Minor performance optimizations to sqlite3_blob_open() and

sqlite3_blob_reopen().

FossilOrigin-Name: 52a61967d920047ea0b4409b79793e05c0128964

manifest

@@ -1,5 +1,5 @@
-C If\scompiled\swith\sSQLITE_INLINE_MEMCPY,\sall\smemcpy()\scalls\sare\sreplaced\swith\nin-line\scode.\s\sWith\sthat\schange,\scachegrind\sshows\swhich\smemcpy()\scalls\nare\staking\sthe\smost\stime.\s\sThis\sis\sa\sperformance-measurement\shack\sonly\sand\nis\snot\sfor\sproduction\suse.
-D 2017-01-19T21:20:11.204
+C Minor\sperformance\soptimizations\sto\ssqlite3_blob_open()\sand\nsqlite3_blob_reopen().
+D 2017-01-20T00:40:26.827
 F Makefile.in 41bd4cad981487345c4a84081074bcdb876e4b2e
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@ -462,7 +462,7 @@ F src/vdbe.h b0866e4191f096f1c987a84b042c3599bdf5423b
 F src/vdbeInt.h 281cb70332dc8b593b8c7afe776f3a2ba7d4255e
 F src/vdbeapi.c d6ebaa465f070eb1af8ba4e7b34583ece87bdd24
 F src/vdbeaux.c 35c9a9908174e5a26c96d15e1f98214814a39147
-F src/vdbeblob.c f4f98ea672b242f807c08c92c7faaa79e5091b65
+F src/vdbeblob.c fe3694fcc3cf2cad395416f5289bd0e935c2659d
 F src/vdbemem.c 3b5a9a5b375458d3e12a50ae1aaa41eeec2175fd
 F src/vdbesort.c eda25cb2d1727efca6f7862fea32b8aa33c0face
 F src/vdbetrace.c 41963d5376f0349842b5fc4aaaaacd7d9cdc0834
@@ -1547,7 +1547,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ffd559afd32dcdce9c733ebccdee88fda9b689cf
-R fad09dad35bb606057a537179db15d76
+P 9ed38521617136223a667988aed40e25797faf84
+R b4a609734c03fe3500908ef05ac99d6b
 U drh
-Z 52e9f95dbec08dacc595dc3f0b2e0450
+Z 622609d2384fcdd28fbe219ab3e3b191

manifest.uuid

@@ -1 +1 @@
-9ed38521617136223a667988aed40e25797faf84
+52a61967d920047ea0b4409b79793e05c0128964

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);