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

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 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 patch eliminates step 2 by taking the lock during first
tuple_update()/tuple_delete() call.  Heap table access method saves some
efforts 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.

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 2023-03-23 00:13:37 +03:00
parent 764da7710b
commit 11470f544e
6 changed files with 285 additions and 186 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

109
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_internal(Relation relation, ItemPointer tid,
Snapshot snapshot, TupleTableSlot *slot,
CommandId cid, LockTupleMode mode,
LockWaitPolicy wait_policy, uint8 flags,
TM_FailureData *tmfd, bool updated);
static void reform_and_rewrite_tuple(HeapTuple tuple,
Relation OldHeap, Relation NewHeap,
Datum *values, bool *isnull, RewriteState rwstate);
@ -299,14 +305,46 @@ 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)
TM_FailureData *tmfd, bool changingPart,
LazyTupleTableSlot *lockedSlot)
{
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, wait,
tmfd, changingPart);
/*
* If the tuple has been concurrently updated, then get the lock on it.
* (Do this if caller asked for tat by providing a 'lockedSlot'.) With the
* lock held retry of delete should succeed even if there are more
* concurrent update attempts.
*/
if (result == TM_Updated && lockedSlot)
{
TupleTableSlot *evalSlot;
Assert(wait);
evalSlot = LAZY_TTS_EVAL(lockedSlot);
result = heapam_tuple_lock_internal(relation, tid, snapshot,
evalSlot, cid, LockTupleExclusive,
LockWaitBlock,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
tmfd, true);
if (result == TM_Ok)
{
tmfd->traversed = true;
return TM_Updated;
}
}
return result;
}
@ -314,7 +352,8 @@ 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)
LockTupleMode *lockmode, TU_UpdateIndexes *update_indexes,
LazyTupleTableSlot *lockedSlot)
{
bool shouldFree = true;
HeapTuple tuple = ExecFetchSlotHeapTuple(slot, true, &shouldFree);
@ -352,6 +391,32 @@ 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 this if caller asked for tat by providing a 'lockedSlot'.) With the
* lock held retry of update should succeed even if there are more
* concurrent update attempts.
*/
if (result == TM_Updated && lockedSlot)
{
TupleTableSlot *evalSlot;
Assert(wait);
evalSlot = LAZY_TTS_EVAL(lockedSlot);
result = heapam_tuple_lock_internal(relation, otid, snapshot,
evalSlot, cid, *lockmode,
LockWaitBlock,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
tmfd, true);
if (result == TM_Ok)
{
tmfd->traversed = true;
return TM_Updated;
}
}
return result;
}
@ -360,10 +425,26 @@ heapam_tuple_lock(Relation relation, ItemPointer tid, Snapshot snapshot,
TupleTableSlot *slot, CommandId cid, LockTupleMode mode,
LockWaitPolicy wait_policy, uint8 flags,
TM_FailureData *tmfd)
{
return heapam_tuple_lock_internal(relation, tid, snapshot, slot, cid,
mode, wait_policy, flags, tmfd, false);
}
/*
* This routine does the work for heapam_tuple_lock(), but also support
* `updated` argument to re-use the work done by heapam_tuple_update() or
* heapam_tuple_delete() on figuring out that tuple was concurrently updated.
*/
static TM_Result
heapam_tuple_lock_internal(Relation relation, ItemPointer tid,
Snapshot snapshot, TupleTableSlot *slot,
CommandId cid, LockTupleMode mode,
LockWaitPolicy wait_policy, uint8 flags,
TM_FailureData *tmfd, bool updated)
{
BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
TM_Result result;
Buffer buffer;
Buffer buffer = InvalidBuffer;
HeapTuple tuple = &bslot->base.tupdata;
bool follow_updates;
@ -374,16 +455,26 @@ heapam_tuple_lock(Relation relation, ItemPointer tid, Snapshot snapshot,
tuple_lock_retry:
tuple->t_self = *tid;
result = heap_lock_tuple(relation, tuple, cid, mode, wait_policy,
follow_updates, &buffer, tmfd);
if (!updated)
result = heap_lock_tuple(relation, tuple, cid, mode, wait_policy,
follow_updates, &buffer, tmfd);
else
result = TM_Updated;
if (result == TM_Updated &&
(flags & TUPLE_LOCK_FLAG_FIND_LAST_VERSION))
{
/* Should not encounter speculative tuple on recheck */
Assert(!HeapTupleHeaderIsSpeculative(tuple->t_data));
if (!updated)
{
/* Should not encounter speculative tuple on recheck */
Assert(!HeapTupleHeaderIsSpeculative(tuple->t_data));
ReleaseBuffer(buffer);
ReleaseBuffer(buffer);
}
else
{
updated = false;
}
if (!ItemPointerEquals(&tmfd->ctid, &tuple->t_self))
{

