Re: SELECT INTO large FKyed table is slow

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On 12/01/2010 05:34 PM, Mladen Gogala wrote:
Mario Splivalo wrote:


Yes, as Mladen Gogala had advised. No noticable change in performance -
it's still slow :)


Declaring constraints as deferrable  doesn't do anything as such, you
have to actually set the constraints deferred to have an effect. You
have to do it within a transaction block. If done outside of the
transaction block, there is no effect:

I understand, I did as you suggested.

Begin; Set constraints all deferred; select my_insert_drones_function(); commit


I was able to insert the same value twice, it only failed at the end of
the transaction.
But, just for the sake of clarification - I tought that DEFERRABLE would
matter if I do a lot of INSERTs, inside a FOR loop or something like
that. Since I'm doing INSERT INTO ... SELECT, does it makes any difference?

You cannot tell which part takes a long time, select or insert, without
profiling. I certainly cannot do it over the internet.

If I first select to a dummy temprary table, that SELECT is fast. Just INSERT INTO SELECT is slow.

I'll try what Pierre suggested, on whole new filesystem. This one did get quite filled with thousands of files that I deleted while the database was working.

	Mario

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