Subject: [PATCH] Fix a defect in the query-flattener optimization

---

 src/select.c      |  8 ++++----

 src/sqliteInt.h   |  1 +

 test/selectA.test | 22 ++++++++++++++++++++++

 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/select.c b/src/select.c

index 88a43df..a513d36 100644

--- a/src/select.c

+++ b/src/select.c

@@ -2686,9 +2686,7 @@ static int multiSelect(

                           selectOpName(p->op)));

         rc = sqlite3Select(pParse, p, &uniondest);

         testcase( rc!=SQLITE_OK );

-        /* Query flattening in sqlite3Select() might refill p->pOrderBy.

-        ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */

-        sqlite3ExprListDelete(db, p->pOrderBy);

+        assert( p->pOrderBy==0 );

         pDelete = p->pPrior;

         p->pPrior = pPrior;

         p->pOrderBy = 0;

@@ -4010,7 +4008,7 @@ static int flattenSubquery(

     ** We look at every expression in the outer query and every place we see

     ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".

     */

-    if( pSub->pOrderBy ){

+    if( pSub->pOrderBy && (pParent->selFlags & SF_NoopOrderBy)==0 ){

       /* At this point, any non-zero iOrderByCol values indicate that the

       ** ORDER BY column expression is identical to the iOrderByCol'th

       ** expression returned by SELECT statement pSub. Since these values

@@ -5633,6 +5631,8 @@ int sqlite3Select(

     sqlite3ExprListDelete(db, p->pOrderBy);

     p->pOrderBy = 0;

     p->selFlags &= ~SF_Distinct;

+    p->selFlags |= SF_NoopOrderBy;

+

   }

   sqlite3SelectPrep(pParse, p, 0);

   if( pParse->nErr || db->mallocFailed ){

diff --git a/src/sqliteInt.h b/src/sqliteInt.h

index 76337f7..60b2ebd 100644

--- a/src/sqliteInt.h

+++ b/src/sqliteInt.h

@@ -2874,6 +2874,7 @@ struct Select {

 #define SF_Converted      0x10000  /* By convertCompoundSelectToSubquery() */

 #define SF_IncludeHidden  0x20000  /* Include hidden columns in output */

 #define SF_ComplexResult  0x40000  /* Result contains subquery or function */

+#define SF_NoopOrderBy   0x0400000 /* ORDER BY is ignored for this query */

 /*

 ** The results of a SELECT can be distributed in several ways, as defined

diff --git a/test/selectA.test b/test/selectA.test

index 838e5f4..2626008 100644

--- a/test/selectA.test

+++ b/test/selectA.test

@@ -1446,5 +1446,27 @@ do_execsql_test 6.1 {

   SELECT * FROM (SELECT a FROM t1 UNION SELECT b FROM t2) WHERE a=a;

 } {12345}

+# 2020-06-15 ticket 8f157e8010b22af0

+#

+reset_db

+do_execsql_test 7.1 {

+  CREATE TABLE t1(c1);     INSERT INTO t1 VALUES(12),(123),(1234),(NULL),('abc');

+  CREATE TABLE t2(c2);     INSERT INTO t2 VALUES(44),(55),(123);

+  CREATE TABLE t3(c3,c4);  INSERT INTO t3 VALUES(66,1),(123,2),(77,3);

+  CREATE VIEW t4 AS SELECT c3 FROM t3;

+  CREATE VIEW t5 AS SELECT c3 FROM t3 ORDER BY c4;

+}

+do_execsql_test 7.2 {

+  SELECT * FROM t1, t2 WHERE c1=(SELECT 123 INTERSECT SELECT c2 FROM t4) AND c1=123;

+} {123 123}

+do_execsql_test 7.3 {

+  SELECT * FROM t1, t2 WHERE c1=(SELECT 123 INTERSECT SELECT c2 FROM t5) AND c1=123;

+} {123 123}

+do_execsql_test 7.4 {

+  CREATE TABLE a(b);

+  CREATE VIEW c(d) AS SELECT b FROM a ORDER BY b;

+  SELECT sum(d) OVER( PARTITION BY(SELECT 0 FROM c JOIN a WHERE b =(SELECT b INTERSECT SELECT d FROM c) AND b = 123)) FROM c;

+} {}

+

 finish_test

-- 

2.24.1