On Tue, 30 Aug 2011, Tom Lane wrote:
Sure enough, that's the problem. pg_upgrade leaves relpages/reltuples
set to zero, but it also imports the visibility map pages from the old
cluster. If the old visibility map shows the table as all-visible,
then this happens when you try to VACUUM ANALYZE the table:
1. VACUUM doesn't process any pages, so it has no tuple density
estimate. It leaves reltuples set to zero, but it does set relpages.
2. ANALYZE scans some part of the table. It gets a tuple density
estimate for those pages ... but if that's only a small fraction of
the table, it believes the zero estimate of tuple density elsewhere.
So you get only a small update of reltuples.
Thanks for figuring this out.
I wonder what should be the best way to proceed for already migrated
databases -- running analyze repeatedly may not be the best way for
very large clusters with large tables...
S
*******************************************************************
Sergey E. Koposov, PhD
Institute for Astronomy, Cambridge/Sternberg Astronomical Institute
Web: http://lnfm1.sai.msu.ru/~math
E-mail: m...@sai.msu.ru
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