hi,Kenichiro,
Thanks for your answer!
Then another question comes: According to 8.4 document 44.1(Most system
catalogs are copied from the template database during database creation and
are thereafter database-specific.),we know that each created database has
their own pg_... tables and thus if a superuser administrator wants to list
all the tables in all the databases,how do the postgresql interval implement
it? will the postgresql interval load all the pg_.... tables in all the
databases to get the final answer?
Thanks!
peng
2010/4/8 Kenichiro Tanaka <ketan...@ashisuto.co.jp>
> Hello sunpeng
>
> First,I answer this question.
>
> >another question:how postgresql internal knows which
> >relations belongs to which database?
>
> When we use "psql" command ,it means "psql -d postgres".
> #you can change default parameter to set PGDATABASE (OS parameter)
>
> "-d" indicate your connecting database and this is the ANSWER.
> So, it is natural that pg_class does not have "database" field.
> We can not access other database with psql without using dblink.
>
> I think we can display some database's pg_class with following command,
> ============================================================
> #DISPLAY "test" and "postgres"'s tables
>
> #Your postgresql have to be installed dblink
> #1)create dblink
> select dblink_connect('test','host=postgres01 port=1843 dbname=test
> user=p843');
> select dblink_connect('postgres','host=postgres01 port=1843 dbname=postgres
> user=p843');
>
> #2) display
> select 'test',* from dblink('test','select oid, relname from pg_class')
> t1(oid oid, relname text)
> union
> select 'postgres',* from dblink('postgres','select oid, relname from
> pg_class') t1(oid oid, relname text);
>
> ============================================================
>
> Thank you
>
>
> once i have created mydb and several relations in it,are there any sql
>> commands used to list all the tables in this mydb?
>> i noticed there are no database( pg_database.oid) field in pg_class
>> table,so i can not use
>> select relname from pg_class,pg_database where pg_database.datname like
>> 'mydb' and pg_class.database = pg_database.oid;
>> anybody knows how to do it?
>> another question:how postgresql internal knows which relations belongs to
>> which database?
>>
>> thanks
>>
>>
>
> --
> ================================================
> Kenichiro Tanaka
> K.K.Ashisuto
> http://www.ashisuto.co.jp/english/index.html
> ================================================
>
>
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