/ Changes On Branch in-scan-vs-index
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Changes In Branch in-scan-vs-index Excluding Merge-Ins

This is equivalent to a diff from 43f7ddad80 to dc4172e6b8

2020-09-30
18:06
Improved query optimization for multi-column indexes where the second or later columns are constrained by an IN operator and the earlier index columns limit the search to a small number of rows. Use the new OP_SeekScan opcode which does scanning of the relevant range of the index but gives up and falls back to doing a seek if the number of rows scanned grows to large, in order to guard against pathological cases where the estimated number of rows to be scanned is far too small. (check-in: 4a43430fd2 user: drh tags: trunk)
18:03
For the OP_SeekScan opcode, adjust the number of steps run before giving up based on the estimated number of comparisons needed to perform a seek. (Closed-Leaf check-in: dc4172e6b8 user: drh tags: in-scan-vs-index)
09:17
Better understanding of savepoint code (check-in: ce6d8d6215 user: shearer tags: trunk)
00:48
Add an sqlite3FaultSim() call to btreeNext() to make it easier to simulate I/O errors in calls to sqlite3BtreeNext(), and in OP_SeekScan. (check-in: 29cca775d3 user: drh tags: in-scan-vs-index)
2020-09-28
19:51
Revisiting the IN-scan optimization to try to fix it for the corner case where the statistics deceive the query planner into using a scan when an indexed lookup would be better. This check-in changes the code generation to do the IN-scan using a new OP_SeekScan opcode. That new opcode is designed to abandon the scan and fall back to a seek if it doesn't find a match quickly enough. For this work-in-progress check-in, OP_SeekScan is still a no-op and OP_SeekGE still ends up doing all the work. (check-in: d720b6981e user: drh tags: in-scan-vs-index)
15:49
Small performance improvement and size reduction by reducing the size of the WhereTerm object. (check-in: 43f7ddad80 user: drh tags: trunk)
13:34
Avoid the possibility of integer overflow on the --pagecache option to the CLI. See [forum:10a2892377|forum post 10a2892377] (check-in: d3d13df31a user: drh tags: trunk)

Changes to src/btree.c.

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      pCur->eState = CURSOR_VALID;
      if( pCur->skipNext>0 ) return SQLITE_OK;
    }
  }

  pPage = pCur->pPage;
  idx = ++pCur->ix;
  if( !pPage->isInit ){
    /* The only known way for this to happen is for there to be a
    ** recursive SQL function that does a DELETE operation as part of a
    ** SELECT which deletes content out from under an active cursor
    ** in a corrupt database file where the table being DELETE-ed from
    ** has pages in common with the table being queried.  See TH3
    ** module cov1/btree78.test testcase 220 (2018-06-08) for an
    ** example. */







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      pCur->eState = CURSOR_VALID;
      if( pCur->skipNext>0 ) return SQLITE_OK;
    }
  }

  pPage = pCur->pPage;
  idx = ++pCur->ix;
  if( !pPage->isInit || sqlite3FaultSim(412) ){
    /* The only known way for this to happen is for there to be a
    ** recursive SQL function that does a DELETE operation as part of a
    ** SELECT which deletes content out from under an active cursor
    ** in a corrupt database file where the table being DELETE-ed from
    ** has pages in common with the table being queried.  See TH3
    ** module cov1/btree78.test testcase 220 (2018-06-08) for an
    ** example. */

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: SeekHit P1 P2 P3 * *
** Synopsis: set P2<=seekHit<=P3
**
** Increase or decrease the seekHit value for cursor P1, if necessary,
** so that it is no less than P2 and no greater than P3.
**
................................................................................
    int i;
    for(i=0; i<r.nField; i++){
      assert( memIsValid(&r.aMem[i]) );
      REGISTER_TRACE(pOp->p3+i, &aMem[pOp->p3+i]);
    }
  }
#endif
  res = 0;  /* Not needed.  Only used to silence a warning. */























  rc = sqlite3VdbeIdxKeyCompare(db, pC, &r, &res);

  assert( (OP_IdxLE&1)==(OP_IdxLT&1) && (OP_IdxGE&1)==(OP_IdxGT&1) );
  if( (pOp->opcode&1)==(OP_IdxLT&1) ){
    assert( pOp->opcode==OP_IdxLE || pOp->opcode==OP_IdxLT );
    res = -res;
  }else{
    assert( pOp->opcode==OP_IdxGE || pOp->opcode==OP_IdxGT );
    res++;
  }
  VdbeBranchTaken(res>0,2);
  if( rc ) goto abort_due_to_error;
  if( res>0 ) goto jump_to_p2;
  break;
}

