pgsql: Make DROP DATABASE command generate less WAL records.
Make DROP DATABASE command generate less WAL records.
Previously DROP DATABASE generated as many XLOG_DBASE_DROP WAL records
as the number of tablespaces that the database to drop uses. This caused
the scans of shared_buffers as many times as the number of the tablespaces
during recovery because WAL replay of one XLOG_DBASE_DROP record needs
that full scan. This could make the recovery time longer especially
when shared_buffers is large.
This commit changes DROP DATABASE so that it generates only one
XLOG_DBASE_DROP record, and registers the information of all the tablespaces
into it. Then, WAL replay of XLOG_DBASE_DROP record needs full scan of
shared_buffers only once, and which may improve the recovery performance.
Author: Fujii Masao
Reviewed-by: Kirk Jamison, Simon Riggs
Discussion: /messages/by-id/CAHGQGwF8YwNH0ZaL+2wjZPkj+ji9UhC+Z4ScnG97WKtVY5L9iw@mail.gmail.com
Branch
------
master
Details
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https://git.postgresql.org/pg/commitdiff/e6d8069522c8bde8239dd1fedfb4984efa4b3a1a
Modified Files
--------------
src/backend/access/rmgrdesc/dbasedesc.c | 7 +++-
src/backend/commands/dbcommands.c | 67 +++++++++++++++++++++++----------
src/include/commands/dbcommands_xlog.h | 5 ++-
3 files changed, 56 insertions(+), 23 deletions(-)
On Thu, Nov 21, 2019 at 12:11:58PM +0000, Fujii Masao wrote:
Make DROP DATABASE command generate less WAL records.
Previously DROP DATABASE generated as many XLOG_DBASE_DROP WAL records
as the number of tablespaces that the database to drop uses. This caused
the scans of shared_buffers as many times as the number of the tablespaces
during recovery because WAL replay of one XLOG_DBASE_DROP record needs
that full scan. This could make the recovery time longer especially
when shared_buffers is large.This commit changes DROP DATABASE so that it generates only one
XLOG_DBASE_DROP record, and registers the information of all the tablespaces
into it. Then, WAL replay of XLOG_DBASE_DROP record needs full scan of
shared_buffers only once, and which may improve the recovery performance.
Fujii-san, you have forgotten to bump XLOG_PAGE_MAGIC in
xlog_internal.h?
--
Michael
On Thu, Nov 21, 2019 at 9:17 PM Michael Paquier <michael@paquier.xyz> wrote:
On Thu, Nov 21, 2019 at 12:11:58PM +0000, Fujii Masao wrote:
Make DROP DATABASE command generate less WAL records.
Previously DROP DATABASE generated as many XLOG_DBASE_DROP WAL records
as the number of tablespaces that the database to drop uses. This caused
the scans of shared_buffers as many times as the number of the tablespaces
during recovery because WAL replay of one XLOG_DBASE_DROP record needs
that full scan. This could make the recovery time longer especially
when shared_buffers is large.This commit changes DROP DATABASE so that it generates only one
XLOG_DBASE_DROP record, and registers the information of all the tablespaces
into it. Then, WAL replay of XLOG_DBASE_DROP record needs full scan of
shared_buffers only once, and which may improve the recovery performance.Fujii-san, you have forgotten to bump XLOG_PAGE_MAGIC in
xlog_internal.h?
Thanks for pointing out that! Since the format of XLOG_DBASE_DROP WAL
record was changed, XLOG_PAGE_MAGIC must be bumped. Will do that.
Regards,
--
Fujii Masao