Function accumArrayResult

src/backend/utils/adt/arrayfuncs.c:5239–5292

* accumArrayResult - accumulate one (more) Datum for an array result * * astate is working state (can be NULL on first call) * dvalue/disnull represent the new Datum to append to the array * element_type is the Datum's type (must be a valid array element type) * rcontext is where to keep working state */

 *	rcontext is where to keep working state
 */
ArrayBuildState *
accumArrayResult(ArrayBuildState *astate,
				 Datum dvalue, bool disnull,
				 Oid element_type,
				 MemoryContext rcontext)
{
	MemoryContext oldcontext;

	if (astate == NULL)
	{
		/* First time through --- initialize */
		astate = initArrayResult(element_type, rcontext, true);
	}
	else
	{
		Assert(astate->element_type == element_type);
	}

	oldcontext = MemoryContextSwitchTo(astate->mcontext);

	/* enlarge dvalues[]/dnulls[] if needed */
	if (astate->nelems >= astate->alen)
	{
		astate->alen *= 2;
		astate->dvalues = (Datum *)
			repalloc(astate->dvalues, astate->alen * sizeof(Datum));
		astate->dnulls = (bool *)
			repalloc(astate->dnulls, astate->alen * sizeof(bool));
	}

	/*
	 * Ensure pass-by-ref stuff is copied into mcontext; and detoast it too if
	 * it's varlena.  (You might think that detoasting is not needed here
	 * because construct_md_array can detoast the array elements later.
	 * However, we must not let construct_md_array modify the ArrayBuildState
	 * because that would mean array_agg_finalfn damages its input, which is
	 * verboten.  Also, this way frequently saves one copying step.)
	 */
	if (!disnull && !astate->typbyval)
	{
		if (astate->typlen == -1)
			dvalue = PointerGetDatum(PG_DETOAST_DATUM_COPY(dvalue));
		else
			dvalue = datumCopy(dvalue, astate->typbyval, astate->typlen);
	}

	astate->dvalues[astate->nelems] = dvalue;
	astate->dnulls[astate->nelems] = disnull;
	astate->nelems++;

	MemoryContextSwitchTo(oldcontext);

	return astate;
}

/*
 * makeArrayResult - produce 1-D final result of accumArrayResult