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Overview
Comment:Add the OP_IfNoHope and OP_SeekHit opcodes used to reduce the number of unnecessary sqlite3BtreeMovetoUnpacked() calls when checking for an early exit on IN-operator loops. Futher optimizations are likely possible here.
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SHA3-256: 6bf251af4347165a470d39457d61ab6d2a06c206db8f30bd8be5dbb388ae8a5b
User & Date: drh 2018-06-05 20:45:20
Context
2018-06-07
14:32
Merge recent trunk enhancements. check-in: e9d7bf4f7b user: drh tags: multikey-opt-idea
2018-06-05
20:45
Add the OP_IfNoHope and OP_SeekHit opcodes used to reduce the number of unnecessary sqlite3BtreeMovetoUnpacked() calls when checking for an early exit on IN-operator loops. Futher optimizations are likely possible here. check-in: 6bf251af43 user: drh tags: multikey-opt-idea
15:16
Use an OP_NotFound opcode to cancel futile IN operators early. The current implementation is suboptimal because it always runs teh OP_NotFound. This still needs to be enhanced to only do the OP_NotFound if no results have been seen on the current loop. check-in: 87a9fc504f user: drh tags: multikey-opt-idea
Changes
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Changes to src/vdbe.c.

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    goto jump_to_p2;
  }else if( eqOnly ){
    assert( pOp[1].opcode==OP_IdxLT || pOp[1].opcode==OP_IdxGT );
    pOp++; /* Skip the OP_IdxLt or OP_IdxGT that follows */
  }
  break;
}




















/* Opcode: Found P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
** P4>0 then register P3 is the first of P4 registers that form an unpacked
** record.
................................................................................
** falls through to the next instruction and P1 is left pointing at the
** matching entry.
**
** This operation leaves the cursor in a state where it cannot be
** advanced in either direction.  In other words, the Next and Prev
** opcodes do not work after this operation.
**
** See also: Found, NotExists, NoConflict



























*/
/* Opcode: NoConflict P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
** P4>0 then register P3 is the first of P4 registers that form an unpacked
** record.
................................................................................
**
** This operation leaves the cursor in a state where it cannot be
** advanced in either direction.  In other words, the Next and Prev
** opcodes do not work after this operation.
**
** See also: NotFound, Found, NotExists
*/








case OP_NoConflict:     /* jump, in3 */
case OP_NotFound:       /* jump, in3 */
case OP_Found: {        /* jump, in3 */
  int alreadyExists;
  int takeJump;
  int ii;
  VdbeCursor *pC;







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    goto jump_to_p2;
  }else if( eqOnly ){
    assert( pOp[1].opcode==OP_IdxLT || pOp[1].opcode==OP_IdxGT );
    pOp++; /* Skip the OP_IdxLt or OP_IdxGT that follows */
  }
  break;
}

/* Opcode: SeekHit P1 P2 * * *
** Synopsis: seekHit=P2
**
** Set the seekHit flag on cursor P1 to the value in P2.
** The seekHit flag is used by the IfNoHope opcode.
**
** P1 must be a valid b-tree cursor.  P2 must be a boolean value,
** either 0 or 1.
*/
case OP_SeekHit: {
  VdbeCursor *pC;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pOp->p2==0 || pOp->p2==1 );
  pC->seekHit = pOp->p2 & 1;
  break;
}

/* Opcode: Found P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
** P4>0 then register P3 is the first of P4 registers that form an unpacked
** record.
................................................................................
** falls through to the next instruction and P1 is left pointing at the
** matching entry.
**
** This operation leaves the cursor in a state where it cannot be
** advanced in either direction.  In other words, the Next and Prev
** opcodes do not work after this operation.
**
** See also: Found, NotExists, NoConflict, IfNoHope
*/
/* Opcode: IfNoHope P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** Register P3 is the first of P4 registers that form an unpacked
** record.
**
** Cursor P1 is on an index btree.  If the seekHit flag is set on P1, then
** this opcode is a no-op.  But if the seekHit flag of P1 is clear, then
** check to see if there is any entry in P1 that matches the
** prefix identified by P3 and P4.  If no entry matches the prefix,
** jump to P2.  Otherwise fall through.
**
** This opcode behaves like OP_NotFound if the seekHit
** flag is clear and it behaves like OP_Noop if the seekHit flag is set.
**
** This opcode is used in IN clause processing for a multi-column key.
** If an IN clause is attached to an element of the key other than the
** left-most element, and if there are no matches on the most recent
** seek over the whole key, then it might be that one of the key element
** to the left is prohibiting a match, and hence there is "no hope" of
** any match regardless of how many IN clause elements are checked.
** In such a case, we abandon the IN clause search early, using this
** opcode.  The opcode name comes from the fact that the
** jump is taken if there is "no hope" of achieving a match.
**
** See also: NotFound, SeekHit
*/
/* Opcode: NoConflict P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]
**
** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
** P4>0 then register P3 is the first of P4 registers that form an unpacked
** record.
................................................................................
**
** This operation leaves the cursor in a state where it cannot be
** advanced in either direction.  In other words, the Next and Prev
** opcodes do not work after this operation.
**
** See also: NotFound, Found, NotExists
*/
case OP_IfNoHope: {     /* jump, in3 */
  VdbeCursor *pC;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  if( pC->seekHit ) break;
  /* Fall through into OP_NotFound */
}
case OP_NoConflict:     /* jump, in3 */
case OP_NotFound:       /* jump, in3 */
case OP_Found: {        /* jump, in3 */
  int alreadyExists;
  int takeJump;
  int ii;
  VdbeCursor *pC;

Changes to src/vdbeInt.h.

