[No MDEV#] Do not start context recorder if querying I_S tables.

This allows to record and save both Optimizer Context and Trace with
straightforward command sequence:

set optimizer_record_context=1, optimizer_trace=1;
explain select ... ;
select context from information_schema.optimizer_context;
select trace from information_schema.optimizer_trace;

mysql-test/main/opt_context_replay_basic.result

@@ -426,4 +426,34 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	4	Using where
 set optimizer_replay_context='';
 drop table t1;
+#
+#
+#
+create table t1 (a varchar(32));
+insert into t1 values ('aaaaaa'),('bbbbbb');
+#
+# Test 1: Reading optimizer context preserves optimizer trace:
+#
+set optimizer_record_context=1, optimizer_trace=1;
+explain select * from t1 where a >'foo' or a < 'bar';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+select context like '%bar%' from information_schema.optimizer_context;
+context like '%bar%'
+1
+select trace like '%foo%' from information_schema.optimizer_trace;
+trace like '%foo%'
+1
+# 
+# Test 2: Reading optimizer trace preserves optimizer context:
+#
+explain select * from t1 where a >'foo' or a < 'bar';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+select trace like '%foo%' from information_schema.optimizer_trace;
+trace like '%foo%'
+1
+select context like '%bar%' from information_schema.optimizer_context;
+context like '%bar%'
+1
 drop database db1;

mysql-test/main/opt_context_replay_basic.test

@@ -203,4 +203,27 @@ set optimizer_replay_context='';
 --remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
 drop table t1;
 
+--echo #
+--echo #
+--echo #
+create table t1 (a varchar(32));
+insert into t1 values ('aaaaaa'),('bbbbbb');
+
+--echo #
+--echo # Test 1: Reading optimizer context preserves optimizer trace:
+--echo #
+set optimizer_record_context=1, optimizer_trace=1;
+explain select * from t1 where a >'foo' or a < 'bar';
+select context like '%bar%' from information_schema.optimizer_context;
+select trace like '%foo%' from information_schema.optimizer_trace;
+
+
+--echo # 
+--echo # Test 2: Reading optimizer trace preserves optimizer context:
+--echo #
+explain select * from t1 where a >'foo' or a < 'bar';
+select trace like '%foo%' from information_schema.optimizer_trace;
+select context like '%bar%' from information_schema.optimizer_context;
+
+
 drop database db1;

sql/opt_context_store_replay.cc

@@ -19,8 +19,8 @@
 #include "opt_context_store_replay.h"
 #include "sql_show.h"
 #include "my_json_writer.h"
-#include "mysql.h"
 #include "hash.h"
+#include "opt_trace.h"
 
 #include "sql_select.h"
 #include "sql_explain.h"
@@ -1486,13 +1486,19 @@ void init_optimizer_context_replay_if_needed(THD *thd)
   }
 }
 
-void init_optimizer_context_recorder_if_needed(THD *thd)
+void init_optimizer_context_recorder_if_needed(THD *thd,
+                                               const TABLE_LIST *query_tables)
 {
   if (thd->spcont)
   {
     /* This is a sub-statement inside SP. Don't do anything */
     return;
   }
+
+  /* Do not record queries that query I_S.OPTIMIZER_{TRACE,CONTEXT} tables */
+  if (list_has_optimizer_trace_table(query_tables))
+    return;
+
   if (!thd->variables.optimizer_record_context)
   {
     clean_captured_ctx(thd);

sql/opt_context_store_replay.h

@@ -33,7 +33,8 @@ class Range_print_enumerator;
 class table_context_for_store;
 class Multi_range_read_const_call_record;
 
-void init_optimizer_context_recorder_if_needed(THD *thd);
+void init_optimizer_context_recorder_if_needed(THD *thd,
+                                               const TABLE_LIST *query_tables);
 
 /*
   Recorder is used to capture the environment during query optimization run.

sql/opt_trace.cc

@@ -29,6 +29,9 @@
 
 const Lex_ident_i_s_table I_S_table_name= "OPTIMIZER_TRACE"_Lex_ident_i_s_table;
 
+const Lex_ident_i_s_table I_S_opt_context_table_name=
+  "OPTIMIZER_CONTEXT"_Lex_ident_i_s_table;
+
 /**
    Whether a list of tables contains information_schema.OPTIMIZER_TRACE.
    @param  tbl  list of tables
@@ -38,13 +41,22 @@ const Lex_ident_i_s_table I_S_table_name= "OPTIMIZER_TRACE"_Lex_ident_i_s_table;
    the OPTIMIZER_TRACE table. So using a stored routine or view to read
    OPTIMIZER_TRACE will overwrite OPTIMIZER_TRACE as it runs and provide
    uninteresting info.
+
+   Also, return true if the query reads from I_S.OPTIMIZER_CONTEXT. This
+   will handle this sequence:
+    Q1: <query>
+    Q2: select * from information_schema.optimizer_context;
+    Q3: select * from information_schema.optimizer_trace;
+
+   Here, Q2 should not overwrite the optimizer trace left by Q1.
 */
 bool list_has_optimizer_trace_table(const TABLE_LIST *tbl)
 {
   for (; tbl; tbl= tbl->next_global)
   {
     if (tbl->schema_table &&
-        I_S_table_name.streq(tbl->schema_table->table_name))
+        (I_S_table_name.streq(tbl->schema_table->table_name) ||
+         I_S_opt_context_table_name.streq(tbl->schema_table->table_name)))
       return true;
   }
   return false;

sql/opt_trace.h

@@ -226,6 +226,8 @@ void opt_trace_disable_if_no_stored_proc_func_access(THD *thd, sp_head *sp);
 */
 int fill_optimizer_trace_info(THD *thd, TABLE_LIST *tables, Item *);
 
+bool list_has_optimizer_trace_table(const TABLE_LIST *tbl);
+
 #define OPT_TRACE_TRANSFORM(thd, object_level0, object_level1, \
                             select_number, from, to)             \
   Json_writer_object object_level0(thd);                         \

sql/sql_parse.cc

@@ -3560,7 +3560,7 @@ mysql_execute_command(THD *thd, bool is_called_from_prepared_stmt)
   thd->last_sql_command= lex->sql_command;
 
   init_optimizer_context_replay_if_needed(thd);
-  init_optimizer_context_recorder_if_needed(thd);
+  init_optimizer_context_recorder_if_needed(thd, all_tables);
 
   /*
     Reset warning count for each query that uses tables