Re: parallel joins, and better parallel explain - Mailing list pgsql-hackers

From Greg Stark
Subject Re: parallel joins, and better parallel explain
Date
Msg-id CAM-w4HNOuoat3nxi3DPCxtB72d+OYi3-M9jkD=9bkBTzXOVqow@mail.gmail.com
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In response to Re: parallel joins, and better parallel explain  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: parallel joins, and better parallel explain  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Mon, Nov 30, 2015 at 4:52 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> Not only does this build only one copy of the hash table instead of N
> copies, but we can parallelize the hash table construction itself by
> having all workers insert in parallel, which is pretty cool.

Hm. The case where you don't want parallel building of the hash table
might be substantially simpler. You could build a hash table and then
copy it into shared memory as single contiguous read-only data
structure optimized for lookups. I have an inkling that there are even
ways of marking the memory as being read-only and not needing cache
synchronization.



-- 
greg



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