Re: Tab completion of SET TRANSACTION ISOLATION

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От Bruce Momjian
Тема Re: Tab completion of SET TRANSACTION ISOLATION
Дата
Msg-id 200602010003.k1103L702952@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Tab completion of SET TRANSACTION ISOLATION  (Greg Stark <gsstark@mit.edu>)
Список pgsql-hackers
Added to TODO:
       o Prevent tab completion of SET TRANSACTION from querying the         database and therefore preventing the
transactionisolation         level from being set.
 
         Currently, SET <tab> causes a database lookup to check all         supported session variables.  This query
causesproblems         because setting the transaction isolation level must be the         first statement of a
transaction.


---------------------------------------------------------------------------

Greg Stark wrote:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
> 
> > Hm, that's a bit nasty.
> > 
> > The only plan I can think of involves reading the list of available
> > variable names in advance and keeping it around.  However, I'm not
> > sure I want psql issuing such a query at connection startup whether
> > or not the info will ever be used :-(
> 
> Well, it could just lazily cache the data if it's ever fetched. That would at
> least limit the occurrence of this problem to only happening once per
> connection.
> 
> psql could also hard code "SET TRANSACTION ISOLATION" specifically. If psql
> knew that "SET TRANS" completes to SET TRANSACTION and "SET TRANSACTION I"
> completes to "SET TRANSACTION ISOLATION" it could avoid doing the query at
> all. 
> 
> That would only fail if someone uses TAB to view the available completions for
> "SET" or any shorter string. And since transaction isolation is strangely
> absent from the list of completions that seems like not such a big concern. If
> he's doing that he's not going to find it anyways.
> 
> -- 
> greg
> 
> 
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