Hi, Alexander! On Apr 09, Alexander Barkov wrote:
Hi Sergei,
I'm looking at this use rule in sql_yacc.yy:
history_point: temporal_literal { $$= Vers_history_point(VERS_TIMESTAMP, $1); } | function_call_keyword_timestamp { $$= Vers_history_point(VERS_TIMESTAMP, $1); } | opt_history_unit simple_expr { $$= Vers_history_point($1, $2); } ;
AS OF DATE 'xxx' - returns Vers_history_point(VERS_TIMESTAMP) AS OF DATE('xxx') - returns Vers_history_point(VERS_UNDEFINED)
I suspect that's ok, because with VERS_UNDEFINED it'll look at the result_type() and will change to VERS_TIMESTAMP. Might've been better to look at cmp_type() though.
AS OF TIMESTAMP('2001-01-01') - returns Vers_history_point(VERS_TIMESTAMP) AS OF COALESCE(TIMESTAMP('2001-01-01')) - returns Vers_history_point(VERS_UNDEFINED)
Same.
Perhaps this is not expected.
Also, this code looks suspicious:
void Vers_history_point::resolve_unit(bool timestamps_only) { if (item && unit == VERS_UNDEFINED) { if (item->type() == Item::FIELD_ITEM || timestamps_only) unit= VERS_TIMESTAMP; else if (item->result_type() == INT_RESULT || item->result_type() == REAL_RESULT) unit= VERS_TRX_ID; else unit= VERS_TIMESTAMP; } }
Why DECIMAL_RESULT is not handled?
Looks like a bug. I think it should be.
Why only Item::FIELD_ITEM is checked?
https://github.com/tempesta-tech/mariadb/issues/397 Vers_history_point::resolve_unit is called too early, fields are not fixed yet, so item->result_type() crashed.
Can't "history_point" be simplified to something like:
history_point: simple_expr { $$= Vers_history_point(VERS_UNDEFINED, $1); } | TRANSACTION_SYM simple_expr { $$= Vers_history_point(VERS_TRX_ID, $2); } ;
I'm saying "something like" because TRANSACTION_SYM will cause a conflict with simple_expr. So probably it should be cought somehow else, by catching Item_ident and checking it name.
Btw, an SP variable with name "TRANSACTION" does not work well:
Good point. That's a bug. Now I can think of more ways of introducing the identifier TRANSACTION there, like CREATE TABLE t1 (TRANSACTION int); CREATE TABLE t2 (...) WITH SYSTEM VERSIONING; ... SELECT (SELECT * FROM t1 FOR SYSTEM TIME AS OF TRANSACTION) FROM t1; Regards, Sergei Chief Architect MariaDB and security@mariadb.org