MDEV-27557 InnoDB unnecessarily commits mtr during secondary index search to preserve clustered index latching order
New function to release latches till savepoint was added in mtr_t. As there is no longer need to limit MDEV-20605 fix usage for locking reads only, the limitation is removed.
This commit is contained in:
Vlad Lesin
parent
157a838b19
commit
dcb2968f90
@ -97,6 +97,15 @@ struct mtr_t {
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/** Commit the mini-transaction. */
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void commit();
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/** Release latches till savepoint. To simplify the code only
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MTR_MEMO_S_LOCK and MTR_MEMO_PAGE_S_FIX slot types are allowed to be
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released, otherwise it would be neccesary to add one more argument in the
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function to point out what slot types are allowed for rollback, and this
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would be overengineering as currently the function is used only in one place
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in the code.
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@param savepoint savepoint, can be obtained with get_savepoint */
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void rollback_to_savepoint(ulint savepoint);
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/** Commit a mini-transaction that is shrinking a tablespace.
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@param space tablespace that is being shrunk */
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ATTRIBUTE_COLD void commit_shrink(fil_space_t &space);
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@ -300,6 +300,50 @@ struct ReleaseAll {
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}
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};
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/** Stops iteration is savepoint is reached */
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template <typename Functor> struct TillSavepoint
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{
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/** Constructor
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@param[in] functor functor which is called if savepoint is not reached
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@param[in] savepoint savepoint value to rollback
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@param[in] used current position in slots container */
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TillSavepoint(const Functor &functor, ulint savepoint, ulint used)
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: functor(functor),
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m_slots_count((used - savepoint) / sizeof(mtr_memo_slot_t))
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{
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ut_ad(savepoint);
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ut_ad(used >= savepoint);
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}
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/** @return true if savepoint is not reached, false otherwise */
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bool operator()(mtr_memo_slot_t *slot)
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{
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#ifdef UNIV_DEBUG
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/** This check is added because the code is invoked only from
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row_search_mvcc() to release latches acquired during clustered index search
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for secondary index record. To make it more universal we could add one more
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member in this functor for debug build to pass only certain slot types,
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but this is currently not necessary. */
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switch (slot->type)
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{
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case MTR_MEMO_S_LOCK:
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case MTR_MEMO_PAGE_S_FIX:
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break;
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default:
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ut_a(false);
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}
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#endif
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return m_slots_count-- && functor(slot);
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}
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private:
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/** functor to invoke */
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const Functor &functor;
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/** slots count left till savepoint */
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ulint m_slots_count;
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};
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#ifdef UNIV_DEBUG
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/** Check that all slots have been handled. */
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struct DebugCheck {
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@ -468,6 +512,21 @@ void mtr_t::commit()
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release_resources();
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}
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/** Release latches till savepoint. To simplify the code only
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MTR_MEMO_S_LOCK and MTR_MEMO_PAGE_S_FIX slot types are allowed to be
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released, otherwise it would be neccesary to add one more argument in the
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function to point out what slot types are allowed for rollback, and this
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would be overengineering as corrently the function is used only in one place
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in the code.
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@param savepoint savepoint, can be obtained with get_savepoint */
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void mtr_t::rollback_to_savepoint(ulint savepoint)
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{
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Iterate<TillSavepoint<ReleaseLatches>> iteration(
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TillSavepoint<ReleaseLatches>(ReleaseLatches(), savepoint,
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get_savepoint()));
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m_memo.for_each_block_in_reverse(iteration);
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}
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/** Shrink a tablespace. */
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struct Shrink
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{
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@ -3588,14 +3588,12 @@ record with the same ordering prefix in in the B-tree index
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@param[in] latch_mode latch mode wished in restoration
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@param[in] pcur cursor whose position has been stored
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@param[in] moves_up true if the cursor moves up in the index
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@param[in] mtr mtr; CAUTION: may commit mtr temporarily!
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@param[in] select_lock_type select lock type
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@param[in,out] mtr mtr; CAUTION: may commit mtr temporarily!
