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!




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