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* measuring WAL creation
@ 2024-08-02 19:16 Scott Ribe <[email protected]>
2024-08-02 20:29 ` Re: measuring WAL creation Tom Lane <[email protected]>
0 siblings, 1 reply; 3+ messages in thread
From: Scott Ribe @ 2024-08-02 19:16 UTC (permalink / raw)
To: Pgsql-admin <[email protected]>
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?
--
Scott Ribe
[email protected]
https://www.linkedin.com/in/scottribe/
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: measuring WAL creation
2024-08-02 19:16 measuring WAL creation Scott Ribe <[email protected]>
@ 2024-08-02 20:29 ` Tom Lane <[email protected]>
2024-08-02 21:13 ` Re: measuring WAL creation Scott Ribe <[email protected]>
0 siblings, 1 reply; 3+ messages in thread
From: Tom Lane @ 2024-08-02 20:29 UTC (permalink / raw)
To: Scott Ribe <[email protected]>; +Cc: Pgsql-admin <[email protected]>
Scott Ribe <[email protected]> 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.
regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: measuring WAL creation
2024-08-02 19:16 measuring WAL creation Scott Ribe <[email protected]>
2024-08-02 20:29 ` Re: measuring WAL creation Tom Lane <[email protected]>
@ 2024-08-02 21:13 ` Scott Ribe <[email protected]>
0 siblings, 0 replies; 3+ messages in thread
From: Scott Ribe @ 2024-08-02 21:13 UTC (permalink / raw)
To: Tom Lane <[email protected]>; +Cc: Pgsql-admin <[email protected]>
> On Aug 2, 2024, at 2:29 PM, Tom Lane <[email protected]> wrote:
>
> Scott Ribe <[email protected]> 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 ;-)
^ permalink raw reply [nested|flat] 3+ messages in thread
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2024-08-02 19:16 measuring WAL creation Scott Ribe <[email protected]>
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