Обсуждение: BEGIN inside transaction should be an error
Hi Yesterday I helped a guy on irc with a locking problem, he thought that locking in postgresql was broken. It turned out that he had a PHP function that he called inside his transaction and the function did BEGIN and COMMIT. Since BEGIN inside a transaction is just a warning what happend was that the inner COMMIT ended the transaction and released the locks. The rest of his commands ran with autocommit and no locks and he got broken data into the database. Could we make BEGIN fail when we already are in a transaction? Looking it up in the sql99 standard I find this: "If a <start transaction statement> statement is executed when an SQL-transaction is currently active, then an exception condition is raised: invalid transaction state - active SQL-transaction." /Dennis
Dennis Bjorklund <db@zigo.dhs.org> writes:
> Yesterday I helped a guy on irc with a locking problem, he thought
> that locking in postgresql was broken. It turned out that he had a PHP
> function that he called inside his transaction and the function did BEGIN
> and COMMIT. Since BEGIN inside a transaction is just a warning what
> happend was that the inner COMMIT ended the transaction and
> released the locks. The rest of his commands ran with autocommit
> and no locks and he got broken data into the database.
> Could we make BEGIN fail when we already are in a transaction?
We could, but it'd probably break about as many apps as it fixed.
I wonder whether php shouldn't be complaining about this, instead
--- doesn't php have its own ideas about controlling where the
transaction commit points are?
regards, tom lane
> We could, but it'd probably break about as many apps as it fixed. > I wonder whether php shouldn't be complaining about this, instead > --- doesn't php have its own ideas about controlling where the > transaction commit points are? All PHP does is when the connection is returned to the pool, if it is still in a transaction, a rollback is issued. The guy needs to do his own tracking of transaction state if he wants to avoid these problems... Chris
Tom Lane wrote: > Dennis Bjorklund <db@zigo.dhs.org> writes: >> Yesterday I helped a guy on irc with a locking problem, he thought >> that locking in postgresql was broken. It turned out that he had a PHP >> function that he called inside his transaction and the function did BEGIN >> and COMMIT. Since BEGIN inside a transaction is just a warning what >> happend was that the inner COMMIT ended the transaction and >> released the locks. The rest of his commands ran with autocommit >> and no locks and he got broken data into the database. > >> Could we make BEGIN fail when we already are in a transaction? > > We could, but it'd probably break about as many apps as it fixed. > I wonder whether php shouldn't be complaining about this, instead > --- doesn't php have its own ideas about controlling where the > transaction commit points are? There are no API calls to start/end transactions in php. However there is a way to get the current transaction status: http://de3.php.net/manual/en/function.pg-transaction-status.php Also whatever decision is made one day PostGreSQL might want to supported nested transactions similar to firebird. regards, Lukas
On 5/10/06, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Dennis Bjorklund <db@zigo.dhs.org> writes: > > Yesterday I helped a guy on irc with a locking problem, he thought > > that locking in postgresql was broken. It turned out that he had a PHP > > function that he called inside his transaction and the function did BEGIN > > and COMMIT. Since BEGIN inside a transaction is just a warning what > > happend was that the inner COMMIT ended the transaction and > > released the locks. The rest of his commands ran with autocommit > > and no locks and he got broken data into the database. > > > Could we make BEGIN fail when we already are in a transaction? > > We could, but it'd probably break about as many apps as it fixed. > I wonder whether php shouldn't be complaining about this, instead > --- doesn't php have its own ideas about controlling where the > transaction commit points are? > > regards, tom lane > AFAIK php doesn't care about that... it just see for success or failure conditions, so if postgres said everything is ok it will continue... -- Atentamente, Jaime Casanova "Programming today is a race between software engineers striving to build bigger and better idiot-proof programs and the universe trying to produce bigger and better idiots. So far, the universe is winning." Richard Cook
Tom Lane wrote: > Dennis Bjorklund <db@zigo.dhs.org> writes: >> Could we make BEGIN fail when we already are in a transaction? > > We could, but it'd probably break about as many apps as it fixed. I'd say that a program that issues BEGIN inside a transaction is already broken, if only by design. I think that the benefit of forced consistency in your transaction handling and standard compliance outweighs the disadvantage of breaking compatibility. Yours, Laurenz Albe
Am Mittwoch, 10. Mai 2006 08:19 schrieb Tom Lane: > Dennis Bjorklund <db@zigo.dhs.org> writes: > > Yesterday I helped a guy on irc with a locking problem, he thought > > that locking in postgresql was broken. It turned out that he had a PHP > > function that he called inside his transaction and the function did BEGIN > > and COMMIT. Since BEGIN inside a transaction is just a warning what > > happend was that the inner COMMIT ended the transaction and > > released the locks. The rest of his commands ran with autocommit > > and no locks and he got broken data into the database. > > > > Could we make BEGIN fail when we already are in a transaction? > > We could, but it'd probably break about as many apps as it fixed. > I wonder whether php shouldn't be complaining about this, instead > --- doesn't php have its own ideas about controlling where the > transaction commit points are? In fact it would break many application, so it should be at least controllable by a setting or GUC.
