Do not flatten the right term of a LEFT join. Ticket #3300. (CVS 5565)

FossilOrigin-Name: 8947c72f93d0b79c8061a3bfd5ab595edfb155a5

manifest

@@ -1,5 +1,5 @@
-C Explicit\scasts\sof\sthe\sreturn\sfrom\sstrlen()\sto\sint\sin\slemon.\s\sThis\shas\nno\seffect\son\sSQLite.\s\sIt\shas\sno\seffect\son\sany\slemon-generated\sparser\nwith\sa\sgrammar\sthat\sis\sless\sthan\s2GB\sin\ssize.\s\sTicket\s#3293.\s(CVS\s5564)
-D 2008-08-13T20:09:07
+C Do\snot\sflatten\sthe\sright\sterm\sof\sa\sLEFT\sjoin.\s\sTicket\s#3300.\s(CVS\s5565)
+D 2008-08-14T00:19:49
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 2713ea64947be3b35f35d9a3158bb8299c90b019
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -142,7 +142,7 @@ F src/pragma.c 6e207b4f69901089758c02c02e0bf86ed12a4d8f
 F src/prepare.c fceb567b359daaa6c6e2a4d04a01dec01ac0c907
 F src/printf.c 2e984b2507291a7e16d89dc9bb60582904f6247d
 F src/random.c 5c754319d38abdd6acd74601ee0105504adc508a
-F src/select.c 390d1bdde0c24f0225e369896da8e60ef2aeffbe
+F src/select.c defdb8cdf7d2d8e1e0df117e50af6378fdaf1329
 F src/shell.c d83b578a8ccdd3e0e7fef4388a0887ce9f810967
 F src/sqlite.h.in 54e51c22e2294c5989156b0aec87aa44168ac1f0
 F src/sqlite3ext.h 1e3887c9bd3ae66cb599e922824b04cd0d0f2c3e
@@ -374,7 +374,7 @@ F test/ioerr2.test 5598405c48842c6c0187daad9eb49eff2c54f80d
 F test/ioerr3.test d3cec5e1a11ad6d27527d0d38573fbff14c71bdd
 F test/ioerr4.test fc6eddfec2efc2f1ed217b9eae4c1c1d3516ce86
 F test/ioerr5.test fe59ee3e3d45a121bcdb8f462b718076e66b4ca7
-F test/join.test fc6c4e2132c40edb8af5ad5f0f49996825d5950d
+F test/join.test e0664af757049ba1f19a0d42c470a58299f36a3e
 F test/join2.test f2171c265e57ee298a27e57e7051d22962f9f324
 F test/join3.test 6f0c774ff1ba0489e6c88a3e77b9d3528fb4fda0
 F test/join4.test 1a352e4e267114444c29266ce79e941af5885916
@@ -618,7 +618,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 4887e8fc4af9e2963b3eff3187dee5b0d6297eb5
-R 6ddaa6c8e2519b5e2a6ee90e75b9e9c6
+P a519cdb2f46fffe16e666f161479a22463616cb3
+R 4f817c5e785c5409dbaded5f21e587f1
 U drh
-Z 904bb51f739e17f7654b323ec4f1ab68
+Z 3d91f3841f779b95c0adaebee822ab63

manifest.uuid

@@ -1 +1 @@
-a519cdb2f46fffe16e666f161479a22463616cb3
+8947c72f93d0b79c8061a3bfd5ab595edfb155a5

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 1.464 2008/08/08 18:06:26 drh Exp $
+** $Id: select.c,v 1.465 2008/08/14 00:19:49 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -2915,8 +2915,8 @@ static void substSelect(
 **
 **   (2)  The subquery is not an aggregate or the outer query is not a join.
 **
-**   (3)  The subquery is not the right operand of a left outer join, or
-**        the subquery is not itself a join.  (Ticket #306)
+**   (3)  The subquery is not the right operand of a left outer join
+**        (Originally ticket #306.  Strenghtened by ticket #3300)
 **
 **   (4)  The subquery is not DISTINCT or the outer query is not a join.
 **
@@ -2938,8 +2938,8 @@ static void substSelect(
 **
 **  (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)
+**  (12)  Not implemented.  Subsumed into restriction (3).  Was previously
+**        a separate restriction deriving from ticket #350.
 **
 **  (13)  The subquery and outer query do not both use LIMIT
 **
@@ -3033,7 +3033,8 @@ static int flattenSubquery(
   }
   if( isAgg && pSub->pOrderBy ) return 0;                /* Restriction (16) */
 
-  /* Restriction 3:  If the subquery is a join, make sure the subquery is 
+  /* OBSOLETE COMMENT 1:
+  ** Restriction 3:  If the subquery is a join, make sure the subquery is 
   ** not used as the right operand of an outer join.  Examples of why this
   ** is not allowed:
   **
@@ -3044,12 +3045,9 @@ static int flattenSubquery(
   **         (t1 LEFT OUTER JOIN t2) JOIN t3
   **
   ** which is not at all the same thing.
-  */
-  if( pSubSrc->nSrc>1 && (pSubitem->jointype & JT_OUTER)!=0 ){
-    return 0;
-  }
-
-  /* Restriction 12:  If the subquery is the right operand of a left outer
+  **
+  ** OBSOLETE COMMENT 2:
+  ** 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:
   **
@@ -3061,8 +3059,13 @@ static int flattenSubquery(
   **
   ** 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.
+  **
+  ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
+  ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
+  ** is fraught with danger.  Best to avoid the whole thing.  If the
+  ** subquery is the right term of a LEFT JOIN, then do not flatten.
   */
-  if( (pSubitem->jointype & JT_OUTER)!=0 && pSub->pWhere!=0 ){
+  if( (pSubitem->jointype & JT_OUTER)!=0 ){
     return 0;
   }
 

test/join.test

@@ -12,7 +12,7 @@
 #
 # This file implements tests for joins, including outer joins.
 #
-# $Id: join.test,v 1.24 2008/07/09 14:47:21 danielk1977 Exp $
+# $Id: join.test,v 1.25 2008/08/14 00:19:49 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -422,6 +422,16 @@ do_test join-8.3 {
     SELECT * FROM v10_11 LEFT JOIN t9 ON( a=x );
   }
 } {1 111 1 11 3 333 {} {}}
+ifcapable subquery {
+  # Constant expressions in a subquery that is the right element of a
+  # LEFT JOIN evaluate to NULL for rows where the LEFT JOIN does not
+  # match.  Ticket #3300
+  do_test join-8.4 {
+    execsql {
+      SELECT * FROM t9 LEFT JOIN (SELECT 44, p, q FROM t11) AS sub1 ON p=a
+    }
+  } {1 11 {} {} {} 2 22 44 2 111}
+}
 } ;# ifcapable view
 
 # Ticket #350 describes a scenario where LEFT OUTER JOIN does not