On Wed, May 25, 2011 at 01:29:05PM -0400, Robert Haas wrote:
> On Wed, May 25, 2011 at 1:06 PM, Greg Smith wrote:
> > On 05/24/2011 04:34 PM, Robert Haas wrote:
>
> > I've been looking into a similar refactoring of the names here, where we
> > bundle all of these speed over safety things (fsync,
On Thu, May 26, 2011 at 12:38 AM, Fujii Masao wrote:
> On Thu, May 26, 2011 at 1:18 PM, Robert Haas wrote:
>>> The replay of the WAL record for A doesn't rely on the content of chunk 1
>>> which B modified. So I don't think that "partial page writes" has such
>>> a problem.
>>> No?
>>
>> Sorry.
On Thu, May 26, 2011 at 1:18 PM, Robert Haas wrote:
>> The replay of the WAL record for A doesn't rely on the content of chunk 1
>> which B modified. So I don't think that "partial page writes" has such
>> a problem.
>> No?
>
> Sorry. WAL records today DO rely on the prior state of the page. If
On Wed, May 25, 2011 at 10:09 PM, Fujii Masao wrote:
> On Wed, May 25, 2011 at 9:34 PM, Robert Haas wrote:
>> On Tue, May 24, 2011 at 10:52 PM, Jeff Davis wrote:
>>> On Tue, 2011-05-24 at 16:34 -0400, Robert Haas wrote:
As I think about it a bit more, we'd
need to XLOG not only the par
On Wed, May 25, 2011 at 9:34 PM, Robert Haas wrote:
> On Tue, May 24, 2011 at 10:52 PM, Jeff Davis wrote:
>> On Tue, 2011-05-24 at 16:34 -0400, Robert Haas wrote:
>>> As I think about it a bit more, we'd
>>> need to XLOG not only the parts of the page we actually modifying, but
>>> any that the W
On Tue, May 24, 2011 at 1:34 PM, Robert Haas wrote:
> 1. Heikki suggested that instead of doing full page writes, we might
> try to write only the parts of the page that have changed. For
> example, if we had 16 bits to play with in the page header (which we
> don't), then we could imagine the pa
On Wed, May 25, 2011 at 1:06 PM, Greg Smith wrote:
> On 05/24/2011 04:34 PM, Robert Haas wrote:
>>
>> we could name this feature "partial full page writes" and enable it
>> either with a setting of full_page_writes=partial
>
> +1 to overloading the initial name, but only if the parameter is named
On 05/24/2011 04:34 PM, Robert Haas wrote:
we could name this feature "partial full page writes" and enable it
either with a setting of full_page_writes=partial
+1 to overloading the initial name, but only if the parameter is named
'maybe', 'sometimes', or 'perhaps'.
I've been looking into a
On Wed, May 25, 2011 at 10:13 AM, Bruce Momjian wrote:
>> > Idempotent does seem like the most promising idea.
>>
>> I tend to agree with you, but I'm worried it won't actually work out
>> to a win. By the time we augment the records with enough additional
>> information we may have eaten up a lo
Robert Haas wrote:
> That idea has the additional advantage of confusing the level of
> detail of our WAL logging (minimal vs. archive vs. hot standby) with
> the mechanism used to protect against torn pages (full page writes vs.
> idempotent WAL records vs. prayer). When they set it wrong and
> d
On Tue, May 24, 2011 at 9:34 PM, Robert Haas wrote:
> I'm not sure that these ideas are much good, but
> for the sake of posterity:
Both (1) and (2) seem promising to me.
Heikki mentioned (2) would only be effective if we managed to change
*all* WAL records. ISTM likely that we would find that
On Tue, May 24, 2011 at 11:52 PM, Bruce Momjian wrote:
> Robert Haas wrote:
>> 2. The other fairly obvious alternative is to adjust our existing WAL
>> record types to be idempotent - i.e. to not rely on the existing page
>> contents. For XLOG_HEAP_INSERT, we currently store the target tid and
>>
On Tue, May 24, 2011 at 10:52 PM, Jeff Davis wrote:
> On Tue, 2011-05-24 at 16:34 -0400, Robert Haas wrote:
>> As I think about it a bit more, we'd
>> need to XLOG not only the parts of the page we actually modifying, but
>> any that the WAL record would need to be correct on replay.
>
> I don't u
Robert Haas wrote:
> 2. The other fairly obvious alternative is to adjust our existing WAL
> record types to be idempotent - i.e. to not rely on the existing page
> contents. For XLOG_HEAP_INSERT, we currently store the target tid and
> the tuple contents. I'm not sure if there's anything else, b
On Tue, 2011-05-24 at 16:34 -0400, Robert Haas wrote:
> As I think about it a bit more, we'd
> need to XLOG not only the parts of the page we actually modifying, but
> any that the WAL record would need to be correct on replay.
I don't understand that statement. Can you clarify?
Regards,
While eating good Indian food and talking about aviation accidents on
the last night of PGCon, Greg Stark, Heikki Linnakangas, and I found
some time to brainstorm about possible ways to reduce the impact of
full_page_writes. I'm not sure that these ideas are much good, but
for the sake of posterit
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