Hello, There was this question raised: Why can't JSON_TABLE code just use the current Name_resolution_context objects? == Context == Name_resolution_context object has these two members that specify a subset of tables to use: TABLE_LIST *first_name_resolution_table; TABLE_LIST *last_name_resolution_table; JSON_TABLE code also introduces this one: table_map ignored_tables; With the meaning that name resolution process will not search for the field of interest in the tables listed in the bitmap. == Rationale == For a JSON_TABLE invocation select ... from json_table(ARG, ...) as JT .... the ARG may refer to any table that precedes JT in the from clause. Let's call the set of the tables ALLOWED_DEPS. Can one take a JSON_TABLE invocation and pick first_name_resolution_table=FIRST, last_name_resolution_table=LAST such that ALLOWED_DEPS = { FIRST, SECOND= FIRST->next_name_resolution_table, THIRD= SECOND->next_name_resolution_table, ... LAST } ? I claim that there are cases where this is not possible. == An example == select * from t1, (t2 natural join (json_table('{}', '$' COLUMNS (d for ordinality)) as JT natural join t3 ) ); Here, JT's ALLOWED_DEPS={t1, t2}. Looking at the data structures (each Table name denotes a TABLE_LIST object referring to the table) select_lex.name_resolution_context.first_name_resolution_table= t1 t1->next_name_resolution_table= $join_nest1 $join_nest1->next_name_resolution_table= NULL $join_nest1->nested_join.join_list= { $join_nest2, t2 } t2->next_name_resolution_table= $join_nest2 $join_nest2->next_name_resolution_table= NULL $join_nest2->nested_join.join_list= {t3, JT} JT->next_name_resolution_table= t3 t3->next_name_resolution_table= NULL Apparently there is no single chain that includes t1 and t2. == Possible objections == "But nested (outer) joins do it" Nested outer joins never need to pick a subset that includes only - one of the tables in a NATURAL JOIN - one of the tables outside that NATURAL JOIN. so there's no comparison. BR Sergei -- Sergei Petrunia, Software Developer MariaDB Corporation | Skype: sergefp | Blog: http://petrunia.net