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Comment:Avoid unnecessary moving of content between registers during an ORDER BY.
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SHA1:4f472accf072d9cb64f209923924b26f21b13d27
User & Date: drh 2014-03-24 18:08:15
Context
2014-03-24
20:19
Omit the sequence value from sorter records used by GROUP BY queries that cannot use an index. check-in: 3f90abdd user: dan tags: orderby-planning
18:08
Avoid unnecessary moving of content between registers during an ORDER BY. check-in: 4f472acc user: drh tags: orderby-planning
09:34
Remove an unnecessary temporary register allocation. check-in: 5d506743 user: dan tags: orderby-planning
Changes
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Changes to src/select.c.

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** through regData+nData-1 onto the sorter.
*/
static void pushOntoSorter(
  Parse *pParse,         /* Parser context */
  SortCtx *pSort,        /* Information about the ORDER BY clause */
  Select *pSelect,       /* The whole SELECT statement */
  int regData,           /* First register holding data to be sorted */
  int nData              /* Number of elements in the data array */

){
  Vdbe *v = pParse->pVdbe;                         /* Stmt under construction */
  int nExpr = pSort->pOrderBy->nExpr;              /* No. of ORDER BY terms */
  int nBase = nExpr + 1 + nData;                   /* Fields in sorter record */
  int regBase = sqlite3GetTempRange(pParse, nBase); /* Regs for sorter record */
  int regRecord = sqlite3GetTempReg(pParse);       /* Assemblied sorter record */
  int nOBSat = pSort->nOBSat;                      /* No. ORDER BY terms to skip */
  int op;                               /* Opcode to add sorter record to sorter */







  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, SQLITE_ECEL_DUP);
  sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);

  sqlite3VdbeAddOp3(v, OP_Move, regData, regBase+nExpr+1, nData);

  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regRecord);
  if( nOBSat>0 ){
    int regPrevKey;   /* The first nOBSat columns of the previous row */
    int addrFirst;    /* Address of the OP_IfNot opcode */
    int addrJmp;      /* Address of the OP_Jump opcode */
    VdbeOp *pOp;      /* Opcode that opens the sorter */
    int nKey;         /* Number of sorting key columns, including OP_Sequence */
................................................................................
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
  if( nOBSat==0 ){
    sqlite3ReleaseTempReg(pParse, regRecord);

    sqlite3ReleaseTempRange(pParse, regBase, nBase);

  }
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
    if( pSelect->iOffset ){
      iLimit = pSelect->iOffset+1;
    }else{
................................................................................
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */
  int regResult;              /* Start of memory holding result set */
  int eDest = pDest->eDest;   /* How to dispose of results */
  int iParm = pDest->iSDParm; /* First argument to disposal method */
  int nResultCol;             /* Number of result columns */


  assert( v );
  assert( pEList!=0 );
  hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
  if( pSort && pSort->pOrderBy==0 ) pSort = 0;
  if( pSort==0 && !hasDistinct ){
    assert( iContinue!=0 );
................................................................................
  }

  /* Pull the requested columns.
  */
  nResultCol = pEList->nExpr;

  if( pDest->iSdst==0 ){




    pDest->iSdst = pParse->nMem+1;
    pParse->nMem += nResultCol;
  }else if( pDest->iSdst+nResultCol > pParse->nMem ){
    /* This is an error condition that can result, for example, when a SELECT
    ** on the right-hand side of an INSERT contains more result columns than
    ** there are columns in the table on the left.  The error will be caught
    ** and reported later.  But we need to make sure enough memory is allocated
................................................................................

    /* Store the result as data using a unique key.
    */
    case SRT_Fifo:
    case SRT_DistFifo:
    case SRT_Table:
    case SRT_EphemTab: {
      int r1 = sqlite3GetTempReg(pParse);
      testcase( eDest==SRT_Table );
      testcase( eDest==SRT_EphemTab );
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1);
#ifndef SQLITE_OMIT_CTE
      if( eDest==SRT_DistFifo ){
        /* If the destination is DistFifo, then cursor (iParm+1) is open
        ** on an ephemeral index. If the current row is already present
        ** in the index, do not write it to the output. If not, add the
        ** current row to the index and proceed with writing it to the
        ** output table as well.  */
................................................................................
        int addr = sqlite3VdbeCurrentAddr(v) + 4;
        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0); VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
        assert( pSort==0 );
      }
#endif
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, r1, 1);
      }else{
        int r2 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
        sqlite3ReleaseTempReg(pParse, r2);
      }
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

#ifndef SQLITE_OMIT_SUBQUERY
    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
    ** then there should be a single item on the stack.  Write this
    ** item into the set table with bogus data.
................................................................................
      pDest->affSdst =
                  sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affSdst);
      if( pSort ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
        pushOntoSorter(pParse, pSort, p, regResult, 1);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult,1,r1, &pDest->affSdst, 1);
        sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }
................................................................................
    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.
    */
    case SRT_Mem: {
      assert( nResultCol==1 );
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, regResult, 1);
      }else{
        sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
        /* The LIMIT clause will jump out of the loop for us */
      }
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    case SRT_Coroutine:       /* Send data to a co-routine */
    case SRT_Output: {        /* Return the results */
      testcase( eDest==SRT_Coroutine );
      testcase( eDest==SRT_Output );
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, regResult, nResultCol);
      }else if( eDest==SRT_Coroutine ){
        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
      }else{
        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nResultCol);
        sqlite3ExprCacheAffinityChange(pParse, regResult, nResultCol);
      }
      break;







