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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Performance optimizations in the column cache of the code generator, and especially the sqlite3ExprCacheRemove() routine.
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SHA1: e35b345cf858018ae0c07f79725f8d58062168db
User & Date: drh 2016-04-11 18:15:37
Context
2016-04-11
18:25
Performance optimization for the sqlite3ExprListDelete() routine. check-in: 2764aeaa user: drh tags: trunk
18:15
Performance optimizations in the column cache of the code generator, and especially the sqlite3ExprCacheRemove() routine. check-in: e35b345c user: drh tags: trunk
16:43
Simplification and performance improvements in sqlite3ExprDup() and its subroutines. More work is possible in this area. check-in: 476cc283 user: drh tags: trunk
Changes
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Changes to src/expr.c.

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        codeReal(v, z, negFlag, iMem);
      }
#endif
    }
  }
}














/*
** Clear a cache entry.
*/
static void cacheEntryClear(Parse *pParse, struct yColCache *p){
  if( p->tempReg ){
    if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
      pParse->aTempReg[pParse->nTempReg++] = p->iReg;
    }
    p->tempReg = 0;
  }



}


/*
** Record in the column cache that a particular column from a
** particular table is stored in a particular register.
*/
................................................................................
    if( p->iReg==0 ){
      p->iLevel = pParse->iCacheLevel;
      p->iTable = iTab;
      p->iColumn = iCol;
      p->iReg = iReg;
      p->tempReg = 0;
      p->lru = pParse->iCacheCnt++;


      return;
    }
  }

  /* Replace the last recently used */
  minLru = 0x7fffffff;
  idxLru = -1;
................................................................................
    p = &pParse->aColCache[idxLru];
    p->iLevel = pParse->iCacheLevel;
    p->iTable = iTab;
    p->iColumn = iCol;
    p->iReg = iReg;
    p->tempReg = 0;
    p->lru = pParse->iCacheCnt++;

    return;
  }
}

/*
** Indicate that registers between iReg..iReg+nReg-1 are being overwritten.
** Purge the range of registers from the column cache.
*/
void sqlite3ExprCacheRemove(Parse *pParse, int iReg, int nReg){
  int i;
  int iLast = iReg + nReg - 1;
  struct yColCache *p;
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int r = p->iReg;
    if( r>=iReg && r<=iLast ){
      cacheEntryClear(pParse, p);
      p->iReg = 0;
    }
  }
}

/*
** Remember the current column cache context.  Any new entries added
** added to the column cache after this call are removed when the
** corresponding pop occurs.
................................................................................
  if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
    printf("POP  to %d\n", pParse->iCacheLevel);
  }
#endif
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
      cacheEntryClear(pParse, p);
      p->iReg = 0;
    }
  }
}

/*
** When a cached column is reused, make sure that its register is
** no longer available as a temp register.  ticket #3879:  that same
................................................................................
  if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
    printf("CLEAR\n");
  }
#endif
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg ){
      cacheEntryClear(pParse, p);
      p->iReg = 0;
    }
  }
}

/*
** Record the fact that an affinity change has occurred on iCount
** registers starting with iStart.
................................................................................
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int r = p->iReg;
    if( r>=iFrom && r<=iTo ) return 1;    /*NO_TEST*/
  }
  return 0;
}
#endif /* SQLITE_DEBUG || SQLITE_COVERAGE_TEST */


/*
** Convert an expression node to a TK_REGISTER
*/
static void exprToRegister(Expr *p, int iReg){
  p->op2 = p->op;
  p->op = TK_REGISTER;







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        codeReal(v, z, negFlag, iMem);
      }
#endif
    }
  }
}

#if defined(SQLITE_DEBUG)
/*
** Verify the consistency of the column cache
*/
static int cacheIsValid(Parse *pParse){
  int i, n;
  for(i=n=0; i<SQLITE_N_COLCACHE; i++){
    if( pParse->aColCache[i].iReg>0 ) n++;
  }
  return n==pParse->nColCache;
}
#endif

/*
** Clear a cache entry.
*/
static void cacheEntryClear(Parse *pParse, struct yColCache *p){
  if( p->tempReg ){
    if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
      pParse->aTempReg[pParse->nTempReg++] = p->iReg;
    }
    p->tempReg = 0;
  }
  p->iReg = 0;
  pParse->nColCache--;
  assert( cacheIsValid(pParse) );
}