6
src/backend/access/table/tableam.c
View File

@ -306,7 +306,8 @@ simple_table_tuple_delete(Relation rel, ItemPointer tid, Snapshot snapshot)
GetCurrentCommandId(true),
snapshot, InvalidSnapshot,
true /* wait for commit */ ,
&tmfd, false /* changingPart */ );
&tmfd, false /* changingPart */ ,
NULL);
switch (result)
{
@ -355,7 +356,8 @@ simple_table_tuple_update(Relation rel, ItemPointer otid,
GetCurrentCommandId(true),
snapshot, InvalidSnapshot,
true /* wait for commit */ ,
&tmfd, &lockmode, update_indexes);
&tmfd, &lockmode, update_indexes,
NULL);
switch (result)
{

288
src/backend/executor/nodeModifyTable.c
View File

@ -1324,26 +1324,62 @@ ExecDeletePrologue(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
return true;
}
/*
* The implementation for LazyTupleTableSlot wrapper for EPQ slot to be passed
* to table_tuple_update()/table_tuple_delete().
*/
typedef struct
{
EPQState *epqstate;
ResultRelInfo *resultRelInfo;
} GetEPQSlotArg;
static TupleTableSlot *
GetEPQSlot(void *arg)
{
GetEPQSlotArg *slotArg = (GetEPQSlotArg *) arg;
return EvalPlanQualSlot(slotArg->epqstate,
slotArg->resultRelInfo->ri_RelationDesc,
slotArg->resultRelInfo->ri_RangeTableIndex);
}
/*
* ExecDeleteAct -- subroutine for ExecDelete
*
* Actually delete the tuple from a plain table.
*
* If the 'lockUpdated' flag is set and the target tuple is updated, then
* the latest version gets locked and fetched into the EPQ slot.
*
* Caller is in charge of doing EvalPlanQual as necessary
*/
static TM_Result
ExecDeleteAct(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
ItemPointer tupleid, bool changingPart)
ItemPointer tupleid, bool changingPart, bool lockUpdated)
{
EState *estate = context->estate;
GetEPQSlotArg slotArg = {context->epqstate, resultRelInfo};
LazyTupleTableSlot lazyEPQSlot,
*lazyEPQSlotPtr;
if (lockUpdated)
{
MAKE_LAZY_TTS(&lazyEPQSlot, GetEPQSlot, &slotArg);
lazyEPQSlotPtr = &lazyEPQSlot;
}
else
{
lazyEPQSlotPtr = NULL;
}
return table_tuple_delete(resultRelInfo->ri_RelationDesc, tupleid,
estate->es_output_cid,
estate->es_snapshot,
estate->es_crosscheck_snapshot,
true /* wait for commit */ ,
&context->tmfd,
changingPart);
changingPart,
lazyEPQSlotPtr);
}
/*
@ -1488,7 +1524,8 @@ ExecDelete(ModifyTableContext *context,
* transaction-snapshot mode transactions.
*/
ldelete:
result = ExecDeleteAct(context, resultRelInfo, tupleid, changingPart);
result = ExecDeleteAct(context, resultRelInfo, tupleid, changingPart,
!IsolationUsesXactSnapshot());
switch (result)
{
@ -1541,103 +1578,49 @@ ldelete:
errmsg("could not serialize access due to concurrent update")));
/*
* Already know that we're going to need to do EPQ, so
* fetch tuple directly into the right slot.
* ExecDeleteAct() has already locked the old tuple for
* us. Now we need to copy it to the right slot.
*/
EvalPlanQualBegin(context->epqstate);
inputslot = EvalPlanQualSlot(context->epqstate, resultRelationDesc,
resultRelInfo->ri_RangeTableIndex);
result = table_tuple_lock(resultRelationDesc, tupleid,
estate->es_snapshot,
inputslot, estate->es_output_cid,
LockTupleExclusive, LockWaitBlock,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
&context->tmfd);
switch (result)
/*
* Save locked table for further processing for RETURNING
* clause.
*/
if (processReturning &&
resultRelInfo->ri_projectReturning &&
!resultRelInfo->ri_FdwRoutine)
{
case TM_Ok:
Assert(context->tmfd.traversed);
TupleTableSlot *returningSlot;
/*
* Save locked tuple for further processing of
* RETURNING clause.
*/
if (processReturning &&
resultRelInfo->ri_projectReturning &&
!resultRelInfo->ri_FdwRoutine)
{
TupleTableSlot *returningSlot;
returningSlot = ExecGetReturningSlot(estate, resultRelInfo);
ExecCopySlot(returningSlot, inputslot);
ExecMaterializeSlot(returningSlot);
}
epqslot = EvalPlanQual(context->epqstate,
resultRelationDesc,
resultRelInfo->ri_RangeTableIndex,
inputslot);
if (TupIsNull(epqslot))
/* Tuple not passing quals anymore, exiting... */
return NULL;
/*
* If requested, skip delete and pass back the
* updated row.
*/
if (epqreturnslot)
{
*epqreturnslot = epqslot;
return NULL;
}
else
goto ldelete;
case TM_SelfModified:
/*
* This can be reached when following an update
* chain from a tuple updated by another session,
* reaching a tuple that was already updated in
* this transaction. If previously updated by this
* command, ignore the delete, otherwise error
* out.
*
* See also TM_SelfModified response to
* table_tuple_delete() above.
*/
if (context->tmfd.cmax != estate->es_output_cid)
ereport(ERROR,
(errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
errmsg("tuple to be deleted was already modified by an operation triggered by the current command"),
errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
return NULL;
case TM_Deleted:
/* tuple already deleted; nothing to do */
return NULL;
default:
/*
* TM_Invisible should be impossible because we're
* waiting for updated row versions, and would
* already have errored out if the first version
* is invisible.
*
* TM_Updated should be impossible, because we're
* locking the latest version via
* TUPLE_LOCK_FLAG_FIND_LAST_VERSION.
*/
elog(ERROR, "unexpected table_tuple_lock status: %u",
result);
return NULL;
returningSlot = ExecGetReturningSlot(estate,
resultRelInfo);
ExecCopySlot(returningSlot, inputslot);
ExecMaterializeSlot(returningSlot);
}
Assert(false);
break;
Assert(context->tmfd.traversed);
epqslot = EvalPlanQual(context->epqstate,
resultRelationDesc,
resultRelInfo->ri_RangeTableIndex,
inputslot);
if (TupIsNull(epqslot))
/* Tuple not passing quals anymore, exiting... */
return NULL;
/*
* If requested, skip delete and pass back the updated
* row.
*/
if (epqreturnslot)
{
*epqreturnslot = epqslot;
return NULL;
}
else
goto ldelete;
}
case TM_Deleted:
@ -1982,12 +1965,15 @@ ExecUpdatePrepareSlot(ResultRelInfo *resultRelInfo,
static TM_Result
ExecUpdateAct(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *slot,
bool canSetTag, UpdateContext *updateCxt)
bool canSetTag, bool lockUpdated, UpdateContext *updateCxt)
{
EState *estate = context->estate;
Relation resultRelationDesc = resultRelInfo->ri_RelationDesc;
bool partition_constraint_failed;
TM_Result result;
GetEPQSlotArg slotArg = {context->epqstate, resultRelInfo};
LazyTupleTableSlot lazyEPQSlot,
*lazyEPQSlotPtr;
updateCxt->crossPartUpdate = false;
@ -2113,13 +2099,23 @@ lreplace:
* for referential integrity updates in transaction-snapshot mode
* transactions.
*/
if (lockUpdated)
{
MAKE_LAZY_TTS(&lazyEPQSlot, GetEPQSlot, &slotArg);
lazyEPQSlotPtr = &lazyEPQSlot;
}
else
{
lazyEPQSlotPtr = NULL;
}
result = table_tuple_update(resultRelationDesc, tupleid, slot,
estate->es_output_cid,
estate->es_snapshot,
estate->es_crosscheck_snapshot,
true /* wait for commit */ ,
&context->tmfd, &updateCxt->lockmode,
&updateCxt->updateIndexes);
&updateCxt->updateIndexes,
lazyEPQSlotPtr);
if (result == TM_Ok)
updateCxt->updated = true;
@ -2273,7 +2269,7 @@ ExecCrossPartitionUpdateForeignKey(ModifyTableContext *context,
static TupleTableSlot *
ExecUpdate(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *slot,
bool canSetTag)
bool canSetTag, bool locked)
{
EState *estate = context->estate;
Relation resultRelationDesc = resultRelInfo->ri_RelationDesc;
@ -2335,7 +2331,8 @@ ExecUpdate(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
*/
redo_act:
result = ExecUpdateAct(context, resultRelInfo, tupleid, oldtuple, slot,
canSetTag, &updateCxt);
canSetTag, !IsolationUsesXactSnapshot(),
&updateCxt);
/*
* If ExecUpdateAct reports that a cross-partition update was done,
@ -2394,81 +2391,39 @@ redo_act:
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
Assert(!locked);
/*
* Already know that we're going to need to do EPQ, so
* fetch tuple directly into the right slot.
* ExecUpdateAct() has already locked the old tuple for
* us. Now we need to copy it to the right slot.
*/
inputslot = EvalPlanQualSlot(context->epqstate, resultRelationDesc,
resultRelInfo->ri_RangeTableIndex);
result = table_tuple_lock(resultRelationDesc, tupleid,
estate->es_snapshot,
inputslot, estate->es_output_cid,
updateCxt.lockmode, LockWaitBlock,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
&context->tmfd);
/* Make sure ri_oldTupleSlot is initialized. */
if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
ExecInitUpdateProjection(context->mtstate,
resultRelInfo);
switch (result)
{
case TM_Ok:
Assert(context->tmfd.traversed);
/*
* Save the locked tuple for further calculation of the
* new tuple.
*/
oldSlot = resultRelInfo->ri_oldTupleSlot;
ExecCopySlot(oldSlot, inputslot);
ExecMaterializeSlot(oldSlot);
Assert(context->tmfd.traversed);
/* Make sure ri_oldTupleSlot is initialized. */
if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
ExecInitUpdateProjection(context->mtstate,
resultRelInfo);
/*
* Save the locked tuple for further calculation
* of the new tuple.
*/
oldSlot = resultRelInfo->ri_oldTupleSlot;
ExecCopySlot(oldSlot, inputslot);
ExecMaterializeSlot(oldSlot);
epqslot = EvalPlanQual(context->epqstate,
resultRelationDesc,
resultRelInfo->ri_RangeTableIndex,
inputslot);
if (TupIsNull(epqslot))
/* Tuple not passing quals anymore, exiting... */
return NULL;
slot = ExecGetUpdateNewTuple(resultRelInfo,
epqslot, oldSlot);
goto redo_act;
case TM_Deleted:
/* tuple already deleted; nothing to do */
return NULL;
case TM_SelfModified:
/*
* This can be reached when following an update
* chain from a tuple updated by another session,
* reaching a tuple that was already updated in
* this transaction. If previously modified by
* this command, ignore the redundant update,
* otherwise error out.
*
* See also TM_SelfModified response to
* table_tuple_update() above.
*/
if (context->tmfd.cmax != estate->es_output_cid)
ereport(ERROR,
(errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
return NULL;
default:
/* see table_tuple_lock call in ExecDelete() */
elog(ERROR, "unexpected table_tuple_lock status: %u",
result);
return NULL;
}
epqslot = EvalPlanQual(context->epqstate,
resultRelationDesc,
resultRelInfo->ri_RangeTableIndex,
inputslot);
if (TupIsNull(epqslot))
/* Tuple not passing quals anymore, exiting... */
return NULL;
slot = ExecGetUpdateNewTuple(resultRelInfo,
epqslot, oldSlot);
goto redo_act;
}
break;
@ -2710,7 +2665,7 @@ ExecOnConflictUpdate(ModifyTableContext *context,
*returning = ExecUpdate(context, resultRelInfo,
conflictTid, NULL,
resultRelInfo->ri_onConflict->oc_ProjSlot,
canSetTag);
canSetTag, true);
/*
* Clear out existing tuple, as there might not be another conflict among
@ -2913,7 +2868,7 @@ lmerge_matched:
break; /* concurrent update/delete */
}
result = ExecUpdateAct(context, resultRelInfo, tupleid, NULL,
newslot, false, &updateCxt);
newslot, false, false, &updateCxt);
if (result == TM_Ok && updateCxt.updated)
{
ExecUpdateEpilogue(context, &updateCxt, resultRelInfo,
@ -2931,7 +2886,8 @@ lmerge_matched:
return true; /* "do nothing" */
break; /* concurrent update/delete */
}
result = ExecDeleteAct(context, resultRelInfo, tupleid, false);
result = ExecDeleteAct(context, resultRelInfo, tupleid,
false, false);
if (result == TM_Ok)
{
ExecDeleteEpilogue(context, resultRelInfo, tupleid, NULL,
@ -3837,7 +3793,7 @@ ExecModifyTable(PlanState *pstate)
/* Now apply the update. */
slot = ExecUpdate(&context, resultRelInfo, tupleid, oldtuple,
slot, node->canSetTag);
slot, node->canSetTag, false);
break;
case CMD_DELETE:

