plv8 | V8 Engine Javascript Procedural Language add-on | Database library

I don't use plv8, but IN works with lists and lists can't be stored in parameters. What you appear to have is an array. For arrays, you use:

I am not familiar with PostgreSQL, but looking at your code sample, here are some comments:

• $TG_OP = 'UPDATE' : string comparison in Perl is done with the eq operator
• $OLD.user_id !== $NEW.user_id : numerical comparison for non-equality should be done using the != operator
• null should probably be undef.
• $userId = OLD.user_id : it seems like $OLD is an object (by looking at your code)? Then you should probably access the user_id attribute using something like $OLD->user_id. The same goes for all other attribute accesses using the dot . operator in Javascript; those should probably be a -> operator in Perl.
• NOTICE 'Update of user_id not allowed: %, at %' : you can throw an exception in Perl using the die function
• IF ... ELSE : In Perl this is if ... else
• Math.max($cashOut - $bet, 0) : In Perl you can use max from the module List::Util

Cycle through "pg_try_advisory_xact_lock(...)" on 5 different lock ids (say 123457 to 123461) (1 real lock holder and 4 more non-holding waiters = 5). Getting one of those then grants you the right to wait on the "real" lock id. Failing to get any of the 5 results in failure. This does mean you have to reserve/coordinate 6 magic constants, rather than 1.

I have two hints pointing in the NO direction:

1. You can use PLV8 in Amazon RDS PosgreSQL. RDS doesn't allow any language which is not trusted. As explained in PostgreSQL documentation:

   TRUSTED

   TRUSTED specifies that the language does not grant access to data that the user would not otherwise have.

   If PLV8 could use libraries, those would (most probably) allow for performing operations such as downloading data via HTTP, or checking the file system, which would contravene this restriction (and possibly, put RDS system at hacking risk).

2. Presentation PLV8 - The PostgreSQL web side by Lucio Grenzi.

   Slide #10:

   PLV8: a trusted language

     [...]

   • no way to load external processing modules from the file system

A possible alternative

I have used the PLPERLu (u meaning untrusted) language. Using that language, you can use libraries. Your libraries should be in the standard locations for the PERL installation being used by PostgreSQL (as defined when you CREATE LANGUAGE).

Try to run commands using && as possible as you can. Example:

You have two options.

1. Store the source code of the function in a special database table and load it using select and eval(). Read about details in this answer: Can plv8 JavaScript language extension call 3rd party libraries?

2. Place the function in an initialization module and set this module using configuration parameter plv8.start_proc so it is executed automatically on start-up. You can find details in the PL/v8 documentation.

The second option is really handy and does not need an additional table, but may seem a bit tricky. A simple example: we want to have a function square_of_sum(a, b) predefined in all our plv8 functions. First, create the initialization function:

I would use common relational approach for M:N cardinality

Example table: