Обсуждение: Regclass and quoted table names

Hi all,

It looks like the behavior of regclass is not consistent when table 
names are quoted. The name is returned without the quotes if the name is 
lower case with eventual trailing numbers, otherwise it is returned with 
quotes.
See some examples here:

tpch=# CREATE VIEW test AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "test1" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "'test2'" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "testcolumnVIEW" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "testcolumnview" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW testcolumnVIEW2 AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "1test" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "1test2abc" AS SELECT * FROM customer;
CREATE VIEW
tpch=# CREATE VIEW "1test2" AS SELECT * FROM customer;
CREATE VIEW
tpch=# select c.oid , c.oid::regclass from pg_class c where c.relname 
like '%test%'; oid  |       oid       
-------+------------------16410 | test16413 | test116416 | "'test2'"16419 | "testcolumnVIEW"16422 | testcolumnview16425
|testcolumnview216428 | "1test2abc"16431 | "1test2"16434 | "1test"
 
(9 rows)


Is this a bug?
manu

-- 
Emmanuel Cecchet
Aster Data Systems
Web: http://www.asterdata.com

Emmanuel Cecchet <manu@asterdata.com> writes:
> It looks like the behavior of regclass is not consistent when table 
> names are quoted. The name is returned without the quotes if the name is 
> lower case with eventual trailing numbers, otherwise it is returned with 
> quotes.

It's intentional that it quotes only when needed.
        regards, tom lane

Tom Lane wrote:
> Emmanuel Cecchet <manu@asterdata.com> writes:
>   
>> It looks like the behavior of regclass is not consistent when table 
>> names are quoted. The name is returned without the quotes if the name is 
>> lower case with eventual trailing numbers, otherwise it is returned with 
>> quotes.
>>     
>
> It's intentional that it quotes only when needed.
>   
This is problematic in situations where the output of the cast is involved in some later join which returns incorrect
resultsbecause of the extra double quotes surrounding the table name. 
 
Is there a way to override the default behavior to have a consistent quoted or non-quoted result?

Thanks,
Emmanuel

-- 
Emmanuel Cecchet
Aster Data Systems
Web: http://www.asterdata.com

On Wed, Mar 4, 2009 at 12:34 PM, Emmanuel Cecchet <manu@asterdata.com> wrote:

> This is problematic in situations where the output of the cast is involved
> in some later join which returns incorrect results because of the extra
> double quotes surrounding the table name. Is there a way to override the
> default behavior to have a consistent quoted or non-quoted result?

regclass's output format is intended for human readers, not for
joining against text columns. Why would you need to be joining between
regclass and text anyways? Normally you would be joining regclass to
either regclass columns or oid columns where it does an integer
comparison.

Actually normally you would just be joining oid columns since most
catalog columns are declared to be oids rather than regfoo columns :(

-- 
greg

Greg Stark <stark@enterprisedb.com> writes:
> On Wed, Mar 4, 2009 at 12:34 PM, Emmanuel Cecchet <manu@asterdata.com> wrote:
>> This is problematic in situations where the output of the cast is involved
>> in some later join which returns incorrect results because of the extra
>> double quotes surrounding the table name. Is there a way to override the
>> default behavior to have a consistent quoted or non-quoted result?

> regclass's output format is intended for human readers, not for
> joining against text columns. Why would you need to be joining between
> regclass and text anyways?

The quoting behavior is the *least* of your problems if you're trying to
do that.  Are you aware of how it works vis-a-vis search_path?  Have you
thought about what will happen when you rename a table?

Use plain oids or regclass values, not a text column, if you are trying
to store table identities.
        regards, tom lane

marcin mank wrote:
>> Use plain oids or regclass values, not a text column, if you are trying
>> to store table identities.
>>     
> wouldn`t oids change on dump/reload?
>   
I don't know. I'd also be interested to know if there is a difference if 
we use pg_restore with a binary format or sql dump, or if that does not 
influence at all the way oids are created.

manu

> Use plain oids or regclass values, not a text column, if you are trying
> to store table identities.
>

wouldn`t oids change on dump/reload?

Greetings
Marcin