MDEV-35701 trx_t::autoinc_locks causes unnecessary dynamic memory allocation #3720
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Mainly we are replacing ib_vector_t* autoinc_locks; with small_vector. So, the possible impact mainly would depend on the stability of small_vector implementation. I think we need to test it well.
I added one comment on passing R value while adding the lock entry which doesn't seem completely right. I need a little more time to complete the review.
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mariadb-DebarunBanerjee
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Jan 15, 2025
…ocation trx_t::autoinc_locks: Use small_vector<lock_t*,4> in order to avoid any dynamic memory allocation in the most common case (a statement is holding AUTO_INCREMENT locks on at most 4 tables or partitions). lock_cancel_waiting_and_release(): Instead of removing elements from the middle, simply assign nullptr, like lock_table_remove_autoinc_lock(). The added test innodb.auto_increment_lock_mode covers the dynamic memory allocation as well as nondeterministically (occasionally) covers the out-of-order lock release in lock_table_remove_autoinc_lock(). Reviewed by: Debarun Banerjee
Let us make some member functions of lock_sys_t non-static to avoid some shuffling of function parameter registers. lock_cancel_waiting_and_release(): Declare static, because there are no external callers. Reviewed by: Debarun Banerjee
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Description
trx_t::autoinc_locks: Usesmall_vector<lock_t*,4>in order to avoid any dynamic memory allocation in the most common case (a statement is holdingAUTO_INCREMENTlocks on at most 4 tables or partitions).lock_cancel_waiting_and_release(): Instead of removing elements from the middle, simply assignnullptr, likelock_table_remove_autoinc_lock().Release Notes
This is a minor performance improvement.
How can this PR be tested?
A simple Sysbench is expected to show some impact. I did not test this yet.
Basing the PR against the correct MariaDB version
mainbranch.PR quality check