Is this SQL databases or No-SQL? [LWN.net]

Is this SQL databases or No-SQL?

Posted Apr 10, 2014 20:14 UTC (Thu) by cladisch (✭ supporter ✭, #50193)
In reply to: Is this SQL databases or No-SQL? by nix
Parent article: A discussion between database and kernel developers

> > […] it will build indices on the fly if they don't exist.

> I don't know of any database system that implements it.

As shown in this example, SQLite is happy to create a temporary index if it is estimated to be faster overall.

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Is this SQL databases or No-SQL?

Posted Apr 15, 2014 14:45 UTC (Tue) by nix (subscriber, #2304) [Link] (2 responses)

Neat!

I did some digging in response: other, bigger RDBMSes (including PostgreSQL) will also create temporary indexes in temporary tablespace if needed. They're not visible to the database user, though, and are thrown away after the query terminates.

Is this SQL databases or No-SQL?

Posted Apr 15, 2014 15:27 UTC (Tue) by intgr (subscriber, #39733) [Link] (1 responses)

> bigger RDBMSes (including PostgreSQL) will also create temporary indexes

I think you are misunderstanding. The "temporary indexes" you speak probably refers to explicitly created indexes CREATE TEMPORARY TABLE tables issued by the client. I guess you were reading this: http://www.postgresql.org/docs/current/static/runtime-con...

PostgreSQL can create temporary in-memory hash tables, do temporary sorts (such as for merge joins or ORDER BY) and mid-query materialization of intermediate results. Sorts and materialized results can spill out to disk when there isn't enough memory to keep them, but they aren't called "temporary indexes" since they don't resemble actual index data structures.

Is this SQL databases or No-SQL?

Posted Apr 20, 2014 18:27 UTC (Sun) by nix (subscriber, #2304) [Link]

Yes, but those appear to be what wol is referring to as 'indexes' (they index the data, after all). They're not SQL-level entities, or user-visible, of course.