Provide hints to the btree layer Next and Previous primitives to let them

know if they can be no-ops if the underlying index is unique.

FossilOrigin-Name: 6c643e45c274e755dc5a1a65673df79261c774be

manifest

@@ -1,5 +1,5 @@
-C Version\s3.8.3
-D 2014-02-03T13:52:03.248
+C Provide\shints\sto\sthe\sbtree\slayer\sNext\sand\sPrevious\sprimitives\sto\slet\sthem\s\nknow\sif\sthey\scan\sbe\sno-ops\sif\sthe\sunderlying\sindex\sis\sunique.
+D 2014-02-03T14:04:11.993
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -166,7 +166,7 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c a729e63cf5cd1829507cb7b8e89f99b95141bb53
 F src/bitvec.c 19a4ba637bd85f8f63fc8c9bae5ade9fb05ec1cb
 F src/btmutex.c 976f45a12e37293e32cae0281b15a21d48a8aaa7
-F src/btree.c 02e1a4e71d8fc37e9fd5216c15d989d148a77c87
+F src/btree.c 7b2c3cd16deedff7f4904f2e871e7b77328b9872
 F src/btree.h a61ddebc78c66795a2b93181321a116746302cc9
 F src/btreeInt.h f038e818bfadf75afbd09819ed93c26a333d39e0
 F src/build.c 7e6c275ab1731510d6f793d0f88373ab3e858e69
@@ -280,7 +280,7 @@ F src/update.c a7df6fffce6bfedc578fda6136dd33e34a63f8ee
 F src/utf.c 6fc6c88d50448c469c5c196acf21617a24f90269
 F src/util.c 15ac2627f548f5481d0d7e6c4eb67be673027695
 F src/vacuum.c 3728d74919d4fb1356f9e9a13e27773db60b7179
-F src/vdbe.c 5fe94e13fa56c50edb75263706b6fbcc860a3980
+F src/vdbe.c e703913e9a3b56d7824f3eb8b76d99f496ff6dc1
 F src/vdbe.h e6c4c610fcabad4fa80ebb1efc6822a9367e2b26
 F src/vdbeInt.h 42db251e9f863401ff847b90d5fe1614c89a6a56
 F src/vdbeapi.c ce4e68ea4842cc6081046f533d088dcf01d247ad
@@ -293,8 +293,8 @@ F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 7dc3966ef98b74422267e7e6e46e07ff6c6eb1b4
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 11edb74d587bc87b33ca96a5173e3ec1b8389e45
-F src/where.c 67ae3b5e97ecff36c70cb61ccc7d74cf228f1596
-F src/whereInt.h 96a75c61f1d2b9d4a8e4bb17d89deb0cf7cba358
+F src/where.c bacb79fb31e082c9c599e68e5e9f161e1d5430ca
+F src/whereInt.h 921f935af8b684ffb49705610bda7284db1db138
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 45c0201e28045ad38a530b5a144b73cd4aa2cfd6
@@ -1152,10 +1152,8 @@ F tool/vdbe-compress.tcl 0cf56e9263a152b84da86e75a5c0cdcdb7a47891
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P af3c775e5d6a399bfc985a5dae27451908766546
-R d59f4c16611ef76ed43b5f579f765c07
-T +bgcolor * #d0c0ff
-T +sym-release *
-T +sym-version-3.8.3 *
+P e816dd924619db5f766de6df74ea2194f3e3b538
+Q +a2c347faf91d82cf8734621bf378a6dd68b00957
+R be5a44c31c2829557525011b36aec00e
 U drh
-Z be66093eab6507921c2b573a40e5f8d7
+Z 23965260487a528a52632de193207045

manifest.uuid

@@ -1 +1 @@
-e816dd924619db5f766de6df74ea2194f3e3b538
+6c643e45c274e755dc5a1a65673df79261c774be

src/btree.c

@@ -4777,6 +4777,15 @@ int sqlite3BtreeEof(BtCursor *pCur){
 ** successful then set *pRes=0.  If the cursor
 ** was already pointing to the last entry in the database before
 ** this routine was called, then set *pRes=1.
+**
+** The calling function will set *pRes to 0 or 1.  The initial *pRes value
+** will be 1 if the cursor being stepped corresponds to an SQL index and
+** if this routine could have been skipped if that SQL index had been
+** a unique index.  Otherwise the caller will have set *pRes to zero.
+** Zero is the common case. The btree implementation is free to use the
+** initial *pRes value as a hint to improve performance, but the current
+** SQLite btree implementation does not. (Note that the comdb2 btree
+** implementation does use this hint, however.)
 */
 int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
   int rc;
@@ -4785,6 +4794,7 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
 
   assert( cursorHoldsMutex(pCur) );
   assert( pRes!=0 );
+  assert( *pRes==0 || *pRes==1 );
   assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
   if( pCur->eState!=CURSOR_VALID ){
     rc = restoreCursorPosition(pCur);
@@ -4863,6 +4873,15 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
 ** successful then set *pRes=0.  If the cursor
 ** was already pointing to the first entry in the database before
 ** this routine was called, then set *pRes=1.
+**
+** The calling function will set *pRes to 0 or 1.  The initial *pRes value
+** will be 1 if the cursor being stepped corresponds to an SQL index and
+** if this routine could have been skipped if that SQL index had been
+** a unique index.  Otherwise the caller will have set *pRes to zero.
+** Zero is the common case. The btree implementation is free to use the
+** initial *pRes value as a hint to improve performance, but the current
+** SQLite btree implementation does not. (Note that the comdb2 btree
+** implementation does use this hint, however.)
 */
 int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
   int rc;
@@ -4870,6 +4889,7 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
 
   assert( cursorHoldsMutex(pCur) );
   assert( pRes!=0 );
+  assert( *pRes==0 || *pRes==1 );
   assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
   pCur->atLast = 0;
   if( pCur->eState!=CURSOR_VALID ){
@@ -7096,7 +7116,7 @@ int sqlite3BtreeDelete(BtCursor *pCur){
   ** sub-tree headed by the child page of the cell being deleted. This makes
   ** balancing the tree following the delete operation easier.  */
   if( !pPage->leaf ){
-    int notUsed;
+    int notUsed = 0;
     rc = sqlite3BtreePrevious(pCur, &notUsed);
     if( rc ) return rc;
   }

src/vdbe.c

@@ -3599,6 +3599,7 @@ case OP_SeekGt: {       /* jump, in3 */
 #endif
   if( oc>=OP_SeekGe ){  assert( oc==OP_SeekGe || oc==OP_SeekGt );
     if( res<0 || (res==0 && oc==OP_SeekGt) ){
+      res = 0;
       rc = sqlite3BtreeNext(pC->pCursor, &res);
       if( rc!=SQLITE_OK ) goto abort_due_to_error;
       pC->rowidIsValid = 0;
@@ -3608,6 +3609,7 @@ case OP_SeekGt: {       /* jump, in3 */
   }else{
     assert( oc==OP_SeekLt || oc==OP_SeekLe );
     if( res>0 || (res==0 && oc==OP_SeekLt) ){
+      res = 0;
       rc = sqlite3BtreePrevious(pC->pCursor, &res);
       if( rc!=SQLITE_OK ) goto abort_due_to_error;
       pC->rowidIsValid = 0;
@@ -4460,7 +4462,7 @@ case OP_Rewind: {        /* jump */
   break;
 }
 
