Function is_true_boolean_expression

src/bin/psql/command.c:2893–2902

* Read a boolean expression, return true if the expression * was a valid boolean expression that evaluated to true. * Otherwise return false. * * Note: conditional stack's top state must be active, else lexer will * fail to expand variables and backticks. */

 * fail to expand variables and backticks.
 */
static bool
is_true_boolean_expression(PsqlScanState scan_state, const char *name)
{
	PQExpBuffer buf = gather_boolean_expression(scan_state);
	bool		value = false;
	bool		success = ParseVariableBool(buf->data, name, &value);

	destroyPQExpBuffer(buf);
	return success && value;
}

/*
 * Read a boolean expression, but do nothing with it.