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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
Download Patch File Download Diff File Expand all files Collapse all files

94
src/backend/access/heap/heapam_handler.c
View File

@@ -45,6 +45,12 @@
#include "utils/builtins.h"
#include "utils/rel.h"
static TM_Result heapam_tuple_lock(Relation relation, ItemPointer tid,
Snapshot snapshot, TupleTableSlot *slot,
CommandId cid, LockTupleMode mode,
LockWaitPolicy wait_policy, uint8 flags,
TM_FailureData *tmfd);
static void reform_and_rewrite_tuple(HeapTuple tuple,
Relation OldHeap, Relation NewHeap,
Datum *values, bool *isnull, RewriteState rwstate);
@@ -300,23 +306,55 @@ heapam_tuple_complete_speculative(Relation relation, TupleTableSlot *slot,
static TM_Result
heapam_tuple_delete(Relation relation, ItemPointer tid, CommandId cid,
Snapshot snapshot, Snapshot crosscheck, bool wait,
TM_FailureData *tmfd, bool changingPart)
Snapshot snapshot, Snapshot crosscheck, int options,
TM_FailureData *tmfd, bool changingPart,
TupleTableSlot *oldSlot)
{
TM_Result result;
/*
* Currently Deleting of index tuples are handled at vacuum, in case if
* the storage itself is cleaning the dead tuples by itself, it is the
* time to call the index tuple deletion also.
*/
return heap_delete(relation, tid, cid, crosscheck, wait, tmfd, changingPart);
result = heap_delete(relation, tid, cid, crosscheck, options,
tmfd, changingPart, oldSlot);
/*
* If the tuple has been concurrently updated, then get the lock on it.
* (Do only if caller asked for this by setting the
* TABLE_MODIFY_LOCK_UPDATED option) With the lock held retry of the
* delete should succeed even if there are more concurrent update
* attempts.
*/
if (result == TM_Updated && (options & TABLE_MODIFY_LOCK_UPDATED))
{
/*
* heapam_tuple_lock() will take advantage of tuple loaded into
* oldSlot by heap_delete().
*/
result = heapam_tuple_lock(relation, tid, snapshot,
oldSlot, cid, LockTupleExclusive,
(options & TABLE_MODIFY_WAIT) ?
LockWaitBlock :
LockWaitSkip,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
tmfd);
if (result == TM_Ok)
return TM_Updated;
}
return result;
}
static TM_Result
heapam_tuple_update(Relation relation, ItemPointer otid, TupleTableSlot *slot,
CommandId cid, Snapshot snapshot, Snapshot crosscheck,
bool wait, TM_FailureData *tmfd,
LockTupleMode *lockmode, TU_UpdateIndexes *update_indexes)
int options, TM_FailureData *tmfd,
LockTupleMode *lockmode, TU_UpdateIndexes *update_indexes,
TupleTableSlot *oldSlot)
{
bool shouldFree = true;
HeapTuple tuple = ExecFetchSlotHeapTuple(slot, true, &shouldFree);
@@ -326,8 +364,8 @@ heapam_tuple_update(Relation relation, ItemPointer otid, TupleTableSlot *slot,
slot->tts_tableOid = RelationGetRelid(relation);
tuple->t_tableOid = slot->tts_tableOid;
result = heap_update(relation, otid, tuple, cid, crosscheck, wait,
tmfd, lockmode, update_indexes);
result = heap_update(relation, otid, tuple, cid, crosscheck, options,
tmfd, lockmode, update_indexes, oldSlot);
ItemPointerCopy(&tuple->t_self, &slot->tts_tid);
/*
@@ -354,6 +392,31 @@ heapam_tuple_update(Relation relation, ItemPointer otid, TupleTableSlot *slot,
if (shouldFree)
pfree(tuple);
/*
* If the tuple has been concurrently updated, then get the lock on it.
* (Do only if caller asked for this by setting the
* TABLE_MODIFY_LOCK_UPDATED option) With the lock held retry of the
* update should succeed even if there are more concurrent update
* attempts.
*/
if (result == TM_Updated && (options & TABLE_MODIFY_LOCK_UPDATED))
{
/*
* heapam_tuple_lock() will take advantage of tuple loaded into
* oldSlot by heap_update().
*/
result = heapam_tuple_lock(relation, otid, snapshot,
oldSlot, cid, *lockmode,
(options & TABLE_MODIFY_WAIT) ?
LockWaitBlock :
LockWaitSkip,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
tmfd);
if (result == TM_Ok)
return TM_Updated;
}
return result;
}
@@ -365,7 +428,6 @@ heapam_tuple_lock(Relation relation, ItemPointer tid, Snapshot snapshot,
{
BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
TM_Result result;
Buffer buffer;
HeapTuple tuple = &bslot->base.tupdata;
bool follow_updates;
@@ -375,9 +437,8 @@ heapam_tuple_lock(Relation relation, ItemPointer tid, Snapshot snapshot,
Assert(TTS_IS_BUFFERTUPLE(slot));
tuple_lock_retry:
tuple->t_self = *tid;
result = heap_lock_tuple(relation, tuple, cid, mode, wait_policy,
follow_updates, &buffer, tmfd);
result = heap_lock_tuple(relation, tid, slot, cid, mode, wait_policy,
follow_updates, tmfd);
if (result == TM_Updated &&
(flags & TUPLE_LOCK_FLAG_FIND_LAST_VERSION))
@@ -385,8 +446,6 @@ tuple_lock_retry:
/* Should not encounter speculative tuple on recheck */
Assert(!HeapTupleHeaderIsSpeculative(tuple->t_data));
ReleaseBuffer(buffer);
if (!ItemPointerEquals(&tmfd->ctid, &tuple->t_self))
{
SnapshotData SnapshotDirty;
@@ -408,6 +467,8 @@ tuple_lock_retry:
InitDirtySnapshot(SnapshotDirty);
for (;;)
{
Buffer buffer = InvalidBuffer;
if (ItemPointerIndicatesMovedPartitions(tid))
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
@@ -502,7 +563,7 @@ tuple_lock_retry:
/*
* This is a live tuple, so try to lock it again.
*/
ReleaseBuffer(buffer);
ExecStorePinnedBufferHeapTuple(tuple, slot, buffer);
goto tuple_lock_retry;
}
@@ -513,7 +574,7 @@ tuple_lock_retry:
*/
if (tuple->t_data == NULL)
{
Assert(!BufferIsValid(buffer));
ReleaseBuffer(buffer);
return TM_Deleted;
}
@@ -566,9 +627,6 @@ tuple_lock_retry:
slot->tts_tableOid = RelationGetRelid(relation);
tuple->t_tableOid = slot->tts_tableOid;
/* store in slot, transferring existing pin */
ExecStorePinnedBufferHeapTuple(tuple, slot, buffer);
return result;
}