Bug#36625752 View with ORDER BY misses a row

As pointed out by the bug reporter, premature optimization leads us to
lose information about the ORDER BY, so that when the view information
is reparsed for use in a SELECT from the view, we see only an empty
table and accordingly produce an empty result set. Without the view
present, we see a single result row for an implicitly grouped query -
as expected.

The optimization removed the ORDER BY when resolving the query of the
view, since it is redundant in the presence of a single row result
set. Normally (when no view is involved) we keep the information that
the query is implicitly grouped even though the ORDER BY is been
optimized away. This is information lost for the view, hence the bug.

Solution: defer the optimization when analyzing the view until we
re-resolve it at view use time, i.e. we make sure the ORDER BY in the
view's definition isn't optimized away.

Change-Id: I22fd3d6a27aba9fb413748234f26667d2b1d9f87

Author: Dag Wanvik

mysql-test/r/group_by.result

@@ -4963,3 +4963,40 @@ SELECT (SELECT f1) FROM t1 GROUP BY f1 HAVING f1 < 1;
 Warnings:
 Warning	1052	Column 'f1' in group statement is ambiguous
 DROP TABLE t1;
+#
+# Bug#36625752 View with ORDER BY misses a row
+#
+CREATE TABLE t1(c0 INT PRIMARY KEY);
+# returns one row as expected
+SELECT 1 FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0));
+1
+1
+CREATE VIEW v AS SELECT 1 FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0));
+# used to return zero rows
+SELECT 1 AS one FROM v;
+one
+1
+SHOW CREATE VIEW v;
+View	Create View	character_set_client	collation_connection
+v	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v` AS select 1 AS `1` from `t1` order by count(0) OVER (PARTITION BY min(`t1`.`c0`) ) 	utf8mb4	utf8mb4_0900_ai_ci
+DROP VIEW v;
+# returns two rows as expected
+(SELECT 1 AS one FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)))
+UNION ALL
+(SELECT 1        FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)));
+one
+1
+1
+CREATE VIEW v AS (SELECT 1 AS one FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)))
+UNION ALL
+(SELECT 1        FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)));
+# used to return zero rows
+SELECT v.one AS one FROM v;
+one
+1
+1
+SHOW CREATE VIEW v;
+View	Create View	character_set_client	collation_connection
+v	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v` AS (select 1 AS `one` from `t1` order by count(0) OVER (PARTITION BY min(`t1`.`c0`) ) ) union all (select 1 AS `1` from `t1` order by count(0) OVER (PARTITION BY min(`t1`.`c0`) ) )	utf8mb4	utf8mb4_0900_ai_ci
+DROP VIEW v;
+DROP TABLE t1;

mysql-test/r/parser.result

@@ -2512,7 +2512,7 @@ ERROR 42000: Multiple COLLATE clauses near 'COLLATE ascii_bin
 CREATE VIEW v1 AS (SELECT 1 ORDER BY 1) UNION (SELECT 3 ORDER BY 1) ORDER BY 1;
 SHOW CREATE VIEW v1;
 View	Create View	character_set_client	collation_connection
-v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select 1 AS `1` union select 3 AS `3` order by `1`	utf8mb4	utf8mb4_0900_ai_ci
+v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS (select 1 AS `1` order by '') union (select 3 AS `3` order by '') order by `1`	utf8mb4	utf8mb4_0900_ai_ci
 DROP VIEW v1;
 #
 # Bug#29871803: REQUIRED PARENTHESES NO LONGER PRINTED FOR CERTAIN UNION

mysql-test/t/group_by.test

@@ -3638,3 +3638,31 @@ DROP TABLE product;
 CREATE TABLE t1(f1 INTEGER);
 SELECT (SELECT f1) FROM t1 GROUP BY f1 HAVING f1 < 1;
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#36625752 View with ORDER BY misses a row
+--echo #
+CREATE TABLE t1(c0 INT PRIMARY KEY);
+let $query =
+SELECT 1 FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0));
+--echo # returns one row as expected
+eval $query;
+eval CREATE VIEW v AS $query;
+--echo # used to return zero rows
+SELECT 1 AS one FROM v;
+SHOW CREATE VIEW v;
+DROP VIEW v;
+
+let $query=
+(SELECT 1 AS one FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)))
+UNION ALL
+(SELECT 1        FROM t1 ORDER BY COUNT(*) OVER (PARTITION BY MIN(t1.c0)));
+--echo # returns two rows as expected
+eval $query;
+eval CREATE VIEW v AS $query;
+--echo # used to return zero rows
+SELECT v.one AS one FROM v;
+SHOW CREATE VIEW v;
+DROP VIEW v;
+
+DROP TABLE t1;

sql/sql_resolver.cc

@@ -4529,7 +4529,7 @@ bool Query_block::check_only_full_group_by(THD *thd) {
 */
 bool Query_block::setup_order_final(THD *thd) {
   DBUG_TRACE;
-  if (is_implicitly_grouped()) {
+  if (is_implicitly_grouped() && !parent_lex->is_view_context_analysis()) {
     // Result will contain zero or one row - ordering is redundant
     return empty_order_list(this);
   }
@@ -4538,7 +4538,7 @@ bool Query_block::setup_order_final(THD *thd) {
     std::pair<bool, bool> result =
         master_query_expression()->query_term()->redundant_order_by(this, 0);
     assert(result.first);  // that we found the block
-    if (result.second) {
+    if (result.second && !parent_lex->is_view_context_analysis()) {
       // Part of set operation which requires global ordering may skip local
       // order
       if (empty_order_list(this)) return true;