/*
** Record in the column cache that a particular column from a
** particular table is stored in a particular register.
*/
................................................................................
    if( p->iReg==0 ){
      p->iLevel = pParse->iCacheLevel;
      p->iTable = iTab;
      p->iColumn = iCol;
      p->iReg = iReg;
      p->tempReg = 0;
      p->lru = pParse->iCacheCnt++;
      pParse->nColCache++;
      assert( cacheIsValid(pParse) );
      return;
    }
  }

  /* Replace the last recently used */
  minLru = 0x7fffffff;
  idxLru = -1;
................................................................................
    p = &pParse->aColCache[idxLru];
    p->iLevel = pParse->iCacheLevel;
    p->iTable = iTab;
    p->iColumn = iCol;
    p->iReg = iReg;
    p->tempReg = 0;
    p->lru = pParse->iCacheCnt++;
    assert( cacheIsValid(pParse) );
    return;
  }
}

/*
** Indicate that registers between iReg..iReg+nReg-1 are being overwritten.
** Purge the range of registers from the column cache.
*/
void sqlite3ExprCacheRemove(Parse *pParse, int iReg, int nReg){
  struct yColCache *p;
  if( iReg<=0 || pParse->nColCache==0 ) return;
  p = &pParse->aColCache[SQLITE_N_COLCACHE-1];
  while(1){
    if( p->iReg >= iReg && p->iReg < iReg+nReg ) cacheEntryClear(pParse, p);
    if( p==pParse->aColCache ) break;
    p--;


  }
}

/*
** Remember the current column cache context.  Any new entries added
** added to the column cache after this call are removed when the
** corresponding pop occurs.
................................................................................
  if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
    printf("POP  to %d\n", pParse->iCacheLevel);
  }
#endif
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
      cacheEntryClear(pParse, p);

    }
  }
}

/*
** When a cached column is reused, make sure that its register is
** no longer available as a temp register.  ticket #3879:  that same
................................................................................
  if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
    printf("CLEAR\n");
  }
#endif
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg ){
      cacheEntryClear(pParse, p);

    }
  }
}

/*
** Record the fact that an affinity change has occurred on iCount
** registers starting with iStart.
................................................................................
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int r = p->iReg;
    if( r>=iFrom && r<=iTo ) return 1;    /*NO_TEST*/
  }
  return 0;
}
#endif /* SQLITE_DEBUG || SQLITE_COVERAGE_TEST */


/*
** Convert an expression node to a TK_REGISTER
*/
static void exprToRegister(Expr *p, int iReg){
  p->op2 = p->op;
  p->op = TK_REGISTER;

Changes to src/sqliteInt.h.

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  u8 nested;           /* Number of nested calls to the parser/code generator */
  u8 nTempReg;         /* Number of temporary registers in aTempReg[] */
  u8 isMultiWrite;     /* True if statement may modify/insert multiple rows */
  u8 mayAbort;         /* True if statement may throw an ABORT exception */
  u8 hasCompound;      /* Need to invoke convertCompoundSelectToSubquery() */
  u8 okConstFactor;    /* OK to factor out constants */
  u8 disableLookaside; /* Number of times lookaside has been disabled */

  int aTempReg[8];     /* Holding area for temporary registers */
  int nRangeReg;       /* Size of the temporary register block */
  int iRangeReg;       /* First register in temporary register block */
  int nErr;            /* Number of errors seen */
  int nTab;            /* Number of previously allocated VDBE cursors */
  int nMem;            /* Number of memory cells used so far */
  int nSet;            /* Number of sets used so far */







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  u8 nested;           /* Number of nested calls to the parser/code generator */
  u8 nTempReg;         /* Number of temporary registers in aTempReg[] */
  u8 isMultiWrite;     /* True if statement may modify/insert multiple rows */
  u8 mayAbort;         /* True if statement may throw an ABORT exception */
  u8 hasCompound;      /* Need to invoke convertCompoundSelectToSubquery() */
  u8 okConstFactor;    /* OK to factor out constants */
  u8 disableLookaside; /* Number of times lookaside has been disabled */
  u8 nColCache;        /* Number of entries in aColCache[] */
  int aTempReg[8];     /* Holding area for temporary registers */
  int nRangeReg;       /* Size of the temporary register block */
  int iRangeReg;       /* First register in temporary register block */
  int nErr;            /* Number of errors seen */
  int nTab;            /* Number of previously allocated VDBE cursors */
  int nMem;            /* Number of memory cells used so far */
  int nSet;            /* Number of sets used so far */