pg_dump 导出文件过大的解决办法
【背景】
L10N 测试时，为了减轻L10N 测试用例执行人员的数据出发成本，常常将DB的数据到给L10N team。这么做的前提是，DB层不涉及L10N的任何翻译，否则就不能这么干了。DB是postgre，因此自然而然的想到用pg_dump命令导出数据。
pg_dump 选项列表：
# pg_dump --help
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 or directory name
-F, --format=c|d|t|p output file format (custom, directory, tar,
plain text (default))
-v, --verbose verbose mode
-V, --version output version information, then exit
-Z, --compress=0-9 compression level for compressed formats
--lock-wait-timeout=TIMEOUT fail after waiting TIMEOUT for a table lock
-?, --help show this help, 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) database objects before recreating
-C, --create include commands to create database in dump
-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 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)
--binary-upgrade for use by upgrade utilities only
--column-inserts dump data as INSERT commands with column names
--disable-dollar-quoting disable dollar quoting, use SQL standard quoting
--disable-triggers disable triggers during data-only restore
--exclude-table-data=TABLE do NOT dump data for the named table(s)
--inserts dump data as INSERT commands, rather than COPY
--no-security-labels do not dump security label assignments
--no-tablespaces do not dump tablespace assignments
--no-unlogged-table-data do not dump unlogged table data
--quote-all-identifiers quote all identifiers, even if not key words
--section=SECTION dump named section (pre-data, data, or post-data)
--serializable-deferrable wait until the dump can run without anomalies
--use-set-session-authorization
use SET 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, --no-password never prompt for password
-W, --password force password prompt (should happen automatically)
--role=ROLENAME do SET ROLE before dump
If no database name is supplied, then the PGDATABASE environment
variable value is used.
Report bugs to .
【问题】
用如下命令导出DB数据
# pg_dump ddei -U sa -a -f data.sql
# du -sh data.sql
1.7G data.sql
一切正常，导出过程中没有报错。但是，悲催的是，一看导出文件大小，吓尿了，直接1.7G。 环境里只有很少的测试数据，而且也用了 “-a” 选项
-a, --data-only dump only the data, not the schema
不合理啊，打开导出文件，发现除了要的数据外，还有如下内容，而且占了绝大部分：
--
-- Data for Name: BLOBS; Type: BLOBS; Schema: -; Owner:
--
SET search_path = pg_catalog;
BEGIN;
SELECT pg_catalog.lo_open('17765', 131072);
这个不是我们需要的，要将其滤掉，问题就解决了。 但是看遍了开头的help 信息， 只找到了如下选项跟blobs有关
-b, --blobs include large objects in dump比较，之前的命令，我们并没有“-b” 选项。到此，问题应该清楚了，这个选项默认是生效的。如何关闭呢，显然简短的 help 信息是不够了。
求助官方文档 http://www.postgresql.org/docs/9.2/static/app-pgdump.html ， 下面这句话很关键
Note: Non-schema objects such as blobs are not dumped when -n is specified. You can add blobs back to the dump with the --blobs switch.
果断加上“-n”
[root@ddei1268 ~]# pg_dump ddei -U sa -n public -f noBlobs.sql
[root@ddei1268 ~]# du -sh noBlobs.sql
760K noBlobs.sql效果相当明显！