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Re: Support "Right Semi Join" plan shapes - Mailing list pgsql-hackers

From wenhui qiu
Subject Re: Support "Right Semi Join" plan shapes
Date
Msg-id CAGjGUAKmg1ae9NH1N5DDdnMnYah52Ox4c3Y+xiJPRzdCg7_XJA@mail.gmail.com
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In response to Re: Support "Right Semi Join" plan shapes  (Alena Rybakina <lena.ribackina@yandex.ru>)
Responses Re: Support "Right Semi Join" plan shapes
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Hi Alena Rybakina
For merge join
+ /*
+ * For now we do not support RIGHT_SEMI join in mergejoin.
+ */
+ if (jointype == JOIN_RIGHT_SEMI)
+ {
+ *mergejoin_allowed = false;
+ return NIL;
+ }
+
Tanks


On Wed, 6 Mar 2024 at 04:10, Alena Rybakina <lena.ribackina@yandex.ru> wrote:

To be honest, I didn't see it in the code, could you tell me where they are, please?

On 05.03.2024 05:44, Richard Guo wrote:

On Tue, Jan 30, 2024 at 2:51 PM Alena Rybakina <lena.ribackina@yandex.ru> wrote:
I have reviewed your patch and I think it is better to add an Assert for
JOIN_RIGHT_SEMI to the ExecMergeJoin and ExecNestLoop functions to
prevent the use of RIGHT_SEMI for these types of connections (NestedLoop
and MergeJoin).

Hmm, I don't see why this is necessary.  The planner should already
guarantee that we won't have nestloops/mergejoins with right-semi joins.

Thanks
Richard
-- 
Regards,
Alena Rybakina
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

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