Updates to Isis

[Kevin Meyer - KMZ <ke...@kmz.co.za>]

Hi all,

I just added support to the Isis core and applib for Paged datastore 
queries.

These extensions don't change any existing behaviour, but do expose 
a new query type to the user space: QueryFindAllPaged

A simple usage example:
    public List<SimpleClass> someSimpleClasses(final long startIndex, final long rowCount) {
        Query<SimpleClass> query = new QueryFindAllPaged<SimpleClass>(SimpleClass.class, startIndex, rowCount);
        return allMatches(query);
    }

Inside PersistenceSession, "QueryFindAllPaged" is mapped onto 
"PersistenceQueryFindPaged", which is available to the data stores.

The SQL-OS has a simple implementation that adds "LIMIT 
<startIndex>, <rowCount>" to the end of the SQL statement.

This will have to be edited for each database engine: I belive mysql 
and postgresql have an incompatible syntax... but I believe it should 
be possible to easily define a way to specify the custom string in the 
properties file.

There is a simple test in SqlDomainObjectRepository that just checks 
that the expected number of instances are returned. It works against 
HSQLDB.

May you find this extension useful! 

Re: Updates to Isis

[Kevin Meyer <ke...@kmz.co.za>]

Hi Jeroen,

Thanks for the reference...

If my suspicion that String.format() supports numbered place holders (e.g. "{1}"), then I suspect non-Oracle databases can be supported with a single definition in isis.properties.

My goal here was two-fold:
1) expose a paging API to the user (domain) space,
2) provide a simple implementation in the SQL objectstore.

The JDO objectstore should be able to pick this up and support it, too.

And if the Wicket paging could be made to use this API, then I'd consider this a success!

Regards,
Kevin

Jeroen van der Wal <je...@stromboli.it> wrote:

>DataNucleus/JDO has covered this for every RDBMS, perhaps you can learn
>from their implementation:
>
>"setRange is implemented efficiently for MySQL, Postgresql, HSQL (using
>the
>LIMIT SQL keyword) and Oracle (using the ROWNUM keyword), with the
>query
>only finding the objects required by the user directly in the
>datastore.
>For other RDBMS the query will retrieve all objects up to the "to"
>record,
>and will not pass any unnecessary objects that are before the "from"
>record."  [1]
>
>[1]
>http://www.datanucleus.org/products/accessplatform_3_2/jdo/jdoql_typesafe.html
>
>
>On Sun, Feb 3, 2013 at 8:41 PM, Kevin Meyer - KMZ <ke...@kmz.co.za>
>wrote:
>
>> Hi all,
>>
>> I just added support to the Isis core and applib for Paged datastore
>> queries.
>>
>> These extensions don't change any existing behaviour, but do expose
>> a new query type to the user space: QueryFindAllPaged
>>
>> A simple usage example:
>>     public List<SimpleClass> someSimpleClasses(final long startIndex,
>> final long rowCount) {
>>         Query<SimpleClass> query = new
>> QueryFindAllPaged<SimpleClass>(SimpleClass.class, startIndex,
>rowCount);
>>         return allMatches(query);
>>     }
>>
>> Inside PersistenceSession, "QueryFindAllPaged" is mapped onto
>> "PersistenceQueryFindPaged", which is available to the data stores.
>>
>> The SQL-OS has a simple implementation that adds "LIMIT
>> <startIndex>, <rowCount>" to the end of the SQL statement.
>>
>> This will have to be edited for each database engine: I belive mysql
>> and postgresql have an incompatible syntax... but I believe it should
>> be possible to easily define a way to specify the custom string in
>the
>> properties file.
>>
>> There is a simple test in SqlDomainObjectRepository that just checks
>> that the expected number of instances are returned. It works against
>> HSQLDB.
>>
>> May you find this extension useful!
>>

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

Re: Updates to Isis

[Jeroen van der Wal <je...@stromboli.it>]

DataNucleus/JDO has covered this for every RDBMS, perhaps you can learn
from their implementation:

"setRange is implemented efficiently for MySQL, Postgresql, HSQL (using the
LIMIT SQL keyword) and Oracle (using the ROWNUM keyword), with the query
only finding the objects required by the user directly in the datastore.
For other RDBMS the query will retrieve all objects up to the "to" record,
and will not pass any unnecessary objects that are before the "from"
record."  [1]

[1]
http://www.datanucleus.org/products/accessplatform_3_2/jdo/jdoql_typesafe.html


On Sun, Feb 3, 2013 at 8:41 PM, Kevin Meyer - KMZ <ke...@kmz.co.za> wrote:

> Hi all,
>
> I just added support to the Isis core and applib for Paged datastore
> queries.
>
> These extensions don't change any existing behaviour, but do expose
> a new query type to the user space: QueryFindAllPaged
>
> A simple usage example:
>     public List<SimpleClass> someSimpleClasses(final long startIndex,
> final long rowCount) {
>         Query<SimpleClass> query = new
> QueryFindAllPaged<SimpleClass>(SimpleClass.class, startIndex, rowCount);
>         return allMatches(query);
>     }
>
> Inside PersistenceSession, "QueryFindAllPaged" is mapped onto
> "PersistenceQueryFindPaged", which is available to the data stores.
>
> The SQL-OS has a simple implementation that adds "LIMIT
> <startIndex>, <rowCount>" to the end of the SQL statement.
>
> This will have to be edited for each database engine: I belive mysql
> and postgresql have an incompatible syntax... but I believe it should
> be possible to easily define a way to specify the custom string in the
> properties file.
>
> There is a simple test in SqlDomainObjectRepository that just checks
> that the expected number of instances are returned. It works against
> HSQLDB.
>
> May you find this extension useful!
>