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Thread: Skip WAL in ALTER TABLE

Skip WAL in ALTER TABLE

From
Itagaki Takahiro
Date:
We can skip writing WAL during COPY and CLUSTER if archive_mode is off,
but we don't use the skipping during tables rewrites in ALTER TABLE.
Also we don't use BulkInsertState there.

Is it possible to use WAL-skipping and BulkInsertState in ATRewriteTable() ?
If ok, I'll submit a patch for the next commitfest.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center

Re: Skip WAL in ALTER TABLE

From
Simon Riggs
Date:
On Tue, 2009-10-13 at 11:39 +0900, Itagaki Takahiro wrote:

> We can skip writing WAL during COPY and CLUSTER if archive_mode is off,
> but we don't use the skipping during tables rewrites in ALTER TABLE.
> Also we don't use BulkInsertState there.
> 
> Is it possible to use WAL-skipping and BulkInsertState in ATRewriteTable() ?
> If ok, I'll submit a patch for the next commitfest.

Yes

-- Simon Riggs           www.2ndQuadrant.com

Re: Skip WAL in ALTER TABLE

From
Itagaki Takahiro
Date:
Simon Riggs <simon@2ndQuadrant.com> wrote:

> > Is it possible to use WAL-skipping and BulkInsertState in ATRewriteTable() ?
> > If ok, I'll submit a patch for the next commitfest.
>
> Yes

Patch attached.
This patch skip WAL writes during table rewrites from ALTER TABLE.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center
Attachment

Re: Skip WAL in ALTER TABLE

From
Simon Riggs
Date:
On Thu, 2009-10-15 at 13:18 +0900, Itagaki Takahiro wrote:
> Simon Riggs <simon@2ndQuadrant.com> wrote:
> 
> > > Is it possible to use WAL-skipping and BulkInsertState in ATRewriteTable() ?
> > > If ok, I'll submit a patch for the next commitfest.
> > 
> > Yes
> 
> Patch attached.
> This patch skip WAL writes during table rewrites from ALTER TABLE.

Looks fine to me, apart from
if (!XLogArchivingActive() || newrel->rd_istemp)hi_options |= HEAP_INSERT_SKIP_WAL;

I think the second condition is unnecessary, so just
if (!XLogArchivingActive())hi_options |= HEAP_INSERT_SKIP_WAL;

which is what COPY does. Temp tables are excluded in heap_insert()

-- Simon Riggs           www.2ndQuadrant.com

Re: Skip WAL in ALTER TABLE

From
Heikki Linnakangas
Date:
Simon Riggs wrote:
> On Thu, 2009-10-15 at 13:18 +0900, Itagaki Takahiro wrote:
>> Simon Riggs <simon@2ndQuadrant.com> wrote:
>>
>>>> Is it possible to use WAL-skipping and BulkInsertState in ATRewriteTable() ?
>>>> If ok, I'll submit a patch for the next commitfest.
>>> Yes
>> Patch attached.
>> This patch skip WAL writes during table rewrites from ALTER TABLE.
> 
> Looks fine to me, apart from
> 
>  if (!XLogArchivingActive() || newrel->rd_istemp)
>     hi_options |= HEAP_INSERT_SKIP_WAL;
> 
> I think the second condition is unnecessary, so just
> 
>  if (!XLogArchivingActive())
>     hi_options |= HEAP_INSERT_SKIP_WAL;
> 
> which is what COPY does. Temp tables are excluded in heap_insert()

Yep.

Committed with the above and some other small changes. I moved the
initialization of BulkInsertState and hi_options outside the if-block.
Feels clearer this way, and they're only needed if newrel==true, not if
only needscan==true.

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