On Wed, May 10, 2006 at 09:41:46AM +0200, Mario Weilguni wrote: > > > Could we make BEGIN fail when we already are in a transaction? > > > > We could, but it'd probably break about as many apps as it fixed. > > I wonder whether php shouldn't be complaining about this, instead > > --- doesn't php have its own ideas about controlling where the > > transaction commit points are? > > In fact it would break many application, so it should be at least controllable > by a setting or GUC. You want to make a GUC that makes: BEGIN; BEGIN; Leave you with an aborted transaction? That seems like a singularly useless feature... Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
Am Mittwoch, 10. Mai 2006 09:41 schrieb Mario Weilguni: > Am Mittwoch, 10. Mai 2006 08:19 schrieb Tom Lane: > > Dennis Bjorklund <db@zigo.dhs.org> writes: > > > Yesterday I helped a guy on irc with a locking problem, he thought > > > that locking in postgresql was broken. It turned out that he had a PHP > > > function that he called inside his transaction and the function did > > > BEGIN and COMMIT. Since BEGIN inside a transaction is just a warning > > > what happend was that the inner COMMIT ended the transaction and > > > released the locks. The rest of his commands ran with autocommit > > > and no locks and he got broken data into the database. > > > > > > Could we make BEGIN fail when we already are in a transaction? > > > > We could, but it'd probably break about as many apps as it fixed. > > I wonder whether php shouldn't be complaining about this, instead > > --- doesn't php have its own ideas about controlling where the > > transaction commit points are? > > In fact it would break many application, so it should be at least > controllable by a setting or GUC. > No, I want that there is a setting or GUC that controls whether an error or a warning is raised when "begin" is executed within a transaction. I know of several php database wrappers that will be seriously broken when errors are raised...
Am Mittwoch, 10. Mai 2006 10:10 schrieb Martijn van Oosterhout: > You want to make a GUC that makes: > > BEGIN; > BEGIN; > > Leave you with an aborted transaction? That seems like a singularly > useless feature... If a command doesn't do what it is supposed to do, then it should be an error. That seems like a throroughly useful feature to me. -- Peter Eisentraut http://developer.postgresql.org/~petere/
--On Mittwoch, Mai 10, 2006 10:14:22 +0200 Mario Weilguni
<mweilguni@sime.com> wrote:
> No, I want that there is a setting or GUC that controls whether an error
> or a warning is raised when "begin" is executed within a transaction. I
> know of several php database wrappers that will be seriously broken when
> errors are raised...
Such a behavior is already broken by design. I think it's not desirable to
blindly do
transaction start or commit without tracking the current transaction state.
So these wrappers
need to be fixed first.
--
Bernd
Am Mittwoch, 10. Mai 2006 10:59 schrieb Peter Eisentraut: > Am Mittwoch, 10. Mai 2006 10:10 schrieb Martijn van Oosterhout: > > You want to make a GUC that makes: > > > > BEGIN; > > BEGIN; > > > > Leave you with an aborted transaction? That seems like a singularly > > useless feature... > > If a command doesn't do what it is supposed to do, then it should be an > error. That seems like a throroughly useful feature to me. Maybe. I just want to emphasize that it will break existing applications.
Am Mittwoch, 10. Mai 2006 11:44 schrieb Bernd Helmle: > --On Mittwoch, Mai 10, 2006 10:14:22 +0200 Mario Weilguni > > <mweilguni@sime.com> wrote: > > No, I want that there is a setting or GUC that controls whether an error > > or a warning is raised when "begin" is executed within a transaction. I > > know of several php database wrappers that will be seriously broken when > > errors are raised... > > Such a behavior is already broken by design. I think it's not desirable to > blindly do > transaction start or commit without tracking the current transaction state. > So these wrappers > need to be fixed first. You mean broken like "transform_null_equals"? Or "add_missing_from"?
