[GRASS-user] Views in pgSQL

[Moritz Lennert]

On 11/04/07 13:48, Jarosław Jasiewicz wrote:
> Moritz Lennert napisał(a):
>> On 11/04/07 13:01, Jarosław Jasiewicz wrote:
>>> Hi
>>>
>>> Is still possible to use pgSQL views to connect vectors?
>>>
>>> Connecting views was possible for or five month ago (in spite of 
>>> error messages during creating views).
>>>
>>> I have some vector joinred to view They still working. But now, when 
>>> I tried to connect new vector with view I recived simple error 
>>> message that there is no table I plan to join
>>
>> What is the exact error message you are receiving.
>>
>>
>>>
>>> If that possibilites was removed (after my post, unfortunatly) please 
>>> let me know
>>
>> I am not aware of any related changes...


Sorry, I spoke to fast. I think I now found the culprit:

revision 1.40
date: 2006/11/28 08:42:02;  author: markus;  state: Exp;  lines: +1 -1
if table doesn't exist: fatal error

Before it was only a warning, not a fatal error, and so the connection 
was established and worked.

This undoes what Radim did two years earlier:

revision 1.24
date: 2004/11/25 13:15:47;  author: radim;  state: Exp;  lines: +2 -2
error -> warning if table does not exist

Markus, what was the reason that you changed this ?

Either we have to revert this again, or we have to find a way to check 
for views as well as tables, which means either implementing 
db_view_exists() (with all the individual implementations, or just 
modify the list_tables functions of the individual drivers to include 
views. In the PostgreSQL driver, the statement used is ( ):

"select * from pg_tables where tablename !~ 'pg_*' order by tablename"

For views this would have to be something like:

SELECT viewname FROM pg_views WHERE schemaname NOT IN 
('pg_catalog','information_schema') AND viewname !~ '^pg_';

So the results of these two calls would have to be combined before 
db__driver_list_tables() returns the results.

I don't know if there are any good reasons not to just include views 
into the list of tables...

In the meantime, you can just modify v.db.connect at line 231 from

         G_fatal_error(_("Table <%s> does not exist in database 
<%s>"),dbtable->answer, dbdatabase->answer);

to

         G_warning(_("Table <%s> does not exist in database 
<%s>"),dbtable->answer, dbdatabase->answer);


> 
> BTW:
> Pg Views are very important for me when I connect-reconnect vector files 
> to different atribute table. I use (used!) views insted of original 
> table to avoid occasional removing original data and to speed up 
> transfer limiting data in views only to these needed for
> (sorry, I think everybody knows it)

I completely agree with you. Being able to connect maps to views is 
fundamental in my eyes.


Moritz