/* Opcode: Destroy P1 P2 P3 * *
**
** Delete an entire database table or index whose root page in the database







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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: SeekScan  P1 * * * *
** Synopsis: Scan-ahead up to P1 rows
**
** This opcode is a prefix opcode to OP_SeekGE.  In other words, this
** opcode must be immediately followed by OP_SeekGE.  Furthermore, the
** OP_SeekGE must be followed by OP_IdxGT.  These constraints are
** checked by assert() statements.
**
** This opcode uses the P1 through P4 operands of the subsequent
** OP_SeekGE.  In the text that follows, the operands of the subsequent
** OP_SeekGE opcode are denoted as SeekOP.P1 through SeekOP.P4.   Only
** the P1 operand of this opcode is used, and it is denoted as This.P1.
**
** This opcode helps to optimize IN operators on a multi-column index
** where the IN operator is on the later terms of the index by avoiding
** unnecessary seeks on the btree, substituting steps to the next row
** of the b-tree instead.  A correct answer is obtained if this opcode
** is omitted or is a no-op.
**
** The SeekGE.P3 and SeekGE.P4 operands identify an unpacked key which
** is the desired entry that we want the cursor SeekGE.P1 to be pointing
** to.  Call this SeekGE.P4/P5 row the "target".
**
** If the SeekGE.P1 cursor is not currently pointing to a valid row,
** then this opcode is a no-op and control passes through into the OP_SeekGE.
**
** If the SeekGE.P1 cursor is pointing to a valid row, then that row
** might be the target row, or it might be near and slightly before the
** target row.  This opcode attempts to position the cursor on the target
** row by, perhaps stepping by invoking sqlite3BtreeStep() on the cursor
** between 0 and This.P1 times.
**
** There are three possible outcomes from this opcode:<ol>
**
** <li> If after This.P1 steps, the cursor is still point to a place that
**      is earlier in the btree than the target row,
**      then fall through into the subsquence OP_SeekGE opcode.
**
** <li> If the cursor is successfully moved to the target row by 0 or more
**      sqlite3BtreeNext() calls, then jump to the first instruction after the
**      OP_IdxGT opcode - or in other words, skip the next two opcodes.
**
** <li> If the cursor ends up past the target row (indicating the the target
**      row does not exist in the btree) then jump to SeekOP.P2. 
** </ol>
*/
case OP_SeekScan: {
  VdbeCursor *pC;
  int res;
  int n;
  UnpackedRecord r;

  assert( pOp[1].opcode==OP_SeekGE );
  assert( pOp[2].opcode==OP_IdxGT );
  assert( pOp[1].p1==pOp[2].p1 );
  assert( pOp[1].p2==pOp[2].p2 );
  assert( pOp[1].p3==pOp[2].p3 );
  assert( pOp[1].p4.i==pOp[2].p4.i );
  assert( pOp->p1>0 );
  pC = p->apCsr[pOp[1].p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( !pC->isTable );
  if( !sqlite3BtreeCursorIsValidNN(pC->uc.pCursor) ){
#ifdef SQLITE_DEBUG
     if( db->flags&SQLITE_VdbeTrace ){
       printf("... cursor not valid - fall through\n");
     }        
#endif
    break;
  }
  n = pOp->p1;
  assert( n>=1 );
  r.pKeyInfo = pC->pKeyInfo;
  r.nField = (u16)pOp[1].p4.i;
  r.default_rc = 0;
  r.aMem = &aMem[pOp[1].p3];
#ifdef SQLITE_DEBUG
  {
    int i;
    for(i=0; i<r.nField; i++){
      assert( memIsValid(&r.aMem[i]) );
      REGISTER_TRACE(pOp[1].p3+i, &aMem[pOp[1].p3+i]);
    }
  }
#endif
  res = 0;  /* Not needed.  Only used to silence a warning. */
  while(1){
    rc = sqlite3VdbeIdxKeyCompare(db, pC, &r, &res);
    if( rc ) goto abort_due_to_error;
    if( res>0 ){
      seekscan_search_fail:
#ifdef SQLITE_DEBUG
      if( db->flags&SQLITE_VdbeTrace ){
        printf("... %d steps and then skip\n", pOp->p1 - n);
      }        
#endif
      VdbeBranchTaken(1,3);
      pOp++;
      goto jump_to_p2;
    }
    if( res==0 ){
#ifdef SQLITE_DEBUG
      if( db->flags&SQLITE_VdbeTrace ){
        printf("... %d steps and then success\n", pOp->p1 - n);
      }        
#endif
      VdbeBranchTaken(2,3);
      pOp += 2;
      break;
    }
    if( n<=0 ){
#ifdef SQLITE_DEBUG
      if( db->flags&SQLITE_VdbeTrace ){
        printf("... fall through after %d steps\n", pOp->p1);
      }        
#endif
      VdbeBranchTaken(0,3);
      break;
    }
    n--;
    rc = sqlite3BtreeNext(pC->uc.pCursor, 0);
    if( rc ){
      if( rc==SQLITE_DONE ){
        rc = SQLITE_OK;
        goto seekscan_search_fail;
      }else{
        goto abort_due_to_error;
      }
    }
  }
  
