Not sure why those are json_agg() instead of array_agg() in that example. Why would you use a JSON array instead of a native properly typed array? Yes, if you have some complex objects for some reason you can use JSON objects. But those where all just arrays of IDs. Also why was it json_agg() and not jsonb_agg()? Is there any reason on why to use JSON over JSONB in PostgreSQL?

If you, for whatever obscure reason, need to preserve whitespace and key ordering, that is you want something that is effectively just a text column, then you should use JSON over JSONB.

I can't think of any case at all, no matter how contrived, where you'd want to use the non-B versions of the JSON aggregate functions though.

The non-B JSON can take up less space on disk and less write time complexity.

I wonder if its just used in a query like that if the generated data structure is only in memory anyway and then serialized to JSON to send to the client. I.e. JSON VS JSONB would not make any difference?

If the queries are sensible, you can always create indexes that index on the queried expressions.

https://www.postgresql.org/docs/current/indexes-expressional...

Hoping for more easy columnar support in databases, which is one of the things that can lead you to storing json in database columns (if your data is truly columnar).

Currently the vendor lock-in or requirements for installing plugins make it hard to do with cloud sql providers. Especially hard since by the time it's a problem you're probably at enough scale to make switching db/vendors hard or impossible.

How does columnar = json? json isn't colunar at all... If you just want to have a schema in json instead of sql, use a no-sql db, postgres nosql features are strong, but the db features are actually much stronger.

json isn't necessarily columnar, but it is a natrual fit for stuff that is columnar that's otherwise harder to model in a traditional relational db

here's my usecase:

- we have a bunch of attributes (all different names by customer, and many different values for each record that a customer stores)

- it's a fairly natural fit for a json value with only one level of key: value mapping

- we use mysql on GCP (no columnar plugins, too hard to switch to postgres)

Someone could go back in time and correctly model it as columns and not json but that ship has sorta sailed. While it's not impossible to change, it would be pretty hard, time will tell if that ends up happening.

I would love to be able to tell mysql "put this column in a collumnar engine and use that when I query on it" (AlloyDB is this for postgres on GCP)

Too bad mysql doesn't even have materialized views - its not a good combination with a json only situation, but you clearly are suffering through that, good luck :) probably etl it to clickhouse and move on.

Could always try and dump to GCP/Parquet/json and use duckdb/bq to just query it all.

great point.

with pg_mooncake v0.2 (launching in ~couple weeks), you'll be able to get a columnar copy of your Postgres that's always synced (<s freshness).

Keep your write path unchanged, and keep your Postgres where it is. Deploy Mooncake as a replica for the columnar queries.

I wish, someone unfortunately picked mysql