TIL

Recently I came across an error using postgres that stumped me for a while so I wanted to document it for next time. I was issuing an update statement to a table that had no numeric columns, but received the error: ERROR: value overflows numeric format. Not only did my statement not affect any numeric columns, the table itself didn’t have any numeric columns. The actual problem ended up being some malformed json that I was trying to insert into a jsonb column. The json had a value like 300e715100 which was actually part of a hashed string, but the json serializer I was using incorreclty identified it as a very large scientific notiation number, and so did not quote it. Because postgres cannot deal with a number that large it throws the error. Quoting the value properly fixed the problem. I also want to note that the error would not happen with json, only with jsonb because postgres is actually parsing the document.

select '{"v": 300e715100}'::jsonb;
-- ERROR:  value overflows numeric format
-- LINE 1: select '{"v": 300e715100}'::jsonb

select '{"v": 300e715100}'::json;
-- this statement executes without error.

You can try the code and see the error for yourself here: http://dbfiddle.uk/?rdbms=postgres_9.6&fiddle=1584330f148ab0e9ed72529dfb466a12

Today I learned that postgres allows you to use a subselect in an update statement using a special syntax. This allows you to update a record from other data in the system easily (without remembering the weird update-with-join syntax) or to have an update syntax that more closely resembles an insert statement. For example:

UPDATE table
SET (foo, bar) =
(SELECT 'foo', 'bar')
WHERE id = 1;

The subselect can be any query, just return your columns in the same order as the column list you provide. Here is the relevant documentation if you want to read further: https://www.postgresql.org/docs/current/static/sql-update.html

There are few things I have learned in my programming career that have paid off like higher order functions. Map, Reduce and Filter with their cousins, along with the concept of passing functions as data in general make code easier to reason about, easier to write, easier to test. I find myself evangelizing these concepts often, so I thought I would try to do my best to give an introduction of them, along with some real world examples of how they can improve your everyday programming life. These examples are in JavaScript, but the concepts are universal.

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At MotorsportReg we have customers all over the world so there is never a good time for maintenance or downtime. Historically, we used multiple application servers with sticky CFML sessions on the load balancer. Deploying code often meant interrupting users to deploy changes which is unacceptable. We needed more flexibility.

Sidecar is our solution, an external session management plugin for ColdFusion. Inspired by sessions in expressjs, we separated the persistence from the session management itself so you can plug in your favorite tech to fill that need - we wrote redis_session_store.cfc for our own needs, but all you have to do is implement the simple API for your preferred backend (memcached, couchdb, database, etc). If you implement your own storage adapter, please get in touch!

Once you have the potential for multiple servers to access session data at the same time, you’ll realize that <cflock> no longer offers the expected protection. We also wrote a separate distributed locking library, cfml-redlock, to make concurrent access safer, click here for some more info on that project).

This software is used in production. We wanted to open source it so that others can benefit but, also, selfishly in the hope that other companies will test it, file issues, or contribute. Implementation is simple - take a look at the tests and you should be able to get around pretty quickly. We plan to support Adobe ColdFusion 10+ and Lucee 4.5+ with this library.

If you have a passion for speed or love cars, motorcycles or karts, check out MotorsportReg. We have more than 5,000 track days, autocross, races and tours you can get involved with - chances are there is something happening near you!

During the development of Sidecar, an external session management plugin for ColdFusion, we selected Redis as our storage backend to support sessions in a cluster. Without relying on sticky sessions, we quickly realized that we needed a way to ensure that we wouldn’t step on our own toes as multiple servers potentially tried to access and modify session data concurrently.

After some research we decided on redlock for a distributed lock. This project is a port of node-redlock to CFML. It is useful outside of session management for any scenario where multiple servers need to run a process with transaction semantics so we have released it as its own library. About the time we finished development, Ben Nadel released his version of redlock. They’re similar but have a different API so check it out as well.

The goal is to support Adobe ColdFusion 10+ and Lucee 4.5+ with this library - like sidecar we are using these libraries in production, so we hope you find them useful and if welcome any contributions, including code, documentation or just reporting issues.