In a query with both ORDER BY and LIMIT, if the inner loop satisfies the

ORDER BY then try to cut short each invocation of the inner loop once the
LIMIT has been satisfied.  This check-in is a partial implementation only.

FossilOrigin-Name: 852d1eda6ecca1171f6ed800b06f5b4854672002

manifest

@@ -1,5 +1,5 @@
-C Fixup\scomments\son\swctrlFlags\svalue\sdefinitions.
-D 2016-05-19T19:31:30.127
+C In\sa\squery\swith\sboth\sORDER\sBY\sand\sLIMIT,\sif\sthe\sinner\sloop\ssatisfies\sthe\s\nORDER\sBY\sthen\stry\sto\scut\sshort\seach\sinvocation\sof\sthe\sinner\sloop\sonce\sthe\nLIMIT\shas\sbeen\ssatisfied.\s\sThis\scheck-in\sis\sa\spartial\simplementation\sonly.
+D 2016-05-19T22:13:37.318
 F Makefile.in f59e0763ff448719fc1bd25513882b0567286317
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 306d73e854b1a92ea06e5d1e637faa5c44de53c7
@@ -378,12 +378,12 @@ F src/printf.c a5f0ca08ddede803c241266abb46356ec748ded1
 F src/random.c ba2679f80ec82c4190062d756f22d0c358180696
 F src/resolve.c cca3aa77b95706df5d635a2141a4d1de60ae6598
 F src/rowset.c 49eb91c588a2bab36647368e031dc5b66928149d
-F src/select.c fd4a7ce2937497181063cfedb92058ac89491a5d
+F src/select.c 131eeddfcaf3777c4acd4727bf742b98af8183b5
 F src/shell.c 14ff7f660530a52b117d110ba3390b7b2eb719b6
 F src/sqlite.h.in 9984129d86243424b765fcb3f147c697bd20bb54
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 98f72cbfe00169c39089115427d06ea05fe4b4a2
-F src/sqliteInt.h 19de316bfce65ff074b379a67b493a446f3cf8ee
+F src/sqliteInt.h 863cf0d421611ccfa30541ee5ffe761c896ffa5b
 F src/sqliteLimit.h c0373387c287c8d0932510b5547ecde31b5da247
 F src/status.c 70912d7be68e9e2dbc4010c93d344af61d4c59ba
 F src/table.c 5226df15ab9179b9ed558d89575ea0ce37b03fc9
@@ -458,8 +458,8 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 4db22ed7e77bcf672b1a685d6ddeffba8d5be302
 F src/wal.h 2f7c831cf3b071fa548bf2d5cac640846a7ff19c
 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354
-F src/where.c 72fd2e1258625c1aee8e33a529914aea2d487422
-F src/whereInt.h 3b1fc240e322613ba4e9dc857ca9c7c3390acc74
+F src/where.c a7454e62ca13f1ff54892339022f8cb0a8bb3728
+F src/whereInt.h 6e18240be400bef8e4dbafea605251707c5dbf49
 F src/wherecode.c e3f18fcda2d7f8218a09dc33cf495dca0efa6e3e
 F src/whereexpr.c eacc0e60d029a082b4fc0cc42ea98544add1319e
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@@ -1489,7 +1489,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P d01305841da94b2d47e32744802f69525bf590df
-R be830660ecf90ba00189952af638cb97
+P 58b516e8c0b00a41bc0364eab267bc2ecb9efeff
+R 766495aa6109f75a3c3b0e829e8d3b47
+T *branch * orderby-limit
+T *sym-orderby-limit *
+T -sym-trunk *
 U drh
-Z 54bddff0ee366139e2fb13081e6cf75a
+Z 1f191cc43f073ab10b6b672b5a12f950

manifest.uuid

@@ -1 +1 @@
-58b516e8c0b00a41bc0364eab267bc2ecb9efeff
+852d1eda6ecca1171f6ed800b06f5b4854672002

src/select.c

@@ -56,6 +56,7 @@ struct SortCtx {
   int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
   int labelDone;        /* Jump here when done, ex: LIMIT reached */
   u8 sortFlags;         /* Zero or more SORTFLAG_* bits */
+  u8 bOrderedInnerLoop; /* ORDER BY correctly sorts the inner loop */
 };
 #define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */
 
