PostgreSQL 常用维护操作
1. 查看数据库到目前为止启动时长。kevin_test=# SELECT date_trunc('second', current_timestamp - pg_postmaster_start_time()) as uptime;uptime----------05:46:47(1 row)kevin_test=#
2.查看启动时间。
kevin_test=# SELECT pg_postmaster_start_time() as start_time;start_time-------------------------------2011-07-18 01:09:36.447192+08(1 row)
kevin_test=#
3,pg的server控制文件pg_controldata，此文件为初始化数据库时产生，有的字段随时更新，请不要试图手工修改它。
# pwd/opt/postgresql/bin#./pg_controldatapg_control version number: 843Catalog version number: 200904091Database system identifier: 5627161982392579794Database cluster state: in productionpg_control last modified: 2011年07月18日 星期一 01时09分36秒Latest checkpoint location: 0/4C722CPrior checkpoint location: 0/4C71E8Latest checkpoint's REDO location: 0/4C722CLatest checkpoint's TimeLineID: 1Latest checkpoint's NextXID: 0/711Latest checkpoint's NextOID: 16420Latest checkpoint's NextMultiXactId:1Latest checkpoint's NextMultiOffset:0Time of latest checkpoint: 2011年07月17日 星期日 16时17分44秒Minimum recovery ending location: 0/0Maximum data alignment: 4Database block size: 8192Blocks per segment of large relation: 131072WAL block size: 8192Bytes per WAL segment: 16777216Maximum length of identifiers: 64Maximum columns in an index: 32Maximum size of a TOAST chunk: 2000Date/time type storage: 64-bit integersFloat4 argument passing: by valueFloat8 argument passing: by reference#
4.查询结果输出格式控制 \x 选项
kevin_test=# \x onExpanded display is on.kevin_test=# select * from pg_database;-[ RECORD 1 ]-+------------------------------------datname | template1datdba | 10encoding | 6datcollate | zh_CN.UTF-8datctype | zh_CN.UTF-8datistemplate | tdatallowconn| tdatconnlimit| -1datlastsysoid | 11563datfrozenxid| 648dattablespace | 1663datconfig |datacl | {=c/postgres,postgres=CTc/postgres}-[ RECORD 2 ]-+------------------------------------datname | template0datdba | 10encoding | 6datcollate | zh_CN.UTF-8datctype | zh_CN.UTF-8datistemplate | tdatallowconn| fdatconnlimit| -1datlastsysoid | 11563datfrozenxid| 648dattablespace | 1663datconfig |datacl | {=c/postgres,postgres=CTc/postgres}-[ RECORD 3 ]-+------------------------------------datname | postgresdatdba | 10encoding | 6datcollate | zh_CN.UTF-8datctype | zh_CN.UTF-8datistemplate | fdatallowconn| tdatconnlimit| -1datlastsysoid | 11563datfrozenxid| 648dattablespace | 1663datconfig |datacl |-[ RECORD 4 ]-+------------------------------------datname | kevin_testdatdba | 10encoding | 6datcollate | zh_CN.UTF-8datctype | zh_CN.UTF-8datistemplate | fdatallowconn| tdatconnlimit| -1datlastsysoid | 11563datfrozenxid| 648dattablespace | 1663datconfig |datacl |-[ RECORD 5 ]-+------------------------------------datname | pg_test_database_3datdba | 16390encoding | 6datcollate | zh_CN.UTF-8datctype | zh_CN.UTF-8datistemplate | fdatallowconn| tdatconnlimit| -1datlastsysoid | 11563datfrozenxid| 648dattablespace | 1663datconfig | {add_missing_from=off}datacl |kevin_test=#kevin_test=#kevin_test=# \x offExpanded display is off.kevin_test=# select * from pg_database;datname | datdba | encoding | datcollate|datctype | datistemplate | datallowconn | datconnlimit | datlastsysoid | datfrozenxid | dattablespace | datconfig | datacl--------------------+--------+----------+-------------+-------------+---------------+--------------+--------------+---------------+--------------+---------------+------------------------+-------------------------------------template1 | 10 | 6 | zh_CN.UTF-8 | zh_CN.UTF-8 | t | t | -1 | 11563 | 648 | 1663 | | {=c/postgres,postgres=CTc/postgres}template0 | 10 | 6 | zh_CN.UTF-8 | zh_CN.UTF-8 | t | f | -1 | 11563 | 648 | 1663 | | {=c/postgres,postgres=CTc/postgres}postgres | 10 | 6 | zh_CN.UTF-8 | zh_CN.UTF-8 | f | t | -1 | 11563 | 648 | 1663 | |kevin_test | 10 | 6 | zh_CN.UTF-8 | zh_CN.UTF-8 | f | t | -1 | 11563 | 648 | 1663 | |pg_test_database_3 |16390 | 6 | zh_CN.UTF-8 | zh_CN.UTF-8 | f | t | -1 | 11563 | 648 | 1663 | {add_missing_from=off} |(5 rows)kevin_test=# 4.查看当前数据库中有多少张用户自己的表。