--On Mittwoch, Mai 10, 2006 12:36:07 +0200 Mario Weilguni
<mweilguni@sime.com> wrote:
>> Such a behavior is already broken by design. I think it's not desirable
>> to blindly do
>> transaction start or commit without tracking the current transaction
>> state. So these wrappers
>> need to be fixed first.
>
> You mean broken like "transform_null_equals"? Or "add_missing_from"?
You missed my point. I don't say that such a GUC won't be useful, but
applications which
don't care about what they are currently doing with a database are broken.
--
Bernd
Peter Eisentraut skrev: > Am Mittwoch, 10. Mai 2006 10:10 schrieb Martijn van Oosterhout: > >> You want to make a GUC that makes: >> >> BEGIN; >> BEGIN; >> >> Leave you with an aborted transaction? That seems like a singularly >> useless feature... >> > > If a command doesn't do what it is supposed to do, then it should be an error. > That seems like a throroughly useful feature to me. > > And it would follow sql99 that demand an error. I'm surprised everyone seems to ignore that part (except maybe Peter who is the one I happend to reply to :-). A guc that people can turn off if they have old broken code, that would work for me. /Dennis
I dont think anyone is arguing that such an application is not broken. We should see how we can stop a developer from writing buggy code. IMO, such a GUC variable _should_ be created and turned on by default. In case an application fails, at the least, the developer knows that his application is broken; then he can choose to turn off the GUC variable to let the old behaviour prevail (he might want to do this to let a production env. continue). In the absence of such a feature, we are encouraging developers to write buggy code. This GUC variable can be removed and the behaviour can be made default over the next couple of releases. My two paise... On 5/10/06, Bernd Helmle <mailings@oopsware.de> wrote: > > > --On Mittwoch, Mai 10, 2006 12:36:07 +0200 Mario Weilguni > <mweilguni@sime.com> wrote: > > >> Such a behavior is already broken by design. I think it's not desirable > >> to blindly do > >> transaction start or commit without tracking the current transaction > >> state. So these wrappers > >> need to be fixed first. > > > > You mean broken like "transform_null_equals"? Or "add_missing_from"? > > You missed my point. I don't say that such a GUC won't be useful, but > applications which > don't care about what they are currently doing with a database are broken. > > > -- > > Bernd > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings >
I would suggest the guy simply use the popular ADODB package for his database abstraction layer so he can make use of its "Smart Transaction" feature. http://phplens.com/lens/adodb/docs-adodb.htm#ex11 <quote> Lastly, StartTrans/CompleteTrans is nestable, and only the outermost block is executed. In contrast, BeginTrans/CommitTrans/RollbackTrans is NOT nestable. $conn->StartTrans(); $conn->Execute($sql); $conn->StartTrans(); # ignored <-------------- if (!CheckRecords()) $conn->FailTrans(); $conn->CompleteTrans();# ignored <-------------- $conn->Execute($Sql2); $conn->CompleteTrans(); </quote> The commands marked "ignored" aren't really ignored, since it keeps track of what level the transactions are nested to, and won't actually commit the transaction until the StartTrans() calls == CompleteTrans() calls. Its worked great for me for many years now. On Wed, 2006-05-10 at 06:19 +0200, Dennis Bjorklund wrote: > Hi > > Yesterday I helped a guy on irc with a locking problem, he thought > that locking in postgresql was broken. It turned out that he had a PHP > function that he called inside his transaction and the function did BEGIN > and COMMIT. Since BEGIN inside a transaction is just a warning what > happend was that the inner COMMIT ended the transaction and > released the locks. The rest of his commands ran with autocommit > and no locks and he got broken data into the database. > > Could we make BEGIN fail when we already are in a transaction? > > Looking it up in the sql99 standard I find this: > > "If a <start transaction statement> statement is executed when an > SQL-transaction is currently active, then an exception condition is > raised: invalid transaction state - active SQL-transaction." > > /Dennis > > ---------------------------(end of broadcast)--------------------------- > TIP 6: explain analyze is your friend -- Mike Benoit <ipso@snappymail.ca>
Martijn van Oosterhout wrote: > On Wed, May 10, 2006 at 09:41:46AM +0200, Mario Weilguni wrote: > >>>>Could we make BEGIN fail when we already are in a transaction? >>> >>>We could, but it'd probably break about as many apps as it fixed. >>>I wonder whether php shouldn't be complaining about this, instead >>>--- doesn't php have its own ideas about controlling where the >>>transaction commit points are? >> >>In fact it would break many application, so it should be at least controllable >>by a setting or GUC. > > > You want to make a GUC that makes: > > BEGIN; > BEGIN; > > Leave you with an aborted transaction? That seems like a singularly > useless feature... > > Have a nice day, Or if you really want to screw things up, you could require COMMIT; COMMIT; to finish off the transaction started by BEGIN; BEGIN; We could just silently keep the transaction alive after the first COMMIT; ;)
