Re: [UPDATED] A GUC variable to replace PGBE_ACTIVITY_SIZE

Thomas Lee wrote:
> An updated patch for the track_activity_query_size GUC variable.

Thanks, committed with some changes.

There was one bug: BackendStatusShmemSize() needs to report the memory 
needed for the activity string buffers; it's used for sizing the single 
fixed size shmem block on postmaster startup. I also fixed the 
documentation to refer to the setting with the right name, noted that 
it's a startup time option, and changed the wording a bit.

I tested the performance between strcpy and memcpy a little bit. As 
expected, strcpy is a lot cheaper if the string is small. I chose 
strcpy, since it's very likely that the buffer is over-sized, and even 
if it's just the right size to hold typical queries, it's going to be 
"<IDLE>" for idle connections.

Another simple optimization occurred to me while looking at this: we 
should skip the memcpy/strcpy altogether if the BackendActivity slot is 
not in use. That seems like a good bet, you usually don't try to max out 
max_connections.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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