Function ExplainBeginOutput

src/backend/commands/explain.c:5892–5918

* Emit the start-of-output boilerplate. * * This is just enough different from processing a subgroup that we need * a separate pair of subroutines. */

 * a separate pair of subroutines.
 */
void
ExplainBeginOutput(ExplainState *es)
{
	switch (es->format)
	{
		case EXPLAIN_FORMAT_TEXT:
			/* nothing to do */
			break;

		case EXPLAIN_FORMAT_XML:
			appendStringInfoString(es->str,
								   "<explain xmlns=\"http://www.postgresql.org/2009/explain\">\n");
			es->indent++;
			break;

		case EXPLAIN_FORMAT_JSON:
			/* top-level structure is an array of plans */
			appendStringInfoChar(es->str, '[');
			es->grouping_stack = lcons_int(0, es->grouping_stack);
			es->indent++;
			break;

		case EXPLAIN_FORMAT_YAML:
			es->grouping_stack = lcons_int(0, es->grouping_stack);
			break;
	}
}

/*
 * Emit the end-of-output boilerplate.