@@ -589,9 +590,29 @@ static void pushOntoSorter(
   sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
   if( iLimit ){
     int addr;
+    int r1 = 0;
+    /* Fill the sorter until it contains LIMIT+OFFSET entries.  (The iLimit
+    ** register is initialized with value of LIMIT+OFFSET.)  After the sorter
+    ** fills up, delete the least entry in the sorter after each insert.
+    ** Thus we never hold more than the LIMIT+OFFSET rows in memory at once */
     addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, 1); VdbeCoverage(v);
     sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
+    if( pSort->bOrderedInnerLoop ){
+      r1 = ++pParse->nMem;
+      sqlite3VdbeAddOp3(v, OP_Column, pSort->iECursor, nExpr, r1);
+      VdbeComment((v, "seq"));
+    }
     sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
+    if( pSort->bOrderedInnerLoop ){
+      /* If the inner loop is driven by an index such that values from
+      ** the same iteration of the inner loop are in sorted order, then
+      ** immediately jump to the next iteration of an inner loop if the
+      ** entry from the current iteration does not fit into the top
+      ** LIMIT+OFFSET entries of the sorter. */
+      int iBrk = sqlite3VdbeCurrentAddr(v) + 2;
+      sqlite3VdbeAddOp3(v, OP_Eq, regBase+nExpr, iBrk, r1);
+      VdbeCoverage(v);
+    }
     sqlite3VdbeJumpHere(v, addr);
   }
 }
@@ -5176,6 +5197,7 @@ int sqlite3Select(
     }
     if( sSort.pOrderBy ){
       sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);
+      sSort.bOrderedInnerLoop = sqlite3WhereOrderedInnerLoop(pWInfo);
       if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
         sSort.pOrderBy = 0;
       }

src/sqliteInt.h

@@ -3637,6 +3637,7 @@ void sqlite3WhereEnd(WhereInfo*);
 LogEst sqlite3WhereOutputRowCount(WhereInfo*);
 int sqlite3WhereIsDistinct(WhereInfo*);
 int sqlite3WhereIsOrdered(WhereInfo*);
+int sqlite3WhereOrderedInnerLoop(WhereInfo*);
 int sqlite3WhereIsSorted(WhereInfo*);
 int sqlite3WhereContinueLabel(WhereInfo*);
 int sqlite3WhereBreakLabel(WhereInfo*);

src/where.c

@@ -51,6 +51,18 @@ int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
   return pWInfo->nOBSat;
 }
 
+/*
+** Return TRUE if the innermost loop of the WHERE clause implementation
+** returns rows in ORDER BY order for complete run of the inner loop.
+**
+** Across multiple iterations of outer loops, the output rows need not be
+** sorted.  As long as rows are sorted for just the innermost loop, this
+** routine can return TRUE.
+*/
+int sqlite3WhereOrderedInnerLoop(WhereInfo *pWInfo){
+  return pWInfo->bOrderedInnerLoop;
+}
+
 /*
 ** Return the VDBE address or label to jump to in order to continue
 ** immediately with the next row of a WHERE clause.
@@ -3898,8 +3910,10 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
       }
     }else{
       pWInfo->nOBSat = pFrom->isOrdered;
-      if( pWInfo->nOBSat<0 ) pWInfo->nOBSat = 0;
       pWInfo->revMask = pFrom->revLoop;
+      if( pWInfo->nOBSat<=0 ){
+        pWInfo->nOBSat = 0;
+      }
     }
     if( (pWInfo->wctrlFlags & WHERE_SORTBYGROUP)
         && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr && nLoop>0

src/whereInt.h

@@ -418,8 +418,9 @@ struct WhereInfo {
   u8 sorted;                /* True if really sorted (not just grouped) */
   u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
   u8 untestedTerms;         /* Not all WHERE terms resolved by outer loop */
-  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values below */
+  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
   u8 nLevel;                /* Number of nested loop */
+  u8 bOrderedInnerLoop;     /* True if only the inner-most loop is ordered */
   int iTop;                 /* The very beginning of the WHERE loop */
   int iContinue;            /* Jump here to continue with next record */
   int iBreak;               /* Jump here to break out of the loop */