> you are not interested in making the approach below more general -
'not interested' is not the right word. Not on my personal list of important
things for me personal - but happy to get patches!
> 4. I have opened OPENJPA2640 and provided a patch
Thanks a lot, trying to get around it the next days. Feel free to poke me for
it ;)
txs and LieGrue,
strub
> On Tuesday, 12 April 2016, 15:51, Francesco Chicchiriccò
> <ilgro...@apache.org> wrote:
> > Hi Mark,
> with reference to my 4 questions below:
>
> 1. I have experimented that, even though UUIDType4HexSeq provides a
> static getInstance() method, it is not called with my use case, so I am
> fine with my UUIDGenerator's constructor being invoked twice (e.g. one
> time for each entity)
>
> 2. I have been able to translate the sequence generator definition to
> orm.xml
>
> 3. I understand that since "some DBs are not really working with it",
> you are not interested in making the approach below more general -
> that's fine, we are going to use it anyway, for the DBs we support
>
> 4. I have opened OPENJPA2640 and provided a patch, please take a look -
> incidentally, I have noticed that 2.4.1 appears as unreleased in JIRA
>
> Regards.
>
>
> On 12/04/2016 09:22, Mark Struberg wrote:
>> Hi Francesco!
>>
>> I usually let the PK be a String and create the UUID myself in Java.
>>
>> The 'uuid' generator is a nice feature but it's not portable.
>>
>> And that might be the reason why some DBs are not really working with it -
> it's simply not that frequently used.
>>
>>
>> There are 3 ways to create the UUID.
>>
>> a.) In the default ct. That might trigger a tad too often and might slow
> down selects, etc.
>> b.) Lazily in getId(). If null -> create a new UUID
>> c.) Via an own ct which takes the UUID pk. You basically create the ID in
> your business layer.
>>
>> I mostly use c) if I need a UUID pk.
>>
>> LieGrue,
>> strub
>>
>>
>>
>>
>>> On Monday, 11 April 2016, 9:02, Francesco Chicchiriccò
> <ilgro...@apache.org> wrote:
>>>> Hi all,
>>> I went further and built a sample POC [10] which mimics the essentials
>>> from Syncope.
>>>
>>> I have defined an UUIDGenerator implementing Seq (and relying on [3]
> for
>>> UUID generation), and declared it via
>>>
>>> @SequenceGenerator(name = "uuid", sequenceName =
>>> "net.tirasa.ilgrosso.uuidpoc.openjpa.UUIDGenerator()")
>>>
>>> in the @MappedSuperclass of both JPA entities available, plus defined
>>>
>>> @Id
>>> @GeneratedValue(strategy = GenerationType.SEQUENCE, generator =
>>> "uuid")
>>> private UUID id;
>>>
>>> in both entities.
>>>
>>> I have also extended the H2Dictionary to support the native UUID type
>>> (without such extension, the id column would have had type BLOB).
>>>
>>> All this above seems to work - at least for the simple JUnit test case
>>> provided; I have some questions, though:
>>>
>>> 1. I have experimented that UUIDGenerator is instantiated twice: would
>>> it be possible to defined it as singleton - as it happens for
> OpenJPA's
>>> UUIDType4HexSeq?
>>>
>>> 2. How would the @SequenceGenerator annotation translates to orm.xml?
>>> I've attempted the bare translation but it did not work.
>>>
>>> 3. The extended logic I have put in my H2Dictionary looks quite poor
> for
>>> the general case - even though good enough for my specific use case:
>>>
>>> @Override
>>> public String getTypeName(final Column col) {
>>> return col.getType() == Types.BLOB &&
> (col.isPrimaryKey() ||
>>> col.isForeignKey())
>>> ? "UUID"
>>> : super.getTypeName(col);
>>> }
>>>
>>> How much difficult would be to make it proper, e.g. recognize when the
>>> class field is java.util.UUID? I'll need such extension for MySQL,
>>> MariaDB, PostgreSQL, MS SQL Server and Oracle dictionaries.
>>>
>>> 4. I am used to rely on openjpa-maven-plugin to generate the
>>> database.sql file; how can I configure it to use my H2Dictionary, and
>>> not the default?
>>>
>>> Thanks for your support.
>>> Regards.
>>>
>>> On 04/04/2016 10:49, Francesco Chicchiriccò wrote:
>>>> Hi all,
>>>> in Syncope we are currently discussing [1] the option to replace
> our
>>>> table generators-based id strategy to something else, based on
> UUID,
>>>> which seem to offer several advantages.
>>>>
>>>> I have found [2], but I would rather prefer to generated UUID
> values
>>>> manually (via [3] which seems to offer better performance and
> more
>>>> features than the standard JDK's).
>>>>
>>>> In order to do so, I would replace the current
>>>>
>>>> @Id
>>>> private Long id;
>>>>
>>>> public Long getKey() {
>>>> return id;
>>>> }
>>>>
>>>> in [4], backed by [5], with something like as
>>>>
>>>> @Id
>>>> private UUID id;
>>>>
>>>> public UUID getKey() {
>>>> synchronized(this) {
>>>> if (key == null) {
>>>> key = ... // generate via JUG [3]
>>>> }
>>>> }
>>>> return key;
>>>> }
>>>>
>>>> As Syncope supports several DBMSes, I would also like to empower
> the
>>>> underlying capabilities for storing such values:
>>>>
>>>> * UUID Type for PostgreSQL [6]
>>>> * UNIQUEIDENTIFIER for SQL Server [7]
>>>> * RAW(16) for Oracle [8]
>>>> * BINARY(16) with some optimizations for MySQL / MariaDB [9] or
>>>> vanilla with H2
>>>>
>>>> Do you have any suggestion about:
>>>>
>>>> (a) the way how I am planning to support UUID generation
>>>> (b) the cleanest way to support DBMS differences (extending the
>>>> respective DB dictionaries?)
>>>>
>>>> TIA
>>>> Regards.
>>>>
>>>> [1] http://markmail.org/message/fhdrwerdwdm3opdx
>>>> [2]
>>>>
>>>
> http://openjpa.apache.org/builds/2.4.1/apache-openjpa/docs/jpa_overview_meta_field.html#jpa_overview_meta_gen
>>>> [3] https://github.com/cowtowncoder/java-uuid-generator
>>>> [4]
>>>>
>>>
> https://github.com/apache/syncope/blob/master/core/persistence-jpa/src/main/java/org/apache/syncope/core/persistence/jpa/entity/user/JPAUser.java
>>>> [5]
>>>>
>>>
> https://github.com/apache/syncope/blob/master/core/persistence-jpa/src/main/resources/META-INF/spring-orm.xml#L87-L94
>>>> [6] http://www.postgresql.org/docs/9.3/static/datatype-uuid.html
>>>> [7]
>>>>
> http://wiki.ispirer.com/sqlways/sql-server/data-types/uniqueidentifier
>>>> [8]
>>>>
>>>
> http://docs.oracle.com/cd/B28359_01/server.111/b28286/functions175.htm#SQLRF51816
>>>> [9]
> https://www.percona.com/blog/2014/12/19/store-uuid-optimized-way/
>>> [10] https://github.com/ilgrosso/OpenJPAUUIDPOC
>
> --
> Francesco Chicchiriccò
>
> Tirasa - Open Source Excellence
> http://www.tirasa.net/
>
> Involved at The Apache Software Foundation:
> member, Syncope PMC chair, Cocoon PMC, Olingo PMC, CXF committer
> http://home.apache.org/~ilgrosso/
>
