Function deparseNullTest

contrib/postgres_fdw/deparse.c:3038–3066

* Deparse IS [NOT] NULL expression. */

 * Deparse IS [NOT] NULL expression.
 */
static void
deparseNullTest(NullTest *node, deparse_expr_cxt *context)
{
	StringInfo	buf = context->buf;

	appendStringInfoChar(buf, '(');
	deparseExpr(node->arg, context);

	/*
	 * For scalar inputs, we prefer to print as IS [NOT] NULL, which is
	 * shorter and traditional.  If it's a rowtype input but we're applying a
	 * scalar test, must print IS [NOT] DISTINCT FROM NULL to be semantically
	 * correct.
	 */
	if (node->argisrow || !type_is_rowtype(exprType((Node *) node->arg)))
	{
		if (node->nulltesttype == IS_NULL)
			appendStringInfoString(buf, " IS NULL)");
		else
			appendStringInfoString(buf, " IS NOT NULL)");
	}
	else
	{
		if (node->nulltesttype == IS_NULL)
			appendStringInfoString(buf, " IS NOT DISTINCT FROM NULL)");
		else
			appendStringInfoString(buf, " IS DISTINCT FROM NULL)");
	}
}

/*
 * Deparse ARRAY[...] construct.