postgresql 备份恢复(一)
备份恢复对于每个数据来说都是非常重要的。一般的数据库都支持冷备份的方式，冷备份可以保证数据库在此刻的完整性。但是其缺点也非常的明显，为保持数据一致性。冷备份期间数据库中相关数据是不能够使用的，就大大影响的系统的可用性。不管怎样冷备份在很多的情况下还是很有用的。数据库的冷备份一般支持两种方式：
1,操作系统级别的命令备份(cp,copy)
2,数据库工具备份(pg_dump)
针对postgresql数据库的pg_dump工具进行了一下测试(还碰到一个小问题)。
pg_dump工具命令与参数的参考：
代码
pg_dump dumps a database as a text file or to other formats.
Usage:
pg_dump ...
General options:
-f, --file=FILENAME output file name
-F, --format=c|t|p output file format (custom, tar, plain text)
-i, --ignore-version proceed even when server version mismatches
pg_dump version
-v, --verbose verbose mode
-Z, --compress=0-9 compression level for compressed formats
--help show this help, then exit
--version output version information, then exit
Options controlling the output content:
-a, --data-only dump only the data, not the schema
-b, --blobs include large objects in dump
-c, --clean clean (drop) schema prior to create
-C, --create include commands to create database in dump
-d, --inserts dump data as INSERT commands, rather than COPY
-D, --column-inserts dump data as INSERT commands with column names
-E, --encoding=ENCODING dump the data in encoding ENCODING
-n, --schema=SCHEMA dump the named schema(s) only
-N, --exclude-schema=SCHEMA do NOT dump the named schema(s)
-o, --oids include OIDs in dump
-O, --no-owner skip restoration of object ownership
in plain text format
-s, --schema-only dump only the schema, no data
-S, --superuser=NAME specify the superuser user name to use in
plain text format
-t, --table=TABLE dump the named table(s) only
-T, --exclude-table=TABLE do NOT dump the named table(s)
-x, --no-privileges do not dump privileges (grant/revoke)
--disable-dollar-quoting disable dollar quoting, use SQL standard quoting
--disable-triggers disable triggers during data-only restore
--use-set-session-authorization
use SESSION AUTHORIZATION commands instead of
ALTER OWNER commands to set ownership
Connection options:
-h, --host=HOSTNAME database server host or socket directory
-p, --port=PORT database server port number
-U, --username=NAME connect as specified database user
-W, --password force password prompt (should happen automatically)
If no database name is supplied, then the PGDATABASE environment
variable value is used.
Report bugs to <pgsql-bugs@postgresql.org>.
通过pg_dump工具分别进行数据库，表，schema方式的备份。
1，数据库备份
代码
$ dropdb wyz
$ createdb wyz
$ psql wyz
Welcome to psql 8.3.10, the PostgreSQL interactive terminal.
Type:\copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
wyz=# create table abc(id integer);
CREATE TABLE
wyz=# insert into abc values(1);
INSERT 0 1
wyz=# \q
$ pg_dump wyz >/usr/local/pgsql/data/wyz.dmp
$ dropdb wyz
$ createdb wyz
$ psql wyz </usr/local/pgsql/data/wyz.dmp
SET
SET
SET
SET
SET
SET
SET
SET
CREATE TABLE
ALTER TABLE
REVOKE
REVOKE
GRANT
GRANT
$ psql wyz
Welcome to psql 8.3.10, the PostgreSQL interactive terminal.
Type:\copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
wyz=# select * from abc;
id
----
1
(1 row)
wyz=#
对于空间不足或者文件较大时可以采用压缩的方式。
$ pg_dump wyz |gzip >/usr/local/pgsql/data/wyz.gz
在恢复数据库时，一定要确认数据库已经创建。
使用pg_dump工具对数据库进行备份只是备份了数据库中的数据，对于配置文件等非数据文件没有一起备份。显然不如使用tar与gzip命令更方便。
2，表备份
代码
$ psql wyz
Welcome to psql 8.3.10, the PostgreSQL interactive terminal.
