suggestion for new custom atomic update

[Elran Dvir <el...@checkpoint.com>]

Hi all,

This is my use  case:
I have a stored field, field_a, which is atomic updated (let's say by "inc"). field_a is stored but not indexed due to the large number of distinct values it can have.
I need to index field_b (I need facet and stats on it) which is not in the document but its value is based on a calculation of the recent (e.g. summed) value of field_a.
There is no way to do it nowadays.
So I thought of a new method: custom atomic update.

There will be a new interface in Solr:

public interface CustomAtomicUpdater {
    public void update(SolrInputDocument oldDoc, String fieldName, Object fieldVal) ;
 }

There will be a new attribute for fields in schema.xml called "customAtomicUpdateClass" (and all support in code, of course).
The value is a class which is an implementation of  CustomAtomicUpdater.
In our example it will be defined for field_a.

In method "getUpdatedDocument" in DistributedUpdateProcessor.java, we will add handling of "custom" case:

   } else if ("custom".equals(key)) {
            updateField = true;
            SchemaField sf = schema.getField(sif.getName());
            String customAtomicUpdaterClassName = sf.getCustomAtomicUpdaterClass();
            if (customAtomicUpdaterClassName == null) {
              throw new SolrException(ErrorCode.BAD_REQUEST, "There is no customAtomicUpdaterClass defined for " + sif + ".");
            }
            CustomAtomicUpdater updater = schema.getResourceLoader()
                    .newInstance(customAtomicUpdaterClassName, CustomAtomicUpdater.class);
            if (updater == null) {
              throw new SolrException(ErrorCode.BAD_REQUEST, "Was unable to create instance of " + customAtomicUpdaterClassName + ".");
            }
            updater.update(oldDoc, sif.getName(), fieldVal);

          }

In my implementation I will sum field_a (oldvalue + newvalue) and update field_b according to my logic.

Example of use:
<add>
  <doc>
    <field name="field_a" update="custom">128</field>
  </doc>
</add>

What do say about my suggestion?

Thanks.