pg_buffercache: Add pg_buffercache_relations() function (v2)#50
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This function returns an aggregation of buffer contents, grouped on a per-relfilenode basis. This is often useful to understand which tables or indexes are currently in cache, and can show cache disruptions due to query activity when sampled over time. The existing pg_buffercache() function can be utilized for this by grouping the result, but passing a large amount of buffer entries (one per page) back to the tuplestore and then aggregating it can be prohibitively expensive with large buffer counts. Even on a small shared buffers (128MB) the new function is 10x faster. Similar to the existing summary functions this new function does not hold buffer partition or buffer header locks whilst gathering its statistics. Author: Lukas Fittl <[email protected]> Reviewed by: Jakub Wartak <[email protected]> Reviewed by: Bertrand Drouvot <[email protected]> Reviewed by: Haibo Yan <[email protected]> Reviewed by: Masahiko Sawada <[email protected]> Reviewed by: Paul A Jungwirth <[email protected]> Reviewed by: Khoa Nguyen <[email protected]> Discussion: https://www.postgresql.org/message-id/flat/CAP53Pkx0=ph0vG_M20yVAoK11yGSTZP=53-rZt36OCP4hBPaDQ@mail.gmail.com
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