If a table is on the rhs of a LEFT JOIN, include only terms from the joins ON(...) clause in the cursor-hint passed via OP_CursorHint.

FossilOrigin-Name: 2a2346b04235c6d0b7a8e64c92ee31018285c29f

manifest

@@ -1,5 +1,5 @@
-C Add\sa\smissing\sOP_ColumnsUsed\sopcode\sto\scode\sfor\sexpressions\slike\s"?\sIN\s(SELECT\s...)"\sin\scases\swhere\sexpression\scan\suse\san\sindex\sthat\smay\scontain\sNULL\svalues.
-D 2016-06-16T17:14:02.375
+C If\sa\stable\sis\son\sthe\srhs\sof\sa\sLEFT\sJOIN,\sinclude\sonly\sterms\sfrom\sthe\sjoins\sON(...)\sclause\sin\sthe\scursor-hint\spassed\svia\sOP_CursorHint.
+D 2016-06-17T14:33:32.727
 F Makefile.in f3f7d2060ce03af4584e711ef3a626ef0b1d6340
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 50149765ef72f4e652b9a0f1f6462c4784bb9423
@@ -464,7 +464,7 @@ F src/wal.h 2f7c831cf3b071fa548bf2d5cac640846a7ff19c
 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354
 F src/where.c 74f0798525b6306682d7234f230ea93f86959b9b
 F src/whereInt.h e5b939701a7ceffc5a3a8188a37f9746416ebcd0
-F src/wherecode.c ba71a4e4bada29aa9842200e6299714bf18c812c
+F src/wherecode.c b9d5f7d8ebed2e09376fd785a111ffd9dfd59ffc
 F src/whereexpr.c c32d47085dbaca0b8fd013210f56693c7d220d48
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test a6d901b436328bd67a79b41bb0ac2663918fe3bd
@@ -617,6 +617,7 @@ F test/cse.test 277350a26264495e86b1785f34d2d0c8600e021c
 F test/csv01.test 0929a9ce47021519512be92861f29e32d2538e5f
 F test/ctime.test 7bd009071e242aac4f18521581536b652b789a47
 F test/cursorhint.test 7bc346788390475e77a345da2b92270d04d35856
+F test/cursorhint2.test 532fdc678653f73e30770b59af0a47f9af0124ee
 F test/date.test 984ac1e3e5e031386866f034006148d3972b4a65
 F test/dbstatus.test 8de104bb5606f19537d23cd553b41349b5ab1204
 F test/dbstatus2.test e93ab03bfae6d62d4d935f20de928c19ca0ed0ab
@@ -1501,7 +1502,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 48b555c42de1cbc031fb6c2c93ef170e491c7d76
-R 7c056b92500e212b6fa7144618e1e6e0
+P 0b1579caf06a2c42433b8bc9dc28c9ad381aa07c
+R 2d1831333befb414525bf922ba35c127
+T *branch * cursor-hints
+T *sym-cursor-hints *
+T -sym-trunk *
 U dan
-Z 6cf13efbb72ea4474e244da36e8952f1
+Z b45fbbd37d7e68d5f1357e6143b6a1f1

manifest.uuid

@@ -1 +1 @@
-0b1579caf06a2c42433b8bc9dc28c9ad381aa07c
+2a2346b04235c6d0b7a8e64c92ee31018285c29f

src/wherecode.c

@@ -678,6 +678,7 @@ static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
 ** Insert an OP_CursorHint instruction if it is appropriate to do so.
 */
 static void codeCursorHint(
+  struct SrcList_item *pTabItem,  /* FROM clause item */
   WhereInfo *pWInfo,    /* The where clause */
   WhereLevel *pLevel,   /* Which loop to provide hints for */
   WhereTerm *pEndRange  /* Hint this end-of-scan boundary term if not NULL */
@@ -708,7 +709,31 @@ static void codeCursorHint(
     pTerm = &pWC->a[i];
     if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
     if( pTerm->prereqAll & pLevel->notReady ) continue;
-    if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
+
+    /* Any terms specified as part of the ON(...) clause for any LEFT 
+    ** JOIN for which the current table is not the rhs are omitted
+    ** from the cursor-hint. 
+    **
+    ** If this table is the rhs of a LEFT JOIN, only terms that were
+    ** specified as part of the ON(...) clause may be included in the 
+    ** hint. This is to address the following:
+    **
+    **   SELECT ... t1 LEFT JOIN t2 ON (t1.a=t2.b) WHERE t2.c IS NULL;
+    **
+    ** If the (t2.c IS NULL) constraint is pushed down to the cursor, it
+    ** might filter out all rows that match (t1.a=t2.b), causing SQLite
+    ** to add a row of NULL values to the output that should not be
+    ** present (since the ON clause does actually match rows within t2).
+    */
+    if( pTabItem->fg.jointype & JT_LEFT ){
+      if( !ExprHasProperty(pTerm->pExpr, EP_FromJoin) 
+       || pTerm->pExpr->iRightJoinTable!=pTabItem->iCursor
+      ){
+        continue;
+      }
+    }else{
+      if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
+    }
 
     /* All terms in pWLoop->aLTerm[] except pEndRange are used to initialize
     ** the cursor.  These terms are not needed as hints for a pure range
@@ -742,7 +767,7 @@ static void codeCursorHint(
   }
 }
 #else
-# define codeCursorHint(A,B,C)  /* No-op */
+# define codeCursorHint(A,B,C,D)  /* No-op */
 #endif /* SQLITE_ENABLE_CURSOR_HINTS */
 
 /*
@@ -998,7 +1023,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       pStart = pEnd;
       pEnd = pTerm;
     }
-    codeCursorHint(pWInfo, pLevel, pEnd);
+    codeCursorHint(pTabItem, pWInfo, pLevel, pEnd);
     if( pStart ){
       Expr *pX;             /* The expression that defines the start bound */
       int r1, rTemp;        /* Registers for holding the start boundary */
@@ -1212,7 +1237,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     ** and store the values of those terms in an array of registers
     ** starting at regBase.
     */
-    codeCursorHint(pWInfo, pLevel, pRangeEnd);
+    codeCursorHint(pTabItem, pWInfo, pLevel, pRangeEnd);
     regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
     assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
     if( zStartAff ) cEndAff = zStartAff[nEq];
@@ -1660,7 +1685,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
       pLevel->op = OP_Noop;
     }else{
-      codeCursorHint(pWInfo, pLevel, 0);
+      codeCursorHint(pTabItem, pWInfo, pLevel, 0);
       pLevel->op = aStep[bRev];
       pLevel->p1 = iCur;
       pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);

test/cursorhint2.test

@@ -0,0 +1,101 @@
+# 2016 June 17
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library. The
+# focus is on testing that cursor-hints are correct for queries
+# involving LEFT JOIN.
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set ::testprefix cursorhint2
+
+ifcapable !cursorhints {
+  finish_test
+  return
+}
+
+proc extract_hints {sql} {
+
+  db eval "SELECT tbl_name, rootpage FROM sqlite_master where rootpage" {
+    set lookup($rootpage) $tbl_name
+  }
+
+  set ret [list]
+  db eval "EXPLAIN $sql" a {
+    switch -- $a(opcode) {
+      OpenRead {
+        set csr($a(p1)) $lookup($a(p2))
+      }
+      CursorHint { 
+        lappend ret $csr($a(p1)) $a(p4) 
+      }
+    }
+  }
+
+  set ret
+}
+
+proc do_extract_hints_test {tn sql ret} {
+  uplevel [list do_test $tn [list extract_hints $sql] [list {*}$ret]]
+}
+
+do_execsql_test 1.0 {
+  PRAGMA automatic_index = 0;
+  CREATE TABLE t1(a, b);
+  CREATE TABLE t2(c, d);
+  CREATE TABLE t3(e, f);
+}
+
+do_extract_hints_test $tn.1.1 {
+  SELECT * FROM t1 WHERE a=1;
+} {
+  t1 EQ(c0,1)
+}
+
+do_extract_hints_test $tn.1.2 {
+  SELECT * FROM t1 CROSS JOIN t2 ON (a=c) WHERE d IS NULL;
+} {
+  t2 {AND(ISNULL(c1),EQ(r[1],c0))}
+}
+
+do_extract_hints_test $tn.1.3 {
+  SELECT * FROM t1 LEFT JOIN t2 ON (a=c) WHERE d IS NULL;
+} {
+  t2 {EQ(r[2],c0)}
+}
+
+do_extract_hints_test $tn.1.4 {
+  SELECT * FROM t1 LEFT JOIN t2 ON (a=c AND a=10) WHERE d IS NULL;
+} {
+  t2 {AND(EQ(r[2],c0),EQ(r[3],10))}
+}
+
+do_extract_hints_test $tn.1.5 {
+  SELECT * FROM t1 CROSS JOIN t2 ON (a=c AND a=10) WHERE d IS NULL;
+} {
+  t1 EQ(c0,10) t2 {AND(ISNULL(c1),EQ(r[3],c0))}
+}
+
+do_extract_hints_test $tn.1.6 {
+  SELECT * FROM t1 LEFT JOIN t2 ON (a=c) LEFT JOIN t3 ON (d=f);
+} {
+  t2 {EQ(r[2],c0)} t3 {EQ(r[6],c1)}
+}
+
+do_extract_hints_test $tn.1.6 {
+  SELECT * FROM t1 LEFT JOIN t2 ON (a=c AND d=e) LEFT JOIN t3 ON (d=f);
+} {
+  t2 {EQ(r[2],c0)} t3 {EQ(r[6],c1)}
+}
+
+finish_test
+