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Comment by dude_abides | Hacker News Reader

To slightly rephrase the OP's question:

  In what use cases does mongo kick postgres's ass?

To the two points you mentioned:

- semi-structured input can be saved as hstore type or as json type;

- and for flexible jobs, you can use pretty much any popular language - PL/R, PL/Python, even PL/C if performance is really critical.

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I would have replied something similar if that was the question :-) (I use PG a lot these days).

Agreed on the first point (but I'm not sure you get exactly the same type of flexibility in all my use cases - I'll have to make a closer comparison).

For the second point, well not having to handle the schema for ETL jobs is sometimes fairly useful and removes a lot of cruft, that was part of my point (those ETL are code-based, only relying on MongoDB as a flexible store).

You can't query JSON easily and hstore is only one level deep. So, no, its not as flexible.

You can't query the json type as easily in postgres. I would guess that is an important use case.

I don't know about JSON type but the annoying thing about hstore is everything is a string; there are no types.

Just because you can write an app using assembler doesn't mean it is the best way to do it.

Very tempted to ask "In what way does postgres compare to an assembler and mongodb to a high level language?" but I think I'll just assume that you're trolling.

Besides, SQL sounds more high-level than map-reduce to me.

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