Comment by martinald | Hacker News Reader

Comment by martinald | Hacker News Reader

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I've had extremely disappointing performance with postgres JSONB columns. I've used it a lot for MVPs and betas where it's much easier to use JSONB and lock in your exact relational schema lately.

I've now decided this path is a mistake because the performance is so bad. Even with low thousands/tens of thousands of rows it becomes a huge problem, queries that would take <1ms on relational stuff quickly start taking hundreds of ms.

Optimizing these with hand rolled queries is painful (I do not like the syntax it uses for jsonb querying) and for some doesn't really fix anything much, and indexes often don't help.

It seems that jsonb is just many many order of magnitudes slower, but I could be doing something wrong. Take for example storing a dictionary of string and int (number?) in a jsonb column. Adding the ints up in jsonb takes thousands of times longer rather than having these as string and int in a standard table.

Perhaps I am doing something wrong; and I'd love to know it if I am!

Did you have arrays in your jsonb data? I don't currently use jsonb for production performance sensitive queries, but in the past what I learned was that it's great at automatically indexing everything except arrays. You have to manually declare indexes on your arrays.

When jsonb works, it's incredible. I've had many... suboptimal experiences with mongo, and jsonb is just superior in my experience (although like I said, I haven't used it for performance critical stuff in production). For a long time, it kinda flew under the radar, and still remains an underappreciated feature of Postgres.

There are, but indeed they're a bit painful to index correctly. I'm planning to add in the future Generated Columns https://www.postgresql.org/docs/current/ddl-generated-column... to give option to extract part of the json as regular column.

> indexes often don't help.

An "index on expression" should perform the same regardless of the input column types. All that matters is the output of the expression. Were you just indexing the whole jsonb column or were you indexing a specific expression?

For example, an index on `foo(user_id)` vs `foo(data->'user_id')` should perform the same.

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