> > 1) To deal with partial/inconsisitent write to the data file at
crash
> > recovery, we need full page writes at the first modification to
pages
> > after each checkpoint. It consumes much of WAL space.
>
> We need to find a way around this someday. Other DBs don't
> do this; it may be becuase they're less durable, or because
> they fixed the problem.
They eighter can only detect a failure later (this may be a very long
time depending on access and verify runs) or they also write page
images. Those that write page images usually write "before images" to a
different area that is cleared periodically (e.g. during checkpoint).
Writing to a different area was considered in pg, but there were more
negative issues than positive.
So imho pg_compresslog is the correct path forward. The current
discussion is only about whether we want a more complex pg_compresslog
and no change to current WAL, or an increased WAL size for a less
complex implementation.
Both would be able to compress the WAL to the same "archive log" size.
Andreas
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