Re: [hibernate-dev] HHH-6726 LONG and LONG RAW column types in Oracle
by Łukasz Antoniak
Currently Oracle supports database versions from 10.1 to 11.2 [1]. LONG
and LONG RAW data types are deprecated since version 8 and 8i (released
before September 2000) [2]. Oracle keeps those column types only for
backward compatibility [3].
I tried the following scenario (Oracle 10gR2):
1. Create schema with "hibernate.hbm2ddl.auto" set to "create". The LONG
column is created.
2. Insert some data.
3. Modify Oracle dialect as Gail suggested. Avoid setting
"hibernate.hbm2ddl.auto".
4. Insert some data.
To my surprise the test actually passed :). However, I think that we
cannot guaranty the proper behavior in every situation.
As for performance, ImageType is extracted by calling
ResultSet.getBytes() method, which fetches all data in one call [4]. I
don't suppose a major performance difference when data is streamed in
another call. oracle.jdbc.driver.LongRawAccessor.getBytes also fetches
data by reading the stream.
The bug reading LONG column affects JDBC drivers since version 10.2.0.4.
I think that we have to choose between:
- changing Oracle10gDialect. Make a not about it in migration guide to
4.0 and update "5.2.2. Basic value types" chapter in Hibernate
documentation.
- introducing Oracle11gDialect. It can sound weird to access Oracle 10g
database with Oracle 11g dialect.
- disabling execution of Hibernate tests that fail because of this issue
with @SkipForDialect (and maybe develop another version of them with
CLOBs and BLOBs, @RequiresDialect). Hibernate is written correctly
according to "Default Mappings Between SQL Types and Java Types"
(referenced earlier by Gail) and this is more Oracle's JDBC
implementation issue. This option came to my mind, but it's weird :P.
I would vote for the first option.
Regards,
Lukasz Antoniak
[1]
http://www.oracle.com/us/support/library/lifetime-support-technology-0691...
(page 4)
[2]
http://download.oracle.com/docs/cd/A91202_01/901_doc/server.901/a90120/ch...
[3]
http://download.oracle.com/docs/cd/B28359_01/server.111/b28318/datatype.htm
[4] "Getting a LONG RAW Data Column with getBytes"
http://download.oracle.com/docs/cd/B19306_01/java.102/b14355/jstreams.htm
Strong Liu pisze:
> I think oracle 11g is the only one supported DB version by oracle, can we just introduce a new oracle dialect with suggested changes, and deprecate all other existed oracle dialects? this won't affects users app
>
> -----------
> Strong Liu <stliu(a)hibernate.org>
> http://hibernate.org
> http://github.com/stliu
>
> On Oct 15, 2011, at 11:14 AM, Scott Marlow wrote:
>
>> How does this impact existing applications? Would they have to convert
>> LONGs to CLOBs (and LONGRAWs to BLOBs) to keep the application working?
>>
>> As far as the advantage of CLOB over TEXT, if you read every character,
>> which one is really faster? I would expect TEXT to be a little faster,
>> since the server side will send the characters before they are asked
>> for. By faster, I mean from the application performance point of view. :)
>>
>> Could this be changed in a custom Oracle dialect? So new
>> applications/databases could perhaps use that and existing applications
>> might use LONGs a bit longer via the existing Oracle dialect.
>>
>> On 10/14/2011 09:22 PM, Gail Badner wrote:
>>> In [1], I am seeing the following type mappings:
>>>
>>> Column type: LONG -> java.sql.Types.LONGVARCHAR -> java.lang.String
>>> Column type: LONGRAW -> java.sql.Types.LONGVARBINARY -> byte[]
>>>
>>> org.hibernate.type.TextType is consistent with the mapping for LONG.
>>>
>>> org.hibernate.type.ImageType is consistent with the mapping for LONGRAW.
>>>
>>> From this standpoint, the current settings are appropriate.
>>>
>>> I understand there are restrictions when LONG and LONGRAW are used and I see from your other message that there is Oracle documentation for migrating to CLOB and BLOB.
>>>
>>> I agree that changing column type registration as follows (for Oracle only) should fix this:
>>> registerColumnType( Types.VARBINARY, 2000, "raw($l)" );
>>> registerColumnType( Types.VARBINARY, "blob" );
>>>
>>> registerColumnType( Types.LONGVARCHAR, "clob" );
>>> registerColumnType( Types.LONGVARBINARY, "blob" );
>>>
>>> registerColumnType( Types.VARCHAR, 4000, "varchar2($l char)" );
>>> registerColumnType( Types.VARCHAR, "clob" );
>>>
>>> Steve, what do you think? Is it too late to make this change for 4.0.0?
>>>
>>> [1] Table 11-1 of Oracle® Database JDBC Developer's Guide and Reference, 11g Release 1 (11.1) (http://download.oracle.com/docs/cd/B28359_01/java.111/b31224/datacc.htm#g...)
>>> [2] Hibernate Core Migration Guide for 3.5 (http://community.jboss.org/wiki/HibernateCoreMigrationGuide35)
>>> [3] Table 2-10 of Oracle® Database SQL Language Reference
>>> 11g Release 1 (11.1) (http://download.oracle.com/docs/cd/B28359_01/server.111/b28286/sql_elemen...)
>>>
>>> ----- Original Message -----
>>>> From: "Łukasz Antoniak"<lukasz.antoniak(a)gmail.com>
>>>> To: hibernate-dev(a)lists.jboss.org
>>>> Sent: Thursday, October 13, 2011 12:50:13 PM
>>>> Subject: [hibernate-dev] HHH-6726 LONG and LONG RAW column types in Oracle
>>>>
>>>> Welcome Community!
>>>>
>>>> I have just subscribed to the list and wanted to discuss HHH-6726
>>>> JIRA
>>>> issue.
>>>>
>>>> Gail Badner wrote
>>>> (http://lists.jboss.org/pipermail/hibernate-dev/2011-October/007208.html):
>>>> HHH-6726 (Oracle : map TextType to clob and ImageType to blob)
>>>> https://hibernate.onjira.com/browse/HHH-6726
>>>> There have been a number of issues opened since the change was made
>>>> to
>>>> map TextType (LONGVARCHAR) 'long' and ImageType (LONGVARBINARY) to
>>>> 'long
>>>> raw'. This change was already documented in the migration notes.
>>>> Should
>>>> the mapping for Oracle (only) be changed back to clob and blob?
>>>>
>>>> HHH-6726 is caused by an issue in Oracle JDBC driver (version
>>>> 10.2.0.4
>>>> and later). This bug appears when LONG or LONG RAW columns are
>>>> accessed
>>>> not as first or last while processing SQL statement.
>>>>
>>>> I have discussed the topic of mapping TextType to CLOB and ImageType
>>>> to
>>>> BLOB (only in Oracle dialect) with Strong Liu. Reasons for doing so:
>>>> - Oracle allows only one LONG / LONG RAW column per table. This might
>>>> be
>>>> the most important from Hibernate's perspective.
>>>> - LONG / LONG RAW - up to 2 GB, BLOB / CLOB - up to 4 GB.
>>>> - In PL/SQL using LOBs is more efficient (random access to data).
>>>> LONG
>>>> only sequential.
>>>> - LONG and LONG RAW are deprecated.
>>>>
>>>> What is your opinion?
>>>>
>>>> Regards,
>>>> Lukasz Antoniak
>>>> _______________________________________________
>>>> hibernate-dev mailing list
>>>> hibernate-dev(a)lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>>
>>> _______________________________________________
>>> hibernate-dev mailing list
>>> hibernate-dev(a)lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>> _______________________________________________
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>
9 years, 3 months
Query handling : Antlr 3 versus Antlr 4
by Steve Ebersole
As most of you know already, we are planning to redesign the current
Antlr-based HQL/JPQL parser in ORM for a variety of reasons.
The current approach in the translator (Antlr 2 based, although Antlr 3
supports the same model) is that we actually define multiple
grammars/parsers which progressively re-write the tree adding more and more
semantic information; think of this as multiple passes or phases. The
current code has 3 phases:
1) parsing - we simply parse the HQL/JPQL query into an AST, although we do
do one interesting (and uber-important!) re-write here where we "hoist" the
from clause in front of all other clauses.
2) rough semantic analysis - the current code, to be honest, sucks here.
The end result of this phase is a tree that mixes normalized semantic
information with lots of SQL fragments. It is extremely fugly
3) rendering to SQL
The idea of phases is still the best way to attack this translation imo. I
just think we did not implement the phases very well before; we were just
learning Antlr at the time. So part of the redesign here is to leverage
our better understanding of Antlr and design some better trees. The other
big reason is to centralize the generation of SQL into one place rather
than the 3 different places we do it today (not to mention the many, many
places we render SQL fragments).
Part of the process here is to decide which parser to use. Antlr 2 is
ancient :) I used Antlr 3 in the initial prototyping of this redesign
because it was the most recent release at that time. In the interim Antlr
4 has been released.
I have been evaluating whether Antlr 4 is appropriate for our needs there.
Antlr 4 is a pretty big conceptual deviation from Antlr 2/3 in quite a few
ways. Generally speaking, Antlr 4 is geared more towards interpreting
rather than translating/transforming. It can handle "transformation" if
the transformation is the final step in the process. Transformations is
where tree re-writing comes in handy.
First lets step back and look at the "conceptual model" of Antlr 4. The
grammar is used to produce:
1) the parser - takes the input and builds a "parse tree" based on the
rules of the lexer and grammar.
2) listener/visitor for parse-tree traversal - can optionally generate
listeners or visitors (or both) for traversing the parse tree (output from
parser).
There are 2 highly-related changes that negatively impact us:
1) no tree grammars/parsers
2) no tree re-writing
Our existing translator is fundamentally built on the concepts of tree
parsers and tree re-writing. Even the initial prototypes for the redesign
(and the current state of hql-parser which Sanne and Gunnar picked up from
there) are built on those concepts. So moving to Antlr 4 in that regard
does represent a risk. How big of a risk, and whether that risk is worth
it, is what we need to determine.
What does all this mean in simple, practical terms? Let's look at a simple
query: "select c.headquarters.state.code from Company c". Simple syntactic
analysis will produce a tree something like:
[QUERY]
[SELECT]
[DOT]
[DOT]
[DOT]
[IDENT, "c"]
[IDENT, "headquarters"]
[IDENT, "state"]
[IDENT, "code"]
[FROM]
[SPACE]
[SPACE_ROOT]
[IDENT, "Customer"]
[IDENT, "c"]
There is not a lot of semantic (meaning) information here. A more semantic
representation of the query would look something like:
[QUERY]
[SELECT]
[ATTRIBUTE_REF]
[ALIAS_REF, "<gen:1>"]
[IDENT, "code"]
[FROM]
[SPACE]
[PERSISTER_REF]
[ENTITY_NAME, "com.acme.Customer"]
[ALIAS, "c"]
[JOIN]
[INNER]
[ATTRIBUTE_JOIN]
[IDENT, "headquarters"]
[ALIAS, "<gen:0>"]
[JOIN]
[INNER]
[ATTRIBUTE_JOIN]
[IDENT, "state"]
[ALIAS, "<gen:1>"]
Notice especially the difference in the tree rules. This is tree
re-writing, and is the major difference affecting us. Consider a specific
thing like the "c.headquarters.state.code" DOT-IDENT sequence. Essentially
Antlr 4 would make us deal with that as a DOT-IDENT sequence through all
the phases - even SQL generation. Quite fugly. The intent of Antlr 4 in
cases like this is to build up an external state table (external to the
tree itself) or what Antlr folks typically refer to as "iterative tree
decoration"[1]. So with Antlr 4, in generating the SQL, we would still be
handling calls in terms of "c.headquarters.state.code" in the SELECT clause
and resolving that through the external symbol tables. Again, with Antlr 4
we would always be walking that initial (non-semantic) tree. Unless I am
missing something. I would be happy to be corrected, if anyone knows Antlr
4 better. I have also asked as part of the antlr-discussion group[2].
