Re: AW: [HACKERS] Begin statement again - Mailing list pgsql-hackers

Andreas wrote:
>
>
> >Zeugswetter Andreas writes:
> >> I meant: why is a transaction always open in an ecpg program
> >
> >Because this is how it works with other embedded SQL systems too. I have
> >done quite some work with Oracle, and it always has the transaction open.
>
> I am well accustomed to the deficiencies of Oracle. But in Oracle you don't have read locks,
> and so a read only program does no harm if it only does one commit when it exits
> (except maybe block the RBS if it did one small update).
> Since postgresql does have read locks, such a program will lock all resources as time goes by,
> if it does not do frequent commits. Not to speak of memory, that does not get freed.

    I'm not that familiar with the C level of Oracle connections.
    But I used oratcl from Tom Poindexter sometimes and that  has
    a  AUTOCOMMIT  ON/OFF statement that sets the autocommit flag
    in the library routines somewhere.  Doesn't embedded SQL  use
    the same libraries to connect to oracle that oratcl uses?

    In  oratcl  autocommit is ON by default and I assumed this is
    the libraries default too. Correct me if I'm wrong.

    Anyway - ecpg could work around. It can manage an  autocommit
    flag and an in_trans status by itself. When autocommit is OFF
    and in_trans is false, it sends down  a  'BEGIN  TRANSACTION'
    right  before  the  next  query  and  sets  in_trans to true.
    Later, when PostgreSQL responds 'COMMIT'  from  a  query,  it
    sets  in_trans back to false and we have the behaviour of the
    AUTOCOMMIT.  This way, a program that doesn't explicitly  set
    autocommit to off might sometimes issue a COMMIT that results
    in an empty BEGIN/COMMIT sequence sent down to the backend  -
    not  too  bad  IMHO.  As  soon  as  a  program  requires real
    transactions, it sets autocommit to false and has  (from  the
    embedded   SQL   programmers  point  of  view)  total  Oracle
    compatibility. And as long as autocommit is ON, there are  no
    open  locks  laying  around  since  ecpg  doesn't send 'BEGIN
    TRANSACTION'  and  PostgreSQL's  default  is  somewhat   like
    autocommit too.

>
> >>
> >>Keep in mind that there is no disconnect command. Instead you go out by
> >>issuing a commit.
>
> Hmmm ? you don't tell the backend when the program exits ?

    Isn't EOF information enough? Must a client say BYE?


Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#======================================== jwieck@debis.com (Jan Wieck) #