Minor performance optimizations to sqlite3_blob_open() and

sqlite3_blob_reopen().

FossilOrigin-Name: 52a61967d920047ea0b4409b79793e05c0128964

1 files changed, 17 insertions, 13 deletions

diff --git a/src/vdbeblob.c b/src/vdbeblob.c
index 520d16c98..b2902ba32 100644
--- a/src/vdbeblob.c
+++ b/src/vdbeblob.c
@@ -57,12 +57,17 @@ static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
   char *zErr = 0;                 /* Error message */
   Vdbe *v = (Vdbe *)p->pStmt;
 
-  /* Set the value of the SQL statements only variable to integer iRow. 
-  ** This is done directly instead of using sqlite3_bind_int64() to avoid 
-  ** triggering asserts related to mutexes.
+  /* Set the value of register r[1] in the SQL statement to integer iRow. 
+  ** This is done directly as a performance optimization
   */
-  assert( v->aVar[0].flags&MEM_Int );
-  v->aVar[0].u.i = iRow;
+  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 ){
@@ -257,12 +262,11 @@ int sqlite3_blob_open(
       static const VdbeOpList openBlob[] = {
         {OP_TableLock,      0, 0, 0},  /* 0: Acquire a read or write lock */
         {OP_OpenRead,       0, 0, 0},  /* 1: Open a cursor */
-        {OP_Variable,       1, 1, 0},  /* 2: Move ?1 into reg[1] */
-        {OP_NotExists,      0, 7, 1},  /* 3: Seek the cursor */
-        {OP_Column,         0, 0, 1},  /* 4  */
-        {OP_ResultRow,      1, 0, 0},  /* 5  */
-        {OP_Goto,           0, 2, 0},  /* 6  */
-        {OP_Halt,           0, 0, 0},  /* 7  */
+        /* blobSeekToRow() will initialize r[1] to the desired rowid */
+        {OP_NotExists,      0, 5, 1},  /* 2: Seek the cursor to rowid=r[1] */
+        {OP_Column,         0, 0, 1},  /* 3  */
+        {OP_ResultRow,      1, 0, 0},  /* 4  */
+        {OP_Halt,           0, 0, 0},  /* 5  */
       };
       Vdbe *v = (Vdbe *)pBlob->pStmt;
       int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
@@ -306,9 +310,9 @@ int sqlite3_blob_open(
         */
         aOp[1].p4type = P4_INT32;
         aOp[1].p4.i = pTab->nCol+1;
-        aOp[4].p2 = pTab->nCol;
+        aOp[3].p2 = pTab->nCol;
 
-        pParse->nVar = 1;
+        pParse->nVar = 0;
         pParse->nMem = 1;
         pParse->nTab = 1;
         sqlite3VdbeMakeReady(v, pParse);