Hi, In PostgreSQL, the pg_stat_io view provides detailed statistics on I/O operations. Background process perform maintenance tasks and other background operations essential to the functioning of the PostgreSQL database. They include processes such as:
1. Autovacuum Workers 2. WAL Writer 3. Background Writer 4. Logical Replication Workers 5. Custom Background Workers In the pg_stat_io view, statistics related to I/O operations performed by these background workers are recorded. Regards, Imtiaz On Wed, 15 May 2024, 01:26 Dimitrios Apostolou, <ji...@gmx.net> wrote: > Hello list, > > what is the "background worker" in the pg_stat_io statistics view? I'm > reading the documentation but can't figure this one out knowing that it is > not autovacuum or bgwriter. And I'm not aware of any extension I might > have with registered background worker. > > Additionally, how can it be evictions > writes? I would expect every > eviction to cause a write. > > Finally about "hits", I understand they are reads found in shared_buffers, > so they never registered into the "reads" counter. So is "reads" in > pg_stat_io the equivalent to misses, i.e. the opposite of "hits", the read > attempts not found in the shared_buffers, that needed to be fetched from > the disk (or OS buffercache)? > > backend_type | object | context | reads | read_time | > writes | write_time | writebacks | writeback_time | extends | extend_time | > op_bytes | hits | evictions | reuses | fsyncs | fsync_time | > stats_reset > > -------------------+---------------+---------+---------+-------------+--------+------------+------------+----------------+---------+-------------+----------+-----------+-----------+--------+--------+------------+------------------------------- > background worker | relation | normal | 5139575 | 2196288.011 | > 63277 | 1766.94 | 0 | 0 | 0 | 0 | > 8192 | 876913705 | 5139653 | | 0 | 0 | 2024-04-08 > 08:50:02.971192+00 > > > Thank you in advance, > Dimitris > > > >
