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

Datum suppress_redundant_updates_trigger

(

PG_FUNCTION_ARGS

)

Definition at line 29 of file trigfuncs.c.

References CALLED_AS_TRIGGER, ereport, errcode(), errmsg(), ERROR, HEAP_XACT_MASK, HeapTupleHeaderGetNatts, HeapTupleHeaderGetOid, HeapTupleHeaderSetOid, memcmp(), offsetof, OidIsValid, PointerGetDatum, RelationData::rd_rel, HeapTupleData::t_data, HeapTupleData::t_len, TriggerData::tg_event, TriggerData::tg_newtuple, TriggerData::tg_relation, TriggerData::tg_trigtuple, TRIGGER_FIRED_BEFORE, TRIGGER_FIRED_BY_UPDATE, and TRIGGER_FIRED_FOR_ROW.

{
    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;

    /*
     * We are called before the OID, if any, has been transcribed from the old
     * tuple to the new (in heap_update).  To avoid a bogus compare failure,
     * copy the OID now.  But check that someone didn't already put another
     * OID value into newtuple.  (That's not actually possible at present, but
     * maybe someday.)
     */
    if (trigdata->tg_relation->rd_rel->relhasoids &&
        !OidIsValid(HeapTupleHeaderGetOid(newheader)))
        HeapTupleHeaderSetOid(newheader, HeapTupleHeaderGetOid(oldheader));

    /* 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) + offsetof(HeapTupleHeaderData, t_bits),
               ((char *) oldheader) + offsetof(HeapTupleHeaderData, t_bits),
               newtuple->t_len - offsetof(HeapTupleHeaderData, t_bits)) == 0)
    {
        /* ... then suppress the update */
        rettuple = NULL;
    }

    return PointerGetDatum(rettuple);
}