= Fast Index Update =

|| '''Date''' || 2012/09/14 ||
|| '''Contact(s)''' || [http://wiki.osgeo.org/wiki/User:Jeichar Jesse Eichar] ||
|| '''Last edited''' || ||
|| '''Status''' || Not proposed. Just brain storm ||
|| '''Assigned to release''' || 2.9.x ||
|| '''Resources''' || Swisstopo ||
|| '''Code''' || https://github.com/jesseeichar/core-geonetwork/tree/improvement/fastupdate ||

== Overview ==

Currently in order to change any fields in the lucene index the metadata document has to be completely reindexed.  This proposal outlines how certain field changes can be efficiently performed.

The types of actions this would make efficient are: 
 * Update popularity
 * Update privileges

=== Proposal Type ===
 * '''Type''': Improvement
 * '''App''': Geonetwork
 * '''Module''': Index

=== Links ===
 
 * '''Email discussions''':
 * '''IRC discussions''':
 * '''Related work''':

 
=== Voting History ===

 * None as yet

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== Proposal == 

'''Background'''

First of all lucene does not support updating a document directly.  The normal way of updating a lucene document is to:

 1. Recreate the lucene document from the source data (in our case the metadata xml)
 1. delete the document from the index
 1. add new (recreated) document to the index

If the recreation of the lucene document is an expensive operation then performing this task is naturally expensive.  There are work arounds for example:

 1. Load document from index
 1. Modify document
 1. delete document from index
 1. insert modified document to index

However this is a naive solution and fails in practice because there are both stored and non-stored fields.  Using this strategy will lose the non-stored fields.  

A potential solution comes to mind:

Lucene 4 has the concept of flexible indexing (http://java.dzone.com/videos/heavy-committing-flexible)  

=== Backwards Compatibility Issues ===

Will require rebuild of index

== Risks ==


== Participants ==
 * As above