Date: 2004-03-03T19:27:01
Editor: ScottEade <[EMAIL PROTECTED]>
Wiki: DB Torque Wiki
Page: PostgreSQLFAQ
URL: http://wiki.apache.org/db-torque/PostgreSQLFAQ
Converted from Usemod wiki.
New Page:
= Can I use Torque with PostgreSQL =
Yes, it would appear that several people are using Torque and PostgreSQL together
successfully. You do however need to be aware of the issues outlined in the rest of
this FAQ.
= I have problems using idMethod='native'. What's up? =
PostgreSQL creates a sequence with a special name for the autoincrement. In order to
get Torque to interact gracefully with this sequence, you need to tell it the sequence
name. In addition, Postgres restricts the sequence name to 30 characters, which means
that the names get truncated strangely. Thus, to get everything to work, you
basically need to do the following:
1. include a <id-method-parameter name="seqName" value="Tablename_columnname_seq"/>
in every table that has an "autoincrement" column.
1. If the "tablename_columnname" combination is longer than 26 letters, it will get
truncated to 26 letters by Postgres . You need to figure out the truncated name. The
best way to find it is:
* create the database via the usual Torque methods.
* go into psql and execute "\ds tablename" - this will show you the name of the
sequence.
* go back to your schema file and set the value parameter to the name of the
sequence.
* recreate the database via the usual Torque methods. Now everything should work.
An example of a table definition (without truncation issues) is:
{{{
<table name="TypeCategory" createLogTable="true">
<column name="TypeCategoryId" autoIncrement="true" required="true"
primaryKey="true" type="INTEGER"/>
<column name="Name" required="true" size="32" type="VARCHAR"/>
<column name="Descr" required="true" size="64" type="VARCHAR" />
<column name="CreateTime" type="TIMESTAMP" />
<column name="UpdateTime" type="TIMESTAMP" />
<unique>
<unique-column name="Name"/>
</unique>
<id-method-parameter name="seqName" value="TypeCategory_typecategoryid_seq"/>
</table>
}}}
An example of a table definition with truncation issues is:
{{{
<table name="AssociateLogin">
<column name="AssociateLoginId" required="true"
autoIncrement="true" primaryKey="true"
type="INTEGER"/>
<column name="AssociateKey" type="INTEGER"/>
<column name="Handle" size="64"
type="VARCHAR" />
<column name="Password" size="250"
type="VARCHAR" />
<column name="CreateTime" type="TIMESTAMP" />
<column name="UpdateTime" type="TIMESTAMP" />
<unique>
<unique-column name="Handle"/>
</unique>
<foreign-key foreignTable="Associate" onDelete="cascade">
<reference local="AssociateKey" foreign="AssociateId"/>
</foreign-key>
<id-method-parameter name="seqName" value="associatelogi_associatelogi_seq"/>
</table>
}}}
The situation with PostgreSQL 7.3 would appear to be quite different. It appears that
in SQL it is enough to simply declare a column as "serial" and the necessary sequence
will be created with the correct name (truncation to 26 characters no longer occurs)
and will be dropped automatically when the table is dropped. This would mean that
Tourque could be updated to not generate the code that creates and drops the sequence
and the the id-method-parameter element is probably no longer necessary (if it is used
as part of the id generation code, and I do not think it is, then the necessary value
can be derrived). -- ScottEade 2003-02-06
It's a valid point. The above code works for 7.2 and Torque 3.0b3, and may be
different for other versions. I think the <id-method-parameter> element is necessary
because the Torque model expects the sequence name to be "tablename_seq" but
Postgresql creates a sequence which is called "tablename_columnname_seq". I think
once an object is inserted into the database, Torque needs a method to find out the ID
of the object. It does this by fetching the current value of the sequence (which
should be equal to the last value inserted into the database.) If Torque cannot
figure out the sequence name correctly, then it cannot find the appropriate ID and
everything goes south. (I might be incorrect about this - it may be only an issue of
making sure the sequence is created and dropped, in which case Scott is absolutely
right.)
--PeterHamlen 2003-02-06
So this is basically a bug in Torque - i.e. it should generate
"tablename_columnname_seq" rather than "tablename_seq" and perhaps still allow for the
<id-method-parameter> element to allow for versions of ["PostgreSQL"] that truncate
the sequence name to 26 characters. -- ScottEade 2003-02-07
To get sequences to work I added the <id-method-parameter> elements mentioned above,
but then had to remove the sql that drops/creates the sequences that was generated by
torque:sql before executing it with torque:insert-sql. -- ScottEade 2003-10-14
= Do I need to patch the PostgreSQL driver to work with Torque? =
You do not need to apply any patches to the Postgres driver in order to use Torque
<strong>unless</strong>
you want to use "large objects" (CLOBS/BLOBS).
The "patch issue" dates from the time when Torque was tightly coupled with Turbine.
It arose primarily because Turbine stored a hashmap
of user information directly in the database. This data was stored as a BLOB.
Now that Torque is decoupled from Turbine, this issue is only relevant if you use
BLOBs into your schema (ie, use the datatypes BLOB or CLOB or LONGVARBINARY or
LONGVARCHAR).
= So what if I am using BLOBS, etc. ? =
1. You will need to patch the driver.
1. The JDBC "BLOB" type should map to the PostgreSQL "oid" column type, but the JDBC
driver does not support this automatically. The JDBC driver returns metadata that
indicates that "oid" columns have JDBC type Types.INTEGER (the type of the oid ID
pointer itself), so Torque (actually, the underlying Village API) doesn't treat the
column properly. This can be fixed by patching the JDBC driver, as mentioned in the
[http://db.apache.org/torque/postgres-howto.html PostgreSQL Howto].
1. Also, for PostgreSQL 7.2 and higher, it is necessary to specify the parameter
"compatible=7.1" on the JDBC URL for {{{PreparedStatement.setBytes()}}} to work
correctly on oid columns. Note that this will also prevent the VARBINARY (bytea) types
from working. Although BLOBs and best for large binary content, the LONGVARBINARY
(bytea) types seem to be more portable between databases and JDBC drivers.
This http://db.apache.org/torque/postgres-howto.html seems out of date since the
Field.java file has none of the code indicated. A recent, or better fix is where? --rnh
= What other issues are there? =
* Three patch issues in Scarab (quoting various values)
[http://nagoya.apache.org/scarab/issues/id/TRQS109
TRQS109][http://nagoya.apache.org/scarab/issues/id/TRQS110
TRQS110][http://nagoya.apache.org/scarab/issues/id/TRQS111 TRQS111] - that these
patches need to be applied in order to use PostgreSQL not totally clear (existing test
cases all pass). (If someone can confirm that these are required, or better still
provide test cases, I will commit them. -- ScottEade 2003-02-05)
* Bill Schneider mentioned on torque-user that "serial" columns are by defaul
defined to be of type int4 and that this could pose a problem (the comment may have
been made prior to Torque switching from BigDecimal to int for object keys). Note
that int4 corresponds to Java int, so this will only be an issue if you need to
support a larger range of values than int provides.
* Foreign keys to TURBINE_USER. If you have extended your schema to include foreign
key references to TURBINE_USER (by way of an alias table definition) the SQL generated
to create your database will include foreign key references to the non-existant alias
table. This would not have been a problem under MySQL as it ignores foreign ket
definitions, however you may need to change your schema in order to be able to use it
with PostgreSQL. Torque needs to use the alias table name rather than the alias when
generating the sql.
* With Turbine 2.3 and the new Torque Security Manager method of extending
!TurbineUser this is no longer an immediate problem, but it should still be addressed
at some stage. -- ScottEade 2003-10-09
* Multiple unique column definitions are currently generated with the same
constraint name.
* I have confirmed that this problem is still present in Torque 3.1 and that it
applies to index as well as unique. The workaround is to provide the name of the
constraint manually using a "name" attribute on the index and unique elements in cases
where more than one exists for a given table. -- ScottEade 2003-10-09
* Columns declared as type CHAR are returned as space padded Strings by PostgreSQL
but are not by MySQL. I'm wondering if Troque shouldn't strip the trailing spaces off
these automatically. The workaround is to add a setter to the non-Base Torque class
for the object that uses String.trim() to remove the spaces. -- ScottEade 2003-11-05
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