Lists: | pgsql-odbc |
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From: | Dmitry Samokhin <sdld(at)mail(dot)ru> |
---|---|
To: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Replacing IDENTITY with lastval() |
Date: | 2007-05-04 11:42:37 |
Message-ID: | E1HjwBJ-000Hnc-00.sdld-mail-ru@f105.mail.ru |
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Lists: | pgsql-odbc |
Accordind to the release notes, "Use lastval() function to replace IDENTITY on 8.1 or later servers" was introduced in release 8.2.0205. This may cause incorrect results: "<...> assumes that your database does not expect any triggers to fire when the INSERT is executed. If a trigger does fire and if that trigger adds another row to a table, the @@IDENTITY global variable would be set to point to that new Identity value—not the one your INSERT generated. <...> work for simple situations, but not when your database gets more sophisticated".
See "Managing an @@IDENTITY Crisis" on MSDN (http://msdn2.microsoft.com/en-us/library/ms971502.aspx) for more details.
The PostgreSQL documentation states that the lastval() function returns the value most recently returned by nextval in the current session. It works the same way as the @@IDENTITY variable in MSSQL. The currval(...) function returns a value of the explicitly specified sequence, this is exactly what we need.
Please consider to revert the code.
Regards,
Dmitry.
From: | Hiroshi Inoue <inoue(at)tpf(dot)co(dot)jp> |
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To: | Dmitry Samokhin <sdld(at)mail(dot)ru> |
Cc: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Re: Replacing IDENTITY with lastval() |
Date: | 2007-05-05 15:56:40 |
Message-ID: | 463CA938.6020206@tpf.co.jp |
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Dmitry Samokhin wrote:
> Accordind to the release notes, "Use lastval() function to replace IDENTITY on 8.1 or later servers" was introduced in release 8.2.0205. This may cause incorrect results: "<...> assumes that your database does not expect any triggers to fire when the INSERT is executed. If a trigger does fire and if that trigger adds another row to a table, the @@IDENTITY global variable would be set to point to that new Identity value—not the one your INSERT generated. <...> work for simple situations, but not when your database gets more sophisticated".
> See "Managing an @@IDENTITY Crisis" on MSDN (http://msdn2.microsoft.com/en-us/library/ms971502.aspx) for more details.
>
> The PostgreSQL documentation states that the lastval() function returns the value most recently returned by nextval in the current session. It works the same way as the @@IDENTITY variable in MSSQL. The currval(...) function returns a value of the explicitly specified sequence, this is exactly what we need.
>
> Please consider to revert the code.
OK I would take care of it in 8.2.0402.
regards,
Hiroshi Inoue
From: | Andreas <maps(dot)on(at)gmx(dot)net> |
---|---|
To: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Re: Replacing IDENTITY with lastval() |
Date: | 2007-05-05 16:47:28 |
Message-ID: | 463CB520.90208@gmx.net |
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So - generally speaking - it is not advised to use lastval() at all?
At least not, if one is not 110% sure what happens in the application
now and on later modifications of the client application.
Thats a pitty, as I have only known lastval() for about 15 minutes when
I looked in the documentation for the sequence stuff.
On the other hand I ran today in troubles with sequences when I was
doing a bit coding on a migration from MS-Access DAO + JET to DAO, ODBC
+ PG.
With pure Access + DAO one can fetch the newly assigned AUTOVALUE by
simply reading it out of the newly created record right after AddNew and
before Update.
With ODBC + PG. as backend the SERIAL is undefined between AddNew and
Update.
And the recordset points not to the new record after Update but to the
first record in the recordset.
I had to use PG's CurrVal respectivly LastVal which would be easier
without having to know the name of the sequence.
I'm happy that I read your post before using LastVal all over the
place. :)
Dmitry Samokhin schrieb:
> Accordind to the release notes, "Use lastval() function to replace IDENTITY on 8.1 or later servers" was introduced in release 8.2.0205. This may cause incorrect results: "<...> assumes that your database does not expect any triggers to fire when the INSERT is executed. If a trigger does fire and if that trigger adds another row to a table, the @@IDENTITY global variable would be set to point to that new Identity value—not the one your INSERT generated. <...> work for simple situations, but not when your database gets more sophisticated".
