EXPLAIN FORMAT=JSON: further development

Writing JSON:
- Fix a bug in Single_line_formatting_helper
- Add Json_writer_nesting_guard - safety class

EXPLAIN JSON support
- Add basic subquery support
- Add tests for UNION/UNION ALL.

1 files changed, 20 insertions, 0 deletions

diff --git a/mysql-test/t/explain_json.test b/mysql-test/t/explain_json.test
index 0b7bfb030d9..32932e0ff69 100644
--- a/mysql-test/t/explain_json.test
+++ b/mysql-test/t/explain_json.test
@@ -39,4 +39,24 @@ explain format=json select * from t2 where a1=1 or (b1=2 and b2=3);
 explain format=json select * from t0,t2 where t2.b1=t0.a and t2.b2=4;
 
 drop table t1,t2;
+
+--echo #
+--echo # Try a UNION
+--echo #
+explain format=json select * from t0 A union     select * from t0 B;
+explain format=json select * from t0 A union all select * from t0 B;
+
+--echo #
+--echo # Subqueries
+--echo #
+create table t1 (a int, b int);
+insert into t1 select a,a from t0;
+explain format=json select a, a > (select max(b) from t1 where t1.b=t0.a) from t0;
+
+explain format=json 
+select * from t0 where 
+  a > (select max(b) from t1 where t1.b=t0.a) or a < 3 ;
+
+drop table t1;
 drop table t0;
+