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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Add the sqlite3VdbeChangeDest() routine that can be used to eliminate OP_Move opcodes.
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SHA1: 8c57bcc327d3d456e0311f7246efed88d6429d3f
User & Date: drh 2014-08-29 11:24:42
Context
2014-08-29
11:24
Add the sqlite3VdbeChangeDest() routine that can be used to eliminate OP_Move opcodes. Closed-Leaf check-in: 8c57bcc3 user: drh tags: experimental
2014-08-28
19:38
Improved WHERETRACE messages for the estimated output row reductions from range scans. check-in: fdd478bb user: drh tags: trunk
Changes
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Changes to src/expr.c.

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** Generate code to move content from registers iFrom...iFrom+nReg-1
** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.
*/
void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
  int i;
  struct yColCache *p;
  assert( iFrom>=iTo+nReg || iFrom+nReg<=iTo );

  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);

  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int x = p->iReg;
    if( x>=iFrom && x<iFrom+nReg ){
      p->iReg += iTo-iFrom;
    }
  }
}







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** Generate code to move content from registers iFrom...iFrom+nReg-1
** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.
*/
void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
  int i;
  struct yColCache *p;
  assert( iFrom>=iTo+nReg || iFrom+nReg<=iTo );
  if( nReg!=1 || sqlite3VdbeChangeDest(pParse->pVdbe, iFrom, iTo)==0 ){
    sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
  }
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int x = p->iReg;
    if( x>=iFrom && x<iFrom+nReg ){
      p->iReg += iTo-iFrom;
    }
  }
}

Changes to src/vdbe.c.

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** register has changed should have this bit set.
**
** If the OPFLAG_LENGTHARG and OPFLAG_TYPEOFARG bits are set on P5 when
** the result is guaranteed to only be used as the argument of a length()
** or typeof() function, respectively.  The loading of large blobs can be
** skipped for length() and all content loading can be skipped for typeof().
*/
case OP_Column: {
  i64 payloadSize64; /* Number of bytes in the record */
  int p2;            /* column number to retrieve */
  VdbeCursor *pC;    /* The VDBE cursor */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  int len;           /* The length of the serialized data for the column */







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** register has changed should have this bit set.
**
** If the OPFLAG_LENGTHARG and OPFLAG_TYPEOFARG bits are set on P5 when
** the result is guaranteed to only be used as the argument of a length()
** or typeof() function, respectively.  The loading of large blobs can be
** skipped for length() and all content loading can be skipped for typeof().
*/
case OP_Column: {                 /* out3 */
  i64 payloadSize64; /* Number of bytes in the record */
  int p2;            /* column number to retrieve */
  VdbeCursor *pC;    /* The VDBE cursor */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  int len;           /* The length of the serialized data for the column */

Changes to src/vdbe.h.

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void sqlite3VdbeChangeP1(Vdbe*, u32 addr, int P1);
void sqlite3VdbeChangeP2(Vdbe*, u32 addr, int P2);
void sqlite3VdbeChangeP3(Vdbe*, u32 addr, int P3);
void sqlite3VdbeChangeP5(Vdbe*, u8 P5);
void sqlite3VdbeJumpHere(Vdbe*, int addr);
void sqlite3VdbeChangeToNoop(Vdbe*, int addr);
int sqlite3VdbeDeletePriorOpcode(Vdbe*, u8 op);

void sqlite3VdbeChangeP4(Vdbe*, int addr, const char *zP4, int N);
void sqlite3VdbeSetP4KeyInfo(Parse*, Index*);
void sqlite3VdbeUsesBtree(Vdbe*, int);
VdbeOp *sqlite3VdbeGetOp(Vdbe*, int);
int sqlite3VdbeMakeLabel(Vdbe*);
void sqlite3VdbeRunOnlyOnce(Vdbe*);
void sqlite3VdbeDelete(Vdbe*);







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void sqlite3VdbeChangeP1(Vdbe*, u32 addr, int P1);
void sqlite3VdbeChangeP2(Vdbe*, u32 addr, int P2);
void sqlite3VdbeChangeP3(Vdbe*, u32 addr, int P3);
void sqlite3VdbeChangeP5(Vdbe*, u8 P5);
void sqlite3VdbeJumpHere(Vdbe*, int addr);
void sqlite3VdbeChangeToNoop(Vdbe*, int addr);
int sqlite3VdbeDeletePriorOpcode(Vdbe*, u8 op);
int sqlite3VdbeChangeDest(Vdbe*, int iOld, int iNew);
void sqlite3VdbeChangeP4(Vdbe*, int addr, const char *zP4, int N);
void sqlite3VdbeSetP4KeyInfo(Parse*, Index*);
void sqlite3VdbeUsesBtree(Vdbe*, int);
VdbeOp *sqlite3VdbeGetOp(Vdbe*, int);
int sqlite3VdbeMakeLabel(Vdbe*);
void sqlite3VdbeRunOnlyOnce(Vdbe*);
void sqlite3VdbeDelete(Vdbe*);

Changes to src/vdbeaux.c.

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  assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
  if( p->db->mallocFailed ){
    return (VdbeOp*)&dummy;
  }else{
    return &p->aOp[addr];
  }
}
























#if defined(SQLITE_ENABLE_EXPLAIN_COMMENTS)
/*
** Return an integer value for one of the parameters to the opcode pOp
** determined by character c.
*/
static int translateP(char c, const Op *pOp){







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  assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
  if( p->db->mallocFailed ){
    return (VdbeOp*)&dummy;
  }else{
    return &p->aOp[addr];
  }
}

/*
** If the previous opcode is not "fixed" (if it has not be jumped over)
** and if its output register is iOldOut, then change the output register
** to iNewOut and return true.  Otherwise return false.
*/
int sqlite3VdbeChangeDest(Vdbe *p, int iOldOut, int iNewOut){
  VdbeOp *pOp;
  u8 opflags;
  if( (p->nOp-1)<=(p->pParse->iFixedOp) ) return 0;
  pOp = &p->aOp[p->nOp-1];
  opflags = sqlite3OpcodeProperty[pOp->opcode];
  if( (opflags & OPFLG_OUT3)!=0 && pOp->p3==iOldOut ){
    pOp->p3 = iNewOut;
    return 1;
  }
  if( (opflags & OPFLG_OUT2)!=0 && pOp->p3==iOldOut ){
    pOp->p2 = iNewOut;
    return 1;
  }
  return 0;
}


#if defined(SQLITE_ENABLE_EXPLAIN_COMMENTS)
/*
** Return an integer value for one of the parameters to the opcode pOp
** determined by character c.
*/
static int translateP(char c, const Op *pOp){