MDEV-28598 Assertion 'got_name == named_item_expected()' failedbb-10.4-MDEV-28598

This assertion triggered on an attempt to write a piece of corrupt
JSON to the optimizer trace:
  "transformation": {
    "select_id": 2,
    "from": "IN (SELECT)",
    "to": "semijoin",
    {
       "join_optimization": {
       "select_id": 3,
       "steps": []
    }
  }

This happened because some parts of the query may be evaluated right
during the optimization stage. To handle such cases Json_writer will now
implicitly add named members with automatically assigned names
"implicitly_added_member_#1", "implicitly_added_member_#2", etc
to preserve JSON document correctness. Also the tail of the JSON document
will be printed to stderr before abort.
Those two improvements only apply for Debug builds, not for Release ones
as the Release builds skip JSON correctness checks

1 files changed, 10 insertions, 0 deletions

diff --git a/mysql-test/main/opt_trace.test b/mysql-test/main/opt_trace.test
index 855ce11aaf5..ab30b23b743 100644
--- a/mysql-test/main/opt_trace.test
+++ b/mysql-test/main/opt_trace.test
@@ -654,5 +654,15 @@ SELECT a FROM t1 WHERE (a,b) in (SELECT @c,@d);
 DROP TABLE t1;
 
 --echo #
+--echo # MDEV-28598: Assertion `got_name == named_item_expected()' failed in Json_writer::on_start_object
+--echo #
+
+CREATE TABLE t1 (a int);
+SET optimizer_trace=1;
+INSERT INTO t1 VALUES (1),(2),(3);
+SELECT * FROM t1 WHERE a IN (SELECT 1 a FROM t1 WHERE EXISTS (select 1));
+DROP TABLE t1;
+
+--echo #
 --echo # End of 10.4 tests
 --echo #