bRev) */
        OP_MoveLe            /* 7: (start_constraints  &&  startEq && bRev) */
      };
      int aEndOp[] = {
        OP_Noop,             /* 0: () */
        OP_IdxGE,            /* 1: (end_constraints && !bRev) */
        OP_IdxLT             /* 2: (end_constraints && bRev) */
      };
      int nEq = pLevel->nEq;
      int isMinQuery = 0;          /* If this is an optimized SELECT min(x).. */
      int regBase;                 /* Base register holding constraint values */
      int r1;                      /* Temp register */

       && (pLevel->flags&WHERE_ORDERBY)
       && (pIdx->nColumn>nEq)
       && (pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq])
      ){
        isMinQuery = 1;
      }

      /* Find the inequality constraint terms for the start and end 
      ** of the range. 
      */
      if( pLevel->flags & WHERE_TOP_LIMIT ){
        pRangeEnd = findTerm(&wc, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
      }
      if( pLevel->flags & WHERE_BTM_LIMIT ){
        pRangeStart = findTerm(&wc, iCur, k, notReady, (WO_GT|WO_GE), pIdx);

        ptr++;
      }else if( isMinQuery ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
        ptr++;
        startEq = 0;
        start_constraints = 1;
      }
      sqlite3VdbeAddOp2(v, OP_Affinity, regBase, (int)ptr);
      sqlite3IndexAffinityStr(v, pIdx);
      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase, ptr, P4_INT32);

      /* Load the value for the inequality constraint at the end of the
      ** range (if any).
      */
      ptr = (char *)(sqlite3_intptr_t)nEq;
      if( pRangeEnd ){
        sqlite3ExprCode(pParse, pRangeEnd->pExpr->pRight, regBase+nEq);
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);

        ptr++;
      }
      sqlite3VdbeAddOp2(v, OP_Affinity, regBase, (int)ptr);
      sqlite3IndexAffinityStr(v, pIdx);

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

      /* Check if the index cursor is past the end of the range. */
      op = aEndOp[((pRangeEnd || nEq)?1:0) * (1 + bRev)];
      sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase, ptr, P4_INT32);

      /* Record the instruction used to terminate the loop. Disable 
      ** WHERE clause terms made redundant by the index range scan.
      */
      pLevel->op = bRev ? OP_Prev : OP_Next;
      pLevel->p1 = iIdxCur;
      disableTerm(pLevel, pRangeStart);
      disableTerm(pLevel, pRangeEnd);
    }else if( pLevel->flags & WHERE_COLUMN_EQ ){
      /* Case 4:  There is an index and all terms of the WHERE clause that
      **          refer to the index using the "==" or "IN" operators.
      */
      int start;
      int nEq = pLevel->nEq;
      int isMinQuery = 0;      /* If this is an optimized SELECT min(x) ... */
      int regBase;             /* Base register of array holding constraints */
      int r1;

      /* Generate code to evaluate all constraint terms using == or IN
      ** and leave the values of those terms on the stack.
      */
      regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 1);
      nxt = pLevel->nxt;

      if( (wflags&WHERE_ORDERBY_MIN)!=0
       && (pLevel->flags&WHERE_ORDERBY) 
       && (pIdx->nColumn>nEq)
       && (pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq])
      ){
        isMinQuery = 1;
        buildIndexProbe(pParse, nEq, pIdx, regBase, pLevel->iMem);
        sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
        r1 = ++pParse->nMem;
        buildIndexProbe(pParse, nEq+1, pIdx, regBase, r1);
      }else{
        /* Generate a single key that will be used to both start and 
        ** terminate the search
        */
        r1 = pLevel->iMem;
        buildIndexProbe(pParse, nEq, pIdx, regBase, r1);
      }

      /* Generate code (1) to move to the first matching element of the table.
      ** Then generate code (2) that jumps to "nxt" after the cursor is past
      ** the last matching element of the table.  The code (1) is executed
      ** once to initialize the search, the code (2) is executed before each
      ** iteration of the scan to see if the scan has finished. */
      if( bRev ){
        /* Scan in reverse order */
        int op;
        if( isMinQuery ){
          op = OP_MoveLt;
        }else{
          op = OP_MoveLe;
        }
        sqlite3VdbeAddOp3(v, op, iIdxCur, nxt, r1);
        start = sqlite3VdbeAddOp3(v, OP_IdxLT, iIdxCur, nxt, pLevel->iMem);
        pLevel->op = OP_Prev;
      }else{
        /* Scan in the forward order */
        int op;
        if( isMinQuery ){
          op = OP_MoveGt;
        }else{
          op = OP_MoveGe;
        }
        sqlite3VdbeAddOp3(v, op, iIdxCur, nxt, r1);
        start = sqlite3VdbeAddOp3(v, OP_IdxGE, iIdxCur, nxt, pLevel->iMem);
        sqlite3VdbeChangeP5(v, 1);
        pLevel->op = OP_Next;
      }
      if( !omitTable ){
        r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, r1);
        sqlite3VdbeAddOp3(v, OP_MoveGe, iCur, 0, r1);  /* Deferred seek */
        sqlite3ReleaseTempReg(pParse, r1);
      }
      pLevel->p1 = iIdxCur;
      pLevel->p2 = start;
    }else{
      /* Case 5:  There is no usable index.  We must do a complete
      **          scan of the entire table.
      */
      assert( omitTable==0 );
      assert( bRev==0 );
      pLevel->op = OP_Next;