possible bug in handling of contrecords in dd38ff28ad (Fix recovery_prefetch with low maintenance_io_concurrency)

Hi,

I think there's some sort of bug in how dd38ff28ad deals with
contrecords. Consider something as simple as

  pgbench -i -s 100

and then doing pg_waldump on the WAL segments, I get this for every
single one:

  pg_waldump: error: error in WAL record at 0/1FFFF98: missing
                     contrecord at 0/1FFFFE0

This only happens since dd38ff28ad, and revert makes it disappear.

It's possible we still have some issue with contrecords, but IIUC we
fixed those. So unless there's some unknown one (and considering this
seems to happen for *every* WAL segment that's hard to believe), this
seems more like an issue in the error detection.


regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
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