In my opinion though, if it comes down to us needing to walk the tree in
that first form across all phases I just do not see the benefit to moving
to Antlr 4.
P.S. When I say SQL above I really just mean the target query language for
the back-end data store whether that be SQL targeting a RDBMS for ORM or a
NoSQL store for OGM.
[1] I still have not fully grokked this paradigm, so I may be missing
something, but... AFAICT even in this paradigm the listener/visitor rules
are defined in terms of the initial parse tree rules rather than more
[2] https://groups.google.com/forum/#!topic/antlr-discussion/hzF_YrzfDKo
9 years, 11 months
Changelog file in Hibernate ORM
by Sanne Grinovero
The file changelog.txt in the root ot the Hibernate ORM project seems outdated.
Is it not maintained anymore? I found it handy.
Sanne
9 years, 11 months
did hibernate.org crash?
by Scott Marlow
Trying to open http://hibernate.org/dtd/hibernate-configuration-3.0.dtd,
gives a:
"
Site temporarily disabled
This page has been temporarily disabled due to a misconfigured custom
domain.
Are you the site owner? Follow the instructions for setting up a custom
domain with GitHub pages to update your site's DNS records to point to
the proper IP address.
You can find more information in our GitHub Pages legacy IP deprecation
blog post. If you have any questions, please contact support.
"
The above causes a WildFly test failure http://pastebin.com/fm8VMCcb
(from org.hibernate.service.internal.JaxbProcessor.unmarshal).
Scott
10 years, 3 months
Re: [hibernate-dev] Need some help for new property types
by Ajay Bhat
Thanks so much, Davide! Could you and/or the community review the below
pull request?
https://github.com/hibernate/hibernate-ogm/pull/461
On Mon Dec 22 2014 at 5:42:14 PM Davide D'Alto <davide(a)hibernate.org> wrote:
> Hi,
> I gave a quick look at the patch, I think the reason it is not working
> with MongoDB is that MongoDB does not support natively Character type.
>
> You need to use a different CharacterType implementation for MongoDB, you
> can do it via the method MongoDBDialect.overrideType(...). You will find
> that we are already doing it for other types like Byte and Calendar for
> example.
> You should do the same for Character (and Short I suspect).
>
> I have also created a branch where I rebased your work to the latest
> changes and fixed the checktyle errors (branch 401 on my repository):
> https://github.com/DavideD/hibernate-ogm/tree/OGM-401
>
> I hope this help,
> Davide
>
> On Mon, Dec 22, 2014 at 10:43 AM, Davide D'Alto <davide(a)hibernate.org>
> wrote:
>>
>> Hi Ajay,
>> sorry we were quiet in these days, we worked hard for the latest OGM
>> release and most of us have started the Christmas holidays.
>>
>> I'm packing for my holidays as well so I don't think I will be able to
>> look at this now.
>> I'll try to have a look at it tomorrow.
>>
>> Cheers,
>> Davide
>>
>>
>> On Mon, Dec 22, 2014 at 2:06 AM, Ajay Bhat <a.ajay.bhat(a)gmail.com> wrote:
>>>
>>> Hi,
>>> I was working on OGM-401 (Implementing new property types) and I
>>> encountered some errors while running the tests. I'd asked about it in
>>> the
>>> IRC, but since there wasn't anyone there at the time, I thought I'd ask
>>> around here.
>>>
>>>
>>> http://transcripts.jboss.org/channel/irc.freenode.org/%23hibernate-dev/20...
>>>
>>> Thanks,
>>> Ajay
>>> _______________________________________________
>>> hibernate-dev mailing list
>>> hibernate-dev(a)lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>
>>
10 years, 4 months
Remove added XML from confiuration
by Vikas Bali
Hi all
I am having problem while adding mapping files dynamically. It takes long time to add after some time. I did not find any way to remove the added XML from configuration object once added. I believe this is an issue of performance. Please suggest.
Thnaks
Vikas
10 years, 5 months
