Re: measuring WAL creation

> On Aug 2, 2024, at 2:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Scott Ribe <scott_ribe(at)elevated-dev(dot)com> writes:
>> I'd like to measure both the amount of WAL created by a long series of data modifications and the compressed size of the generated WAL files.
>> I suppose I need to set wal_keep_size high, and pay attention to segment numbers to make sure it was high enough. Then I can look at segments created while the commands were running.
>
>> But question: can I simply delete all WAL after a clean shutdown?
>
> As a general rule, never do that manually --- the risk/reward ratio is
> unattractive. A checkpoint will release all safely-releasable WAL.
> You can checkpoint via a shutdown if you insist, but a plain
> CHECKPOINT command should be enough.

Oh, I thought at a checkpoint it would keep around some minimum, wal_keep_size, or wal_min_size. But I suppose I could set those to 0 if needed. Anyway, this would be a database solely for the purpose of running these tests, starting empty, so risk is not a factor unless I keep corrupting it between test stages ;-)