---------------------pg元資料相關start---------------------
--記錄表和幾乎所有具有列或者像表的東西，包括索引主鍵之類的
select * from pg_class;
--資料庫相關資訊
select * from pg_database;
--表相關資訊(檢視)
select * from pg_tables where tablename = 'test_24';
--表字段相關資訊
select * from information_schema.columns where table_name = 'test_user_p';
--表列資訊attrelid=pg_class.oid,列名：attname，非空約束
select * from pg_attribute;
--檢查、主鍵、唯
一、外來鍵和排他約束
select * from pg_constraint;
--表繼承關係（分割槽表） inhparent：父表oid inhrelid：子表oid
select * from pg_inherits;
--名字空間(模式),即schema
select * from pg_namespace;
--資料庫角色資訊(檢視) rolconnlimit最大連線數
select * from pg_roles;
--資料庫授權識別符號(角色)資訊 --可修改角色連線數
select * from pg_authid;
update pg_authid set rolconnlimit=-1 where rolname='test';
--資料庫使用者(檢視) 有許可權訪問限制
select * from pg_shadow;
--資料庫使用者(檢視) 是pg_shadow的公共可讀檢視，消除了口令域
select * from pg_user;
--檢視資訊 提供資料庫中每個檢視的具體資訊
select * from pg_views;
---------------------pg元資料相關end---------------------
---------------------slot相關start---------------------
--檢視slot
select * from pg_replication_slots
--建立物理slot
select * from pg_create_physical_replication_slot('slot_1')
--建立邏輯slot
select * from pg_create_logical_replication_slot('logical_slot_test', 'wal2json');
--刪除slot
select pg_drop_replication_slot('logical_slot_test')
---------------------slot相關end---------------------
---------------------連線數相關start---------------------
--檢視過期連線
select * from pg_stat_activity where state = 'idle'
--刪除連線，括號裡傳pid
select pg_terminate_backend(25837);
--檢視最大連線數
show max_connections;
--修改最大連線數，需要superuser許可權
alter system set max_connections= 1000;
--too many connections for role "test"
select * from pg_stat_activity where usename='test'
---------------------連線數相關end---------------------
---------------------查詢表名、字段、主鍵相關start---------------------
--查詢表名(含主鍵的)
select a.tablename as tablename from pg_tables a
join (select bb.relname as tablename from pg_constraint aa inner join pg_class bb on aa.conrelid = bb.oid where aa.contype='p') t on a.tablename=t.tablename
where a.schemaname='public'
order by a.tablename;
--查詢表列名
select c.column_name as name,case when c.column_name=t.colname then true else false end as iskey from information_schema.columns c
left join (select b.relname,c.attname as colname from pg_constraint a inner join pg_class b on a.conrelid = b.oid
inner join pg_attribute c on c.attrelid = b.oid and c.attnum = a.conkey[1] where a.contype='p') t on c.table_name=t.relname
where c.table_name = 'test_user_p';
--postgresql分割槽表-父表資訊查詢
select nmsp_parent.nspname as parent_schema, parent.relname as parent,nmsp_child.nspname as child_schema,child.relname as child
from pg_inherits
join pg_class parent on pg_inherits.inhparent = parent.oid
join pg_class child on pg_inherits.inhrelid = child.oid
join pg_namespace nmsp_parent on nmsp_parent.oid = parent.relnamespace
join pg_namespace nmsp_child on nmsp_child.oid = child.relnamespace;
--查詢表名並標識是否分割槽表及主鍵字段
select a.tablename,case when c.inhparent is null then false else true end ispartitiontable,t.colname as pkey from pg_tables a
join (select bb.oid,bb.relname as tablename,cc.attname as colname from pg_constraint aa inner join pg_class bb on aa.conrelid = bb.oid inner join pg_attribute cc on cc.attrelid = bb.oid and cc.attnum = aa.conkey[1] where aa.contype='p') t on a.tablename=t.tablename
left join (select distinct inhparent from pg_inherits) c on t.oid=c.inhparent
left join pg_inherits d on t.oid=d.inhrelid
where a.schemaname='public' and d.inhrelid is null
order by a.tablename;
--根據主表名稱查詢分割槽表名
select t.tablename parent,a.tablename child from pg_tables a
join pg_class b on a.tablename=b.relname
join pg_inherits c on b.oid=c.inhrelid
join (select bb.oid,aa.schemaname,aa.tablename from pg_tables aa join pg_class bb on aa.tablename=bb.relname) t on c.inhparent=t.oid
where t.schemaname='public' and t.tablename in ('test_user','test_user_p','parent');
---------------------查詢表名、字段、主鍵相關end---------------------
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