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#include "executor/spi.h" /* this is what you need to work with SPI */
#include "commands/trigger.h" /* -"- and triggers */
#include "commands/sequence.h" /* for nextval() */
extern Datum autoinc(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(autoinc);
Datum
autoinc(PG_FUNCTION_ARGS)
{
TriggerData *trigdata = (TriggerData *) fcinfo->context;
Trigger *trigger; /* to get trigger name */
int nargs; /* # of arguments */
int *chattrs; /* attnums of attributes to change */
int chnattrs = 0; /* # of above */
Datum *newvals; /* vals of above */
char **args; /* arguments */
char *relname; /* triggered relation name */
Relation rel; /* triggered relation */
HeapTuple rettuple = NULL;
TupleDesc tupdesc; /* tuple description */
bool isnull;
int i;
if (!CALLED_AS_TRIGGER(fcinfo))
elog(ERROR, "autoinc: not fired by trigger manager");
if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
elog(ERROR, "autoinc: can't process STATEMENT events");
if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
elog(ERROR, "autoinc: must be fired before event");
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
rettuple = trigdata->tg_trigtuple;
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
rettuple = trigdata->tg_newtuple;
else
elog(ERROR, "autoinc: can't process DELETE events");
rel = trigdata->tg_relation;
relname = SPI_getrelname(rel);
trigger = trigdata->tg_trigger;
nargs = trigger->tgnargs;
if (nargs <= 0 || nargs % 2 != 0)
elog(ERROR, "autoinc (%s): even number gt 0 of arguments was expected", relname);
args = trigger->tgargs;
tupdesc = rel->rd_att;
chattrs = (int *) palloc(nargs / 2 * sizeof(int));
newvals = (Datum *) palloc(nargs / 2 * sizeof(Datum));
for (i = 0; i < nargs;)
{
int attnum = SPI_fnumber(tupdesc, args[i]);
int32 val;
Datum seqname;
if (attnum < 0)
elog(ERROR, "autoinc (%s): there is no attribute %s",
relname, args[i]);
if (SPI_gettypeid(tupdesc, attnum) != INT4OID)
elog(ERROR, "autoinc (%s): attribute %s must be of INT4 type",
relname, args[i]);
val = DatumGetInt32(SPI_getbinval(rettuple, tupdesc, attnum, &isnull));
if (!isnull && val != 0)
{
i += 2;
continue;
}
i++;
chattrs[chnattrs] = attnum;
seqname = DirectFunctionCall1(textin,
CStringGetDatum(args[i]));
newvals[chnattrs] = DirectFunctionCall1(nextval, seqname);
if (DatumGetInt32(newvals[chnattrs]) == 0)
newvals[chnattrs] = DirectFunctionCall1(nextval, seqname);
pfree(DatumGetTextP(seqname));
chnattrs++;
i++;
}
if (chnattrs > 0)
{
rettuple = SPI_modifytuple(rel, rettuple, chnattrs, chattrs, newvals, NULL);
if (rettuple == NULL)
elog(ERROR, "autoinc (%s): %d returned by SPI_modifytuple",
relname, SPI_result);
}
pfree(relname);
pfree(chattrs);
pfree(newvals);
return PointerGetDatum(rettuple);
}
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