[pksunkara]

I think a stored generated column allows you to create an index on it directly. Isn't it better approach?

[tczMUFlmoNk]

The article explains why they want to avoid this option:

> Starting at version 14, PostgreSQL supports generated columns - these are columns that are automatically populated with an expression when we insert the row. Sounds exactly like what we need but there is a caveat - the result of the expression is materialized - this means additional storage, which is what we were trying to save in the first place!

[pksunkara]

Thanks, missed that part. I would still be interested in knowing how much additional storage that adds, if the OP is interested in updating the article.

[zenmac]

>I think a stored generated column allows you to create an index on it directly. Isn't it better approach?

Is it also possible to create index (maybe partial index) on expressions?

[masklinn]

That's the first solution (a function based index), however it has the drawback of fragility: a seemingly innocent change to the query can lead to not matching the index's expression anymore). Which is why the article moves on to generated columns.

[rpsw]

I assume it would increase the storage usage, which they say they are trying to avoid in that example.