Re: [HACKERS] Partition-wise join for join between (declaratively)partitioned tables - Mailing list pgsql-hackers

From Ashutosh Bapat
Subject Re: [HACKERS] Partition-wise join for join between (declaratively)partitioned tables
Date
Msg-id CAFjFpRdEXxtRd0y_7E6wM9x2mJkxuMQQXz4dFmUUomjn9tCyMg@mail.gmail.com
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In response to Re: [HACKERS] Partition-wise join for join between (declaratively)partitioned tables  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
>
>> I don't think we will get away by supporting just scan paths, since
>> the inner side of lateral join can be any paths not just scan path. Or
>> you are suggesting that we disable partition-wise lateral join and
>> support reparameterization of only scan paths?
>
> I think if you can do a straight-up partitionwise nested loop between
> two tables A and B, that's pretty bad.

Ok.

> But if there are more complex
> cases that involve parameterizing entire join trees which aren't
> covered, that's less bad.  Parallel query almost entirely punts on
> LATERAL right now, and nobody's complained yet.  I'm sure that'll need
> to get fixed someday, but not today.
>
Ok.

I am suggesting this possibility in case we run of time to review and
commit reparameterize_path_by_child() entirely. If we can do that, I
will be happy.

In case, we have to include a stripped down version of
reparameterize_path_by_child(), with which I am fine too, we will need
to disable LATERAL joins, so that we don't end up with an error "could
not devise a query plan for the given query".

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company



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