On 10-05-2009 10:12:19 -0400, Mag Gam wrote:

I am running a query, similar to this:

SELECT distinct extract(day from time), extract (month from time) from T;

The query takes a long time because the table T has over 280 Million records. However I was curious to run an strace on the mserver5 process and I notced "nanosleep".

Is the process sleeping or waiting?

strace -p 25984 Process 25984 attached - interrupt to quit restart_syscall(<... resuming interrupted call ...>) = 0 nanosleep({5, 0}, {5, 0}) = 0 nanosleep({5, 0}, {5, 0}) = 0 nanosleep({5, 0}, {5, 0}) = 0

Those are various threads that just wait for a while before they look if they have to do something again.

Mag Gam wrote:

I am running a query, similar to this:

SELECT distinct extract(day from time), extract (month from time) from T;

The query takes a long time because the table T has over 280 Million records. However I was curious to run an strace on the mserver5 process and I notced "nanosleep".

Is the process sleeping or waiting?

strace -p 25984 Process 25984 attached - interrupt to quit restart_syscall(<... resuming interrupted call ...>) = 0 nanosleep({5, 0}, {5, 0}) = 0 nanosleep({5, 0}, {5, 0}) = 0 nanosleep({5, 0}, {5, 0}) = 0

there are multiple processes running, including one to manage your memory, which is not always running

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