PostgreSQL Source Code git master
trigfuncs.c
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1/*-------------------------------------------------------------------------
2 *
3 * trigfuncs.c
4 * Builtin functions for useful trigger support.
5 *
6 *
7 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 * src/backend/utils/adt/trigfuncs.c
11 *
12 *-------------------------------------------------------------------------
13 */
14#include "postgres.h"
15
16#include "access/htup_details.h"
17#include "commands/trigger.h"
18#include "utils/fmgrprotos.h"
19
20
21/*
22 * suppress_redundant_updates_trigger
23 *
24 * This trigger function will inhibit an update from being done
25 * if the OLD and NEW records are identical.
26 */
29{
30 TriggerData *trigdata = (TriggerData *) fcinfo->context;
31 HeapTuple newtuple,
32 oldtuple,
33 rettuple;
34 HeapTupleHeader newheader,
35 oldheader;
36
37 /* make sure it's called as a trigger */
38 if (!CALLED_AS_TRIGGER(fcinfo))
40 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
41 errmsg("suppress_redundant_updates_trigger: must be called as trigger")));
42
43 /* and that it's called on update */
44 if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
46 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
47 errmsg("suppress_redundant_updates_trigger: must be called on update")));
48
49 /* and that it's called before update */
50 if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
52 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
53 errmsg("suppress_redundant_updates_trigger: must be called before update")));
54
55 /* and that it's called for each row */
56 if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
58 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
59 errmsg("suppress_redundant_updates_trigger: must be called for each row")));
60
61 /* get tuple data, set default result */
62 rettuple = newtuple = trigdata->tg_newtuple;
63 oldtuple = trigdata->tg_trigtuple;
64
65 newheader = newtuple->t_data;
66 oldheader = oldtuple->t_data;
67
68 /* if the tuple payload is the same ... */
69 if (newtuple->t_len == oldtuple->t_len &&
70 newheader->t_hoff == oldheader->t_hoff &&
71 (HeapTupleHeaderGetNatts(newheader) ==
72 HeapTupleHeaderGetNatts(oldheader)) &&
73 ((newheader->t_infomask & ~HEAP_XACT_MASK) ==
74 (oldheader->t_infomask & ~HEAP_XACT_MASK)) &&
75 memcmp(((char *) newheader) + SizeofHeapTupleHeader,
76 ((char *) oldheader) + SizeofHeapTupleHeader,
77 newtuple->t_len - SizeofHeapTupleHeader) == 0)
78 {
79 /* ... then suppress the update */
80 rettuple = NULL;
81 }
82
83 return PointerGetDatum(rettuple);
84}
int errcode(int sqlerrcode)
Definition: elog.c:853
int errmsg(const char *fmt,...)
Definition: elog.c:1070
#define ERROR
Definition: elog.h:39
#define ereport(elevel,...)
Definition: elog.h:149
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
#define HeapTupleHeaderGetNatts(tup)
Definition: htup_details.h:577
#define SizeofHeapTupleHeader
Definition: htup_details.h:185
#define HEAP_XACT_MASK
Definition: htup_details.h:215
if(TABLE==NULL||TABLE_index==NULL)
Definition: isn.c:76
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:327
uintptr_t Datum
Definition: postgres.h:69
uint32 t_len
Definition: htup.h:64
HeapTupleHeader t_data
Definition: htup.h:68
TriggerEvent tg_event
Definition: trigger.h:34
HeapTuple tg_newtuple
Definition: trigger.h:37
HeapTuple tg_trigtuple
Definition: trigger.h:36
Datum suppress_redundant_updates_trigger(PG_FUNCTION_ARGS)
Definition: trigfuncs.c:28
#define TRIGGER_FIRED_BEFORE(event)
Definition: trigger.h:128
#define CALLED_AS_TRIGGER(fcinfo)
Definition: trigger.h:26
#define TRIGGER_FIRED_FOR_ROW(event)
Definition: trigger.h:122
#define TRIGGER_FIRED_BY_UPDATE(event)
Definition: trigger.h:116