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Add tg_updatedcols to TriggerData
This allows a trigger function to determine for an UPDATE trigger which columns were actually updated. This allows some optimizations in generic trigger functions such as lo_manage and tsvector_update_trigger. Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://www.postgresql.org/message-id/flat/11c5f156-67a9-0fb5-8200-2a8018eb2e0c@2ndquadrant.com
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7 files changed

+68
-9
lines changed

7 files changed

+68
-9
lines changed

‎contrib/lo/expected/lo.out

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,14 @@ SELECT lo_get(43214);
3636
\x
3737
(1 row)
3838

39+
-- test updating of unrelated column
40+
UPDATE image SET title = 'beautiful picture' WHERE title = 'beautiful image';
41+
SELECT lo_get(43214);
42+
lo_get
43+
--------
44+
\x
45+
(1 row)
46+
3947
DELETE FROM image;
4048
SELECT lo_get(43214);
4149
ERROR: large object 43214 does not exist

‎contrib/lo/lo.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -74,7 +74,8 @@ lo_manage(PG_FUNCTION_ARGS)
7474
* Here, if the value of the monitored attribute changes, then the large
7575
* object associated with the original value is unlinked.
7676
*/
77-
if (newtuple != NULL)
77+
if (newtuple != NULL &&
78+
bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
7879
{
7980
char *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
8081
char *newv = SPI_getvalue(newtuple, tupdesc, attnum);

‎contrib/lo/sql/lo.sql

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,11 @@ UPDATE image SET raster = 43214 WHERE title = 'beautiful image';
1818
SELECT lo_get(43213);
1919
SELECT lo_get(43214);
2020

21+
-- test updating of unrelated column
22+
UPDATE image SET title = 'beautiful picture' WHERE title = 'beautiful image';
23+
24+
SELECT lo_get(43214);
25+
2126
DELETE FROM image;
2227

2328
SELECT lo_get(43214);

‎doc/src/sgml/trigger.sgml

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -517,6 +517,7 @@ typedef struct TriggerData
517517
TupleTableSlot *tg_newslot;
518518
Tuplestorestate *tg_oldtable;
519519
Tuplestorestate *tg_newtable;
520+
const Bitmapset *tg_updatedcols;
520521
} TriggerData;
521522
</programlisting>
522523

@@ -759,6 +760,30 @@ typedef struct Trigger
759760
</listitem>
760761
</varlistentry>
761762

763+
<varlistentry>
764+
<term><structfield>tg_updatedcols</structfield></term>
765+
<listitem>
766+
<para>
767+
For <literal>UPDATE</literal> triggers, a bitmap set indicating the
768+
columns that were updated by the triggering command. Generic trigger
769+
functions can use this to optimize actions by not having to deal with
770+
columns that were not changed.
771+
</para>
772+
773+
<para>
774+
As an example, to determine whether a column with attribute number
775+
<varname>attnum</varname> (1-based) is a member of this bitmap set,
776+
call <literal>bms_is_member(attnum -
777+
FirstLowInvalidHeapAttributeNumber,
778+
trigdata->tg_updatedcols))</literal>.
779+
</para>
780+
781+
<para>
782+
For triggers other than <literal>UPDATE</literal> triggers, this will
783+
be <symbol>NULL</symbol>.
784+
</para>
785+
</listitem>
786+
</varlistentry>
762787
</variablelist>
763788
</para>
764789

‎src/backend/commands/trigger.c

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2591,6 +2591,7 @@ ExecBSUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
25912591
LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
25922592
TRIGGER_EVENT_BEFORE;
25932593
LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
2594+
LocTriggerData.tg_updatedcols = updatedCols;
25942595
for (i = 0; i < trigdesc->numtriggers; i++)
25952596
{
25962597
Trigger *trigger = &trigdesc->triggers[i];
@@ -2699,6 +2700,7 @@ ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
26992700
TRIGGER_EVENT_BEFORE;
27002701
LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
27012702
updatedCols = GetAllUpdatedColumns(relinfo, estate);
2703+
LocTriggerData.tg_updatedcols = updatedCols;
27022704
for (i = 0; i < trigdesc->numtriggers; i++)
27032705
{
27042706
Trigger *trigger = &trigdesc->triggers[i];
@@ -3255,6 +3257,7 @@ typedef struct AfterTriggerSharedData
32553257
Oid ats_relid; /* the relation it's on */
32563258
CommandId ats_firing_id; /* ID for firing cycle */
32573259
struct AfterTriggersTableData *ats_table; /* transition table access */
3260+
Bitmapset *ats_modifiedcols; /* modified columns */
32583261
} AfterTriggerSharedData;
32593262