kevin_test=# SELECT count(*) FROM information_schema.tableskevin_test-# WHERE table_schemakevin_test-# NOT IN ('information_schema', 'pg_catalog');count-------1(1 row)kevin_test=#kevin_test=#kevin_test=# SELECT * FROM information_schema.tablesWHERE table_schemaNOT IN ('information_schema', 'pg_catalog');table_catalog | table_schema |table_name | table_type | self_referencing_column_name | reference_generation | user_defined_type_catalog | user_defined_type_schema | user_defined_type_name | is_insertable_into | is_typed | commit_action---------------+--------------+---------------+------------+------------------------------+----------------------+---------------------------+--------------------------+------------------------+--------------------+----------+---------------kevin_test | public | tbl_test_port | BASE TABLE | || | | | YES | NO|(1 row)kevin_test=# 附：视图information_schema.tables的结构。
kevin_test=# \d information_schema.tablesView "information_schema.tables"Column | Type | Modifiers------------------------------+-----------------------------------+-----------table_catalog | information_schema.sql_identifier |table_schema | information_schema.sql_identifier |table_name | information_schema.sql_identifier |table_type | information_schema.character_data |self_referencing_column_name | information_schema.sql_identifier |reference_generation | information_schema.character_data |user_defined_type_catalog | information_schema.sql_identifier |user_defined_type_schema | information_schema.sql_identifier |user_defined_type_name | information_schema.sql_identifier |is_insertable_into | information_schema.character_data |is_typed | information_schema.character_data |commit_action | information_schema.character_data |View definition:SELECT current_database()::information_schema.sql_identifier AS table_catalog, nc.nspname::information_schema.sql_identifier AS table_schema, c.relname::information_schema.sql_identifier AS table_name,CASEWHEN nc.oid = pg_my_temp_schema() THEN 'LOCAL TEMPORARY'::textWHEN c.relkind = 'r'::"char" THEN 'BASE TABLE'::textWHEN c.relkind = 'v'::"char" THEN 'VIEW'::textELSE NULL::textEND::information_schema.character_data AS table_type, NULL::character varying::information_schema.sql_identifier AS self_referencing_column_name, NULL::character varying::information_schema.character_data AS reference_generation, NULL::character varying::information_schema.sql_identifier AS user_defined_type_catalog, NULL::character varying::information_schema.sql_identifier AS user_defined_type_schema, NULL::character varying::information_schema.sql_identifier AS user_defined_type_name,CASEWHEN c.relkind = 'r'::"char" OR c.relkind = 'v'::"char" AND (EXISTS ( SELECT 1FROM pg_rewriteWHERE pg_rewrite.ev_class = c.oid AND pg_rewrite.ev_type = '3'::"char" AND pg_rewrite.is_instead)) THEN 'YES'::textELSE 'NO'::textEND::information_schema.character_data AS is_insertable_into, 'NO'::character varying::information_schema.character_data AS is_typed,CASEWHEN nc.oid = pg_my_temp_schema() THEN 'PRESERVE'::textELSE NULL::textEND::information_schema.character_data AS commit_actionFROM pg_namespace nc, pg_class cWHERE c.relnamespace = nc.oid AND (c.relkind = ANY (ARRAY['r'::"char", 'v'::"char"])) AND NOT pg_is_other_temp_schema(nc.oid) AND (pg_has_role(c.relowner, 'USAGE'::text) OR has_table_privilege(c.oid, 'SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR has_any_column_privilege(c.oid, 'SELECT, INSERT, UPDATE, REFERENCES'::text));kevin_test=#
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