This is a classic piece, and I love the contradictions in the text. It encapsulates my feelings on good software and code that it almost becomes an art than a science.

TIL this exists

I also like the POSIX “seconds since 1970” standard, but I feel that should only be used in RAM when performing operations (time differences in timers etc.). It irks me when it’s used for serialising to text/JSON/XML/CSV.

I’ve seen bugs where programmers tried to represent date in epoch time in seconds or milliseconds in json. So something like “pay date” would be presented by a timestamp, and would get off-by-one errors because whatever time library the programmer was using would do time zone conversions on a timestamp then truncate the date portion.

If the programmer used ISO 8601 style formatting, I don’t think they would have included the timepart and the bug could have been avoided.

Use dates when you need dates and timestamps when you need timestamps!

Do you use it? When?

Parquet is really used for big data batch data processing. It’s columnar-based file format and is optimized for large, aggregation queries. It’s non-human readable so you need a library like apache arrow to read/write to it.

I would use parquet in the following circumstances (or combination of circumstances):

• The data is very large
• I’m integrating this into an analytical query engine (Presto, etc.)
• I’m transporting data that needs to land in an analytical data warehouse (Snowflake, BigQuery, etc.)
• Consumed by data scientists, machine learning engineers, or other data engineers

Since the data is columnar-based, doing queries like select sum(sales) from revenue is much cheaper and faster if the underlying data is in parquet than csv.

The big advantage of csv is that it’s more portable. csv as a data file format has been around forever, so it is used in a lot of places where parquet can’t be used.

Most of us have bad memories of over-complex hierarchies we regret seeing, but this is probably due to the dominance of OOP in recent decades.

This sentence here is why inheritance gets a bad reputation, rightly or wrongly. Inheritance sounds intuitive when you’re inheriting Vehicle in your Bicycle class, but it falls apart when dealing with more abstract ideas. Thus, it’s not immediately clear when and why you should use inheritance, and it soon becomes a tangled mess.

Thus, OO programs can easily fall into a trap of organizing code into false hierarchies. And those hierarchies may not make sense from developer to developer who is reading the code.

I’m not a fan of OO programming, but I do think it can occasionally be a useful tool.

Ehhh, I don’t quite agree with this. I’ve done the same thing where I used a timestamp field to replace a boolean. However, they are technically not the same thing. In databases, boolean fields can be nullable so you actually have 3-valued boolean logic: true, false, and null. You can technically only replace a non-nullable field to a timestamp column because you are treating null in timestamp as false.

Two examples:

1. A table of generated documents for employees to sign. There’s a field where they need to agree to something, but it’s optional. You want to differentiate between employees who agreed, employees who disagreed, and employees who have yet to agree. You can’t change the column from is_agreed to agreed_at.

2. Adding a boolean column to an existing table. These columns need to either default to an value (which is fair) or be nullable.