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** through regData+nData-1 onto the sorter.
*/
static void pushOntoSorter(
  Parse *pParse,         /* Parser context */
  SortCtx *pSort,        /* Information about the ORDER BY clause */
  Select *pSelect,       /* The whole SELECT statement */
  int regData,           /* First register holding data to be sorted */
  int nData,             /* Number of elements in the data array */
  int nPrefixReg         /* No. of reg prior to regData available for use */
){
  Vdbe *v = pParse->pVdbe;                         /* Stmt under construction */
  int nExpr = pSort->pOrderBy->nExpr;              /* No. of ORDER BY terms */
  int nBase = nExpr + 1 + nData;                   /* Fields in sorter record */
  int regBase;                                     /* Regs for sorter record */
  int regRecord = sqlite3GetTempReg(pParse);       /* Assemblied sorter record */
  int nOBSat = pSort->nOBSat;                      /* No. ORDER BY terms to skip */
  int op;                               /* Opcode to add sorter record to sorter */

  if( nPrefixReg ){
    assert( nPrefixReg==nExpr+1 );
    regBase = regData - nExpr - 1;
  }else{
    regBase = sqlite3GetTempRange(pParse, nBase);
  }
  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, SQLITE_ECEL_DUP);
  sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
  if( nPrefixReg==0 ){
    sqlite3VdbeAddOp3(v, OP_Move, regData, regBase+nExpr+1, nData);
  }
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regRecord);
  if( nOBSat>0 ){
    int regPrevKey;   /* The first nOBSat columns of the previous row */
    int addrFirst;    /* Address of the OP_IfNot opcode */
    int addrJmp;      /* Address of the OP_Jump opcode */
    VdbeOp *pOp;      /* Opcode that opens the sorter */
    int nKey;         /* Number of sorting key columns, including OP_Sequence */
................................................................................
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
  if( nOBSat==0 ){
    sqlite3ReleaseTempReg(pParse, regRecord);
    if( nPrefixReg==0 ){
      sqlite3ReleaseTempRange(pParse, regBase, nBase);
    }
  }
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
    if( pSelect->iOffset ){
      iLimit = pSelect->iOffset+1;
    }else{
................................................................................
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */
  int regResult;              /* Start of memory holding result set */
  int eDest = pDest->eDest;   /* How to dispose of results */
  int iParm = pDest->iSDParm; /* First argument to disposal method */
  int nResultCol;             /* Number of result columns */
  int nPrefixReg = 0;         /* Number of extra registers before regResult */

  assert( v );
  assert( pEList!=0 );
  hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
  if( pSort && pSort->pOrderBy==0 ) pSort = 0;
  if( pSort==0 && !hasDistinct ){
    assert( iContinue!=0 );
................................................................................
  }

  /* Pull the requested columns.
  */
  nResultCol = pEList->nExpr;

  if( pDest->iSdst==0 ){
    if( pSort ){
      nPrefixReg = pSort->pOrderBy->nExpr + 1;
      pParse->nMem += nPrefixReg;
    }
    pDest->iSdst = pParse->nMem+1;
    pParse->nMem += nResultCol;
  }else if( pDest->iSdst+nResultCol > pParse->nMem ){
    /* This is an error condition that can result, for example, when a SELECT
    ** on the right-hand side of an INSERT contains more result columns than
    ** there are columns in the table on the left.  The error will be caught
    ** and reported later.  But we need to make sure enough memory is allocated
................................................................................

    /* Store the result as data using a unique key.
    */
    case SRT_Fifo:
    case SRT_DistFifo:
    case SRT_Table:
    case SRT_EphemTab: {
      int r1 = sqlite3GetTempRange(pParse, nPrefixReg+1);
      testcase( eDest==SRT_Table );
      testcase( eDest==SRT_EphemTab );
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1+nPrefixReg);
#ifndef SQLITE_OMIT_CTE
      if( eDest==SRT_DistFifo ){
        /* If the destination is DistFifo, then cursor (iParm+1) is open
        ** on an ephemeral index. If the current row is already present
        ** in the index, do not write it to the output. If not, add the
        ** current row to the index and proceed with writing it to the
        ** output table as well.  */
................................................................................
        int addr = sqlite3VdbeCurrentAddr(v) + 4;
        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0); VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
        assert( pSort==0 );
      }
#endif
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, r1+nPrefixReg, 1, nPrefixReg);
      }else{
        int r2 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
        sqlite3ReleaseTempReg(pParse, r2);
      }
      sqlite3ReleaseTempRange(pParse, r1, nPrefixReg+1);
      break;
    }

#ifndef SQLITE_OMIT_SUBQUERY
    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
    ** then there should be a single item on the stack.  Write this
    ** item into the set table with bogus data.
................................................................................
      pDest->affSdst =
                  sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affSdst);
      if( pSort ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
        pushOntoSorter(pParse, pSort, p, regResult, 1, nPrefixReg);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult,1,r1, &pDest->affSdst, 1);
        sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }
................................................................................
    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.
    */
    case SRT_Mem: {
      assert( nResultCol==1 );
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, regResult, 1, nPrefixReg);
      }else{
        sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
        /* The LIMIT clause will jump out of the loop for us */
      }
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    case SRT_Coroutine:       /* Send data to a co-routine */
    case SRT_Output: {        /* Return the results */
      testcase( eDest==SRT_Coroutine );
      testcase( eDest==SRT_Output );
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, regResult, nResultCol, nPrefixReg);
      }else if( eDest==SRT_Coroutine ){
        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
      }else{
        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nResultCol);
        sqlite3ExprCacheAffinityChange(pParse, regResult, nResultCol);
      }
      break;