Simplifications to the VDBE bytecode that handles LIMIT and OFFSET.

FossilOrigin-Name: 041df7c2f14b95868a08090354ebb3308050790e

manifest

@@ -1,5 +1,5 @@
-C Optimizations\sfor\sfts5\sexpressions\sthat\sfilter\son\scolumn.\sMore\sstill\sto\scome.
+C Simplifications\sto\sthe\sVDBE\sbytecode\sthat\shandles\sLIMIT\sand\sOFFSET.
-D 2015-10-06T20:53:26.753
+D 2015-10-06T21:07:06.319
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2143eeef6d0cc26006ae5fc4bb242a4a8b973412
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -335,14 +335,14 @@ F src/parse.y f599aa5e871a493330d567ced93de696f61f48f7
 F src/pcache.c 24be750c79272e0ca7b6e007bc94999700f3e5ef
 F src/pcache.h 9968603796240cdf83da7e7bef76edf90619cea9
 F src/pcache1.c e822007159d53a7ea7aa040d6e28964ddb6de083
-F src/pragma.c 234814978bcd35bce6e2874dfb2f5b5e28e7fb38
+F src/pragma.c dcfe3a35d2de935feeaba1455528b4a5c4f1208c
 F src/pragma.h 631a91c8b0e6ca8f051a1d8a4a0da4150e04620a
 F src/prepare.c 82e5db1013846a819f198336fed72c44c974e7b1
 F src/printf.c 0c4bcdd1c2e2521024f0a69cb5eb334f86b3652a
 F src/random.c ba2679f80ec82c4190062d756f22d0c358180696
 F src/resolve.c 1954a0f01bf65d78d7d559aea3d5c67f33376d91
 F src/rowset.c eccf6af6d620aaa4579bd3b72c1b6395d9e9fa1e
-F src/select.c 8fb8cb0230aed9b12b3582ddc366ffbc549041d7
+F src/select.c 2c4bfdf7c797df9b43121ed7850bf939b6f27405
 F src/shell.c dfd18e56fcb88dd79378774e9bc3246a9bd52243
 F src/sqlite.h.in 4b76d74d69af48c534c58fb723137dc6944bdedc
 F src/sqlite3.rc 992c9f5fb8285ae285d6be28240a7e8d3a7f2bad
@@ -405,7 +405,7 @@ F src/update.c a134027f59c7eb6e63ed18e2d5dd8ef0ce7f8ff8
 F src/utf.c fc6b889ba0779b7722634cdeaa25f1930d93820c
 F src/util.c fc612367108b74573c5fd13a85d0a23027f438bd
 F src/vacuum.c 2ddd5cad2a7b9cef7f9e431b8c7771634c6b1701
-F src/vdbe.c 5048103aa6bc9c01bf1a4620729256d1e873bb6c
+F src/vdbe.c d263ec6b29d8e8e8178235b8403a00ccb48748d0
 F src/vdbe.h 4bc88bd0e06f8046ee6ab7487c0015e85ad949ad
 F src/vdbeInt.h 8b867eac234e28627ffcace3cd4b4b79bbec664b
 F src/vdbeapi.c 020681b943e77766b32ae1cddf86d7831b7374ca
@@ -1392,7 +1392,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 4b631364354068af95a01630469cb6fbfe8b52fd
+P bf1607ac155018573ca40fb58aca62c5fea7e60b
-R 8d25a208807a117d422df371476abd9e
+R f75f4370adf88bb173a9ed2d414ba858
-U dan
+U drh
-Z f7ba9c7b6fd75653c93e200489a4e473
+Z 3f5b7bfbaf5afcf9be7e111589aea155

manifest.uuid

@@ -1 +1 @@
-bf1607ac155018573ca40fb58aca62c5fea7e60b
+041df7c2f14b95868a08090354ebb3308050790e

src/pragma.c

@@ -1361,8 +1361,9 @@ void sqlite3Pragma(
     */
     static const int iLn = VDBE_OFFSET_LINENO(2);
     static const VdbeOpList endCode[] = {
-      { OP_IfNeg,       1, 0,        0},    /* 0 */
+      { OP_AddImm,      1, 0,        0},    /* 0 */
-      { OP_String8,     0, 3,        0},    /* 1 */
+      { OP_If,          1, 0,        0},    /* 1 */
+      { OP_String8,     0, 3,        0},    /* 2 */
       { OP_ResultRow,   3, 1,        0},
     };
 
