Re: proposal: enhancing slow query log, and autoexplain log about waiting on lock before query exec time

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От Pavel Stehule
Тема Re: proposal: enhancing slow query log, and autoexplain log about waiting on lock before query exec time
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Msg-id CAFj8pRCA91OoG2M1VHn=9rJtQKTU44bSkjq15Ve-L6_Ej2y6Ag@mail.gmail.com
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Ответ на Re: proposal: enhancing slow query log, and autoexplain log about waiting on lock before query exec time  (Pavel Stehule <pavel.stehule@gmail.com>)
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Hi



What would be useful logging-wise is if the log line for the query itself could contain lock wait time, but that doesn't sound like what you're proposing?

I hope, so I propose this idea. First time I wanted talk about the idea. Next step is the talk about format.

Some enhancement should to have two parts:

a) introduce new function GetCurrentStatementStartExecutionTimestamp(). This function can be used  for calculation of initial lock waiting duration.

b) introduce new GUC log_min_lock_duration_statement. It is similar to log_min_duration_statement. When any statement waits longer time than this number, then statement is logged similar to other slow statement.

example:

log_min_duration_statement = 1000 .. log any slower than 1sec
log_min_lock_duration_statement = 100 log when waiting is longer than 100 ms

entry in log:

LOG: duration:843 ms  start lock duration: 156 ms  statement: .....

This logic is simple - for some more complicated models, we can introduce some monitoring logs hooks and complex custom logging can be solved in extension.

When log_min_lock_duration_statement is -1, then "start lock duration" isn't printed to log.

Comments, notes?

Regards

Pavel





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