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Overview
Comment:Change sqlite3_blob_reopen() to call sqlite3VdbeExec() directly rather than going through sqlite3_step(). Performance enhancement.
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SHA1: 347df3c1fd7322e7aacaf1e9f8be81830947c482
User & Date: drh 2017-01-21 16:27:56
Context
2017-01-22
00:11
Fix an initialized variable in kvtest. check-in: ed62c5a6 user: drh tags: trunk
2017-01-21
16:54
B-tree optimization: When seeking on a rowid table that has already been positioned, check to see if the new row happens to be the next row on the same leaf page. That is a reasonably common case, and if it is true it avoids a full binary search. check-in: 8e5cfb20 user: drh tags: btree-moveto-neighbor
16:27
Change sqlite3_blob_reopen() to call sqlite3VdbeExec() directly rather than going through sqlite3_step(). Performance enhancement. check-in: 347df3c1 user: drh tags: trunk
15:55
In the kvtest.c test utility, reuse the buffer into which blobs are read, rather than reallocating it for each row. This is a closer match to how other test programs work, and thus provides a better comparison. check-in: 0d1ad13a user: drh tags: trunk
Changes
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Changes to src/vdbeblob.c.

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** Valid sqlite3_blob* handles point to Incrblob structures.
*/
typedef struct Incrblob Incrblob;
struct Incrblob {
  int nByte;              /* Size of open blob, in bytes */
  int iOffset;            /* Byte offset of blob in cursor data */
  u16 iCol;               /* Table column this handle is open on */
  u8 isPureKV;            /* True if pTab is a pure key/value table */
  BtCursor *pCsr;         /* Cursor pointing at blob row */
  sqlite3_stmt *pStmt;    /* Statement holding cursor open */
  sqlite3 *db;            /* The associated database */
  char *zDb;              /* Database name */
  Table *pTab;            /* Table object */
};

................................................................................
** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will 
** immediately return SQLITE_ABORT.
*/
static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
  int rc;                         /* Error code */
  char *zErr = 0;                 /* Error message */
  Vdbe *v = (Vdbe *)p->pStmt;


  /* Set the value of register r[1] in the SQL statement to integer iRow. 
  ** This is done directly as a performance optimization
  */
  v->aMem[1].flags = MEM_Int;
  v->aMem[1].u.i = iRow;

  /* If the statement has been run before (and is paused at the OP_ResultRow)
  ** then back it up to the point where it does the OP_SeekRowid.  This could
  ** have been down with an extra OP_Goto, but simply setting the program
  ** counter is faster. */
  if( v->pc>3 ) v->pc = 3;






  rc = sqlite3_step(p->pStmt);

  if( rc==SQLITE_ROW ){
    VdbeCursor *pC = v->apCsr[0];
    u32 type = pC->aType[p->iCol];
    if( type<12 ){
      zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
          type==0?"null": type==7?"real": "integer"
      );
................................................................................
        pParse->nVar = 0;
        pParse->nMem = 1;
        pParse->nTab = 1;
        sqlite3VdbeMakeReady(v, pParse);
      }
    }
   
    pBlob->isPureKV = (pTab->nCol==2 && pTab->iPKey==0);
    pBlob->iCol = iCol;
    pBlob->db = db;
    sqlite3BtreeLeaveAll(db);
    if( db->mallocFailed ){
      goto blob_open_out;
    }
    rc = blobSeekToRow(pBlob, iRow, &zErr);







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** Valid sqlite3_blob* handles point to Incrblob structures.
*/
typedef struct Incrblob Incrblob;
struct Incrblob {
  int nByte;              /* Size of open blob, in bytes */
  int iOffset;            /* Byte offset of blob in cursor data */
  u16 iCol;               /* Table column this handle is open on */

  BtCursor *pCsr;         /* Cursor pointing at blob row */
  sqlite3_stmt *pStmt;    /* Statement holding cursor open */
  sqlite3 *db;            /* The associated database */
  char *zDb;              /* Database name */
  Table *pTab;            /* Table object */
};

................................................................................
** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will 
** immediately return SQLITE_ABORT.
*/
static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
  int rc;                         /* Error code */
  char *zErr = 0;                 /* Error message */
  Vdbe *v = (Vdbe *)p->pStmt;
  sqlite3 *db = v->db;

  /* Set the value of register r[1] in the SQL statement to integer iRow. 
  ** This is done directly as a performance optimization
  */
  v->aMem[1].flags = MEM_Int;
  v->aMem[1].u.i = iRow;

  /* If the statement has been run before (and is paused at the OP_ResultRow)
  ** then back it up to the point where it does the OP_SeekRowid.  This could
  ** have been down with an extra OP_Goto, but simply setting the program
  ** counter is faster. */
  if( v->pc>3 ){

    v->pc = 3;
    db->nVdbeExec++;
    rc = sqlite3VdbeExec((Vdbe*)p->pStmt);
    db->nVdbeExec--;
  }else{
    rc = sqlite3_step(p->pStmt);
  }
  if( rc==SQLITE_ROW ){
    VdbeCursor *pC = v->apCsr[0];
    u32 type = pC->aType[p->iCol];
    if( type<12 ){
      zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
          type==0?"null": type==7?"real": "integer"
      );
................................................................................
        pParse->nVar = 0;
        pParse->nMem = 1;
        pParse->nTab = 1;
        sqlite3VdbeMakeReady(v, pParse);
      }
    }
   

    pBlob->iCol = iCol;
    pBlob->db = db;
    sqlite3BtreeLeaveAll(db);
    if( db->mallocFailed ){
      goto blob_open_out;
    }
    rc = blobSeekToRow(pBlob, iRow, &zErr);