Function transformSubLink

src/backend/parser/parse_expr.c:1766–2001

}

static Node *
transformSubLink(ParseState *pstate, SubLink *sublink)
{
	Node	   *result = (Node *) sublink;
	Query	   *qtree;
	const char *err;

	/*
	 * Check to see if the sublink is in an invalid place within the query. We
	 * allow sublinks everywhere in SELECT/INSERT/UPDATE/DELETE, but generally
	 * not in utility statements.
	 */
	err = NULL;
	switch (pstate->p_expr_kind)
	{
		case EXPR_KIND_NONE:
			Assert(false);		/* can't happen */
			break;
		case EXPR_KIND_OTHER:
			/* Accept sublink here; caller must throw error if wanted */
			break;
		case EXPR_KIND_JOIN_ON:
		case EXPR_KIND_JOIN_USING:
		case EXPR_KIND_FROM_SUBSELECT:
		case EXPR_KIND_FROM_FUNCTION:
		case EXPR_KIND_WHERE:
		case EXPR_KIND_POLICY:
		case EXPR_KIND_HAVING:
		case EXPR_KIND_FILTER:
		case EXPR_KIND_WINDOW_PARTITION:
		case EXPR_KIND_WINDOW_ORDER:
		case EXPR_KIND_WINDOW_FRAME_RANGE:
		case EXPR_KIND_WINDOW_FRAME_ROWS:
		case EXPR_KIND_WINDOW_FRAME_GROUPS:
		case EXPR_KIND_SELECT_TARGET:
		case EXPR_KIND_INSERT_TARGET:
		case EXPR_KIND_UPDATE_SOURCE:
		case EXPR_KIND_UPDATE_TARGET:
		case EXPR_KIND_GROUP_BY:
		case EXPR_KIND_ORDER_BY:
		case EXPR_KIND_DISTINCT_ON:
		case EXPR_KIND_LIMIT:
		case EXPR_KIND_OFFSET:
		case EXPR_KIND_RETURNING:
		case EXPR_KIND_VALUES:
		case EXPR_KIND_VALUES_SINGLE:
		case EXPR_KIND_CYCLE_MARK:
			/* okay */
			break;
		case EXPR_KIND_CHECK_CONSTRAINT:
		case EXPR_KIND_DOMAIN_CHECK:
			err = _("cannot use subquery in check constraint");
			break;
		case EXPR_KIND_COLUMN_DEFAULT:
		case EXPR_KIND_FUNCTION_DEFAULT:
			err = _("cannot use subquery in DEFAULT expression");
			break;
		case EXPR_KIND_INDEX_EXPRESSION: