PostgreSQL删除pg_xlog日志

PostgreSQL的pg_xlog下有大量日志,空间不足,如何删除?
Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>ls
000000010000000000000008.00000028.backup  00000001000000000000009D  0000000100000000000000C9  0000000100000000000000F5  000000010000000100000021  00000001000000010000004D
000000010000000000000072                  00000001000000000000009E  0000000100000000000000CA  0000000100000000000000F6  000000010000000100000022  00000001000000010000004E
000000010000000000000073                  00000001000000000000009F  0000000100000000000000CB  0000000100000000000000F7  000000010000000100000023  00000001000000010000004F
......


Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>ll|wc -l
263


Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>du -sh /usr/local/pgsql/data/pg_xlog/
4.1G    /usr/local/pgsql/data/pg_xlog/


清理步骤:
pg_resetxlog用来清理WAL日志,当数据库服务启动的情况下,是不能使用的,所以执行之前需要停机。


(1)停机
Darren1:postgres:/usr/local/pgsql/bin:>pg_ctl stop -m fast


(2)查看NextXID和NextOID(发生checkpoint的时候,这两个值会发生改变)
Darren1:postgres:/usr/local/pgsql/bin:>pg_controldata
pg_control version number:            960
Catalog version number:              201608131
Database system identifier:          6446917631406040181
Database cluster state:              shut down
pg_control last modified:            Thu 27 Jul 2017 05:04:12 AM CST
Latest checkpoint location:          1/73000028
Prior checkpoint location:            1/720048F8
Latest checkpoint's REDO location:    1/73000028
Latest checkpoint's REDO WAL file:    000000010000000100000073
Latest checkpoint's TimeLineID:      1
Latest checkpoint's PrevTimeLineID:  1
Latest checkpoint's full_page_writes: on
Latest checkpoint's NextXID:          0:19545
Latest checkpoint's NextOID:          16646
......


(3)使用pg_resetxlog,指定oid和xid
Darren1:postgres:/usr/local/pgsql/bin:>pg_resetxlog -o 16646 -x 19545 -f /usr/local/pgsql/data/
Transaction log reset
Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>ll
-rw-------. 1 postgres dba      302 Jul 26 12:12 000000010000000000000008.00000028.backup
-rw-------. 1 postgres dba 16777216 Jul 27 05:07 000000010000000100000077
drwx------. 2 postgres dba    20480 Jul 27 05:07 archive_status
Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>du -sh /usr/local/pgsql/data/pg_xlog/
17M    /usr/local/pgsql/data/pg_xlog/


(4)启动数据库
Darren1:postgres:/usr/local/pgsql/data/pg_xlog:>pg_ctl start

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