28
src/include/access/tableam.h
View File

@ -530,7 +530,8 @@ typedef struct TableAmRoutine
Snapshot crosscheck,
bool wait,
TM_FailureData *tmfd,
bool changingPart);
bool changingPart,
LazyTupleTableSlot *lockedSlot);
/* see table_tuple_update() for reference about parameters */
TM_Result (*tuple_update) (Relation rel,
@ -542,7 +543,8 @@ typedef struct TableAmRoutine
bool wait,
TM_FailureData *tmfd,
LockTupleMode *lockmode,
TU_UpdateIndexes *update_indexes);
TU_UpdateIndexes *update_indexes,
LazyTupleTableSlot *lockedSlot);
/* see table_tuple_lock() for reference about parameters */
TM_Result (*tuple_lock) (Relation rel,
@ -1457,7 +1459,7 @@ table_multi_insert(Relation rel, TupleTableSlot **slots, int nslots,
}
/*
* Delete a tuple.
* Delete a tuple (or lock last tuple version if lockedSlot is given).
*
* NB: do not call this directly unless prepared to deal with
* concurrent-update conditions. Use simple_table_tuple_delete instead.
@ -1473,6 +1475,8 @@ table_multi_insert(Relation rel, TupleTableSlot **slots, int nslots,
* tmfd - filled in failure cases (see below)
* changingPart - true iff the tuple is being moved to another partition
* table due to an update of the partition key. Otherwise, false.
* lockedSlot - lazy slot to save the locked tuple if should lock the last
* row version during the concurrent update. NULL if not needed.
*
* Normal, successful return value is TM_Ok, which means we did actually
* delete it. Failure return codes are TM_SelfModified, TM_Updated, and
@ -1485,15 +1489,17 @@ table_multi_insert(Relation rel, TupleTableSlot **slots, int nslots,
static inline TM_Result
table_tuple_delete(Relation rel, ItemPointer tid, CommandId cid,
Snapshot snapshot, Snapshot crosscheck, bool wait,
TM_FailureData *tmfd, bool changingPart)
TM_FailureData *tmfd, bool changingPart,
LazyTupleTableSlot *lockedSlot)
{
return rel->rd_tableam->tuple_delete(rel, tid, cid,
snapshot, crosscheck,
wait, tmfd, changingPart);
wait, tmfd, changingPart,
lockedSlot);
}
/*
* Update a tuple.
* Update a tuple (or lock last tuple version if lockedSlot is given).
*
* NB: do not call this directly unless you are prepared to deal with
* concurrent-update conditions. Use simple_table_tuple_update instead.
@ -1511,7 +1517,9 @@ table_tuple_delete(Relation rel, ItemPointer tid, CommandId cid,
* lockmode - filled with lock mode acquired on tuple
* update_indexes - in success cases this is set to true if new index entries
* are required for this tuple
*
* lockedSlot - lazy slot to save the locked tuple if should lock the last
* row version during the concurrent update. NULL if not needed.
* Normal, successful return value is TM_Ok, which means we did actually
* update it. Failure return codes are TM_SelfModified, TM_Updated, and
* TM_BeingModified (the last only possible if wait == false).
@ -1530,12 +1538,14 @@ static inline TM_Result
table_tuple_update(Relation rel, ItemPointer otid, TupleTableSlot *slot,
CommandId cid, Snapshot snapshot, Snapshot crosscheck,
bool wait, TM_FailureData *tmfd, LockTupleMode *lockmode,
TU_UpdateIndexes *update_indexes)
TU_UpdateIndexes *update_indexes,
LazyTupleTableSlot *lockedSlot)
{
return rel->rd_tableam->tuple_update(rel, otid, slot,
cid, snapshot, crosscheck,
wait, tmfd,
lockmode, update_indexes);
lockmode, update_indexes,
lockedSlot);
}
/*

