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 [OPTION]... [DBNAME]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 exitOptions 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 ownershipConnection 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 environmentvariable 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
[postgre@daduxiong bin]$ dropdb wyz[postgre@daduxiong bin]$ createdb wyz[postgre@daduxiong bin]$ psql wyzWelcome 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 quitwyz=# create table abc(id integer);CREATE TABLEwyz=# insert into abc values(1);INSERT 0 1wyz=# \q[postgre@daduxiong bin]$ pg_dump wyz >/usr/local/pgsql/data/wyz.dmp[postgre@daduxiong bin]$ dropdb wyz[postgre@daduxiong bin]$ createdb wyz[postgre@daduxiong bin]$ psql wyz </usr/local/pgsql/data/wyz.dmp SETSETSETSETSETSETSETSETCREATE TABLEALTER TABLEREVOKEREVOKEGRANTGRANT[postgre@daduxiong bin]$ psql wyzWelcome 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 quitwyz=# 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。[postgre@daduxiong bin]$ 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
[postgre@daduxiong ~]$ psql wyzWelcome 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 quitwyz=# select * from abc; id ---- 1(1 row)wyz=# insert into abc values(2);INSERT 0 1wyz=# \q[postgre@daduxiong ~]$ pg_dump wyz --table abc >/usr/local/pgsql/data/abc.sql[postgre@daduxiong ~]$ psql wyzWelcome 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 quitwyz=# drop table abc;DROP TABLEwyz=# \q[postgre@daduxiong ~]$ 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;12\.---- PostgreSQL database dump complete--[postgre@daduxiong ~]$ psql wyz </usr/local/pgsql/data/abc.sql SETSETSETSETSETSETSETSETCREATE TABLEALTER TABLE[postgre@daduxiong ~]$ psql wyzWelcome 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 quitwyz=# 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
[postgre@daduxiong ~]$ rm -rf /usr/local/pgsql/data/123.sql [postgre@daduxiong ~]$ pg_dump wyz -N postgre -h daduxiong -f /usr/local/pgsql/data/123.sql[postgre@daduxiong ~]$ pg_dump wyz -N wyz -h daduxiong -f /usr/local/pgsql/data/234.sql[postgre@daduxiong ~]$ 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;12\.---- 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--[postgre@daduxiong ~]$ 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;12\.---- 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。
[postgre@daxuxiong ~]$ pg_dump wyz -n wyz -f /usr/local/pgsql/data/456.sqlpg_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
来源：https://www.cnblogs.com/daduxiong/archive/2010/08/30/1812403.html