Re: [HACKERS] Foreign Join pushdowns not working properly for outer joins - Mailing list pgsql-hackers

From Ashutosh Bapat
Subject Re: [HACKERS] Foreign Join pushdowns not working properly for outer joins
Date
Msg-id CAFjFpRd1fbtHWMg25xV4PHPfzrJt34y6Qe2YQMa_4BU6mYdWEg@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] Foreign Join pushdowns not working properly for outer joins  (David Rowley <david.rowley@2ndquadrant.com>)
Responses Re: [HACKERS] Foreign Join pushdowns not working properly for outerjoins  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
List pgsql-hackers
On Thu, Apr 13, 2017 at 7:35 AM, David Rowley
<david.rowley@2ndquadrant.com> wrote:
> On 13 April 2017 at 11:22, Peter Eisentraut
> <peter.eisentraut@2ndquadrant.com> wrote:
>> Is this patch considered ready for review as a backpatch candidate?
>
> Yes, however, the v5 patch is based on master. The v4 patch should
> apply to 9.6. Diffing the two patches I see another tiny change to a
> comment, of which I think needs re-worded anyway.
>
> + * This function should usually set FDW options in fpinfo after the join is
> + * deemed safe to push down to save some CPU cycles. But We need server
> + * specific options like extensions to decide push-down safety. For
> + * checking extension shippability, we need foreign server as well.
> + */
>
> This might be better written as:
>
> Ordinarily, we might be tempted into delaying the merging of the FDW
> options until we've deemed the foreign join to be ok. However, we must
> do this before performing this test so that we know which quals can be
> evaluated on the foreign server. This may depend on the
> shippable_extensions.
>

This looks better. Here are patches for master and 9.6.
Since join pushdown was supported in 9.6 the patch should be
backported to 9.6 as well. Attached is the patch (_96) for 9.6,
created by rebasing on 9.6 branch and removing conflict. _v6 is
applicable on master.

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

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