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#ifdef SQLITE_DEBUG
  u8 seekOp;              /* Most recent seek operation on this cursor */
  u8 wrFlag;              /* The wrFlag argument to sqlite3BtreeCursor() */
#endif
  Bool isEphemeral:1;     /* True for an ephemeral table */
  Bool useRandomRowid:1;  /* Generate new record numbers semi-randomly */
  Bool isOrdered:1;       /* True if the table is not BTREE_UNORDERED */

  Btree *pBtx;            /* Separate file holding temporary table */
  i64 seqCount;           /* Sequence counter */
  int *aAltMap;           /* Mapping from table to index column numbers */

  /* Cached OP_Column parse information is only valid if cacheStatus matches
  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of
  ** CACHE_STALE (0) and so setting cacheStatus=CACHE_STALE guarantees that







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#ifdef SQLITE_DEBUG
  u8 seekOp;              /* Most recent seek operation on this cursor */
  u8 wrFlag;              /* The wrFlag argument to sqlite3BtreeCursor() */
#endif
  Bool isEphemeral:1;     /* True for an ephemeral table */
  Bool useRandomRowid:1;  /* Generate new record numbers semi-randomly */
  Bool isOrdered:1;       /* True if the table is not BTREE_UNORDERED */
  Bool seekHit:1;         /* See the OP_SeekHit and OP_IfNoHope opcodes */
  Btree *pBtx;            /* Separate file holding temporary table */
  i64 seqCount;           /* Sequence counter */
  int *aAltMap;           /* Mapping from table to index column numbers */

  /* Cached OP_Column parse information is only valid if cacheStatus matches
  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of
  ** CACHE_STALE (0) and so setting cacheStatus=CACHE_STALE guarantees that

Changes to src/where.c.

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      struct InLoop *pIn;
      int j;
      sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
      for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
        sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
        if( pIn->eEndLoopOp!=OP_Noop ){
          if( pIn->nPrefix ){
            sqlite3VdbeAddOp4Int(v, OP_NotFound, pLevel->iIdxCur,
                              sqlite3VdbeCurrentAddr(v)+2,
                              pIn->iBase, pIn->nPrefix);
            VdbeCoverage(v);
          }
          sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);
          VdbeCoverage(v);
          VdbeCoverageIf(v, pIn->eEndLoopOp==OP_PrevIfOpen);







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      struct InLoop *pIn;
      int j;
      sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
      for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
        sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
        if( pIn->eEndLoopOp!=OP_Noop ){
          if( pIn->nPrefix ){
            sqlite3VdbeAddOp4Int(v, OP_IfNoHope, pLevel->iIdxCur,
                              sqlite3VdbeCurrentAddr(v)+2,
                              pIn->iBase, pIn->nPrefix);
            VdbeCoverage(v);
          }
          sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);
          VdbeCoverage(v);
          VdbeCoverageIf(v, pIn->eEndLoopOp==OP_PrevIfOpen);

Changes to src/wherecode.c.

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    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
      /* The skip-scan logic inside the call to codeAllEqualityConstraints()
      ** above has already left the cursor sitting on the correct row,
      ** so no further seeking is needed */
    }else{



      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      assert( op!=0 );
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      VdbeCoverage(v);
      VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
      VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
      VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
................................................................................
      op = aEndOp[bRev*2 + endEq];
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
    }





    /* Seek the table cursor, if required */
    if( omitTable ){
      /* pIdx is a covering index.  No need to access the main table. */
    }else if( HasRowid(pIdx->pTable) ){
      if( (pWInfo->wctrlFlags & WHERE_SEEK_TABLE) || (
          (pWInfo->wctrlFlags & WHERE_SEEK_UNIQ_TABLE) 







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    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
      /* The skip-scan logic inside the call to codeAllEqualityConstraints()
      ** above has already left the cursor sitting on the correct row,
      ** so no further seeking is needed */
    }else{
      if( pLoop->wsFlags & WHERE_IN_ABLE ){
        sqlite3VdbeAddOp1(v, OP_SeekHit, iIdxCur);
      }
      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      assert( op!=0 );
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      VdbeCoverage(v);
      VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
      VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
      VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
................................................................................
      op = aEndOp[bRev*2 + endEq];
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
    }

    if( pLoop->wsFlags & WHERE_IN_ABLE ){
      sqlite3VdbeAddOp2(v, OP_SeekHit, iIdxCur, 1);
    }

    /* Seek the table cursor, if required */
    if( omitTable ){
      /* pIdx is a covering index.  No need to access the main table. */
    }else if( HasRowid(pIdx->pTable) ){
      if( (pWInfo->wctrlFlags & WHERE_SEEK_TABLE) || (
          (pWInfo->wctrlFlags & WHERE_SEEK_UNIQ_TABLE)