Re: AUTO_INCREMENT patch

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От des@des.no (Dag-Erling Smørgrav)
Тема Re: AUTO_INCREMENT patch
Дата
Msg-id xzpwudvwznk.fsf@dwp.des.no
обсуждение исходный текст
Ответ на Re: AUTO_INCREMENT patch  (Rod Taylor <rbt@rbt.ca>)
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Rod Taylor <rbt@rbt.ca> writes:
> Yeah.. JBoss is very annoying in this regard. A temporary solution seems
> to be to use BEFORE triggers to force the sequence to be used for the
> default value.  You could also do this with an INSTEAD rule (something
> like the below):
>
> CREATE OR REPLACE RULE rulename AS ON INSERT
>   TO tablename
>   DO INSTEAD
>    INSERT INTO tablename
>              ( id, col1, ...)
>       VALUES ( DEFAULT, NEW.col1, ...);

That's a good workaround for 3.2.1.  As regards the upcoming 3.2.2, I
just found out that it has PostgreSQL-specific code to handle this,
though it's an incomplete fix.  To summarize:
- add <entity-command>postgresql-fetch-seq</entity-command> to each  affected entity (or the <defaults> section) in
jbosscmp-jdbc.xml; this resolves the "failed to insert null" problem and also makes  sure JBoss knows the id of the
newlycreated row. 
- apply my auto_increment patch
- replace the bogus auto-increment template in the PostgreSQL and  PostgreSQL 7.2 mappings in standardjbosscmp-jdbc.xml
withthe  following: 
     <auto-increment-template>?1 AUTO_INCREMENT</auto-increment-template>
  the current template (?1) works if you set the corresponding  <cmp-field>'s <sql-type> to SERIAL - but if you define
arelation  that involves that field, the other endpoint will also be defined  as SERIAL!  Obviously that's not a recipe
forsuccess. 

> AUTO_INCREMENT is non-standard (MySQL only?), however the SQL200X
> proposals do have support for the more common IDENTITY syntax which can
> accomplish the same job as well as many others. (PostgreSQL does NOT
> have the general identity implementation yet)

the IDENTITY syntax is very similar to AUTO_INCREMENT, in fact you can
apply s/auto_increment/identity/ to my patch and have a useful subset
of it :) JBoss already knows about IDENTITY, since Hypersonic SQL and
MS SQL both support it.

(interestingly, JBoss doesn't seem to know that DB/2 also supports it)

> What you're looking for is the ability to force the column to use the
> IDENTITY even when the client provides a specific value:
>
> CREATE TABLE test(col integer GENERATED ALWAYS AS IDENTITY);

as mentioned above, that's no longer a problem with JBoss 3.2.2.

> See sections 10.22, 10.23, 11.3, and 11.4 of the SQL200X working draft
> for full details.
>
> ftp://sqlstandards.org/SC32/WG3/Progression_Documents/FCD/4FCD1-02-Foundation-2002-01.pdf

I believe this is more up to date:

ftp://sqlstandards.org/SC32/WG3/Progression_Documents/FDIS/4FDIS1-02-Foundation-2003.pdf

DES
--
Dag-Erling Smørgrav - des@des.no


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