@@ -1563,9 +1564,9 @@ void sqlite3Pragma(
       } 
     }
     addr = sqlite3VdbeAddOpList(v, ArraySize(endCode), endCode, iLn);
-    sqlite3VdbeChangeP3(v, addr, -mxErr);
+    sqlite3VdbeChangeP2(v, addr, -mxErr);
-    sqlite3VdbeJumpHere(v, addr);
+    sqlite3VdbeJumpHere(v, addr+1);
-    sqlite3VdbeChangeP4(v, addr+1, "ok", P4_STATIC);
+    sqlite3VdbeChangeP4(v, addr+2, "ok", P4_STATIC);
   }
   break;
 #endif /* SQLITE_OMIT_INTEGRITY_CHECK */

src/select.c

@@ -579,7 +579,7 @@ static void pushOntoSorter(
     }else{
       iLimit = pSelect->iLimit;
     }
-    addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, -1); VdbeCoverage(v);
+    addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, 1); VdbeCoverage(v);
     sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
     sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
     sqlite3VdbeJumpHere(v, addr);
@@ -595,11 +595,8 @@ static void codeOffset(
   int iContinue     /* Jump here to skip the current record */
 ){
   if( iOffset>0 ){
-    int addr;
+    sqlite3VdbeAddOp3(v, OP_IfPos, iOffset, iContinue, 1); VdbeCoverage(v);
-    addr = sqlite3VdbeAddOp3(v, OP_IfNeg, iOffset, 0, -1); VdbeCoverage(v);
+    VdbeComment((v, "OFFSET"));
-    sqlite3VdbeGoto(v, iContinue);
-    VdbeComment((v, "skip OFFSET records"));
-    sqlite3VdbeJumpHere(v, addr);
   }
 }
 
@@ -1815,7 +1812,7 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
   Vdbe *v = 0;
   int iLimit = 0;
   int iOffset;
-  int addr1, n;
+  int n;
   if( p->iLimit ) return;
 
   /* 
@@ -1850,14 +1847,10 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
       sqlite3ExprCode(pParse, p->pOffset, iOffset);
       sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
       VdbeComment((v, "OFFSET counter"));
-      addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset); VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iOffset, iOffset, 0);
-      sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
-      sqlite3VdbeJumpHere(v, addr1);
       sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
       VdbeComment((v, "LIMIT+OFFSET"));
-      addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit); VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iLimit, iOffset+1, -1);
-      sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
-      sqlite3VdbeJumpHere(v, addr1);
     }
   }
 }
@@ -2274,14 +2267,9 @@ static int multiSelect(
         addr = sqlite3VdbeAddOp1(v, OP_IfNot, p->iLimit); VdbeCoverage(v);
         VdbeComment((v, "Jump ahead if LIMIT reached"));
         if( p->iOffset ){
-          int addr2;
+          sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iOffset, p->iOffset, 0);
           sqlite3VdbeAddOp3(v, OP_Add, p->iLimit, p->iOffset, p->iOffset+1);
-          addr2 = sqlite3VdbeAddOp1(v, OP_IfPos, p->iOffset); VdbeCoverage(v);
+          sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iLimit, p->iOffset+1, -1);
-          sqlite3VdbeAddOp2(v, OP_SCopy, p->iLimit, p->iOffset+1);
-          sqlite3VdbeJumpHere(v, addr2);
-          addr2 = sqlite3VdbeAddOp1(v, OP_IfPos, p->iLimit); VdbeCoverage(v);
-          sqlite3VdbeAddOp2(v, OP_Integer, -1, p->iOffset+1);
-          sqlite3VdbeJumpHere(v, addr2);
         }
       }
       explainSetInteger(iSub2, pParse->iNextSelectId);

src/vdbe.c

@@ -5671,12 +5671,12 @@ case OP_MemMax: {        /* in2 */
 }
 #endif /* SQLITE_OMIT_AUTOINCREMENT */
 
-/* Opcode: IfPos P1 P2 * * *
+/* Opcode: IfPos P1 P2 P3 * *
-** Synopsis: if r[P1]>0 goto P2
+** Synopsis: if r[P1]>0 then r[P1]-=P3, goto P2
 **
 ** Register P1 must contain an integer.
-** If the value of register P1 is 1 or greater, jump to P2 and
+** If the value of register P1 is 1 or greater, subtrace P3 from the
-** add the literal value P3 to register P1.
+** value in P1 and jump to P2.
 **
 ** If the initial value of register P1 is less than 1, then the
 ** value is unchanged and control passes through to the next instruction.
@@ -5685,38 +5685,44 @@ case OP_IfPos: {        /* jump, in1 */
   pIn1 = &aMem[pOp->p1];
   assert( pIn1->flags&MEM_Int );
   VdbeBranchTaken( pIn1->u.i>0, 2);
-  if( pIn1->u.i>0 ) goto jump_to_p2;
+  if( pIn1->u.i>0 ){
+    pIn1->u.i -= pOp->p3;
+    goto jump_to_p2;
+  }
   break;
 }
 
-/* Opcode: IfNeg P1 P2 P3 * *
+/* Opcode: SetIfNotPos P1 P2 P3 * *
-** Synopsis: r[P1]+=P3, if r[P1]<0 goto P2
+** Synopsis: if r[P1]<=0 then r[P2]=P3
 **
-** Register P1 must contain an integer.  Add literal P3 to the value in
+** Register P1 must contain an integer.
-** register P1 then if the value of register P1 is less than zero, jump to P2. 
+** If the value of register P1 is not positive (if it is less than 1) then
+** set the value of register P2 to be the integer P3.
 */
-case OP_IfNeg: {        /* jump, in1 */
+case OP_SetIfNotPos: {        /* in1, in2 */
   pIn1 = &aMem[pOp->p1];
   assert( pIn1->flags&MEM_Int );
-  pIn1->u.i += pOp->p3;
+  if( pIn1->u.i<=0 ){
-  VdbeBranchTaken(pIn1->u.i<0, 2);
+    pOut = out2Prerelease(p, pOp);
-  if( pIn1->u.i<0 ) goto jump_to_p2;
+    pOut->u.i = pOp->p3;
+  }
   break;
 }
 
 /* Opcode: IfNotZero P1 P2 P3 * *
-** Synopsis: if r[P1]!=0 then r[P1]+=P3, goto P2
+** Synopsis: if r[P1]!=0 then r[P1]-=P3, goto P2
 **
 ** Register P1 must contain an integer.  If the content of register P1 is
-** initially nonzero, then add P3 to P1 and jump to P2.  If register P1 is
+** initially nonzero, then subtrace P3 from the value in register P1 and
-** initially zero, leave it unchanged and fall through.
+** jump to P2.  If register P1 is initially zero, leave it unchanged
+** and fall through.
 */
 case OP_IfNotZero: {        /* jump, in1 */
   pIn1 = &aMem[pOp->p1];
   assert( pIn1->flags&MEM_Int );
   VdbeBranchTaken(pIn1->u.i<0, 2);
   if( pIn1->u.i ){
-     pIn1->u.i += pOp->p3;
+     pIn1->u.i -= pOp->p3;
      goto jump_to_p2;
   }
   break;