On Wed, May 10, 2006 at 12:31:52PM +0200, Mario Weilguni wrote: > Am Mittwoch, 10. Mai 2006 10:59 schrieb Peter Eisentraut: > > Am Mittwoch, 10. Mai 2006 10:10 schrieb Martijn van Oosterhout: > > > You want to make a GUC that makes: > > > > > > BEGIN; > > > BEGIN; > > > > > > Leave you with an aborted transaction? That seems like a singularly > > > useless feature... > > > > If a command doesn't do what it is supposed to do, then it should be an > > error. That seems like a throroughly useful feature to me. > > Maybe. I just want to emphasize that it will break existing applications. If the existing application is trying to start a new transaction from within an existing one, I'd say it's already broken and we're just hiding that fact. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
On Wed, May 10, 2006 at 04:03:51PM -0500, Jim C. Nasby wrote: > On Wed, May 10, 2006 at 12:31:52PM +0200, Mario Weilguni wrote: > > Maybe. I just want to emphasize that it will break existing applications. > > If the existing application is trying to start a new transaction from > within an existing one, I'd say it's already broken and we're just > hiding that fact. Well maybe, except the extra BEGIN is harmless. I'm thinking of the situation where a connection library sends a BEGIN on startup because it wants to emulate a non-autocommit mode. The application then proceeds to handle transactions itself, sending another BEGIN and going from there. We'll have just broken this perfectly working application because it failed the purity test. The backward compatability issues are huge and it doesn't actually bring any benefits. How do other database deal with this? Either they nest BEGIN/COMMIT or they probably throw an error without aborting the transaction, which is pretty much what we do. Is there a database that actually aborts a whole transaction just for an extraneous begin? Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
Martijn van Oosterhout <kleptog@svana.org> writes:
> How do other database deal with this? Either they nest BEGIN/COMMIT or
> they probably throw an error without aborting the transaction, which is
> pretty much what we do. Is there a database that actually aborts a
> whole transaction just for an extraneous begin?
Probably not. The SQL99 spec does say (in describing START TRANSACTION,
which is the standard spelling of BEGIN)
1) If a <start transaction statement> statement is executed when an SQL-transaction is currently
active,then an exception condition is raised: invalid transaction state - active SQL-transaction.
*However*, they are almost certainly expecting that that condition only
causes the START command to be ignored; not that it should bounce the
whole transaction. So I think the argument that this is required by
the spec is a bit off base.
regards, tom lane
On 5/10/06, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Martijn van Oosterhout <kleptog@svana.org> writes: > > How do other database deal with this? Either they nest BEGIN/COMMIT or > > they probably throw an error without aborting the transaction, which is > > pretty much what we do. Is there a database that actually aborts a > > whole transaction just for an extraneous begin? > > Probably not. The SQL99 spec does say (in describing START TRANSACTION, > which is the standard spelling of BEGIN) > > 1) If a <start transaction statement> statement is executed when an > SQL-transaction is currently active, then an exception condition > is raised: invalid transaction state - active SQL-transaction. > > *However*, they are almost certainly expecting that that condition only > causes the START command to be ignored; not that it should bounce the > whole transaction. So I think the argument that this is required by > the spec is a bit off base. > > regards, tom lane > Well, actually informix throw an error... at least, my 4gl programs always abort when a second "begin work" is found inside a transaction... -- regards, Jaime Casanova "Programming today is a race between software engineers striving to build bigger and better idiot-proof programs and the universe trying to produce bigger and better idiots. So far, the universe is winning." Richard Cook
Tom Lane skrev: > The SQL99 spec does say (in describing START TRANSACTION, > which is the standard spelling of BEGIN) > > 1) If a <start transaction statement> statement is executed when an > SQL-transaction is currently active, then an exception condition > is raised: invalid transaction state - active SQL-transaction. > > *However*, they are almost certainly expecting that that condition only > causes the START command to be ignored; not that it should bounce the > whole transaction. What is the definition of an "exception condition"? I thought that it ment that a transaction should fail and that "completion condition" are used for warnings that doesn't abort transactions. As an example I looked up division by zero in sql99 and it say this: "If the value of a divisor is zero, then an exception condition is raised: data exception - division by zero." Do you mean that some exception conditions fail transactions and some doesn't? /Dennis
