Do not flatten a subquery which is the right term of a LEFT OUTER JOIN

if the subquery contains a WHERE clause.  Ticket #350. (CVS 1027)

FossilOrigin-Name: dd8943e8583cf7ed3b662570a5607856fd246dac

manifest

@@ -1,5 +1,5 @@
-C Preserve\sblank\slines\sin\sthe\smiddle\sof\sSQL\sstatements\sin\sthe\sshell.\nTicket\s#352\s(CVS\s1026)
-D 2003-06-16T00:16:41
+C Do\snot\sflatten\sa\ssubquery\swhich\sis\sthe\sright\sterm\sof\sa\sLEFT\sOUTER\sJOIN\nif\sthe\ssubquery\scontains\sa\sWHERE\sclause.\s\sTicket\s#350.\s(CVS\s1027)
+D 2003-06-16T00:40:35
 F Makefile.in 9ad23ed4ca97f9670c4496432e3fbd4b3760ebde
 F Makefile.linux-gcc b86a99c493a5bfb402d1d9178dcdc4bd4b32f906
 F README f1de682fbbd94899d50aca13d387d1b3fd3be2dd
@@ -43,7 +43,7 @@ F src/parse.y 917250e5d86bdee752355e6617ea2e8ee12438bf
 F src/pragma.c 3b4f5a800e7a2145bc1930f323232e297d4eb782
 F src/printf.c 12ab57e638c8201033c96717df7af59e06933314
 F src/random.c 19e8e00fe0df32a742f115773f57651be327cabe
-F src/select.c 76b3a5cda76421cfe82d6a96c72308c2518cb2f9
+F src/select.c 29c53228a4e66bfcebd797b7539678fcd0e2cf64
 F src/shell.c 3ed268908fd69c8fd4b28dbe415075cbf0e3991a
 F src/shell.tcl 27ecbd63dd88396ad16d81ab44f73e6c0ea9d20e
 F src/sqlite.h.in 54619fa5df4c83b22def66bb3d24808fd03dcbae
@@ -87,7 +87,7 @@ F test/insert.test a17b7f7017097afb2727aa5b67ceeb7ab0a120a1
 F test/insert2.test c288375a64dad3295044714f0dfed4a193cf067f
 F test/intpkey.test 9320af48415c594afd4e15f8ef0daa272e05502e
 F test/ioerr.test 5dbaf09f96b56ee01cf3edd762b96eb4ad2c9ca4
-F test/join.test 16c91ec27170c20e2a10796775e62c5c3dcbda44
+F test/join.test 54e770b74fc8cfc7769d5d0bb05657085641b3c4
 F test/limit.test 9ffb965a0f5bf7152187ef3d8d1249b96e5620bf
 F test/lock.test 388a3a10962d2d571c0c1821cc35bf069ee73473
 F test/main.test 6a851b5992c4881a725a3d9647e629199df8de9d
@@ -165,7 +165,7 @@ F www/speed.tcl 296cc5632d069b56d3ef5409ca0df90f486c10fb
 F www/sqlite.tcl 4bd1729e320f5fa9125f0022b281fbe839192125
 F www/tclsqlite.tcl 1db15abeb446aad0caf0b95b8b9579720e4ea331
 F www/vdbe.tcl 14fdcc7fe8a60a6ba8584903636db8dc37eef26a
-P 38461a7acb5281edd7078b1b3f227bb45f281757
-R 46499a749b6ee84c69c37552983b6d8c
+P bcf5eeecdfd9897bc7c257119d7515fd34d222c1
+R ffe0cc5608b1ae6c3500625d1dc9cf93
 U drh
-Z b3ef2420e7aa106912624a6b067565c3
+Z d81db5180d17921ff4a8ae510148f465

manifest.uuid

@@ -1 +1 @@
-bcf5eeecdfd9897bc7c257119d7515fd34d222c1
+dd8943e8583cf7ed3b662570a5607856fd246dac

src/select.c

@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.140 2003/05/31 16:21:13 drh Exp $
+** $Id: select.c,v 1.141 2003/06/16 00:40:35 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -1578,6 +1578,9 @@ substExprList(ExprList *pList, int iTable, ExprList *pEList){
 **
 **  (11)  The subquery and the outer query do not both have ORDER BY clauses.
 **
+**  (12)  The subquery is not the right term of a LEFT OUTER JOIN or the
+**        subquery has no WHERE clause.  (added by ticket #350)
+**
 ** In this routine, the "p" parameter is a pointer to the outer query.
 ** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
 ** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
@@ -1637,6 +1640,24 @@ static int flattenSubquery(
     return 0;
   }
 
+  /* Restriction 12:  If the subquery is the right operand of a left outer
+  ** join, make sure the subquery has no WHERE clause.
+  ** An examples of why this is not allowed:
+  **
+  **         t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
+  **
+  ** If we flatten the above, we would get
+  **
+  **         (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
+  **
+  ** But the t2.x>0 test will always fail on a NULL row of t2, which
+  ** effectively converts the OUTER JOIN into an INNER JOIN.
+  */
+  if( iFrom>0 && (pSrc->a[iFrom-1].jointype & JT_OUTER)!=0 
+      && pSub->pWhere!=0 ){
+    return 0;
+  }
+
   /* If we reach this point, it means flattening is permitted for the
   ** iFrom-th entry of the FROM clause in the outer query.
   */

test/join.test

@@ -12,7 +12,7 @@
 #
 # This file implements tests for joins, including outer joins.
 #
-# $Id: join.test,v 1.9 2003/05/06 20:35:17 drh Exp $
+# $Id: join.test,v 1.10 2003/06/16 00:40:35 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -398,9 +398,48 @@ do_test join-8.1 {
   }
 } {1 11 1 111 2 22 {} {}}
 do_test join-8.2 {
+  execsql {
+    SELECT * FROM t9 LEFT JOIN (SELECT x, q FROM t10, t11 WHERE t10.y=t11.p)
+         ON( a=x);
+  }
+} {1 11 1 111 2 22 {} {}}
+do_test join-8.3 {
   execsql {
     SELECT * FROM v10_11 LEFT JOIN t9 ON( a=x );
   }
 } {1 111 1 11 3 333 {} {}}
 
+# Ticket #350 describes a scenario where LEFT OUTER JOIN does not
+# function correctly if the right table in the join is really
+# subquery.
+#
+# To test the problem, we generate the same LEFT OUTER JOIN in two
+# separate selects but with on using a subquery and the other calling
+# the table directly.  Then connect the two SELECTs using an EXCEPT.
+# Both queries should generate the same results so the answer should
+# be an empty set.
+#
+do_test join-9.1 {
+  execsql {
+    BEGIN;
+    CREATE TABLE t12(a,b);
+    INSERT INTO t12 VALUES(1,11);
+    INSERT INTO t12 VALUES(2,22);
+    CREATE TABLE t13(b,c);
+    INSERT INTO t13 VALUES(22,222);
+    COMMIT;
+    SELECT * FROM t12 NATURAL LEFT JOIN t13
+      EXCEPT
+      SELECT * FROM t12 NATURAL LEFT JOIN (SELECT * FROM t13 WHERE b>0);
+  }
+} {}
+do_test join-9.2 {
+  execsql {
+    CREATE VIEW v13 AS SELECT * FROM t13 WHERE b>0;
+    SELECT * FROM t12 NATURAL LEFT JOIN t13
+      EXCEPT
+      SELECT * FROM t12 NATURAL LEFT JOIN v13;
+  }
+} {}
+
 finish_test