Fixed bug mdev-11820.

The fields st_select_lex::cond_pushed_into_where and
st_select_lex::cond_pushed_into_having should be re-initialized
for the unit specifying a derived table at every re-execution
of the query that uses this derived table, because the result
of condition pushdown may be different for different executions.

mysql-test/r/derived_cond_pushdown.result

@@ -8241,3 +8241,112 @@ SELECT * FROM v1 WHERE v1.d IN ( SELECT MIN(d) FROM t2 WHERE 0 );
 d
 DROP VIEW v1;
 DROP TABLE t1,t2;
+#
+# MDEV-11820: second execution of PS for query 
+#             with false subquery predicate in WHERE 
+#
+CREATE TABLE t1 (c VARCHAR(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('foo'),('bar');
+CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
+CREATE TABLE t2 (a INT);
+INSERT INTO t2 VALUES (3), (4);
+PREPARE stmt1 FROM 
+" SELECT * FROM v1 WHERE 1 IN (SELECT a FROM t2) OR c = 'foo'";
+PREPARE stmt2 FROM 
+"EXPLAIN FORMAT=JSON 
+ SELECT * FROM v1 WHERE 1 IN (SELECT a FROM t2) OR c = 'foo'";
+EXECUTE stmt1;
+c
+foo
+EXECUTE stmt2;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "<derived3>",
+      "access_type": "ALL",
+      "rows": 2,
+      "filtered": 100,
+      "attached_condition": "v1.c = 'foo'",
+      "materialized": {
+        "query_block": {
+          "select_id": 3,
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 2,
+            "filtered": 100,
+            "attached_condition": "t1.c = 'foo'"
+          }
+        }
+      }
+    },
+    "subqueries": [
+      {
+        "query_block": {
+          "select_id": 2,
+          "table": {
+            "table_name": "t2",
+            "access_type": "ALL",
+            "rows": 2,
+            "filtered": 100,
+            "attached_condition": "1 = t2.a"
+          }
+        }
+      }
+    ]
+  }
+}
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+EXECUTE stmt1;
+c
+foo
+EXECUTE stmt2;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "<derived3>",
+      "access_type": "ALL",
+      "rows": 2,
+      "filtered": 100,
+      "attached_condition": "<in_optimizer>(1,<exists>(subquery#2)) or v1.c = 'foo'",
+      "materialized": {
+        "query_block": {
+          "select_id": 3,
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 2,
+            "filtered": 100
+          }
+        }
+      }
+    },
+    "subqueries": [
+      {
+        "query_block": {
+          "select_id": 2,
+          "table": {
+            "table_name": "t2",
+            "access_type": "ALL",
+            "rows": 128,
+            "filtered": 100,
+            "attached_condition": "1 = t2.a"
+          }
+        }
+      }
+    ]
+  }
+}
+DEALLOCATE PREPARE stmt1;
+DEALLOCATE PREPARE stmt2;
+DROP VIEW v1;
+DROP TABLE t1,t2;

mysql-test/t/derived_cond_pushdown.test

@@ -1319,3 +1319,37 @@ SELECT * FROM v1 WHERE v1.d IN ( SELECT MIN(d) FROM t2 WHERE 0 );
 
 DROP VIEW v1;
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-11820: second execution of PS for query 
+--echo #             with false subquery predicate in WHERE 
+--echo #
+
+CREATE TABLE t1 (c VARCHAR(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('foo'),('bar');
+CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
+CREATE TABLE t2 (a INT);
+INSERT INTO t2 VALUES (3), (4);
+
+PREPARE stmt1 FROM 
+" SELECT * FROM v1 WHERE 1 IN (SELECT a FROM t2) OR c = 'foo'";
+PREPARE stmt2 FROM 
+"EXPLAIN FORMAT=JSON 
+ SELECT * FROM v1 WHERE 1 IN (SELECT a FROM t2) OR c = 'foo'";
+EXECUTE stmt1;
+EXECUTE stmt2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+INSERT INTO t2 SELECT a+1 FROM t2;
+EXECUTE stmt1;
+EXECUTE stmt2;
+DEALLOCATE PREPARE stmt1;
+# the result here will change after the merge with the fix for mdev-11859 
+DEALLOCATE PREPARE stmt2;
+
+DROP VIEW v1;
+DROP TABLE t1,t2;
+

sql/sql_derived.cc

@@ -1099,6 +1099,11 @@ bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived)
   unit->types.empty();
   /* for derived tables & PS (which can't be reset by Item_subselect) */
   unit->reinit_exec_mechanism();
+  for (st_select_lex *sl= unit->first_select(); sl; sl= sl->next_select())
+  {
+    sl->cond_pushed_into_where= NULL;
+    sl->cond_pushed_into_having= NULL;
+  }
   unit->set_thd(thd);
   DBUG_RETURN(FALSE);
 }