| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | David Christensen <david(at)endpoint(dot)com>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org>, Josh Berkus <josh(at)agliodbs(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Subject: | Re: [DESIGN] Incremental checksums |
| Date: | 2015-07-15 08:24:24 |
| Message-ID: | 20150715082424.GD5520@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
On 2015-07-15 12:48:40 +0530, Amit Kapila wrote:
> If during scan of a relation, after doing checksum for half of the
> blocks in relation, system crashes, then in the above scheme a
> restart would need to again read all the blocks even though some
> of the blocks are already checksummed in previous cycle, this is
> okay if it happens for few small or medium size relations, but assume
> it happens when multiple large size relations are at same state
> (half blocks are checksummed) when the crash occurs, then it could
> lead to much more IO than required.
I don't think this is worth worrying about. If you crash frequently
enough for this to be a problem you should fix that. Adding complexity
for such an uncommon case spreads the cost to many more people.
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