Thread: AW: [HACKERS] Begin statement again
>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. >> >>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 ? > What I am saying here is, that an ecpg program should be able to run with > autocommit mode on. (Michael Meskes) > >I tend to agree. But all embedded SQL programs I've seen so far only use >commit. I never saw one that issues a begin work since I stopped using >Ingres. Try Informix, and you will love the difference and speed in these points. The begin work statement is also a fundamental part of postgres. I simply would not hide it. Andreas
Zeugswetter Andreas writes: > 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. You got a point with this. > Hmmm ? you don't tell the backend when the program exits ? So far I don't. Does anyone know whether there's a disconnect command somewhere? In embedded SQL that is. Oracle uses 'commit work release'. The function I have to call does exist already. > Try Informix, and you will love the difference and speed in these points. > The begin work statement is also a fundamental part of postgres. I simply would not hide it. I do not hide it all. But I'd like to be as compatible to Oracle as possible. Maybe we could add an autotransaction flag somehow. Michael -- Dr. Michael Meskes, Project-Manager | topsystem Systemhaus GmbH meskes@topsystem.de | Europark A2, Adenauerstr. 20 meskes@debian.org | 52146 Wuerselen Go SF49ers! Go Rhein Fire! | Tel: (+49) 2405/4670-44 Use Debian GNU/Linux! | Fax: (+49) 2405/4670-10
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) #
Jan Wieck writes: > 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? Don't know. > 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 Wait a moment. This is almost as it is handled currently. ecpg issues a 'BEGIN TRANSACTION' before the next statement if commited (as the variable is called) is set to TRUE. Then it sets commited back to FALSE. Issuing a COMMIT sets it back to TRUE. > 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 Oracle compatibility means exactly the behaviour we currently have. BEGIN TRANSACTION is issued automatically. COMMIT has to be called by hand. But what we were talking about is forcing both to be called by the programmer. > open locks laying around since ecpg doesn't send 'BEGIN > TRANSACTION' and PostgreSQL's default is somewhat like > autocommit too. > ... > Isn't EOF information enough? Must a client say BYE? No, it need not. But it would be nice if it does, wouldn't it? Michael -- Dr. Michael Meskes, Project-Manager | topsystem Systemhaus GmbH meskes@topsystem.de | Europark A2, Adenauerstr. 20 meskes@debian.org | 52146 Wuerselen Go SF49ers! Go Rhein Fire! | Tel: (+49) 2405/4670-44 Use Debian GNU/Linux! | Fax: (+49) 2405/4670-10
On Wed, 25 Mar 1998, Michael Meskes wrote:
> Zeugswetter Andreas writes:
> > 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.
>
> You got a point with this.
>
> > Hmmm ? you don't tell the backend when the program exits ?
>
> So far I don't. Does anyone know whether there's a disconnect command
> somewhere? In embedded SQL that is. Oracle uses 'commit work release'.
>
The DISCONNECT statement is used to terminate an inactive
SQL-Connection. A SQL-Connection can be closed whether it is the
current SQL-Connection or a dormant SQL-Connection, but may not
closed while a transaction is on-going for its associated
SQL-session.
The required syntax for the DISCONNECT statement is:
DISCONNECT
<Connection Name> |
DEFAULT |
CURRENT |
ALL
Ciao, Jose'