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Overview
Comment:Enhance the use of the column cache for UPDATE statements, making them more efficient for the case where a column is modified to be an expression of other unmodified columns.
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Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 871e091df651b2275a672c35ff938bd4b6db0d7f
User & Date: drh 2015-10-15 19:21:51
References
2018-04-26
12:45 New ticket [d85fffd6] VDBE program uses an expired value. artifact: 4af45294 user: drh
Context
2015-10-15
21:30
Performance optimization for the OP_Column opcode. check-in: 076be547 user: drh tags: trunk
21:13
Merge updates from trunk. Leaf check-in: 40493680 user: mistachkin tags: mutexInitIsInitReCheck
21:12
Merge updates from trunk. Leaf check-in: a447cf90 user: mistachkin tags: mutexInitSimpleCmpSwap
20:17
Experiments with an OP_Unpack opcode that extracts multiple columns from a record without caching. Leaf check-in: 39ae92f5 user: drh tags: unpack-opcode
19:21
Enhance the use of the column cache for UPDATE statements, making them more efficient for the case where a column is modified to be an expression of other unmodified columns. check-in: 871e091d user: drh tags: trunk
18:04
Add the OP_IntCopy opcode - an optimized version of OP_SCopy that only works for integer values. check-in: 3a2f73a4 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/expr.c.

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  if( iCol>=0 ){
    sqlite3ColumnDefault(v, pTab, iCol, regOut);
  }
}

/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in a register.  An effort

** is made to store the column value in register iReg, but this is
** not guaranteed.  The location of the column value is returned.



**
** There must be an open cursor to pTab in iTable when this routine
** is called.  If iColumn<0 then code is generated that extracts the rowid.
*/
int sqlite3ExprCodeGetColumn(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg,        /* Store results here */
  u8 p5            /* P5 value for OP_Column */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct yColCache *p;

  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn ){
................................................................................
  if( p5 ){
    sqlite3VdbeChangeP5(v, p5);
  }else{   
    sqlite3ExprCacheStore(pParse, iTable, iColumn, iReg);
  }
  return iReg;
}












/*
** Clear all column cache entries.
*/
void sqlite3ExprCacheClear(Parse *pParse){
  int i;
  struct yColCache *p;







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  if( iCol>=0 ){
    sqlite3ColumnDefault(v, pTab, iCol, regOut);
  }
}

/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in a register. 
**
** An effort is made to store the column value in register iReg.  This

** is not garanteeed for GetColumn() - the result can be stored in
** any register.  But the result is guaranteed to land in register iReg
** for GetColumnToReg().
**
** There must be an open cursor to pTab in iTable when this routine
** is called.  If iColumn<0 then code is generated that extracts the rowid.
*/
int sqlite3ExprCodeGetColumn(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg,        /* Store results here */
  u8 p5            /* P5 value for OP_Column + FLAGS */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct yColCache *p;

  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn ){
................................................................................
  if( p5 ){
    sqlite3VdbeChangeP5(v, p5);
  }else{   
    sqlite3ExprCacheStore(pParse, iTable, iColumn, iReg);
  }
  return iReg;
}
void sqlite3ExprCodeGetColumnToReg(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg         /* Store results here */
){
  int r1 = sqlite3ExprCodeGetColumn(pParse, pTab, iColumn, iTable, iReg, 0);
  if( r1!=iReg ) sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, r1, iReg);
}


/*
** Clear all column cache entries.
*/
void sqlite3ExprCacheClear(Parse *pParse){
  int i;
  struct yColCache *p;

Changes to src/select.c.

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        sqlite3ExprCacheClear(pParse);
        sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0, 0);
        j = nGroupBy;
        for(i=0; i<sAggInfo.nColumn; i++){
          struct AggInfo_col *pCol = &sAggInfo.aCol[i];
          if( pCol->iSorterColumn>=j ){
            int r1 = j + regBase;
            int r2;

            r2 = sqlite3ExprCodeGetColumn(pParse, 
                               pCol->pTab, pCol->iColumn, pCol->iTable, r1, 0);
            if( r1!=r2 ){
              sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
            }
            j++;
          }
        }
        regRecord = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
        sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
        sqlite3ReleaseTempReg(pParse, regRecord);







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        sqlite3ExprCacheClear(pParse);
        sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0, 0);
        j = nGroupBy;
        for(i=0; i<sAggInfo.nColumn; i++){
          struct AggInfo_col *pCol = &sAggInfo.aCol[i];
          if( pCol->iSorterColumn>=j ){
            int r1 = j + regBase;


            sqlite3ExprCodeGetColumnToReg(pParse, 
                               pCol->pTab, pCol->iColumn, pCol->iTable, r1);



            j++;
          }
        }
        regRecord = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
        sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
        sqlite3ReleaseTempReg(pParse, regRecord);

Changes to src/sqliteInt.h.

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int sqlite3WhereBreakLabel(WhereInfo*);
int sqlite3WhereOkOnePass(WhereInfo*, int*);
#define ONEPASS_OFF      0        /* Use of ONEPASS not allowed */
#define ONEPASS_SINGLE   1        /* ONEPASS valid for a single row update */
#define ONEPASS_MULTI    2        /* ONEPASS is valid for multiple rows */
void sqlite3ExprCodeLoadIndexColumn(Parse*, Index*, int, int, int);
int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, u8);

void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
void sqlite3ExprCodeMove(Parse*, int, int, int);
void sqlite3ExprCacheStore(Parse*, int, int, int);
void sqlite3ExprCachePush(Parse*);
void sqlite3ExprCachePop(Parse*);
void sqlite3ExprCacheRemove(Parse*, int, int);
void sqlite3ExprCacheClear(Parse*);







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int sqlite3WhereBreakLabel(WhereInfo*);
int sqlite3WhereOkOnePass(WhereInfo*, int*);
#define ONEPASS_OFF      0        /* Use of ONEPASS not allowed */
#define ONEPASS_SINGLE   1        /* ONEPASS valid for a single row update */
#define ONEPASS_MULTI    2        /* ONEPASS is valid for multiple rows */
void sqlite3ExprCodeLoadIndexColumn(Parse*, Index*, int, int, int);
int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, u8);
void sqlite3ExprCodeGetColumnToReg(Parse*, Table*, int, int, int);
void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
void sqlite3ExprCodeMove(Parse*, int, int, int);
void sqlite3ExprCacheStore(Parse*, int, int, int);
void sqlite3ExprCachePush(Parse*);
void sqlite3ExprCachePop(Parse*);
void sqlite3ExprCacheRemove(Parse*, int, int);
void sqlite3ExprCacheClear(Parse*);

Changes to src/update.c.

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        /* This branch loads the value of a column that will not be changed 
        ** into a register. This is done if there are no BEFORE triggers, or
        ** if there are one or more BEFORE triggers that use this value via
        ** a new.* reference in a trigger program.
        */
        testcase( i==31 );
        testcase( i==32 );
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, regNew+i);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
      }
    }
  }

  /* Fire any BEFORE UPDATE triggers. This happens before constraints are







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        /* This branch loads the value of a column that will not be changed 
        ** into a register. This is done if there are no BEFORE triggers, or
        ** if there are one or more BEFORE triggers that use this value via
        ** a new.* reference in a trigger program.
        */
        testcase( i==31 );
        testcase( i==32 );
        sqlite3ExprCodeGetColumnToReg(pParse, pTab, i, iDataCur, regNew+i);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
      }
    }
  }

  /* Fire any BEFORE UPDATE triggers. This happens before constraints are

Changes to src/wherecode.c.

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              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];
                int rx;
                rx = sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur,r+iPk,0);
                if( rx!=r+iPk ){
                  sqlite3VdbeAddOp2(v, OP_SCopy, rx, r+iPk);
                }
              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.







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              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];

                sqlite3ExprCodeGetColumnToReg(pParse, pTab, iCol, iCur, r+iPk);



              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.