Function array_agg_serialize

src/backend/utils/adt/array_userfuncs.c:655–743

* array_agg_serialize * Serialize ArrayBuildState into bytea. */

 *		Serialize ArrayBuildState into bytea.
 */
Datum
array_agg_serialize(PG_FUNCTION_ARGS)
{
	ArrayBuildState *state;
	StringInfoData buf;
	bytea	   *result;

	/* cannot be called directly because of internal-type argument */
	Assert(AggCheckCallContext(fcinfo, NULL));

	state = (ArrayBuildState *) PG_GETARG_POINTER(0);

	pq_begintypsend(&buf);

	/*
	 * element_type. Putting this first is more convenient in deserialization
	 */
	pq_sendint(&buf, state->element_type, sizeof(Oid));

	/*
	 * nelems -- send first so we know how large to make the dvalues and
	 * dnulls array during deserialization.
	 */
	pq_sendint64(&buf, state->nelems);

	/* alen can be decided during deserialization */

	/* typlen */
	pq_sendint(&buf, state->typlen, sizeof(int16));

	/* typbyval */
	pq_sendbyte(&buf, state->typbyval);

	/* typalign */
	pq_sendbyte(&buf, state->typalign);

	/* dnulls */
	pq_sendbytes(&buf, (char *) state->dnulls, sizeof(bool) * state->nelems);

	/*
	 * dvalues.  By agreement with array_agg_deserialize, when the element
	 * type is byval, we just transmit the Datum array as-is, including any
	 * null elements.  For by-ref types, we must invoke the element type's
	 * send function, and we skip null elements (which is why the nulls flags
	 * must be sent first).
	 */
	if (state->typbyval)
		pq_sendbytes(&buf, (char *) state->dvalues,
					 sizeof(Datum) * state->nelems);
	else
	{
		SerialIOData *iodata;
		int			i;

		/* Avoid repeat catalog lookups for typsend function */
		iodata = (SerialIOData *) fcinfo->flinfo->fn_extra;
		if (iodata == NULL)
		{