On Thu, 7 May 2020 at 18:12, Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Thu, May 7, 2020 at 2:23 PM Masahiko Sawada > <masahiko.saw...@2ndquadrant.com> wrote: > > > > Hi, > > > > The following description in pg_buffercace is no longer true. > > > > When the pg_buffercache view is accessed, internal buffer manager > > locks are taken for long enough to copy all the buffer state data that > > the view will display. This ensures that the view produces a > > consistent set of results, while not blocking normal buffer activity > > longer than necessary. Nonetheless there could be some impact on > > database performance if this view is read often. > > > > We changed pg_buffercache_page so that it doesn't take buffer manager > > locks in commit 6e654546fb6. Therefore from version 10, > > pg_buffercache_page has less impact on normal buffer activity less but > > might not return a consistent snapshot across all buffers instead. > > > > +1. > > There is a typo in the patch (queris/queries). How about if slightly > reword it as "Since buffer manager locks are not taken to copy the > buffer state data that the view will display, accessing > <structname>pg_buffercache</structname> view has less impact on normal > buffer activity but it doesn't provide a consistent set of results > across all buffers. However, we ensure that the information of each > buffer is self-consistent."?
Thank you for your idea. Agreed. Attached the updated version patch. Regards, -- Masahiko Sawada http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
pg_buffercache_doc_v2.patch
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