-/* Opcode: Next P1 P2 * * P5
+/* Opcode: Next P1 P2 P3 * P5
 **
 ** Advance cursor P1 so that it points to the next key/data pair in its
 ** table or index.  If there are no more key/value pairs then fall through
@@ -4470,6 +4472,11 @@ case OP_Rewind: {        /* jump */
 ** The P1 cursor must be for a real table, not a pseudo-table.  P1 must have
 ** been opened prior to this opcode or the program will segfault.
 **
+** The P3 value is a hint to the btree implementation. If P3==1, that
+** means P1 is an SQL index and that this instruction could have been
+** omitted if that index had been unique.  P3 is usually 0.  P3 is
+** always either 0 or 1.
+**
 ** P4 is always of type P4_ADVANCE. The function pointer points to
 ** sqlite3BtreeNext().
 **
@@ -4478,12 +4485,12 @@ case OP_Rewind: {        /* jump */
 **
 ** See also: Prev, NextIfOpen
 */
-/* Opcode: NextIfOpen P1 P2 * * P5
+/* Opcode: NextIfOpen P1 P2 P3 * P5
 **
 ** This opcode works just like OP_Next except that if cursor P1 is not
 ** open it behaves a no-op.
 */
-/* Opcode: Prev P1 P2 * * P5
+/* Opcode: Prev P1 P2 P3 * P5
 **
 ** Back up cursor P1 so that it points to the previous key/data pair in its
 ** table or index.  If there is no previous key/value pairs then fall through
@@ -4493,13 +4500,18 @@ case OP_Rewind: {        /* jump */
 ** The P1 cursor must be for a real table, not a pseudo-table.  If P1 is
 ** not open then the behavior is undefined.
 **
+** The P3 value is a hint to the btree implementation. If P3==1, that
+** means P1 is an SQL index and that this instruction could have been
+** omitted if that index had been unique.  P3 is usually 0.  P3 is
+** always either 0 or 1.
+**
 ** P4 is always of type P4_ADVANCE. The function pointer points to
 ** sqlite3BtreePrevious().
 **
 ** If P5 is positive and the jump is taken, then event counter
 ** number P5-1 in the prepared statement is incremented.
 */
-/* Opcode: PrevIfOpen P1 P2 * * P5
+/* Opcode: PrevIfOpen P1 P2 P3 * P5
 **
 ** This opcode works just like OP_Prev except that if cursor P1 is not
 ** open it behaves a no-op.
@@ -4521,9 +4533,12 @@ case OP_Next:          /* jump */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   assert( pOp->p5<ArraySize(p->aCounter) );
   pC = p->apCsr[pOp->p1];
+  res = pOp->p3;
   assert( pC!=0 );
   assert( pC->deferredMoveto==0 );
   assert( pC->pCursor );
+  assert( res==0 || (res==1 && pC->isTable==0) );
+  testcase( res==1 );
   assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
   assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );
   assert( pOp->opcode!=OP_NextIfOpen || pOp->p4.xAdvance==sqlite3BtreeNext );

src/where.c

@@ -3184,6 +3184,8 @@ static Bitmask codeOneLoopStart(
       pLevel->op = OP_Next;
     }
     pLevel->p1 = iIdxCur;
+    assert( (WHERE_UNQ_WANTED>>16)==1 );
+    pLevel->p3 = (pLoop->wsFlags>>16)&1;
     if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
       pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
     }else{
@@ -3986,12 +3988,13 @@ static int whereLoopAddBtreeIndex(
         || nInMul==0
       );
       pNew->wsFlags |= WHERE_COLUMN_EQ;
-      if( iCol<0  
-       || (pProbe->onError!=OE_None && nInMul==0
-           && pNew->u.btree.nEq==pProbe->nKeyCol-1)
-      ){
+      if( iCol<0 || (nInMul==0 && pNew->u.btree.nEq==pProbe->nKeyCol-1)){
         assert( (pNew->wsFlags & WHERE_COLUMN_IN)==0 || iCol<0 );
-        pNew->wsFlags |= WHERE_ONEROW;
+        if( iCol>=0 && pProbe->onError==OE_None ){
+          pNew->wsFlags |= WHERE_UNQ_WANTED;
+        }else{
+          pNew->wsFlags |= WHERE_ONEROW;
+        }
       }
       pNew->u.btree.nEq++;
       pNew->nOut = nRowEst + nInMul;
@@ -5785,7 +5788,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
     pLoop = pLevel->pWLoop;
     sqlite3VdbeResolveLabel(v, pLevel->addrCont);
     if( pLevel->op!=OP_Noop ){
-      sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
+      sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
       sqlite3VdbeChangeP5(v, pLevel->p5);
     }
     if( pLoop->wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){

src/whereInt.h

@@ -70,7 +70,7 @@ struct WhereLevel {
   int addrFirst;        /* First instruction of interior of the loop */
   int addrBody;         /* Beginning of the body of this loop */
   u8 iFrom;             /* Which entry in the FROM clause */
-  u8 op, p5;            /* Opcode and P5 of the opcode that ends the loop */
+  u8 op, p3, p5;        /* Opcode, P3 & P5 of the opcode that ends the loop */
   int p1, p2;           /* Operands of the opcode used to ends the loop */
   union {               /* Information that depends on pWLoop->wsFlags */
     struct {
@@ -457,3 +457,4 @@ struct WhereInfo {
 #define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
 #define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
 #define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
+#define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/