Add the OP_ReopenIdx opcode that works like OP_OpenRead except that it becomes

a no-op if the cursor is already open on the same index.  Update the
OR-optimization logic to make use of OP_ReopenIdx in order to avoid
unnecessary cursor open requests sent to the B-Tree layer.

FossilOrigin-Name: 77f412caf0192d3e7fecb377d6d72123d8b64424

manifest

@@ -1,5 +1,5 @@
-C The\soptimization\sof\scheck-in\s[b67a6e33f2]\sdoes\snot\swork\s(it\sgenerates\nincorrect\sVDBE\scode)\sif\san\sOR\sterm\sis\sAND-ed\swith\sa\sconstant\sexpression.\nSo\sback\sthat\soptimization\sout\sand\sadd\sa\stest\scase\sto\smake\ssure\sit\sdoes\snot\nget\sadded\sback\sin.
+C Add\sthe\sOP_ReopenIdx\sopcode\sthat\sworks\slike\sOP_OpenRead\sexcept\sthat\sit\sbecomes\na\sno-op\sif\sthe\scursor\sis\salready\sopen\son\sthe\ssame\sindex.\s\sUpdate\sthe\nOR-optimization\slogic\sto\smake\suse\sof\sOP_ReopenIdx\sin\sorder\sto\savoid\nunnecessary\scursor\sopen\srequests\ssent\sto\sthe\sB-Tree\slayer.
-D 2014-07-22T19:14:42.618
+D 2014-07-22T20:02:19.743
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5eb79e334a5de69c87740edd56af6527dd219308
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -227,7 +227,7 @@ F src/shell.c 566aee8213372a2e81ba0eb34e9759f7b2574009
 F src/sqlite.h.in fd8e3a36b0aded082dc93a4b89c1e85324b4cf75
 F src/sqlite3.rc 11094cc6a157a028b301a9f06b3d03089ea37c3e
 F src/sqlite3ext.h 886f5a34de171002ad46fae8c36a7d8051c190fc
-F src/sqliteInt.h 5dbcdcf81cb15e77df16f88699a15f7af491c580
+F src/sqliteInt.h b72a09326d7cbd8375ec3d9a04ea5e0cf476beb3
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 7ac05a5c7017d0b9f0b4bcd701228b784f987158
 F src/table.c 2cd62736f845d82200acfa1287e33feb3c15d62e
@@ -283,9 +283,9 @@ F src/update.c 01564b3c430f6c7b0a35afaf7aba7987206fa3a5
 F src/utf.c a0314e637768a030e6e84a957d0c4f6ba910cc05
 F src/util.c 049fe1d3c0e2209c1bee107aec2fcff6285f909f
 F src/vacuum.c 3728d74919d4fb1356f9e9a13e27773db60b7179
-F src/vdbe.c 2f3f0582dfacce292d3d6f22d129fe1abe3ddd00
+F src/vdbe.c fa74c6563486022920db4d73897bd9b837c7441d
 F src/vdbe.h c63fad052c9e7388d551e556e119c0bcf6bebdf8
-F src/vdbeInt.h 5df5e9afe9b7839cd17256220fc4f7af84b8b1cd
+F src/vdbeInt.h f41a7cf5a40e7abd994d5fe3a04589ae3e1154e7
 F src/vdbeapi.c 24e40422382beb774daab11fe9fe9d37e8a04949
 F src/vdbeaux.c 1ffe0bbc3a2c8aedd95622de9be6b6d07b3d3c6b
 F src/vdbeblob.c 9205ce9d3b064d9600f8418a897fc88b5687d9ac
@@ -296,7 +296,7 @@ F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 264df50a1b33124130b23180ded2e2c5663c652a
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 11edb74d587bc87b33ca96a5173e3ec1b8389e45
-F src/where.c 4e7e6bc639a938eb35c433bdca2aad80478fece4
+F src/where.c 0ffd586e04cd069ed6ce7f820194ccaa6cbd669e
 F src/whereInt.h 929c1349b5355fd44f22cee5c14d72b3329c58a6
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
@@ -1183,8 +1183,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 438c348a40383796a710499e4e1b7a6b08f75778
+P eed754fe93644f4df082eac0c0a7ffc5c78ccd10
-Q -b67a6e33f23ce5f5d9a545fa9d6700a7ed636901
+R 09dedf30e4922c66cabf472458c9ab58
-R 086bb10698e6defd83e7aae53f79809b
 U drh
-Z 6c73d4c61d83e0b2dc5ff58e1c82716d
+Z 96627cd265c0a3b75631b3111ef23fd4

manifest.uuid

@@ -1 +1 @@
-eed754fe93644f4df082eac0c0a7ffc5c78ccd10
+77f412caf0192d3e7fecb377d6d72123d8b64424

src/sqliteInt.h

@@ -2136,6 +2136,7 @@ struct SrcList {
 #define WHERE_DISTINCTBY       0x0200 /* pOrderby is really a DISTINCT clause */
 #define WHERE_WANT_DISTINCT    0x0400 /* All output needs to be distinct */
 #define WHERE_SORTBYGROUP      0x0800 /* Support sqlite3WhereIsSorted() */
+#define WHERE_REOPEN_IDX       0x1000 /* Try to use OP_ReopenIdx */
 
