Re: [HACKERS] WAL logging problem in 9.4.3?

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: noah(at)leadboat(dot)com
Cc: pgsql-hackers(at)postgresql(dot)org, 9erthalion6(at)gmail(dot)com, andrew(dot)dunstan(at)2ndquadrant(dot)com, hlinnaka(at)iki(dot)fi, robertmhaas(at)gmail(dot)com, michael(at)paquier(dot)xyz
Subject: Re: [HACKERS] WAL logging problem in 9.4.3?
Date: 2019-05-21 12:29:48
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At Mon, 20 May 2019 15:54:30 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20190520(dot)155430(dot)215084510(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> > I suspect the design in the last
> > paragraph will be simpler, not more complex. In the implementation I'm
> > envisioning, smgrDoPendingDeletes() would change name, perhaps to
> > AtEOXact_Storage(). For every relfilenode it does not delete, it would ensure
> > durability by syncing (for large nodes) or by WAL-logging each page (for small
> > nodes). RelationNeedsWAL() would return false whenever the applicable
> > relfilenode appears in pendingDeletes. Access methods would remove their
> > smgrimmedsync() calls, but they would otherwise not change. Would anyone like
> > to try implementing that?
> Following this direction, the attached PoC works *at least for*
> the wal_optimization TAP tests, but doing pending flush not in
> smgr but in relcache. This is extending skip-wal feature to
> indexes. And makes the old 0002 patch on nbtree useless.

This is a tidier version of the patch.

- Passes regression tests including

- Move the substantial work to table/index AMs.

Each AM can decide whether to support WAL skip or not.
Currently heap and nbtree support it.

- The timing of sync is moved from AtEOXact to PreCommit. This is
because heap_sync() needs xact state = INPROGRESS.

- matview and cluster is broken, since swapping to new
relfilenode doesn't change rd_newRelfilenodeSubid. I'll address


Kyotaro Horiguchi
NTT Open Source Software Center

Attachment Content-Type Size
v13-0001-TAP-test-for-copy-truncation-optimization.patch text/x-patch 10.7 KB
v13-0002-Fix-WAL-skipping-feature.patch text/x-patch 22.4 KB

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