Type:\copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
wyz=# select * from abc;
id
----
1
(1 row)
wyz=# insert into abc values(2);
INSERT 0 1
wyz=# \q
$ pg_dump wyz --table abc >/usr/local/pgsql/data/abc.sql
$ psql wyz
Welcome to psql 8.3.10, the PostgreSQL interactive terminal.
Type:\copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
wyz=# drop table abc;
DROP TABLE
wyz=# \q
$ more /usr/local/pgsql/data/abc.sql
--
-- PostgreSQL database dump
--
SET client_encoding = 'UTF8';
SET standard_conforming_strings = off;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET escape_string_warning = off;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: abc; Type: TABLE; Schema: public; Owner: postgre; Tablespace:
--
CREATE TABLE abc (
id integer
);
ALTER TABLE public.abc OWNER TO postgre;
--
-- Data for Name: abc; Type: TABLE DATA; Schema: public; Owner: postgre
--
COPY abc (id) FROM stdin;
1
2
\.
--
-- PostgreSQL database dump complete
--
$ psql wyz </usr/local/pgsql/data/abc.sql
SET
SET
SET
SET
SET
SET
SET
SET
CREATE TABLE
ALTER TABLE
$ psql wyz
Welcome to psql 8.3.10, the PostgreSQL interactive terminal.
Type:\copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
wyz=# select count(*) from abc;
count
-------
2
(1 row)
wyz=#
表备份时还可以根据参数的选用将表的数据dump成insert语句。
3，SCHEMA备份
代码
$ rm -rf /usr/local/pgsql/data/123.sql
$ pg_dump wyz -N postgre -h daduxiong -f /usr/local/pgsql/data/123.sql
$ pg_dump wyz -N wyz-h daduxiong -f /usr/local/pgsql/data/234.sql
$ more /usr/local/pgsql/data/123.sql
--
-- PostgreSQL database dump
--
SET client_encoding = 'UTF8';
SET standard_conforming_strings = off;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET escape_string_warning = off;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: abc; Type: TABLE; Schema: public; Owner: postgre; Tablespace:
--
CREATE TABLE abc (
id integer
);
ALTER TABLE public.abc OWNER TO postgre;
--
-- Data for Name: abc; Type: TABLE DATA; Schema: public; Owner: postgre
--
COPY abc (id) FROM stdin;
1
2
\.
--
-- Name: public; Type: ACL; Schema: -; Owner: postgre
--
REVOKE ALL ON SCHEMA public FROM PUBLIC;
REVOKE ALL ON SCHEMA public FROM postgre;
GRANT ALL ON SCHEMA public TO postgre;
GRANT ALL ON SCHEMA public TO PUBLIC;
--
-- PostgreSQL database dump complete
--
$ more /usr/local/pgsql/data/234.sql
--
-- PostgreSQL database dump
--
SET client_encoding = 'UTF8';
SET standard_conforming_strings = off;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET escape_string_warning = off;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: abc; Type: TABLE; Schema: public; Owner: postgre; Tablespace:
--
CREATE TABLE abc (
id integer
);
ALTER TABLE public.abc OWNER TO postgre;
--
-- Data for Name: abc; Type: TABLE DATA; Schema: public; Owner: postgre
--
COPY abc (id) FROM stdin;
1
2
\.
--
-- Name: public; Type: ACL; Schema: -; Owner: postgre
--
REVOKE ALL ON SCHEMA public FROM PUBLIC;
REVOKE ALL ON SCHEMA public FROM postgre;
GRANT ALL ON SCHEMA public TO postgre;
GRANT ALL ON SCHEMA public TO PUBLIC;
--
-- PostgreSQL database dump complete
--
在我的wyz数据库中有两个用户(postgre,wyz),可备份测试的时候都是备份的postgre用户的数据。
在采用参数-n的时候，提示命令错误。
$ pg_dump wyz -n wyz -f /usr/local/pgsql/data/456.sql
pg_dump: No matching schemas were found.
怀疑是bug，有不同结果的朋友请指正。
postgresql当前版本：8.3.10
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