Function deconstruct_composite_datum

src/pl/plpgsql/src/pl_exec.c:7319–7339

* deconstruct_composite_datum extract tuple+tupdesc from composite Datum * * The caller must supply a HeapTupleData variable, in which we set up a * tuple header pointing to the composite datum's body. To make the tuple * value outlive that variable, caller would need to apply heap_copytuple... * but current callers only need a short-lived tuple value anyway. * * Returns a pointer to the

 * Also, best to call this in a short-lived context, as it might leak memory.
 */
static TupleDesc
deconstruct_composite_datum(Datum value, HeapTupleData *tmptup)
{
	HeapTupleHeader td;
	Oid			tupType;
	int32		tupTypmod;

	/* Get tuple body (note this could involve detoasting) */
	td = DatumGetHeapTupleHeader(value);

	/* Build a temporary HeapTuple control structure */
	tmptup->t_len = HeapTupleHeaderGetDatumLength(td);
	ItemPointerSetInvalid(&(tmptup->t_self));
	tmptup->t_tableOid = InvalidOid;
	tmptup->t_data = td;

	/* Extract rowtype info and find a tupdesc */
	tupType = HeapTupleHeaderGetTypeId(td);
	tupTypmod = HeapTupleHeaderGetTypMod(td);
	return lookup_rowtype_tupdesc(tupType, tupTypmod);
}

/*
 * exec_move_row_from_datum		Move a composite Datum into a record or row