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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Optimizations to two VDBE accessory routines for a 0.2% performance increase.
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SHA1: 66d033b9c9a8c16b9a342be0b325bd85b8487c03
User & Date: drh 2015-06-17 01:31:28
Context
2015-06-17
02:11
Make getCellInfo() a real function instead of a macro, for a size reduction and a 0.2% performance gain. check-in: 55c393ea user: drh tags: trunk
01:31
Optimizations to two VDBE accessory routines for a 0.2% performance increase. check-in: 66d033b9 user: drh tags: trunk
2015-06-16
16:39
Ensure that the CREATE TABLE AS statement correctly undoes partial changes to the sqlite_master table if the SELECT on the right-hand side aborts with an error. Fix for ticket [873cae2b6e25b] check-in: 400e025e user: drh tags: trunk
Changes
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Changes to src/vdbeaux.c.

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}
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
/*
** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
*/
void sqlite3VdbeLeave(Vdbe *p){
  int i;
  sqlite3 *db;
  Db *aDb;
  int nDb;
  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
  db = p->db;
  aDb = db->aDb;
  nDb = db->nDb;
  for(i=0; i<nDb; i++){
    if( i!=1 && DbMaskTest(p->lockMask,i) && ALWAYS(aDb[i].pBt!=0) ){
      sqlite3BtreeLeave(aDb[i].pBt);
    }
  }




}
#endif

#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
/*
** Print a single opcode.  This routine is used for debugging only.
*/







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}
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
/*
** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
*/
static SQLITE_NOINLINE void vdbeLeave(Vdbe *p){
  int i;
  sqlite3 *db;
  Db *aDb;
  int nDb;

  db = p->db;
  aDb = db->aDb;
  nDb = db->nDb;
  for(i=0; i<nDb; i++){
    if( i!=1 && DbMaskTest(p->lockMask,i) && ALWAYS(aDb[i].pBt!=0) ){
      sqlite3BtreeLeave(aDb[i].pBt);
    }
  }
}
void sqlite3VdbeLeave(Vdbe *p){
  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
  vdbeLeave(p);
}
#endif

#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
/*
** Print a single opcode.  This routine is used for debugging only.
*/

Changes to src/vdbemem.c.

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** pMem->zMalloc space will be allocated if necessary.  The calling routine
** is responsible for making sure that the pMem object is eventually
** destroyed.
**
** If this routine fails for any reason (malloc returns NULL or unable
** to read from the disk) then the pMem is left in an inconsistent state.
*/


























int sqlite3VdbeMemFromBtree(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  u32 offset,       /* Offset from the start of data to return bytes from. */
  u32 amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
................................................................................
  assert( zData!=0 );

  if( offset+amt<=available ){
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
    pMem->n = (int)amt;
  }else{
    pMem->flags = MEM_Null;
    if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+2)) ){
      if( key ){
        rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
      }else{
        rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
      }
      if( rc==SQLITE_OK ){
        pMem->z[amt] = 0;
        pMem->z[amt+1] = 0;
        pMem->flags = MEM_Blob|MEM_Term;
        pMem->n = (int)amt;
      }else{
        sqlite3VdbeMemRelease(pMem);
      }
    }
  }

  return rc;
}

/*
** The pVal argument is known to be a value other than NULL.







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** pMem->zMalloc space will be allocated if necessary.  The calling routine
** is responsible for making sure that the pMem object is eventually
** destroyed.
**
** If this routine fails for any reason (malloc returns NULL or unable
** to read from the disk) then the pMem is left in an inconsistent state.
*/
static SQLITE_NOINLINE int vdbeMemFromBtreeResize(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  u32 offset,       /* Offset from the start of data to return bytes from. */
  u32 amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
  int rc;
  pMem->flags = MEM_Null;
  if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+2)) ){
    if( key ){
      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
    }else{
      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
    }
    if( rc==SQLITE_OK ){
      pMem->z[amt] = 0;
      pMem->z[amt+1] = 0;
      pMem->flags = MEM_Blob|MEM_Term;
      pMem->n = (int)amt;
    }else{
      sqlite3VdbeMemRelease(pMem);
    }
  }
  return rc;
}
int sqlite3VdbeMemFromBtree(
  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
  u32 offset,       /* Offset from the start of data to return bytes from. */
  u32 amt,          /* Number of bytes to return. */
  int key,          /* If true, retrieve from the btree key, not data. */
  Mem *pMem         /* OUT: Return data in this Mem structure. */
){
................................................................................
  assert( zData!=0 );

  if( offset+amt<=available ){
    pMem->z = &zData[offset];
    pMem->flags = MEM_Blob|MEM_Ephem;
    pMem->n = (int)amt;
  }else{



    rc = vdbeMemFromBtreeResize(pCur, offset, amt, key, pMem);












  }

  return rc;
}

/*
** The pVal argument is known to be a value other than NULL.