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Make DROP DATABASE command generate less WAL records.

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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: https://postgr.es/m/CAHGQGwF8YwNH0ZaL+2wjZPkj+ji9UhC+Z4ScnG97WKtVY5L9iw@mail.gmail.com
This commit is contained in:
Fujii Masao
2019-11-21 21:10:37 +09:00
parent 30840c92ac
commit e6d8069522
3 changed files with 59 additions and 26 deletions
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7
src/backend/access/rmgrdesc/dbasedesc.c
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@@ -35,9 +35,12 @@ dbase_desc(StringInfo buf, XLogReaderState *record)
else if (info == XLOG_DBASE_DROP)
{
xl_dbase_drop_rec *xlrec = (xl_dbase_drop_rec *) rec;
int i;
appendStringInfo(buf, "dir %u/%u",
xlrec->tablespace_id, xlrec->db_id);
appendStringInfo(buf, "dir");
for (i = 0; i < xlrec->ntablespaces; i++)
appendStringInfo(buf, " %u/%u",
xlrec->tablespace_ids[i], xlrec->db_id);
}
}