[ http://issues.apache.org/jira/browse/LUCENE-662?page=comments#action_12437644 ] Nicolas Lalevée commented on LUCENE-662: ----------------------------------------
It is due to lazy loading. A lazy field, when being retreived data, have to know how to read the stream. In the current trunk, a special implementation of Field is doing this. Here, we don't have control of the implemenation of Fieldable it will be. As I wanted to keep the lazy loading mechanism controlled internally in Lucene, being transparent to the user, I had to force every Fieldable implementation to know how about retreiving data lazily. So I switched the interface to an abstract class : in fact I have moved AbstractField to Fieldable. But as I already raised, I still have an issue about it : the lazy loading mechanism isn't totally internal. The function Fieldable.setLazyData() shouldn't be public but default. > Extendable writer and reader of field data > ------------------------------------------ > > Key: LUCENE-662 > URL: http://issues.apache.org/jira/browse/LUCENE-662 > Project: Lucene - Java > Issue Type: Improvement > Components: Store > Reporter: Nicolas Lalevée > Priority: Minor > Attachments: generic-fieldIO-2.patch, generic-fieldIO.patch > > > As discussed on the dev mailing list, I have modified Lucene to allow to > define how the data of a field is writen and read in the index. > Basically, I have introduced the notion of IndexFormat. It is in fact a > factory of FieldsWriter and FieldsReader. So the IndexReader, the indexWriter > and the SegmentMerger are using this factory and not doing a "new > FieldsReader/Writer()". > I have also introduced the notion of FieldData. It handles every data of a > field, and also the writing and the reading in a stream. I have done this way > because in the current design of Lucene, Fiedable is an interface, so methods > with a protected or package visibility cannot be defined. > A FieldsWriter just writes data into a stream via the FieldData of the field. > A FieldsReader instanciates a FieldData depending on the field name. Then it > use the field data to read the stream. And finnaly it instanciates a Field > with the field data. > About compatibility, I think it is kept, as I have writen a > DefaultIndexFormat that provides some DefaultFieldsWriter and > DefaultFieldsReader. These implementations do the exact job that is done > today. > To acheive this modification, some classes and methods had to be moved from > private and/or final to public or protected. > About the lazy fields, I have implemented them in a more general way in the > implementation of the abstract class FieldData, so it will be totally > transparent for the Lucene user that will extends FieldData. The stream is > kept in the fieldData and used as soon as the stringValue (or something else) > is called. Implementing this way allowed me to handle the recently introduced > LOAD_FOR_MERGE; it is just a lazy field data, and when read() is called on > this lazy field data, the saved input stream is directly copied in the output > stream. > I have a last issue with this patch. The current design allow to read an > index in an old format, and just do a writer.addIndexes() into a new format. > With the new design, you cannot, because the writer will use the > FieldData.write provided by the reader. > enjoy ! -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
