4 files changed, 201 insertions, 9 deletions

diff --git a/mysql-test/r/select_found.result b/mysql-test/r/select_found.result
index 7b38515cf70..7db4ad0a474 100644
--- a/mysql-test/r/select_found.result
+++ b/mysql-test/r/select_found.result
@@ -363,3 +363,132 @@ select found_rows();
 found_rows()
 5
 drop table t1;
+CREATE TABLE t1(id1 INT);
+CREATE TABLE t2(id2 INT);
+INSERT INTO t1 VALUES(1),(2);
+INSERT INTO t2 VALUES(2),(3);
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL SELECT "bar";
+foo
+foo
+bar
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL SELECT "bar" LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL SELECT id2 FROM t2;
+id1
+1
+2
+2
+3
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL SELECT id2 FROM t2 LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+4
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL (SELECT "bar");
+foo
+foo
+bar
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL (SELECT "bar") LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL (SELECT id2 FROM t2);
+id1
+1
+2
+2
+3
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+4
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar");
+foo
+foo
+bar
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar") LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2);
+id1
+1
+2
+2
+3
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+4
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL SELECT "bar";
+foo
+foo
+bar
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL SELECT "bar" LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL SELECT id2 FROM t2 LIMIT 0;
+id1
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL SELECT id2 FROM t2 LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+4
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar" LIMIT 0);
+foo
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar" LIMIT 0) LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+0
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2 LIMIT 0);
+id1
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2 LIMIT 0) LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+0
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar");
+foo
+bar
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar") LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2);
+id1
+2
+3
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar" LIMIT 0);
+foo
+foo
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar" LIMIT 0) LIMIT 0;
+foo
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2 LIMIT 0);
+id1
+1
+2
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2 LIMIT 0) LIMIT 0;
+id1
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+2
+DROP TABLE t1,t2;
diff --git a/mysql-test/t/select_found.test b/mysql-test/t/select_found.test
index 33613697722..49395fbaebf 100644
--- a/mysql-test/t/select_found.test
+++ b/mysql-test/t/select_found.test
@@ -287,3 +287,61 @@ select found_rows();
 select sql_calc_found_rows * from t1 order by c1 limit 2,1;
 select found_rows();
 drop table t1;
+
+#
+#MDEV-18202 SQL_CALC_FOUND_ROWS do not work with UNION ALL
+#
+#
+# NO LIMIT IN BRACES
+#
+CREATE TABLE t1(id1 INT);
+CREATE TABLE t2(id2 INT);
+INSERT INTO t1 VALUES(1),(2);
+INSERT INTO t2 VALUES(2),(3);
+
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL SELECT "bar";
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL SELECT "bar" LIMIT 0;
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL SELECT id2 FROM t2;
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL SELECT id2 FROM t2 LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL (SELECT "bar");
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL (SELECT "bar") LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL (SELECT id2 FROM t2);
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar");
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar") LIMIT 0;
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2);
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL SELECT "bar";
+(SELECT SQL_CALC_FOUND_ROWS "foo") UNION ALL SELECT "bar" LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL SELECT id2 FROM t2 LIMIT 0;
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1) UNION ALL SELECT id2 FROM t2 LIMIT 0;
+SELECT FOUND_ROWS();
+#
+#LIMIT IN BRACES
+#
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar" LIMIT 0);
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar" LIMIT 0) LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2 LIMIT 0);
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2 LIMIT 0) LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar");
+(SELECT SQL_CALC_FOUND_ROWS "foo" LIMIT 0) UNION ALL (SELECT "bar") LIMIT 0;
+SELECT FOUND_ROWS();
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2);
+(SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 LIMIT 0) UNION ALL (SELECT id2 FROM t2) LIMIT 0;
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar" LIMIT 0);
+SELECT SQL_CALC_FOUND_ROWS "foo" UNION ALL (SELECT "bar" LIMIT 0) LIMIT 0;
+SELECT FOUND_ROWS();
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2 LIMIT 0);
+SELECT SQL_CALC_FOUND_ROWS id1 FROM t1 UNION ALL (SELECT id2 FROM t2 LIMIT 0) LIMIT 0;
+SELECT FOUND_ROWS();
+DROP TABLE t1,t2;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 647dee80188..b964db4077d 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2650,12 +2650,12 @@ void JOIN::exec_inner()
         send_records= 0;
       if (!error)
       {
+        /* Single select (without union) always returns 0 or 1 row */
+        thd->limit_found_rows= send_records;
         join_free();                      // Unlock all cursors
         error= (int) result->send_eof();
       }
     }
-    /* Single select (without union) always returns 0 or 1 row */
-    thd->limit_found_rows= send_records;
     thd->set_examined_row_count(0);
     DBUG_VOID_RETURN;
   }
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 38de2d592ed..d334bc9a694 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -767,10 +767,12 @@ bool st_select_lex_unit::optimize()
           we don't calculate found_rows() per union part.
           Otherwise, SQL_CALC_FOUND_ROWS should be done on all sub parts.
         */
-        sl->join->select_options= 
-          (select_limit_cnt == HA_POS_ERROR || sl->braces) ?
-          sl->options & ~OPTION_FOUND_ROWS : sl->options | found_rows_for_union;
-
+        sl->join->select_options=
+            (!found_rows_for_union) ? (sl->options & ~OPTION_FOUND_ROWS) :
+                                      ((sl->braces) ? ((select_limit_cnt==HA_POS_ERROR) ?
+                                                       (sl->options | found_rows_for_union) :
+                                                      (sl->options & ~OPTION_FOUND_ROWS)) :
+                                      (sl->options | found_rows_for_union));
 	saved_error= sl->join->optimize();
       }
 
@@ -848,9 +850,12 @@ bool st_select_lex_unit::exec()
           we don't calculate found_rows() per union part.
           Otherwise, SQL_CALC_FOUND_ROWS should be done on all sub parts.
         */
-        sl->join->select_options= 
-          (select_limit_cnt == HA_POS_ERROR || sl->braces) ?
-          sl->options & ~OPTION_FOUND_ROWS : sl->options | found_rows_for_union;
+        sl->join->select_options=
+            (!found_rows_for_union) ? (sl->options & ~OPTION_FOUND_ROWS) : 
+                                      ((sl->braces) ? ((select_limit_cnt==HA_POS_ERROR) ?
+                                                       (sl->options | found_rows_for_union) :
+                                                      (sl->options & ~OPTION_FOUND_ROWS)) :
+                                      (sl->options | found_rows_for_union));
 	saved_error= sl->join->optimize();
       }
       if (!saved_error)