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Re: [HACKERS] [PERFORM] WAL Optimisation - configuration and usage

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: simon(at)2ndquadrant(dot)com
Cc: "'Neil Conway'" <neilc(at)samurai(dot)com>, josh(at)agliodbs(dot)com,"'Rob Fielding'" <rob(at)dsvr(dot)net>, pgsql-performance(at)postgresql(dot)org,pgsql-hackers-pitr(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] [PERFORM] WAL Optimisation - configuration and usage
Date: 2004-03-03 23:46:23
Message-ID: 19294.1078357583@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-hackers-pitrpgsql-performance
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> The behaviour I wish to add is:
> Keep wal_debug as a value between 0 and 16.
> If =0 then no debug output (default).
> Use following bitmasks against the value
> Mask 1 = XLOG Checkpoints get logged
> Mask 2 = Archive API calls get logged
> Mask 4 = Transaction - commits get logged
> Mask 8 = Flush & INSERTs get logged

I see no value in reverting Neil's change.  The above looks way too much
like old-line assembler-programmer thinking to me, anyway.  Why not
invent a separate, appropriately named boolean variable for each thing
you want to control?  Even C programmers manage to avoid doing the sort
of mental arithmetic that the above would force onto DBAs.

As for whether it should be #ifdef'd or not, I'd have no objection to
turning WAL_DEBUG on by default in pg_config_manual.h for the duration
of PITR development.  One should not however confuse short-term
debugging needs with features that the average user is going to need
indefinitely.  (It was not too long ago that there was still debugging
code for btree index building in there, for crissakes.)

			regards, tom lane

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