> See "Managing an @@IDENTITY Crisis" on MSDN (http://msdn2.microsoft.com/en-us/library/ms971502.aspx) for more details.
>
> The PostgreSQL documentation states that the lastval() function returns the value most recently returned by nextval in the current session. It works the same way as the @@IDENTITY variable in MSSQL. The currval(...) function returns a value of the explicitly specified sequence, this is exactly what we need.
>
> Please consider to revert the code.
>
> Regards,
> Dmitry.
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>
>
From: | "Ben Trewern" <ben(dot)trewern(at)mowlem(dot)com> |
---|---|
To: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Re: Replacing IDENTITY with lastval() |
Date: | 2007-06-01 15:00:28 |
Message-ID: | f3pc9f$2lbv$1@news.hub.org |
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Lists: | pgsql-odbc |
Shouldn't you be using INSERT ... RETURNING .. ; for this? Seems like the
perfect useage.
Regards,
Ben
"Andreas" <maps(dot)on(at)gmx(dot)net> wrote in message news:463CB520(dot)90208(at)gmx(dot)net(dot)(dot)(dot)
>
> So - generally speaking - it is not advised to use lastval() at all?
> At least not, if one is not 110% sure what happens in the application now
> and on later modifications of the client application.
>
> Thats a pitty, as I have only known lastval() for about 15 minutes when I
> looked in the documentation for the sequence stuff.
>
> On the other hand I ran today in troubles with sequences when I was doing
> a bit coding on a migration from MS-Access DAO + JET to DAO, ODBC + PG.
> With pure Access + DAO one can fetch the newly assigned AUTOVALUE by
> simply reading it out of the newly created record right after AddNew and
> before Update.
>
> With ODBC + PG. as backend the SERIAL is undefined between AddNew and
> Update.
> And the recordset points not to the new record after Update but to the
> first record in the recordset.
> I had to use PG's CurrVal respectivly LastVal which would be easier
> without having to know the name of the sequence.
>
> I'm happy that I read your post before using LastVal all over the place.
> :)
>
>
> Dmitry Samokhin schrieb:
>> Accordind to the release notes, "Use lastval() function to replace
>> IDENTITY on 8.1 or later servers" was introduced in release 8.2.0205.
>> This may cause incorrect results: "<...> assumes that your database does
>> not expect any triggers to fire when the INSERT is executed. If a trigger
>> does fire and if that trigger adds another row to a table, the @@IDENTITY
>> global variable would be set to point to that new Identity valuenot the
>> one your INSERT generated. <...> work for simple situations, but not when
>> your database gets more sophisticated".
>> See "Managing an @@IDENTITY Crisis" on MSDN
>> (http://msdn2.microsoft.com/en-us/library/ms971502.aspx) for more
>> details.
>>
>> The PostgreSQL documentation states that the lastval() function returns
>> the value most recently returned by nextval in the current session. It
>> works the same way as the @@IDENTITY variable in MSSQL. The currval(...)
>> function returns a value of the explicitly specified sequence, this is
>> exactly what we need.
>>
>> Please consider to revert the code.
>>
>> Regards,
>> Dmitry.
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 2: Don't 'kill -9' the postmaster
>>
>>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 7: You can help support the PostgreSQL project by donating at
>
> http://www.postgresql.org/about/donate
>
From: | "Ben Trewern" <ben(dot)trewern(at)mowlem(dot)com> |
---|---|
To: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Re: Replacing IDENTITY with lastval() |
Date: | 2007-06-01 15:10:13 |
Message-ID: | f3pcrn$2tr3$1@news.hub.org |
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Lists: | pgsql-odbc |
> Shouldn't you be using INSERT ... RETURNING .. ; for this? Seems like
> the perfect useage.
>
Sorry to reply to myself but I just looked this up and it is only supported
from 8.2 onwards. :-(
Ben