Am Mittwoch, 10. Mai 2006 22:23 schrieb Mark Dilger: > Martijn van Oosterhout wrote: > > On Wed, May 10, 2006 at 09:41:46AM +0200, Mario Weilguni wrote: > >>>>Could we make BEGIN fail when we already are in a transaction? ... > > Or if you really want to screw things up, you could require COMMIT; COMMIT; > to finish off the transaction started by BEGIN; BEGIN; We could just > silently keep the transaction alive after the first COMMIT; ;) > > ---------------------------(end of broadcast)--------------------------- > TIP 2: Don't 'kill -9' the postmaster I would expect after a COMMIT without an error, that my transaction is committed. When the system accidently issued a second BEGIN, this would not be the case. And what about BEGIN; BEGIN; ROLLBACK; COMMIT; then? Should the rollback be ignored also? I'd vote for breaking broken applications and leave the database-administrator reactivate this currently broken behavior of postgresql via GUC. Tommi
On 5/11/06, Martijn van Oosterhout <kleptog@svana.org> wrote: > On Wed, May 10, 2006 at 04:03:51PM -0500, Jim C. Nasby wrote: > > If the existing application is trying to start a new transaction from > > within an existing one, I'd say it's already broken and we're just > > hiding that fact. > > Well maybe, except the extra BEGIN is harmless. It _not_ harmless as it will be probably followed by 'extra' commit. Those few cases where it does not happen do not matter in light of cases where it happens. -- marko
On Thu, May 11, 2006 at 08:05:57AM +0200, Tommi Maekitalo wrote: > I'd vote for breaking broken applications and leave the database-administrator > reactivate this currently broken behavior of postgresql via GUC. +1... As for whether this should or shouldn't abort the current transaction, I'd argue that it should. Otherwise it's likely that your first commit is actually bogus, which means you just hosed yourself. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
On Wed, 2006-05-10 at 21:24 -0400, Tom Lane wrote: > Martijn van Oosterhout <kleptog@svana.org> writes: > > How do other database deal with this? Either they nest BEGIN/COMMIT or > > they probably throw an error without aborting the transaction, which is > > pretty much what we do. Is there a database that actually aborts a > > whole transaction just for an extraneous begin? > > Probably not. The SQL99 spec does say (in describing START TRANSACTION, > which is the standard spelling of BEGIN) > > 1) If a <start transaction statement> statement is executed when an > SQL-transaction is currently active, then an exception condition > is raised: invalid transaction state - active SQL-transaction. > > *However*, they are almost certainly expecting that that condition only > causes the START command to be ignored; not that it should bounce the > whole transaction. So I think the argument that this is required by > the spec is a bit off base. If you interpret the standard that way then the correct behaviour in the face of *any* exception condition should be *not* abort the transaction. In PostgreSQL, all exception conditions do abort the transaction, so why not this one? Why would we special-case this? -- Simon Riggs EnterpriseDB http://www.enterprisedb.com
Am Donnerstag, 11. Mai 2006 22:16 schrieb Simon Riggs: > On Wed, 2006-05-10 at 21:24 -0400, Tom Lane wrote: > > Martijn van Oosterhout <kleptog@svana.org> writes: > > > How do other database deal with this? Either they nest BEGIN/COMMIT or > > > they probably throw an error without aborting the transaction, which is > > > pretty much what we do. Is there a database that actually aborts a > > > whole transaction just for an extraneous begin? > > > > Probably not. The SQL99 spec does say (in describing START TRANSACTION, > > which is the standard spelling of BEGIN) > > > > 1) If a <start transaction statement> statement is executed when > > an SQL-transaction is currently active, then an exception condition is > > raised: invalid transaction state - active SQL-transaction. > > > > *However*, they are almost certainly expecting that that condition only > > causes the START command to be ignored; not that it should bounce the > > whole transaction. So I think the argument that this is required by > > the spec is a bit off base. > > If you interpret the standard that way then the correct behaviour in the > face of *any* exception condition should be *not* abort the transaction. > In PostgreSQL, all exception conditions do abort the transaction, so why > not this one? Why would we special-case this? IMO it's ok to raise an exception - if this is configurable for at least one releasy cycle - giving developers time to fix applications. It's no good behaviour to change something like this without any (at least time-limited ) backward compatible option. regardsmario weilguni
