Re: increasing the default WAL segment size

Hello,

On Sat, Mar 25, 2017 at 10:32 PM, Peter Eisentraut <
peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:

> At this point, I suggest splitting this patch up into several
> potentially less controversial pieces.
>
> One big piece is that we currently don't support segment sizes larger
> than 64 GB, for various internal arithmetic reasons. Your patch appears
> to address that. So I suggest isolating that. Assuming it works
> correctly, I think there would be no great concern about it.
>
> The next piece would be making the various tools aware of varying
> segment sizes without having to rely on a built-in value.
>
> The third piece would then be the rest that allows you to set the size
> at initdb
>
> If we take these in order, we would make it easier to test various sizes
> and see if there are any more unforeseen issues when changing sizes. It
> would also make it easier to do performance testing so we can address
> the original question of what the default size should be.
>

PFA the patches divided into 3 parts:

02-increase-max-wal-segsize.patch - Increases the wal-segsize and changes
the internal representation of max_wal_size and min_wal_size to mb.

03-modify-tools.patch - Makes XLogSegSize into a variable, currently set as
XLOG_SEG_SIZE and modifies the tools to fetch the size instead of using
inbuilt value.

04-initdb-walsegsize.patch - Adds the initdb option to set wal-segsize and
make related changes. Update pg_test_fsync to use DEFAULT_XLOG_SEG_SIZE
instead of XLOG_SEG_SIZE

> One concern I have is that your patch does not contain any tests. There
> should probably be lots of tests.

05-initdb_tests.patch adds tap tests to initialize cluster with different
wal_segment_size and then check the config values. What other tests do you
have in mind? Checking the various tools?

--
Beena Emerson

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