Basically during the document processing stage, ESP will decide to do the partial update or full update (Add Document).For that we need to enable the Partial Update option in our custom processor/Pipeline.
1. $FASTHOME\etc\processors\ProcessorServer.xml
2. Add the Partial Update element in our custom processors.
3. Change the XMLMapper.xml to enable the Partial Update.
We can do the same via web Analyzer tool also .
Partial Update considerations :
The update methods provides a means for partial document updates and have certain limitations.
As a general rule these methods should only be used to update metadata or numeric elements that does not require any document processing. datetime elements can also be updated.
This means that if you need to update the actual content of an HTML page, PDF document or XML file the add methods must be used.
It is possible to implement custom document processing that supports partial update
