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Allow locking updated tuples in tuple_update() and tuple_delete()

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Currently, in read committed transaction isolation mode (default), we have the
following sequence of actions when tuple_update()/tuple_delete() finds
the tuple updated by the concurrent transaction.

1. Attempt to update/delete tuple with tuple_update()/tuple_delete(), which
   returns TM_Updated.
2. Lock tuple with tuple_lock().
3. Re-evaluate plan qual (recheck if we still need to update/delete and
   calculate the new tuple for update).
4. Second attempt to update/delete tuple with tuple_update()/tuple_delete().
   This attempt should be successful, since the tuple was previously locked.

This commit eliminates step 2 by taking the lock during the first
tuple_update()/tuple_delete() call.  The heap table access method saves some
effort by checking the updated tuple once instead of twice.  Future
undo-based table access methods, which will start from the latest row version,
can immediately place a lock there.

Also, this commit makes tuple_update()/tuple_delete() optionally save the old
tuple into the dedicated slot.  That saves efforts on re-fetching tuples in
certain cases.

The code in nodeModifyTable.c is simplified by removing the nested switch/case.

Discussion: https://postgr.es/m/CAPpHfdua-YFw3XTprfutzGp28xXLigFtzNbuFY8yPhqeq6X5kg%40mail.gmail.com
Reviewed-by: Aleksander Alekseev, Pavel Borisov, Vignesh C, Mason Sharp
Reviewed-by: Andres Freund, Chris Travers
This commit is contained in:
Alexander Korotkov
2024-03-26 01:27:56 +02:00
parent c7076ba6ad
commit 87985cc925
9 changed files with 502 additions and 346 deletions
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19
src/backend/executor/execReplication.c
View File

@@ -577,6 +577,7 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
{
List *recheckIndexes = NIL;
TU_UpdateIndexes update_indexes;
TupleTableSlot *oldSlot = NULL;
/* Compute stored generated columns */
if (rel->rd_att->constr &&
@@ -590,8 +591,12 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
if (rel->rd_rel->relispartition)
ExecPartitionCheck(resultRelInfo, slot, estate, true);
if (resultRelInfo->ri_TrigDesc &&
resultRelInfo->ri_TrigDesc->trig_update_after_row)
oldSlot = ExecGetTriggerOldSlot(estate, resultRelInfo);
simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
&update_indexes);
&update_indexes, oldSlot);
if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
@@ -602,7 +607,7 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
/* AFTER ROW UPDATE Triggers */
ExecARUpdateTriggers(estate, resultRelInfo,
NULL, NULL,
tid, NULL, slot,
NULL, oldSlot, slot,
recheckIndexes, NULL, false);
list_free(recheckIndexes);
@@ -636,12 +641,18 @@ ExecSimpleRelationDelete(ResultRelInfo *resultRelInfo,
if (!skip_tuple)
{
TupleTableSlot *oldSlot = NULL;
if (resultRelInfo->ri_TrigDesc &&
resultRelInfo->ri_TrigDesc->trig_delete_after_row)
oldSlot = ExecGetTriggerOldSlot(estate, resultRelInfo);
/* OK, delete the tuple */
simple_table_tuple_delete(rel, tid, estate->es_snapshot);
simple_table_tuple_delete(rel, tid, estate->es_snapshot, oldSlot);
/* AFTER ROW DELETE Triggers */
ExecARDeleteTriggers(estate, resultRelInfo,
tid, NULL, NULL, false);
NULL, oldSlot, NULL, false);
}
}