On 5/12/06, Mario Weilguni <mweilguni@sime.com> wrote: > Am Donnerstag, 11. Mai 2006 22:16 schrieb Simon Riggs: > > On Wed, 2006-05-10 at 21:24 -0400, Tom Lane wrote: > > > Martijn van Oosterhout <kleptog@svana.org> writes: > > > > How do other database deal with this? Either they nest BEGIN/COMMIT or > > > > they probably throw an error without aborting the transaction, which is > > > > pretty much what we do. Is there a database that actually aborts a > > > > whole transaction just for an extraneous begin? > > > > > > Probably not. The SQL99 spec does say (in describing START TRANSACTION, > > > which is the standard spelling of BEGIN) > > > > > > 1) If a <start transaction statement> statement is executed when > > > an SQL-transaction is currently active, then an exception condition is > > > raised: invalid transaction state - active SQL-transaction. > > > > > > *However*, they are almost certainly expecting that that condition only > > > causes the START command to be ignored; not that it should bounce the > > > whole transaction. So I think the argument that this is required by > > > the spec is a bit off base. > > > > If you interpret the standard that way then the correct behaviour in the > > face of *any* exception condition should be *not* abort the transaction. > > In PostgreSQL, all exception conditions do abort the transaction, so why > > not this one? Why would we special-case this? > > IMO it's ok to raise an exception - if this is configurable for at least one > releasy cycle - giving developers time to fix applications. It's no good > behaviour to change something like this without any (at least time-limited ) > backward compatible option. > if an option to change it is put in place, maybe it will be there forever (with a different default behavior)... i am all in favor of a second begin to throw an exception "already in transaction" or something else (http://archives.postgresql.org/pgsql-hackers/2005-12/msg00813.php), but if we do it we should do it the only behavior... i don't think it's good to introduce a new GUC for that things (we will finish with GUCs to turn off every fix) -- regards, Jaime Casanova "Programming today is a race between software engineers striving to build bigger and better idiot-proof programs and the universe trying to produce bigger and better idiots. So far, the universe is winning." Richard Cook
Added to TODO: * Add a GUC to control whether BEGIN inside a transcation should abort the transaction. --------------------------------------------------------------------------- Jaime Casanova wrote: > On 5/12/06, Mario Weilguni <mweilguni@sime.com> wrote: > > Am Donnerstag, 11. Mai 2006 22:16 schrieb Simon Riggs: > > > On Wed, 2006-05-10 at 21:24 -0400, Tom Lane wrote: > > > > Martijn van Oosterhout <kleptog@svana.org> writes: > > > > > How do other database deal with this? Either they nest BEGIN/COMMIT or > > > > > they probably throw an error without aborting the transaction, which is > > > > > pretty much what we do. Is there a database that actually aborts a > > > > > whole transaction just for an extraneous begin? > > > > > > > > Probably not. The SQL99 spec does say (in describing START TRANSACTION, > > > > which is the standard spelling of BEGIN) > > > > > > > > 1) If a <start transaction statement> statement is executed when > > > > an SQL-transaction is currently active, then an exception condition is > > > > raised: invalid transaction state - active SQL-transaction. > > > > > > > > *However*, they are almost certainly expecting that that condition only > > > > causes the START command to be ignored; not that it should bounce the > > > > whole transaction. So I think the argument that this is required by > > > > the spec is a bit off base. > > > > > > If you interpret the standard that way then the correct behaviour in the > > > face of *any* exception condition should be *not* abort the transaction. > > > In PostgreSQL, all exception conditions do abort the transaction, so why > > > not this one? Why would we special-case this? > > > > IMO it's ok to raise an exception - if this is configurable for at least one > > releasy cycle - giving developers time to fix applications. It's no good > > behaviour to change something like this without any (at least time-limited ) > > backward compatible option. > > > > if an option to change it is put in place, maybe it will be there > forever (with a different default behavior)... > > i am all in favor of a second begin to throw an exception "already in > transaction" or something else > (http://archives.postgresql.org/pgsql-hackers/2005-12/msg00813.php), > but if we do it we should do it the only behavior... i don't think > it's good to introduce a new GUC for that things (we will finish with > GUCs to turn off every fix) > > -- > regards, > Jaime Casanova > > "Programming today is a race between software engineers striving to > build bigger and better idiot-proof programs and the universe trying > to produce bigger and better idiots. > So far, the universe is winning." > Richard Cook > > ---------------------------(end of broadcast)--------------------------- > TIP 1: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly > -- Bruce Momjian http://candle.pha.pa.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +