MDEV-19714: JOIN::pseudo_bits_cond is not visible in EXPLAIN FORMAT=JSON

Make it visible

mysql-test/r/subselect_no_semijoin.result

@@ -7291,5 +7291,60 @@ pk	i	c	pk	i	c
 1	10	foo	1	10	foo
 DROP TABLE t;
 # End of 10.2 tests
+#
+# MDEV-19714: JOIN::pseudo_bits_cond is not visible in EXPLAIN FORMAT=JSON
+#
+CREATE TABLE t1 ( a INT );
+INSERT INTO t1 VALUES (1),(5);
+CREATE TABLE t2 ( b INT ) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1);
+CREATE TABLE t3 ( c INT );
+INSERT INTO t3 VALUES (4),(5);
+SET @tmp19714=@@optimizer_switch;
+SET optimizer_switch='subquery_cache=off';
+explain format=json
+SELECT ( SELECT b FROM t2 WHERE b = a OR EXISTS ( SELECT c FROM t3 WHERE c = b ) ) FROM t1;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "t1",
+      "access_type": "ALL",
+      "rows": 2,
+      "filtered": 100
+    },
+    "subqueries": [
+      {
+        "query_block": {
+          "select_id": 2,
+          "pseudo_bits_condition": "1 = t1.a or <in_optimizer>(1,<exists>(subquery#3))",
+          "table": {
+            "table_name": "t2",
+            "access_type": "system",
+            "rows": 1,
+            "filtered": 100
+          },
+          "subqueries": [
+            {
+              "query_block": {
+                "select_id": 3,
+                "table": {
+                  "table_name": "t3",
+                  "access_type": "ALL",
+                  "rows": 2,
+                  "filtered": 100,
+                  "attached_condition": "1 = t3.c"
+                }
+              }
+            }
+          ]
+        }
+      }
+    ]
+  }
+}
+SET optimizer_switch=@tmp19714;
+drop table t1,t2,t3;
 set @optimizer_switch_for_subselect_test=null;
 set @join_cache_level_for_subselect_test=NULL;

mysql-test/t/subselect_no_semijoin.test

@@ -8,5 +8,28 @@ set @join_cache_level_for_subselect_test=@@join_cache_level;
 
 --source t/subselect.test
 
+--echo #
+--echo # MDEV-19714: JOIN::pseudo_bits_cond is not visible in EXPLAIN FORMAT=JSON
+--echo #
+CREATE TABLE t1 ( a INT );
+INSERT INTO t1 VALUES (1),(5);
+
+# t2 must be MyISAM or Aria and contain 1 row
+CREATE TABLE t2 ( b INT ) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1);
+
+CREATE TABLE t3 ( c INT );
+INSERT INTO t3 VALUES (4),(5);
+
+SET @tmp19714=@@optimizer_switch;
+SET optimizer_switch='subquery_cache=off';
+
+explain format=json
+SELECT ( SELECT b FROM t2 WHERE b = a OR EXISTS ( SELECT c FROM t3 WHERE c = b ) ) FROM t1;
+
+SET optimizer_switch=@tmp19714;
+
+drop table t1,t2,t3;
+
 set @optimizer_switch_for_subselect_test=null; 
 set @join_cache_level_for_subselect_test=NULL;

sql/sql_explain.cc

@@ -857,6 +857,11 @@ void Explain_select::print_explain_json(Explain_query *query,
       writer->add_member("outer_ref_condition");
       write_item(writer, outer_ref_cond);
     }
+    if (pseudo_bits_cond)
+    {
+      writer->add_member("pseudo_bits_condition");
+      write_item(writer, pseudo_bits_cond);
+    }
 
     /* we do not print HAVING which always evaluates to TRUE */
     if (having || (having_value == Item::COND_FALSE))

sql/sql_explain.h

@@ -232,6 +232,7 @@ class Explain_select : public Explain_basic_join
   /* Expensive constant condition */
   Item *exec_const_cond;
   Item *outer_ref_cond;
+  Item *pseudo_bits_cond;
 
   /* HAVING condition */
   Item *having;

sql/sql_select.cc

@@ -25025,6 +25025,7 @@ int JOIN::save_explain_data_intern(Explain_query *output,
 
     xpl_sel->exec_const_cond= exec_const_cond;
     xpl_sel->outer_ref_cond= outer_ref_cond;
+    xpl_sel->pseudo_bits_cond= pseudo_bits_cond;
     if (tmp_having)
       xpl_sel->having= tmp_having;
     else