Thread: pg_stat_all_tables.last_vacuum not always correct.
I ran `VACUUM VERBOSE` on 10-28. After the VACUUM completed, I ran the query
`SELECT relname, last_vacuum FROM pg_stat_all_tables ORDER BY 2;`
This query returned:
relname | last_vacuum -------------------------+------------------------------- <table> | 2018-10-24 11:15:31.943684+00 <table2> | 2018-10-24 11:15:31.963803+00 <table3> | 2018-10-26 07:24:06.877427+00 <table4> | 2018-10-26 07:24:06.884089+00 <table5> | 2018-10-26 07:24:06.926874+00 <table6> | 2018-10-26 07:24:06.927982+00...
I took some of these tables and grep'd the VERBOSE logs for them, getting results like:
INFO: vacuuming "<table>"...INFO: "<table>": found 0 removable, 198 nonremovable row versions in 28 out of 104513 pagesINFO: vacuuming "<table2>"INFO: index "<table2>" now contains 1816 row versions in 7 pagesINFO: "<table2>": found 0 removable, 6 nonremovable row versions in 1 out of 325 pagesINFO: vacuuming "<table3>"...INFO: "<table3>": found 0 removable, 1 nonremovable row versions in 1 out of 10924 pagesINFO: vacuuming "<table4>"...INFO: "<table4>": found 0 removable, 21 nonremovable row versions in 4 out of 4 pagesINFO: vacuuming "<table5>"INFO: "<table5>": found 0 removable, 2 nonremovable row versions in 1 out of 412 pagesINFO: vacuuming "<table6>"...INFO: "<table6>": found 0 removable, 0 nonremovable row versions in 0 out of 0 pagesSo, at least according to the VERBOSE logs, it seems like these tables _were_ vacuumed. Why the discrepancy?
Kathleen Emerson <heavylivestock@gmail.com> writes:
> I ran `VACUUM VERBOSE` on 10-28. After the VACUUM completed, I ran the
> query
> `SELECT relname, last_vacuum FROM pg_stat_all_tables ORDER BY 2;`
> [ and saw old timestamps for some ]
> So, at least according to the VERBOSE logs, it seems like these tables
> _were_ vacuumed. Why the discrepancy?
The pg_stats mechanism is designed to drop messages when under sufficient
load, so if there was a whole lot going on besides the VACUUM, maybe
that would explain it.
regards, tom lane