Re: Convert table to view 9.1 - Mailing list pgsql-general

From Albe Laurenz
Subject Re: Convert table to view 9.1
Date
Msg-id A737B7A37273E048B164557ADEF4A58B17C7FD3E@ntex2010i.host.magwien.gv.at
Whole thread Raw
In response to Re: Convert table to view 9.1  (salah jubeh <s_jubeh@yahoo.com>)
Responses Re: Convert table to view 9.1  (salah jubeh <s_jubeh@yahoo.com>)
List pgsql-general
salah jubeh wrote:
>> http://www.postgresql.org/docs/current/static/catalog-pg-class.html
>> relhastriggers bool    True if table has (or once had) triggers
> 
>> This is what is queried when you try to convert the table into a view.
>> So there is no way to convert your table to a view unless you are
>> wiling to tamper with the pg_class.

> I have tried the follwoing and itworks, I need to update also relhasindex
> 
> UPDATE  pg_class SET relhastriggers = FALSE WHERE oid = 'b'::regclass;
> UPDATE  pg_class SET relhasindex = FALSE WHERE oid = 'b'::regclass;
> 
> To be honest I do not like to play with catalog tables, so my question would be, what are the reason
> for "(or recently had)" in the case of index, or (or once had) in the case of triggers. I find the
> ability to convert a table to a view an extremly handy in applications were buisnes logic is modelled
> as views. For example, I need to refactor b, but keep it for backward compatability as updatabale
> view.

You are right to be reluctant to tamper with pg_class.

This comment in backend/commands/trigger.c explains why
relhastriggers is left "true":

    /*
     * We do not bother to try to determine whether any other triggers remain,
     * which would be needed in order to decide whether it's safe to clear the
     * relation's relhastriggers.  (In any case, there might be a concurrent
     * process adding new triggers.)  Instead, just force a relcache inval to
     * make other backends (and this one too!) rebuild their relcache entries.
     * There's no great harm in leaving relhastriggers true even if there are
     * no triggers left.
     */

So I guess it is just left because nobody cared enough.

What keeps you from creating a copy of b:

CREATE TABLE b_copy(LIKE b EXCLUDING CONSTRAINTS);
DROP TABLE b;
ALTER TABLE b_copy RENAME TO b;

Yours,
Laurenz Albe

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