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Replace implementation of pg_log as a relation accessed through the

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buffer manager with 'pg_clog', a specialized access method modeled
on pg_xlog.  This simplifies startup (don't need to play games to
open pg_log; among other things, OverrideTransactionSystem goes away),
should improve performance a little, and opens the door to recycling
commit log space by removing no-longer-needed segments of the commit
log.  Actual recycling is not there yet, but I felt I should commit
this part separately since it'd still be useful if we chose not to
do transaction ID wraparound.
This commit is contained in:
Tom Lane
2001-08-25 18:52:43 +00:00
parent 4699d81dc9
commit 2589735da0
39 changed files with 1248 additions and 1128 deletions
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8
doc/src/sgml/backup.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v 2.11 2001/08/16 04:30:41 ishii Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v 2.12 2001/08/25 18:52:41 tgl Exp $ -->
<chapter id="backup">
<title>Backup and Restore</title>
@ -339,11 +339,11 @@ tar -cf backup.tar /usr/local/pgsql/data
individual tables or databases from their respective files or
directories. This will <emphasis>not</> work because the
information contained in these files contains only half the
truth. The other half is in the file
<filename>pg_log</filename>, which contains the commit status of
truth. The other half is in the commit log files
<filename>pg_clog/*</filename>, which contain the commit status of
all transactions. A table file is only usable with this
information. Of course it is also impossible to restore only a
table and the associated <filename>pg_log</filename> file
table and the associated <filename>pg_clog</filename> data
because that will render all other tables in the database
cluster useless.
</para>

8
doc/src/sgml/wal.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.7 2001/05/17 21:50:16 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.8 2001/08/25 18:52:41 tgl Exp $ -->
<chapter id="wal">
<title>Write-Ahead Logging (<acronym>WAL</acronym>)</title>
@ -83,12 +83,12 @@
In this first release of <acronym>WAL</acronym>, UNDO operation is
not implemented, because of lack of time. This means that changes
made by aborted transactions will still occupy disk space and that
we still need a permanent <filename>pg_log</filename> file to hold
we still need a permanent <filename>pg_clog</filename> file to hold
the status of transactions, since we are not able to re-use
transaction identifiers. Once UNDO is implemented,
<filename>pg_log</filename> will no longer be required to be
<filename>pg_clog</filename> will no longer be required to be
permanent; it will be possible to remove
<filename>pg_log</filename> at shutdown, split it into segments
<filename>pg_clog</filename> at shutdown, split it into segments
and remove old segments.
</para>