32603263
typedef struct AfterTriggerEventData *AfterTriggerEvent;
@@ -3954,6 +3957,8 @@ AfterTriggerExecute(EState *estate,
39543957
LocTriggerData.tg_event =
39553958
evtshared->ats_event & (TRIGGER_EVENT_OPMASK | TRIGGER_EVENT_ROW);
39563959
LocTriggerData.tg_relation = rel;
3960+
if (TRIGGER_FOR_UPDATE(LocTriggerData.tg_trigger->tgtype))
3961+
LocTriggerData.tg_updatedcols = evtshared->ats_modifiedcols;
39573962

39583963
MemoryContextReset(per_tuple_context);
39593964

@@ -5641,6 +5646,7 @@ AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
56415646
new_shared.ats_table = transition_capture->tcs_private;
56425647
else
56435648
new_shared.ats_table = NULL;
5649+
new_shared.ats_modifiedcols = modifiedCols;
56445650

56455651
afterTriggerAddEvent(&afterTriggers.query_stack[afterTriggers.query_depth].events,
56465652
&new_event, &new_shared);

‎src/backend/utils/adt/tsvector_op.c

Lines changed: 21 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -2416,6 +2416,7 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
24162416
bool isnull;
24172417
text *txt;
24182418
Oid cfgId;
2419+
bool update_needed;
24192420

24202421
/* Check call context */
24212422
if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
@@ -2428,9 +2429,15 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
24282429
elog(ERROR, "tsvector_update_trigger: must be fired BEFORE event");
24292430

24302431
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
2432+
{
24312433
rettuple = trigdata->tg_trigtuple;
2434+
update_needed = true;
2435+
}
24322436
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
2437+
{
24332438
rettuple = trigdata->tg_newtuple;
2439+
update_needed = false; /* computed below */
2440+
}
24342441
else
24352442
elog(ERROR, "tsvector_update_trigger: must be fired for INSERT or UPDATE");
24362443

@@ -2518,6 +2525,9 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
25182525
errmsg("column \"%s\" is not of a character type",
25192526
trigger->tgargs[i])));
25202527

2528+
if (bms_is_member(numattr - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
2529+
update_needed = true;
2530+
25212531
datum = SPI_getbinval(rettuple, rel->rd_att, numattr, &isnull);
25222532
if (isnull)
25232533
continue;
@@ -2530,16 +2540,19 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
25302540
pfree(txt);
25312541
}
25322542

2533-
/* make tsvector value */
2534-
datum = TSVectorGetDatum(make_tsvector(&prs));
2535-
isnull = false;
2543+
if (update_needed)
2544+
{
2545+
/* make tsvector value */
2546+
datum = TSVectorGetDatum(make_tsvector(&prs));
2547+
isnull = false;
25362548

2537-
/* and insert it into tuple */
2538-
rettuple = heap_modify_tuple_by_cols(rettuple, rel->rd_att,
2539-
1, &tsvector_attr_num,
2540-
&datum, &isnull);
2549+
/* and insert it into tuple */
2550+
rettuple = heap_modify_tuple_by_cols(rettuple, rel->rd_att,
2551+
1, &tsvector_attr_num,
2552+
&datum, &isnull);
25412553

2542-
pfree(DatumGetPointer(datum));
2554+
pfree(DatumGetPointer(datum));
2555+
}
25432556

25442557
return PointerGetDatum(rettuple);
25452558
}

‎src/include/commands/trigger.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -39,6 +39,7 @@ typedef struct TriggerData
3939
TupleTableSlot *tg_newslot;
4040
Tuplestorestate *tg_oldtable;
4141
Tuplestorestate *tg_newtable;
42+
const Bitmapset *tg_updatedcols;
4243
} TriggerData;
4344

4445
/*

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