  break;
}


/* Opcode: SeekHit P1 P2 P3 * *
** Synopsis: set P2<=seekHit<=P3
**
** Increase or decrease the seekHit value for cursor P1, if necessary,
** so that it is no less than P2 and no greater than P3.
**
................................................................................
    int i;
    for(i=0; i<r.nField; i++){
      assert( memIsValid(&r.aMem[i]) );
      REGISTER_TRACE(pOp->p3+i, &aMem[pOp->p3+i]);
    }
  }
#endif


  /* Inlined version of sqlite3VdbeIdxKeyCompare() */
  {
    i64 nCellKey = 0;
    BtCursor *pCur;
    Mem m;

    assert( pC->eCurType==CURTYPE_BTREE );
    pCur = pC->uc.pCursor;
    assert( sqlite3BtreeCursorIsValid(pCur) );
    nCellKey = sqlite3BtreePayloadSize(pCur);
    /* nCellKey will always be between 0 and 0xffffffff because of the way
    ** that btreeParseCellPtr() and sqlite3GetVarint32() are implemented */
    if( nCellKey<=0 || nCellKey>0x7fffffff ){
      rc = SQLITE_CORRUPT_BKPT;
      goto abort_due_to_error;
    }
    sqlite3VdbeMemInit(&m, db, 0);
    rc = sqlite3VdbeMemFromBtreeZeroOffset(pCur, (u32)nCellKey, &m);
    if( rc ) goto abort_due_to_error;
    res = sqlite3VdbeRecordCompareWithSkip(m.n, m.z, &r, 0);
    sqlite3VdbeMemRelease(&m);
  }
  /* End of inlined sqlite3VdbeIdxKeyCompare() */

  assert( (OP_IdxLE&1)==(OP_IdxLT&1) && (OP_IdxGE&1)==(OP_IdxGT&1) );
  if( (pOp->opcode&1)==(OP_IdxLT&1) ){
    assert( pOp->opcode==OP_IdxLE || pOp->opcode==OP_IdxLT );
    res = -res;
  }else{
    assert( pOp->opcode==OP_IdxGE || pOp->opcode==OP_IdxGT );
    res++;
  }
  VdbeBranchTaken(res>0,2);
  assert( rc==SQLITE_OK );
  if( res>0 ) goto jump_to_p2;
  break;
}

/* Opcode: Destroy P1 P2 P3 * *
**
** Delete an entire database table or index whose root page in the database

Changes to src/where.c.

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        M = pProbe->aiRowLogEst[saved_nEq];
        logK = estLog(nIn);
        safetyMargin = 10;  /* TUNING: extra weight for indexed IN */
        if( M + logK + safetyMargin < nIn + rLogSize ){
          WHERETRACE(0x40,
            ("Scan preferred over IN operator on column %d of \"%s\" (%d<%d)\n",
             saved_nEq, pProbe->zName, M+logK+10, nIn+rLogSize));
          continue;
        }else{
          WHERETRACE(0x40,
            ("IN operator preferred on column %d of \"%s\" (%d>=%d)\n",
             saved_nEq, pProbe->zName, M+logK+10, nIn+rLogSize));
        }
      }
      pNew->wsFlags |= WHERE_COLUMN_IN;
................................................................................
      assert( iIndexCur>=0 );
      if( op ){
        sqlite3VdbeAddOp3(v, op, iIndexCur, pIx->tnum, iDb);
        sqlite3VdbeSetP4KeyInfo(pParse, pIx);
        if( (pLoop->wsFlags & WHERE_CONSTRAINT)!=0
         && (pLoop->wsFlags & (WHERE_COLUMN_RANGE|WHERE_SKIPSCAN))==0
         && (pLoop->wsFlags & WHERE_BIGNULL_SORT)==0

         && (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0
         && pWInfo->eDistinct!=WHERE_DISTINCT_ORDERED
        ){
          sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ);
        }
        VdbeComment((v, "%s", pIx->zName));
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
................................................................................
      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 ){


            assert( pLoop->wsFlags & WHERE_IN_EARLYOUT );
            if( pLevel->iLeftJoin ){
              /* For LEFT JOIN queries, cursor pIn->iCur may not have been
              ** opened yet. This occurs for WHERE clauses such as
              ** "a = ? AND b IN (...)", where the index is on (a, b). If
              ** the RHS of the (a=?) is NULL, then the "b IN (...)" may
              ** never have been coded, but the body of the loop run to
              ** return the null-row. So, if the cursor is not open yet,
              ** jump over the OP_Next or OP_Prev instruction about to
              ** be coded.  */
              sqlite3VdbeAddOp2(v, OP_IfNotOpen, pIn->iCur, 
                  sqlite3VdbeCurrentAddr(v) + 2 + 
                     ((pLoop->wsFlags & WHERE_VIRTUALTABLE)==0)
              );
              VdbeCoverage(v);
            }
            if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 ){

              sqlite3VdbeAddOp4Int(v, OP_IfNoHope, pLevel->iIdxCur,
                  sqlite3VdbeCurrentAddr(v)+2,
                  pIn->iBase, pIn->nPrefix);
              VdbeCoverage(v);
            }
          }
          sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);







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        M = pProbe->aiRowLogEst[saved_nEq];
        logK = estLog(nIn);
        safetyMargin = 10;  /* TUNING: extra weight for indexed IN */
        if( M + logK + safetyMargin < nIn + rLogSize ){
          WHERETRACE(0x40,
            ("Scan preferred over IN operator on column %d of \"%s\" (%d<%d)\n",
             saved_nEq, pProbe->zName, M+logK+10, nIn+rLogSize));
          pNew->wsFlags |= WHERE_IN_SEEKSCAN;
        }else{
          WHERETRACE(0x40,
            ("IN operator preferred on column %d of \"%s\" (%d>=%d)\n",
             saved_nEq, pProbe->zName, M+logK+10, nIn+rLogSize));
        }
      }
      pNew->wsFlags |= WHERE_COLUMN_IN;
................................................................................
      assert( iIndexCur>=0 );
      if( op ){
        sqlite3VdbeAddOp3(v, op, iIndexCur, pIx->tnum, iDb);
        sqlite3VdbeSetP4KeyInfo(pParse, pIx);
        if( (pLoop->wsFlags & WHERE_CONSTRAINT)!=0
         && (pLoop->wsFlags & (WHERE_COLUMN_RANGE|WHERE_SKIPSCAN))==0
         && (pLoop->wsFlags & WHERE_BIGNULL_SORT)==0
         && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0
         && (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0
         && pWInfo->eDistinct!=WHERE_DISTINCT_ORDERED
        ){
          sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ);
        }
        VdbeComment((v, "%s", pIx->zName));
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
................................................................................
      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 ){
            int bEarlyOut = 
                (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
                 && (pLoop->wsFlags & WHERE_IN_EARLYOUT)!=0;
            if( pLevel->iLeftJoin ){
              /* For LEFT JOIN queries, cursor pIn->iCur may not have been
              ** opened yet. This occurs for WHERE clauses such as
              ** "a = ? AND b IN (...)", where the index is on (a, b). If
              ** the RHS of the (a=?) is NULL, then the "b IN (...)" may
              ** never have been coded, but the body of the loop run to
              ** return the null-row. So, if the cursor is not open yet,
              ** jump over the OP_Next or OP_Prev instruction about to
              ** be coded.  */
              sqlite3VdbeAddOp2(v, OP_IfNotOpen, pIn->iCur, 
                  sqlite3VdbeCurrentAddr(v) + 2 + bEarlyOut);


              VdbeCoverage(v);
            }

            if( bEarlyOut ){
              sqlite3VdbeAddOp4Int(v, OP_IfNoHope, pLevel->iIdxCur,
                  sqlite3VdbeCurrentAddr(v)+2,
                  pIn->iBase, pIn->nPrefix);
              VdbeCoverage(v);
            }
          }
          sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);

Changes to src/whereInt.h.

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#define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
#define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
#define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
#define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
#define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
#define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
#define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */


#endif /* !defined(SQLITE_WHEREINT_H) */







>


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#define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
#define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
#define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
#define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
#define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
#define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
#define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */
#define WHERE_IN_SEEKSCAN  0x00100000  /* Seek-scan optimization for IN */

#endif /* !defined(SQLITE_WHEREINT_H) */

Changes to src/wherecode.c.

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    VdbeCoverageIf(v, !bRev);
    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );

    pLoop->wsFlags |= WHERE_IN_ABLE;
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(pParse);
    }
    if( iEq>0 ){
      pLoop->wsFlags |= WHERE_IN_EARLYOUT;
    }

    i = pLevel->u.in.nIn;
    pLevel->u.in.nIn += nEq;
    pLevel->u.in.aInLoop =
       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
................................................................................
            }
          }else{
            pIn->eEndLoopOp = OP_Noop;
          }
          pIn++;
        }
      }
      if( iEq>0 ){
        sqlite3VdbeAddOp3(v, OP_SeekHit, pLevel->iIdxCur, 0, iEq);
      }
    }else{
      pLevel->u.in.nIn = 0;
    }
    sqlite3DbFree(pParse->db, aiMap);
#endif
................................................................................
      if( regBignull ){
        sqlite3VdbeAddOp2(v, OP_Integer, 1, regBignull);
        VdbeComment((v, "NULL-scan pass ctr"));
      }

      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 );
      VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
      VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
................................................................................
                           nConstraint+bSeekPastNull);
      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_EARLYOUT ){
      sqlite3VdbeAddOp3(v, OP_SeekHit, iIdxCur, nEq, nEq);
    }

    /* Seek the table cursor, if required */
    omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0;
    if( omitTable ){







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    VdbeCoverageIf(v, !bRev);
    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );

    pLoop->wsFlags |= WHERE_IN_ABLE;
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(pParse);
    }
    if( iEq>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0 ){
      pLoop->wsFlags |= WHERE_IN_EARLYOUT;
    }

    i = pLevel->u.in.nIn;
    pLevel->u.in.nIn += nEq;
    pLevel->u.in.aInLoop =
       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
................................................................................
            }
          }else{
            pIn->eEndLoopOp = OP_Noop;
          }
          pIn++;
        }
      }
      if( iEq>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0 ){
        sqlite3VdbeAddOp3(v, OP_SeekHit, pLevel->iIdxCur, 0, iEq);
      }
    }else{
      pLevel->u.in.nIn = 0;
    }
    sqlite3DbFree(pParse->db, aiMap);
#endif
................................................................................
      if( regBignull ){
        sqlite3VdbeAddOp2(v, OP_Integer, 1, regBignull);
        VdbeComment((v, "NULL-scan pass ctr"));
      }

      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      assert( op!=0 );
      if( (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){
        assert( op==OP_SeekGE );
        assert( regBignull==0 );
        /* TUNING:  The OP_SeekScan opcode seeks to reduce the number
        ** of expensive seek operations by replacing a single seek with
        ** 1 or more step operations.  The question is, how many steps
        ** should we try before giving up and going with a seek.  The cost
        ** of a seek is proportional to the logarithm of the of the number
        ** of entries in the tree, so basing the number of steps to try
        ** on the estimated number of rows in the btree seems like a good
        ** guess. */
        sqlite3VdbeAddOp1(v, OP_SeekScan, (pIdx->aiRowLogEst[0]+9)/10);
        VdbeCoverage(v);
      }
      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 );
      VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
      VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
................................................................................
                           nConstraint+bSeekPastNull);
      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_EARLYOUT)!=0 ){
      sqlite3VdbeAddOp3(v, OP_SeekHit, iIdxCur, nEq, nEq);
    }

    /* Seek the table cursor, if required */
    omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0;
    if( omitTable ){