The push-down optimization was being too aggressive such that it sometimes

generated incorrect results.  Reinstate the restriction (4) (with
qualifications) that was removed by check-ins
[b5d3dd8cb0b1e4] and [dd568c27b1d765].

FossilOrigin-Name: f08c1731b0b1dddcba190b094a35306a159713d3db939330f73075ff1d72c81e

manifest

@@ -1,5 +1,5 @@
-C Provide\sthe\sability\sfor\sthe\sVFS\sto\sdo\sa\sblocking\swait\son\slocks\sif\scompiled\nwith\sSQLITE_ENABLE_SETLK_TIMEOUT.
-D 2018-03-27T13:57:31.556
+C The\spush-down\soptimization\swas\sbeing\stoo\saggressive\ssuch\sthat\sit\ssometimes\ngenerated\sincorrect\sresults.\s\sReinstate\sthe\srestriction\s(4)\s(with\nqualifications)\sthat\swas\sremoved\sby\scheck-ins\n[b5d3dd8cb0b1e4]\sand\s[dd568c27b1d765].
+D 2018-03-27T15:13:43.312
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in 7016fc56c6b9bfe5daac4f34be8be38d8c0b5fab79ccbfb764d3b23bf1c6fff3
@@ -491,7 +491,7 @@ F src/printf.c d3b7844ddeb11fbbdd38dd84d09c9c1ac171d21fb038473c3aa97981201cc660
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 66c73fcb7719b8ff0e841b58338f13604ff3e2b50a723f9b8f383595735262f6
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
-F src/select.c 2c408ab9b4bfc807e6a9d3d45337d20ebe72a8b7ac793854710bf9d572e7ab6d
+F src/select.c e51efe5479d1cb4f48defe0b97cdba7391df42a755ba9592b9159510d03cf738
 F src/shell.c.in d6a07811aa9f3b10200c15ab8dd4b6b998849a3b0c8b125bfa980329a33c26a6
 F src/sqlite.h.in 56e6c8fb785b09dac31331d19680f7133d84cb96fc073a47847f1066e03fc2ff
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -1006,7 +1006,7 @@ F test/ioerr5.test 2edfa4fb0f896f733071303b42224df8bedd9da4
 F test/ioerr6.test a395a6ab144b26a9e3e21059a1ab6a7149cca65b
 F test/istrue.test d6e659764da5ccc03adcdba18fe77d7917ba5e4abd04ef14bd4e4cf43e024b5b
 F test/join.test 730e3e8d511289531efca01f8684f98da1e6de51eacf95c5960d0c46e77719e3
-F test/join2.test 2339e3a8089178607a718c7fa1f6c3826579132396f5304a0f8e9dbefa60c84f
+F test/join2.test f5ea0fd3b0a441c8e439706339dcd17cec63a896a755c04a30bfd442ecce1190
 F test/join3.test 6f0c774ff1ba0489e6c88a3e77b9d3528fb4fda0
 F test/join4.test 1a352e4e267114444c29266ce79e941af5885916
 F test/join5.test c6bd62effc37a152bea735f9ef241b19bb967bd4593dc99b20e2fc55ae707e38
@@ -1717,8 +1717,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P c7473bdb1055df06dc6a93a39ba7f56116f6866292784c4938d843531500c368 5474e560eeb0269964b70bcd876bb86b4197c4fb164bc13454fb8204f083062c
-R 6c455877087c47966ac2965f617b41ed
-T +closed 5474e560eeb0269964b70bcd876bb86b4197c4fb164bc13454fb8204f083062c
+P e7dff982be753bc93123db6a0e8fefd56f2a14fd1c9a8699af0b6b75bc88fc15
+R 8a3586de3bb11cc1f485806813b62194
 U drh
-Z 6e1769ba8ee258d77420d4f502f17cc1
+Z b155dbaac537f3a53a88186e0aba231b

manifest.uuid

@@ -1 +1 @@
-e7dff982be753bc93123db6a0e8fefd56f2a14fd1c9a8699af0b6b75bc88fc15
+f08c1731b0b1dddcba190b094a35306a159713d3db939330f73075ff1d72c81e

src/select.c

@@ -3857,8 +3857,9 @@ static int flattenSubquery(
 **   (3) The inner query has a LIMIT clause (since the changes to the WHERE
 **       close would change the meaning of the LIMIT).
 **
-**   (4) (** This restriction was removed on 2018-03-21.  It used to read:
-**       The inner query is the right operand of a LEFT JOIN. **)
+**   (4) The inner query is the right operand of a LEFT JOIN and the
+**       expression to be pushed down does not come from the ON clause
+**       on that LEFT JOIN.
 **
 **   (5) The WHERE clause expression originates in the ON or USING clause
 **       of a LEFT JOIN where iCursor is not the right-hand table of that
@@ -3880,7 +3881,8 @@ static int pushDownWhereTerms(
   Parse *pParse,        /* Parse context (for malloc() and error reporting) */
   Select *pSubq,        /* The subquery whose WHERE clause is to be augmented */
   Expr *pWhere,         /* The WHERE clause of the outer query */
-  int iCursor           /* Cursor number of the subquery */
+  int iCursor,          /* Cursor number of the subquery */
+  int isLeftJoin        /* True if pSubq is the right term of a LEFT JOIN */
 ){
   Expr *pNew;
   int nChng = 0;
@@ -3904,9 +3906,16 @@ static int pushDownWhereTerms(
     return 0; /* restriction (3) */
   }
   while( pWhere->op==TK_AND ){
-    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight, iCursor);
+    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight,
+                                iCursor, isLeftJoin);
     pWhere = pWhere->pLeft;
   }
+  if( isLeftJoin
+   && (ExprHasProperty(pWhere,EP_FromJoin)==0
+         || pWhere->iRightJoinTable!=iCursor)
+  ){
+    return 0; /* restriction (4) */
+  }
   if( ExprHasProperty(pWhere,EP_FromJoin) && pWhere->iRightJoinTable!=iCursor ){
     return 0; /* restriction (5) */
   }
@@ -5374,7 +5383,8 @@ int sqlite3Select(
     ** inside the subquery.  This can help the subquery to run more efficiently.
     */
     if( OptimizationEnabled(db, SQLITE_PushDown)
-     && pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor)
+     && pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor,
+                           (pItem->fg.jointype & JT_OUTER)!=0)
     ){
 #if SELECTTRACE_ENABLED
       if( sqlite3SelectTrace & 0x100 ){

test/join2.test

@@ -265,4 +265,18 @@ do_eqp_test 6.1 {
   0 0 0 {SCAN TABLE u2}
 }
 
+db close
+sqlite3 db :memory:
+do_execsql_test 7.0 {
+  CREATE TABLE t1(a,b);  INSERT INTO t1 VALUES(1,2),(3,4),(5,6);
+  CREATE TABLE t2(c,d);  INSERT INTO t2 VALUES(2,4),(3,6);
+  CREATE TABLE t3(x);    INSERT INTO t3 VALUES(9);
+  CREATE VIEW test AS
+    SELECT *, 'x'
+      FROM t1 LEFT JOIN (SELECT * FROM t2, t3) ON (c=b AND x=9)
+      WHERE c IS NULL;
+  SELECT * FROM test;
+} {3 4 {} {} {} x 5 6 {} {} {} x}
+
+
 finish_test