Обсуждение: pgsql: Add single-item cache when looking at topmost XID of a subtrans

Add single-item cache when looking at topmost XID of a subtrans XID

This change affects SubTransGetTopmostTransaction(), used to find the
topmost transaction ID of a given transaction ID.  The cache is able to
store one value, so as we can save the backend from unnecessary lookups
at pg_subtrans/ on repetitive calls of this routine.  There is a similar
practice in transam.c, for example.

Author: Simon Riggs
Reviewed-by: Andrey Borodin, Julien Rouhaud
Discussion: https://postgr.es/m/CANbhV-G8Co=yq4v4BkW7MJDqVt68K_8A48nAZ_+8UQS7LrwLEQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/06f5295af673df795e8e70e28c43d61c2817b6df

Modified Files
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src/backend/access/transam/subtrans.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)