We’d be open to adding support, but it must not be the default behavior, so there will be need to be some kind of flag.
Can you log a JIRA case with the subject ’Support variables with “@" and “@@" prefixes (like MySQL)’. Then we can write a specification and you can submit a pull request. At the RexNode level I think there are already constructs for referencing variables to this change would be confined to the parser. Julian > On Mar 28, 2022, at 4:04 AM, Adolfo Ochagavía <ado...@ochagavia.nl> wrote: > > Would you be open to a patch to add proper support for this kind of MySQL > variables, or do you consider it to be outside the scope of Calcite? > > On 2022/03/22 21:52:09 Justin Swanhart wrote: >> MySQL support two categories of variables, user variables which are >> prefixed with the @character and session/global SERVER variables which are >> prefixed with @@. >> >> You can also access them via: >> >> Select @@session.session_var; >> Select @@global.global_var; >> select @@session_or_global_var; >> >> for example: >> mysql> select @@warp_adjust_table_stats_for_joins; >> +-------------------------------------+ >> | @@warp_adjust_table_stats_for_joins | >> +-------------------------------------+ >> | 1 | >> +-------------------------------------+ >> 1 row in set (0.00 sec) >> >> mysql> set warp_adjust_table_stats_for_joins= false; >> Query OK, 0 rows affected (0.00 sec) >> >> mysql> select @@warp_adjust_table_stats_for_joins; >> +-------------------------------------+ >> | @@warp_adjust_table_stats_for_joins | >> +-------------------------------------+ >> | 0 | >> +-------------------------------------+ >> 1 row in set (0.00 sec) >> >> mysql> select @@session.warp_adjust_table_stats_for_joins; >> +---------------------------------------------+ >> | @@session.warp_adjust_table_stats_for_joins | >> +---------------------------------------------+ >> | 0 | >> +---------------------------------------------+ >> 1 row in set (0.00 sec) >> >> mysql> select @@global.warp_adjust_table_stats_for_joins; >> +--------------------------------------------+ >> | @@global.warp_adjust_table_stats_for_joins | >> +--------------------------------------------+ >> | 1 | >> +--------------------------------------------+ >> 1 row in set (0.00 sec) >> >> >> On Tue, Mar 22, 2022 at 5:02 PM Julian Hyde <jh...@gmail.com >> <http://gmail.com/>> wrote: >> >>> The ‘@@‘ prefix is not standard SQL, and Calcite does not support it. >>> >>> Can you do some research to find out how MySQL handles it. Is it >>> considered to be part of the variable name? Or is it a prefix (like $ in >>> bash) that means ‘what comes next is a variable’? In other words, does the >>> parser say there is a reference to a variable called >>> '@@character_set_server’ or a variable called ‘character_set_server’? And >>> is ‘@‘ a legal part of a variable name? >>> >>> Also, is it handled by the core SQL parser or by a preprocessor? >>> >>> Julian >>> >>> >>>> On Mar 22, 2022, at 2:17 AM, Adolfo Ochagavía <ad...@ochagavia.nl >>>> <http://ochagavia.nl/>> >>> wrote: >>>> >>>> Hi there, >>>> >>>> I am writing a MySQL-compatible server that talks the MySQL protocol. >>> Some clients are sending special queries to autoconfigure themselves, like >>> "SELECT @@character_set_server". I would like to use calcite to parse such >>> queries, but parsing fails with an exception, seemingly related to the >>> usage of "@@" in variable names. Is this unsupported or am I doing >>> something wrong? >>>> >>>> The code: >>>>> var config = SqlParser.Config.DEFAULT.withLex(Lex.MYSQL); >>>>> var parser = SqlParser.create("SELECT @@character_set_server", config); >>>>> var parsed = parser.parseQuery(); >>>> >>>> The exception: org.apache.calcite.sql.parser.SqlParseException: Lexical >>> error at line 1, column 9. Encountered: "@" (64), after : "" >>>> >>>> Any help is appreciated! >>>> Adolfo
