MDEV-7904: ANALYZE FORMAT=JSON doesn't print r_rows for union output

Print r_rows. There is no table tracking for reading from tmp table, yet.

1 files changed, 17 insertions, 0 deletions

diff --git a/sql/sql_explain.cc b/sql/sql_explain.cc
index c1f1b0218b5..900017e2476 100644
--- a/sql/sql_explain.cc
+++ b/sql/sql_explain.cc
@@ -514,6 +514,23 @@ void Explain_union::print_explain_json(Explain_query *query,
   make_union_table_name(table_name_buffer);
   writer->add_member("table_name").add_str(table_name_buffer);
   writer->add_member("access_type").add_str("ALL"); // not very useful
+
+  /* r_loops (not present in tabular output) */
+  if (is_analyze)
+  {
+    writer->add_member("r_loops").add_ll(fake_select_lex_tracker.get_loops());
+  }
+
+  /* `r_rows` */
+  if (is_analyze)
+  {
+    writer->add_member("r_rows");
+    if (fake_select_lex_tracker.has_scans())
+      writer->add_double(fake_select_lex_tracker.get_avg_rows());
+    else
+      writer->add_null();
+  }
+
   writer->add_member("query_specifications").start_array();
 
   for (int i= 0; i < (int) union_members.elements(); i++)