CREATE FUNCTION test_sql_error() RETURNS void AS $$ plv8.execute("ERROR") $$ LANGUAGE plv8;
SELECT test_sql_error();
ERROR:  syntax error at or near "ERROR"
CONTEXT:  test_sql_error() LINE 1:  plv8.execute("ERROR") 
CREATE FUNCTION catch_sql_error() RETURNS void AS $$
try {
	plv8.execute("throw SQL error");
	plv8.elog(NOTICE, "should not come here");
} catch (e) {
	plv8.elog(NOTICE, e);
}
$$ LANGUAGE plv8;
SELECT catch_sql_error();
NOTICE:  Error: syntax error at or near "throw"
 catch_sql_error 
-----------------
 
(1 row)

CREATE FUNCTION catch_sql_error_2() RETURNS text AS $$
try {
	plv8.execute("throw SQL error");
	plv8.elog(NOTICE, "should not come here");
} catch (e) {
	plv8.elog(NOTICE, e);
	return plv8.execute("select 'and can execute queries again' t").shift().t;
}
$$ LANGUAGE plv8;
SELECT catch_sql_error_2();
NOTICE:  Error: syntax error at or near "throw"
       catch_sql_error_2       
-------------------------------
 and can execute queries again
(1 row)

CREATE FUNCTION catch_sql_error_3() RETURNS text AS $$
try {
	plv8.execute("throw SQL error");
	plv8.elog(NOTICE, "should not come here");
} catch (e) {
	plv8.elog(NOTICE, e.sqlerrcode);
	return e.sqlerrcode;
}
$$ LANGUAGE plv8;
SELECT catch_sql_error_3();
NOTICE:  42601
 catch_sql_error_3 
-------------------
 42601
(1 row)

-- subtransaction()
CREATE TABLE subtrant(a int);
CREATE FUNCTION test_subtransaction_catch() RETURNS void AS $$
try {
	plv8.subtransaction(function(){
		plv8.execute("INSERT INTO subtrant VALUES(1)");
		plv8.execute("INSERT INTO subtrant VALUES(1/0)");
	});
} catch (e) {
	plv8.elog(NOTICE, e);
	plv8.execute("INSERT INTO subtrant VALUES(2)");
}
$$ LANGUAGE plv8;
SELECT test_subtransaction_catch();
NOTICE:  Error: division by zero
 test_subtransaction_catch 
---------------------------
 
(1 row)

SELECT * FROM subtrant;
 a 
---
 2
(1 row)

TRUNCATE subtrant;
CREATE FUNCTION test_subtransaction_throw() RETURNS void AS $$
plv8.subtransaction(function(){
	plv8.execute("INSERT INTO subtrant VALUES(1)");
	plv8.execute("INSERT INTO subtrant VALUES(1/0)");
});
$$ LANGUAGE plv8;
SELECT test_subtransaction_throw();
ERROR:  division by zero
CONTEXT:  test_subtransaction_throw() LINE 2: plv8.subtransaction(function(){
SELECT * FROM subtrant;
 a 
---
(0 rows)

-- exception handling
CREATE OR REPLACE FUNCTION v8_test_throw() RETURNS float AS
$$ 
throw new Error('Error');
$$
LANGUAGE plv8;
CREATE OR REPLACE FUNCTION v8_test_catch_throw() RETURNS text AS
$$
 try{
   var res = plv8.execute('select * from  v8_test_throw()');
 } catch(e) {
   return JSON.stringify({"result": "error"});
 }
$$
language plv8;
SELECT v8_test_catch_throw();
 v8_test_catch_throw 
---------------------
 {"result":"error"}
(1 row)

CREATE FUNCTION catch_elog_error() RETURNS void AS $$
function f (){
}
f.prototype.toString = function(){
        throw 'custom exception';
}
try {
	plv8.elog(NOTICE, (new f));
	plv8.elog(NOTICE, "should not come here");
} catch (e) {
	plv8.elog(NOTICE, 'catch result:'+ e);
}
$$ LANGUAGE plv8;
SELECT catch_elog_error();
NOTICE:  catch result:custom exception
 catch_elog_error 
------------------
 
(1 row)

CREATE FUNCTION catch_elog_error2() RETURNS void AS $$
function f (){
}
f.prototype.toString = function(){
        throw 'custom exception';
}

plv8.elog(NOTICE, (new f));
plv8.elog(NOTICE, "should not come here");

$$ LANGUAGE plv8;
SELECT catch_elog_error2();
ERROR:  custom exception
CONTEXT:  catch_elog_error2() LINE 5:         throw 'custom exception';