 /* Allowed return values from sqlite3WhereIsDistinct()
 */

src/vdbe.c

@@ -3205,7 +3205,21 @@ case OP_SetCookie: {       /* in3 */
 ** sequence of the index being opened. Otherwise, if P4 is an integer 
 ** value, it is set to the number of columns in the table.
 **
-** See also OpenWrite.
+** See also: OpenWrite, ReopenIdx
+*/
+/* Opcode: ReopenIdx P1 P2 P3 P4 P5
+** Synopsis: root=P2 iDb=P3
+**
+** The ReopenIdx opcode works exactly like ReadOpen except that it first
+** checks to see if the cursor on P1 is already open with a root page
+** number of P2 and if it is this opcode becomes a no-op.  In other words,
+** if the cursor is already open, do not reopen it.
+**
+** The ReopenIdx opcode may only be used with P5==0 and with P4 being
+** a P4_KEYINFO object.  Furthermore, the P3 value must be the same as
+** every other ReopenIdx or OpenRead for the same cursor number.
+**
+** See the OpenRead opcode documentation for additional information.
 */
 /* Opcode: OpenWrite P1 P2 P3 P4 P5
 ** Synopsis: root=P2 iDb=P3
@@ -3227,6 +3241,19 @@ case OP_SetCookie: {       /* in3 */
 **
 ** See also OpenRead.
 */
+case OP_ReopenIdx: {
+  VdbeCursor *pCur;
+
+  assert( pOp->p5==0 );
+  assert( pOp->p4type==P4_KEYINFO );
+  pCur = p->apCsr[pOp->p1];
+  if( pCur && pCur->pgnoRoot==pOp->p2 ){
+    assert( pCur->iDb==pOp->p3 );      /* Guaranteed by the code generator */
+    break;
+  }
+  /* If the cursor is not currently open or is open on a different
+  ** index, then fall through into OP_OpenRead to force a reopen */
+}
 case OP_OpenRead:
 case OP_OpenWrite: {
   int nField;
@@ -3241,7 +3268,8 @@ case OP_OpenWrite: {
   assert( (pOp->p5&(OPFLAG_P2ISREG|OPFLAG_BULKCSR))==pOp->p5 );
   assert( pOp->opcode==OP_OpenWrite || pOp->p5==0 );
   assert( p->bIsReader );
-  assert( pOp->opcode==OP_OpenRead || p->readOnly==0 );
+  assert( pOp->opcode==OP_OpenRead || pOp->opcode==OP_ReopenIdx
+          || p->readOnly==0 );
 
   if( p->expired ){
     rc = SQLITE_ABORT;
@@ -3298,6 +3326,7 @@ case OP_OpenWrite: {
   if( pCur==0 ) goto no_mem;
   pCur->nullRow = 1;
   pCur->isOrdered = 1;
+  pCur->pgnoRoot = p2;
   rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
   pCur->pKeyInfo = pKeyInfo;
   assert( OPFLAG_BULKCSR==BTREE_BULKLOAD );

src/vdbeInt.h

@@ -76,6 +76,7 @@ struct VdbeCursor {
   Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
   Bool isTable:1;       /* True if a table requiring integer keys */
   Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
+  Pgno pgnoRoot;        /* Root page of the open btree cursor */
   sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
   i64 seqCount;         /* Sequence counter */
   i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */

src/where.c

@@ -3422,6 +3422,7 @@ static Bitmask codeOneLoopStart(
     int iRetInit;                             /* Address of regReturn init */
     int untestedTerms = 0;             /* Some terms not completely tested */
     int ii;                            /* Loop counter */
+    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
     Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
     Table *pTab = pTabItem->pTab;
    
@@ -3517,6 +3518,8 @@ static Bitmask codeOneLoopStart(
     ** eliminating duplicates from other WHERE clauses, the action for each
     ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
     */
+    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
+                  WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY;
     for(ii=0; ii<pOrWc->nTerm; ii++){
       WhereTerm *pOrTerm = &pOrWc->a[ii];
       if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
@@ -3529,8 +3532,7 @@ static Bitmask codeOneLoopStart(
         }
         /* Loop through table entries that match term pOrTerm. */
         pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
-                        WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
+                                      wctrlFlags, iCovCur);
-                        WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY, iCovCur);
         assert( pSubWInfo || pParse->nErr || db->mallocFailed );
         if( pSubWInfo ){
           WhereLoop *pSubLoop;
@@ -3621,6 +3623,7 @@ static Bitmask codeOneLoopStart(
           ){
             assert( pSubWInfo->a[0].iIdxCur==iCovCur );
             pCov = pSubLoop->u.btree.pIndex;
+            wctrlFlags |= WHERE_REOPEN_IDX;
           }else{
             pCov = 0;
           }
@@ -6219,6 +6222,7 @@ WhereInfo *sqlite3WhereBegin(
         pWInfo->aiCurOnePass[1] = iIndexCur;
       }else if( iIdxCur && (wctrlFlags & WHERE_ONETABLE_ONLY)!=0 ){
         iIndexCur = iIdxCur;
+        if( wctrlFlags & WHERE_REOPEN_IDX ) op = OP_ReopenIdx;
       }else{
         iIndexCur = pParse->nTab++;
       }