trigfuncs.c File Reference

#include "postgres.h"
#include "access/htup_details.h"
#include "commands/trigger.h"
#include "utils/builtins.h"
#include "utils/rel.h"

Include dependency graph for trigfuncs.c:

Go to the source code of this file.

Functions
Datum	suppress_redundant_updates_trigger (PG_FUNCTION_ARGS)

Function Documentation

suppress_redundant_updates_trigger()

Datum suppress_redundant_updates_trigger

(

PG_FUNCTION_ARGS

)

Definition at line 29 of file trigfuncs.c.

{
    TriggerData *trigdata = (TriggerData *) fcinfo->context;
    HeapTuple   newtuple,
                oldtuple,
                rettuple;
    HeapTupleHeader newheader,
                oldheader;
 
    /* make sure it's called as a trigger */
    if (!CALLED_AS_TRIGGER(fcinfo))
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("suppress_redundant_updates_trigger: must be called as trigger")));
 
    /* and that it's called on update */
    if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("suppress_redundant_updates_trigger: must be called on update")));
 
    /* and that it's called before update */
    if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("suppress_redundant_updates_trigger: must be called before update")));
 
    /* and that it's called for each row */
    if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("suppress_redundant_updates_trigger: must be called for each row")));
 
    /* get tuple data, set default result */
    rettuple = newtuple = trigdata->tg_newtuple;
    oldtuple = trigdata->tg_trigtuple;
 
    newheader = newtuple->t_data;
    oldheader = oldtuple->t_data;
 
    /* if the tuple payload is the same ... */
    if (newtuple->t_len == oldtuple->t_len &&
        newheader->t_hoff == oldheader->t_hoff &&
        (HeapTupleHeaderGetNatts(newheader) ==
         HeapTupleHeaderGetNatts(oldheader)) &&
        ((newheader->t_infomask & ~HEAP_XACT_MASK) ==
         (oldheader->t_infomask & ~HEAP_XACT_MASK)) &&
        memcmp(((char *) newheader) + SizeofHeapTupleHeader,
               ((char *) oldheader) + SizeofHeapTupleHeader,
               newtuple->t_len - SizeofHeapTupleHeader) == 0)
    {
        /* ... then suppress the update */
        rettuple = NULL;
    }
 
    return PointerGetDatum(rettuple);
}

References CALLED_AS_TRIGGER, ereport, errcode(), errmsg(), ERROR, HEAP_XACT_MASK, HeapTupleHeaderGetNatts, if(), PointerGetDatum(), SizeofHeapTupleHeader, HeapTupleData::t_data, HeapTupleData::t_len, TriggerData::tg_event, TriggerData::tg_newtuple, TriggerData::tg_trigtuple, TRIGGER_FIRED_BEFORE, TRIGGER_FIRED_BY_UPDATE, and TRIGGER_FIRED_FOR_ROW.