38
src/include/executor/tuptable.h
View File

@ -300,6 +300,44 @@ typedef struct MinimalTupleTableSlot
#define TupIsNull(slot) \
((slot) == NULL || TTS_EMPTY(slot))
/*----------
* LazyTupleTableSlot -- a lazy version of TupleTableSlot.
*
* Sometimes caller might need to pass to the function a slot, which most
* likely will reain undemanded. Preallocating such slot would be a waste of
* resources in the majority of cases. Lazy slot is aimed to resolve this
* problem. It is basically a promise to allocate the slot once it's needed.
* Once callee needs the slot, it could get it using LAZY_TTS_EVAL(lazySlot)
* macro.
*/
typedef struct
{
TupleTableSlot *slot; /* cached slot or NULL if not yet allocated */
TupleTableSlot *(*getSlot) (void *arg); /* callback for slot allocation */
void *getSlotArg; /* argument for the callback above */
} LazyTupleTableSlot;
/*
* A constructor for the lazy slot.
*/
#define MAKE_LAZY_TTS(lazySlot, callback, arg) \
do { \
(lazySlot)->slot = NULL; \
(lazySlot)->getSlot = callback; \
(lazySlot)->getSlotArg = arg; \
} while (false)
/*
* Macro for lazy slot evaluation. NULL lazy slot evaluates to NULL slot.
* Cached version is used if present. Use the callback otherwise.
*/
#define LAZY_TTS_EVAL(lazySlot) \
((lazySlot) ? \
((lazySlot)->slot ? \
(lazySlot)->slot : \
((lazySlot)->slot = (lazySlot)->getSlot((lazySlot)->getSlotArg))) : \
NULL)
/* in executor/execTuples.c */
extern TupleTableSlot *MakeTupleTableSlot(TupleDesc tupleDesc,
const TupleTableSlotOps *tts_ops);

2
src/tools/pgindent/typedefs.list
View File

@ -955,6 +955,7 @@ GenerationPointer
GenericCosts
GenericXLogState
GeqoPrivateData
GetEPQSlotArg
GetForeignJoinPaths_function
GetForeignModifyBatchSize_function
GetForeignPaths_function
@ -1399,6 +1400,7 @@ LagTracker
LargeObjectDesc
LastAttnumInfo
Latch
LazyTupleTableSlot
LerpFunc
LexDescr
LexemeEntry