A fix and a test case for
Bug#21483 "Server abort or deadlock on INSERT DELAYED with another implicit insert" Also fixes and adds test cases for bugs: 20497 "Trigger with INSERT DELAYED causes Error 1165" 21714 "Wrong NEW.value and server abort on INSERT DELAYED to a table with a trigger". Post-review fixes. Problem: In MySQL INSERT DELAYED is a way to pipe all inserts into a given table through a dedicated thread. This is necessary for simplistic storage engines like MyISAM, which do not have internal concurrency control or threading and thus can not achieve efficient INSERT throughput without support from SQL layer. DELAYED INSERT works as follows: For every distinct table, which can accept DELAYED inserts and has pending data to insert, a dedicated thread is created to write data to disk. All user connection threads that attempt to delayed-insert into this table interact with the dedicated thread in producer/consumer fashion: all records to-be inserted are pushed into a queue of the dedicated thread, which fetches the records and writes them. In this design, client connection threads never open or lock the delayed insert table. This functionality was introduced in version 3.23 and does not take into account existence of triggers, views, or pre-locking. E.g. if INSERT DELAYED is called from a stored function, which, in turn, is called from another stored function that uses the delayed table, a deadlock can occur, because delayed locking by-passes pre-locking. Besides: * the delayed thread works directly with the subject table through the storage engine API and does not invoke triggers * even if it was patched to invoke triggers, if triggers, in turn, used other tables, the delayed thread would have to open and lock involved tables (use pre-locking). * even if it was patched to use pre-locking, without deadlock detection the delayed thread could easily lock out user connection threads in case when the same table is used both in a trigger and on the right side of the insert query: the delayed thread would not release locks until all inserts are complete, and user connection can not complete inserts without having locks on the tables used on the right side of the query. Solution: These considerations suggest two general alternatives for the future of INSERT DELAYED: * it is considered a full-fledged alternative to normal INSERT * it is regarded as an optimisation that is only relevant for simplistic engines. Since we missed our chance to provide complete support of new features when 5.0 was in development, the first alternative currently renders infeasible. However, even the second alternative, which is to detect new features and convert DELAYED insert into a normal insert, is not easy to implement. The catch-22 is that we don't know if the subject table has triggers or is a view before we open it, and we only open it in the delayed thread. We don't know if the query involves pre-locking until we have opened all tables, and we always first create the delayed thread, and only then open the remaining tables. This patch detects the problematic scenarios and converts DELAYED INSERT to a normal INSERT using the following approach: * if the statement is executed under pre-locking (e.g. from within a stored function or trigger) or the right side may require pre-locking, we detect the situation before creating a delayed insert thread and convert the statement to a conventional INSERT. * if the subject table is a view or has triggers, we shutdown the delayed thread and convert the statement to a conventional INSERT. mysql-test/r/insert.result: Update test results. mysql-test/t/insert.test: Add a test case for Bug#21483, Bug#20497, Bug#21714 (INSERT DELAYED and stored routines, triggers). sql/sp_head.cc: Upgrade lock type to TL_WRITE when computing the pre-locking set. sql/sql_base.cc: Use a new method. sql/sql_insert.cc: INSERT DELAYED and pre-locking: - if under pre-locking, upgrade the lock type to TL_WRITE and proceed as a normal write - if DELAYED table has triggers, also request a lock upgrade. - make sure errors in the delayed thread are propagated correctly sql/sql_lex.h: Add a method to check if a parsed tree refers to stored routines.
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