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@return true if we may need to process the record the cursor is now
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positioned on (i.e. we should not go to the next record yet) */
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static bool sel_restore_position_for_mysql(bool *same_user_rec,
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ulint latch_mode, btr_pcur_t *pcur,
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bool moves_up, mtr_t *mtr,
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lock_mode select_lock_type)
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bool moves_up, mtr_t *mtr)
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{
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auto status = btr_pcur_restore_position(latch_mode, pcur, mtr);
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@ -3618,8 +3616,7 @@ static bool sel_restore_position_for_mysql(bool *same_user_rec,
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switch (pcur->rel_pos) {
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case BTR_PCUR_ON:
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if (!*same_user_rec && moves_up) {
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if (status == btr_pcur_t::SAME_UNIQ
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&& select_lock_type != LOCK_NONE)
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if (status == btr_pcur_t::SAME_UNIQ)
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return true;
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next:
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if (btr_pcur_move_to_next(pcur, mtr)
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@ -4303,7 +4300,7 @@ row_search_mvcc(
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const rec_t* clust_rec;
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Row_sel_get_clust_rec_for_mysql row_sel_get_clust_rec_for_mysql;
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ibool unique_search = FALSE;
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ibool mtr_has_extra_clust_latch = FALSE;
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ulint mtr_extra_clust_savepoint = 0;
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bool moves_up = false;
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/* if the returned record was locked and we did a semi-consistent
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read (fetch the newest committed version), then this is set to
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@ -4673,7 +4670,7 @@ wait_table_again:
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bool need_to_process = sel_restore_position_for_mysql(
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&same_user_rec, BTR_SEARCH_LEAF,
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pcur, moves_up, &mtr, prebuilt->select_lock_type);
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pcur, moves_up, &mtr);
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if (UNIV_UNLIKELY(need_to_process)) {
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if (UNIV_UNLIKELY(prebuilt->row_read_type
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@ -5355,7 +5352,7 @@ requires_clust_rec:
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/* It was a non-clustered index and we must fetch also the
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clustered index record */
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mtr_has_extra_clust_latch = TRUE;
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mtr_extra_clust_savepoint = mtr.get_savepoint();
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ut_ad(!vrow);
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/* The following call returns 'offsets' associated with
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@ -5643,27 +5640,15 @@ next_rec:
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/* No need to do store restore for R-tree */
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mtr.commit();
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mtr.start();
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mtr_has_extra_clust_latch = FALSE;
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} else if (mtr_has_extra_clust_latch) {
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/* If we have extra cluster latch, we must commit
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mtr if we are moving to the next non-clustered
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mtr_extra_clust_savepoint = 0;
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} else if (mtr_extra_clust_savepoint) {
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/* We must release any clustered index latches
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if we are moving to the next non-clustered
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index record, because we could break the latching
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order if we would access a different clustered
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index page right away without releasing the previous. */
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btr_pcur_store_position(pcur, &mtr);
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mtr.commit();
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mtr_has_extra_clust_latch = FALSE;
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mtr.start();
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if (sel_restore_position_for_mysql(&same_user_rec,
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BTR_SEARCH_LEAF,
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pcur, moves_up, &mtr,
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prebuilt->select_lock_type)
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) {
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goto rec_loop;
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}
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mtr.rollback_to_savepoint(mtr_extra_clust_savepoint);
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mtr_extra_clust_savepoint = 0;
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}
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if (moves_up) {
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@ -5723,7 +5708,7 @@ page_read_error:
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lock_table_wait:
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mtr.commit();
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mtr_has_extra_clust_latch = FALSE;
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mtr_extra_clust_savepoint = 0;
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trx->error_state = err;
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@ -5752,7 +5737,7 @@ lock_table_wait:
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if (!dict_index_is_spatial(index)) {
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sel_restore_position_for_mysql(
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&same_user_rec, BTR_SEARCH_LEAF, pcur,
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moves_up, &mtr, prebuilt->select_lock_type);
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moves_up, &mtr);
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}
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if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
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