86 lines
2.6 KiB
C
86 lines
2.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* trigfuncs.c
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* Builtin functions for useful trigger support.
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*
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*
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* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/backend/utils/adt/trigfuncs.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/htup_details.h"
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#include "commands/trigger.h"
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#include "utils/builtins.h"
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#include "utils/rel.h"
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/*
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* suppress_redundant_updates_trigger
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*
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* This trigger function will inhibit an update from being done
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* if the OLD and NEW records are identical.
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*/
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Datum
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suppress_redundant_updates_trigger(PG_FUNCTION_ARGS)
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{
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TriggerData *trigdata = (TriggerData *) fcinfo->context;
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HeapTuple newtuple,
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oldtuple,
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rettuple;
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HeapTupleHeader newheader,
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oldheader;
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/* make sure it's called as a trigger */
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if (!CALLED_AS_TRIGGER(fcinfo))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("suppress_redundant_updates_trigger: must be called as trigger")));
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/* and that it's called on update */
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if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("suppress_redundant_updates_trigger: must be called on update")));
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/* and that it's called before update */
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if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("suppress_redundant_updates_trigger: must be called before update")));
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/* and that it's called for each row */
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if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("suppress_redundant_updates_trigger: must be called for each row")));
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/* get tuple data, set default result */
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rettuple = newtuple = trigdata->tg_newtuple;
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oldtuple = trigdata->tg_trigtuple;
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newheader = newtuple->t_data;
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oldheader = oldtuple->t_data;
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/* if the tuple payload is the same ... */
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if (newtuple->t_len == oldtuple->t_len &&
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newheader->t_hoff == oldheader->t_hoff &&
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(HeapTupleHeaderGetNatts(newheader) ==
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HeapTupleHeaderGetNatts(oldheader)) &&
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((newheader->t_infomask & ~HEAP_XACT_MASK) ==
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(oldheader->t_infomask & ~HEAP_XACT_MASK)) &&
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memcmp(((char *) newheader) + SizeofHeapTupleHeader,
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((char *) oldheader) + SizeofHeapTupleHeader,
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newtuple->t_len - SizeofHeapTupleHeader) == 0)
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{
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/* ... then suppress the update */
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rettuple = NULL;
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}
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return PointerGetDatum(rettuple);
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}
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