Re: summary of new features in JDBC 3.0 - Mailing list pgsql-jdbc

On Wednesday 27 October 2004 17:16, Oliver Jowett wrote:
> >     * Connection pool configuration
>
> What does this entail?

Section 3.1 (p. 21) of the spec says,

  | * Connection pool configuration
  |
  |   Defined a number of properties for the ConnectionPoolDataSource
  |   interface. These properties can be used to describe how
  |   PooledConnection objects created by DataSource objects should be
  |   pooled.

From my cursory reading of some of the sections that seem relevant, I
think this means the following. Section 9.4.1 "DataSource Properties"
(p. 58) defines the following DataSource properties:

 TABLE 9-1 Standard Data Source Properties

 +------------------------------------------------------------------------+
 |  Property Name  |  Type  |                 Description                 |
 |-----------------+--------+---------------------------------------------|
 | databaseName    | String | name of a particular database on a server   |
 |-----------------+--------+---------------------------------------------|
 | dataSourceName  | String | a data source name; used to name an         |
 |                 |        | underlying XADataSource object or           |
 |                 |        | ConnectionPoolDataSource object when        |
 |                 |        | pooling of connections is done              |
 |-----------------+--------+---------------------------------------------|
 | description     | String | description of this data source             |
 |-----------------+--------+---------------------------------------------|
 | networkProtocol | String | network protocol used to communicate with   |
 |                 |        | the server                                  |
 |-----------------+--------+---------------------------------------------|
 | password        | String | a database password                         |
 |-----------------+--------+---------------------------------------------|
 | portNumber      | int    | port number where a server is listening for |
 |                 |        | requests                                    |
 |-----------------+--------+---------------------------------------------|
 | roleName        | String | the initial SQL rolename                    |
 |-----------------+--------+---------------------------------------------|
 | serverName      | String | database server name                        |
 |-----------------+--------+---------------------------------------------|
 | user            | String | user 's account name                        |
 +------------------------------------------------------------------------+


In addition to these, Section 11.7 "ConnectionPoolDataSource
Properties" (p. 78), defines these:

 TABLE 11-1  Standard Connection Pool Properties

 +------------------------------------------------------------------------+
 |  Property Name  | Type |                  Description                  |
 |-----------------+------+-----------------------------------------------|
 | maxStatements   | int  | The total number of statements that the pool  |
 |                 |      | should keep open. 0 (zero) indicates that     |
 |                 |      | caching of statements is disabled.            |
 |-----------------+------+-----------------------------------------------|
 | initialPoolSize | int  | The number of physical connections the pool   |
 |                 |      | should contain when it is created             |
 |-----------------+------+-----------------------------------------------|
 | minPoolSize     | int  | The number of physical connections the pool   |
 |                 |      | should keep available at all times. 0 (zero)  |
 |                 |      | indicates that connections should be created  |
 |                 |      | as needed.                                    |
 |-----------------+------+-----------------------------------------------|
 | maxPoolSize     | int  | The maximum number of physical connections    |
 |                 |      | that the pool should contain. 0 (zero)        |
 |                 |      | indicates no maximum size.                    |
 |-----------------+------+-----------------------------------------------|
 | maxIdleTime     | int  | The number of seconds that a physical         |
 |                 |      | connection should remain unused in the pool   |
 |                 |      | before the connection is closed. 0 (zero)     |
 |                 |      | indicates no limit.                           |
 |-----------------+------+-----------------------------------------------|
 | propertyCycle   | int  | The interval, in seconds, that the pool       |
 |                 |      | should wait before enforcing the current      |
 |                 |      | policy defined by the values of the above     |
 |                 |      | connection pool properties                    |
 +------------------------------------------------------------------------+


> Aren't connection pools in the realm of the appserver?

Perhaps.  I can neither confirm nor deny untill I read the spec, which I
haven't done yet.

> >     * Making internal updates to the data in Blob and Clob objects
>
> I assume this is the positioned write stuff? Not implemented, but
> doesn't look too hard to do. See the todo list.

Yes, I think you're right.  The spec says (Section 3.1):

  | * Making internal updates to the data in Blob and Clob objects
  |
  |   Added methods to allow the data contained in Blob and Clob objects
  |   to be altered.

They appear to be talking about these added methods:
  http://people.redhat.com/~vadimn/scratch/pgsql-jdbc/api-diff/java.sql.Blob.html
  http://people.redhat.com/~vadimn/scratch/pgsql-jdbc/api-diff/java.sql.Clob.html

> >     * Transform groups and type mapping
>
> If this is the SQL type maps stuff, then not implemented. Kris is
> working on SQLInput/SQLOutput implementations that would allow this
> to be implemented. See the todo list.

I'm not sure what this is about.  First time I've ever heard of
"transform groups".  Section 3.1 says

  | * Transform groups and type mapping
  |
  |   Described the effect of transform groups and how this is
  |   reflected in the metadata.


Section 17.5 "Effect of Transform Groups" goes on to say

  | Transform groups (SQL99) can be used to convert a user-defined SQL
  | type into predefined SQL types. This transformation is performed
  | by the underlying data source before it is returned to the JDBC
  | driver.
  |
  | If transform groups are used for a user-defined type, and the
  | application has not defined a mapping for that type to a Java
  | class, then the ResultSetMetaData method getColumnClass should
  | return the Java class corresponding to the data type produced by
  | the transformation function (that is, String for a VARCHAR).


> >     * Relationship between the JDBC SPI (Service Provider Interface) and
> >       the Connector architecture
>
> I don't think this imposes any implementation requirements on the driver?

I think it does, if you choose to implement what Section 19.2 refers
to as the "Mapping Connector System Contracts to JDBC Interfaces".

Thanks for your answers.


Vadim