Line data    Source code

       1              : /*-------------------------------------------------------------------------
       2              :  *
       3              :  * trigfuncs.c
       4              :  *    Builtin functions for useful trigger support.
       5              :  *
       6              :  *
       7              :  * Portions Copyright (c) 1996-2026, 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              :  */
      27              : Datum
      28           15 : suppress_redundant_updates_trigger(PG_FUNCTION_ARGS)
      29              : {
      30           15 :     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           15 :     if (!CALLED_AS_TRIGGER(fcinfo))
      39            0 :         ereport(ERROR,
      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           15 :     if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
      45            0 :         ereport(ERROR,
      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           15 :     if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
      51            0 :         ereport(ERROR,
      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           15 :     if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
      57            0 :         ereport(ERROR,
      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           15 :     rettuple = newtuple = trigdata->tg_newtuple;
      63           15 :     oldtuple = trigdata->tg_trigtuple;
      64              : 
      65           15 :     newheader = newtuple->t_data;
      66           15 :     oldheader = oldtuple->t_data;
      67              : 
      68              :     /* if the tuple payload is the same ... */
      69           15 :     if (newtuple->t_len == oldtuple->t_len &&
      70           12 :         newheader->t_hoff == oldheader->t_hoff &&
      71           12 :         (HeapTupleHeaderGetNatts(newheader) ==
      72           12 :          HeapTupleHeaderGetNatts(oldheader)) &&
      73           12 :         ((newheader->t_infomask & ~HEAP_XACT_MASK) ==
      74           12 :          (oldheader->t_infomask & ~HEAP_XACT_MASK)) &&
      75           12 :         memcmp(((char *) newheader) + SizeofHeapTupleHeader,
      76              :                ((char *) oldheader) + SizeofHeapTupleHeader,
      77           12 :                newtuple->t_len - SizeofHeapTupleHeader) == 0)
      78              :     {
      79              :         /* ... then suppress the update */
      80            6 :         rettuple = NULL;
      81              :     }
      82              : 
      83           15 :     return PointerGetDatum(rettuple);
      84              : }