On 25/03/2019 09:57, David Steele wrote:
On 2/6/19 2:08 PM, Andrey Lepikhov wrote:
The patchset had a problem with all-zero pages, has appeared at index
build stage: the generic_log_relation() routine sends all pages into the
WAL. So lsn field at all-zero page was initialized and the
PageIsVerified() routine detects it as a bad page.
The solution may be:
1. To improve index build algorithms and eliminate the possibility of
not used pages appearing.
2. To mark each page as 'dirty' right after initialization. In this case
we will got 'empty' page instead of the all-zeroed.
3. Do not write into the WAL all-zero pages.
Hmm. When do we create all-zero pages during index build? That seems
pretty surprising.
On 04.02.2019 10:04, Michael Paquier wrote:
On Tue, Dec 18, 2018 at 10:41:48AM +0500, Andrey Lepikhov wrote:
Ok. It is used only for demonstration.
The latest patch set needs a rebase, so moved to next CF, waiting on
author as this got no reviews.
The patch no longer applies so marked Waiting on Author.
Alexander, Heikki, are either of you planning to review the patch in
this CF?
I had another quick look.
I still think using the "generic xlog AM" for this is a wrong level of
abstraction, and we should use the XLOG_FPI records for this directly.
We can extend XLOG_FPI so that it can store multiple pages in a single
record, if it doesn't already handle it.
Another counter-point to using the generic xlog record is that you're
currently doing unnecessary two memcpy's of all pages in the index, in
GenericXLogRegisterBuffer() and GenericXLogFinish(). That's not free.
I guess the generic_log_relation() function can stay where it is, but it
should use XLogRegisterBuffer() and XLogInsert() directly.
- Heikki
