Обсуждение: has_table/schema_privilige() returns incorrect info on temp tables

Hi,

While running 2 sessions in different terminals for the same user, what
happens in the second session here looks a bit weird:

=========
<session 1>
=========
db=# create temp table t_test (id int);
CREATE TABLE

db=# select table_schema from information_schema.tables
    where table_name = 't_test';
 table_schema
--------------
 pg_temp_2
(1 row)

db=# select has_schema_privilege('pg_temp_2', 'usage');
 has_schema_privilege
----------------------
 t
(1 row)

db=# select has_table_privilege('pg_temp_2.t_test', 'insert');
 has_table_privilege
---------------------
 t
(1 row)

db=# select has_table_privilege('t_test', 'insert');
 has_table_privilege
---------------------
 t
(1 row)

db=# insert into t_test values (1);
INSERT 0 1

=========
<session 2>
=========

db=# select table_schema from information_schema.tables
    where table_name = 't_test';
 table_schema
--------------
 pg_temp_2
(1 row)

db=# select has_schema_privilege('pg_temp_2', 'usage');
 has_schema_privilege
----------------------
 t
(1 row)

db=# select has_table_privilege('pg_temp_2.t_test', 'insert');
 has_table_privilege
---------------------
 t
(1 row)

db=# select has_table_privilege('t_test', 'insert');
ERROR:  relation "t_test" does not exist

db=# insert into t_test values (1);
ERROR:  relation "t_test" does not exist



db=# select version();
                                version
------------------------------------------------------------------------
 PostgreSQL 8.1.3 on i586-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.3
(1 row)



In this light, is there a possibility to find out what schema will be used for
temporary tables created during the current session? I need to find out
whether a specific temporary table exists and is accessible for the current
user in the current session.



--
Best,




Frank.

Frank van Vugt <ftm.van.vugt@foxi.nl> writes:
> While running 2 sessions in different terminals for the same user, what
> happens in the second session here looks a bit weird:

In the first place, you are evidently running as superuser, which means
that has_foo_privilege will ALWAYS say 't' (except possibly if the
target object doesn't exist, in which case I think you get an error).
In the second place, trying to access another session's temp table is
unsupported.

> In this light, is there a possibility to find out what schema will be used for
> temporary tables created during the current session?

After you've created at least one temp table, you can look at the result
of "current_schemas(true)".  There's no guarantee that the schema even
exists before you've created something...


regression=# select current_schemas(true);
   current_schemas
---------------------
 {pg_catalog,public}
(1 row)

regression=# create temp table t(f1 int);
CREATE TABLE
regression=# select current_schemas(true);
        current_schemas
-------------------------------
 {pg_temp_1,pg_catalog,public}
(1 row)

regression=# select (current_schemas(true))[1];
 current_schemas
-----------------
 pg_temp_1
(1 row)

regression=#

            regards, tom lane

Hi,

> In the first place, you are evidently running as superuser, which means
> that has_foo_privilege will ALWAYS say 't'

Ok, seems reasonable ;)

> (except possibly if the
> target object doesn't exist, in which case I think you get an error).

Yep, one does.

> In the second place, trying to access another session's temp table is
> unsupported.

I understand, it's more the opposite, I was fixing a bug in a plpgsql function
that would fail when the user has created a certain (temporary) table in a
second session, because the code only checked the existence of the table_name
without taking into account the proper schema.

> After you've created at least one temp table, you can look at the result
> of "current_schemas(true)".  There's no guarantee that the schema even
> exists before you've created something...

Got that, looks like an acceptable workaround in this case, though.

Is there a guaranteed order of the resulting array, i.e. is this guaranteed to
return the temp schema, given there is one:

    'select (current_schemas(true))[1]'.....?

(obviously, regexp's will also do the trick, I'm just asking)



--
Best,




Frank.

Frank van Vugt <ftm.van.vugt@foxi.nl> writes:
>> After you've created at least one temp table, you can look at the result
>> of "current_schemas(true)".  There's no guarantee that the schema even
>> exists before you've created something...

> Is there a guaranteed order of the resulting array, i.e. is this guaranteed to
> return the temp schema, given there is one:

>     'select (current_schemas(true))[1]'.....?

Yes, in the current implementation and for the foreseeable future (else
temp tables would fail to mask permanent tables).

            regards, tom lane