| From: | Dmitry Lazurkin <dilaz03(at)gmail(dot)com> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Perfomance of IN-clause with many elements and possible solutions |
| Date: | 2017-08-01 16:24:13 |
| Message-ID: | 66821561-f2f6-21e4-8f91-37a2b23b768e@gmail.com |
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| Lists: | pgsql-general |
On 08/01/2017 07:13 PM, Jeff Janes wrote:
> I think that HashSet is a Java-specific term. It is just a hash table
> in which there is no data to store, just the key itself (and probably
> a cash of the hashcode of that key), correct?
Yes. And in Java HashSet implemented on top of HashMap (:
> I think a more general solution would be to get the planner and
> executor to run the in-list query using the Hash Join, the same way it
> runs the in-VALUES one.
Have additional plan nodes big overhead?
> I was impressed at how well the JSON and hstore worked, you might want
> to look at how they do it. It is must be using an internal hash table
> of some sort.
JSONB and HSTORE keep sorted pairs and use binary search.
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