Int and Float field types should use their corresponding Sort types

[romseygeek]

Description

The int and float field types in Elasticsearch use long and double sort types. This mismatch means that we can't make use of lucene's sorting shortcuts for these field types.

A complication here is that just changing the sort types used at runtime may run into problems when dealing with sorted indexes, which will have already written the old, wider sort type into their index metadata.

[elasticmachine]

Pinging @elastic/es-search (Team:Search)

[LeeTgk]

Hi. I would like to try working on this issue.

[benwtrent]

Reading a little into this, I tracked down places where this logic needs updated.

First, we need to create new set SortField objects that provide FieldComparator objects that appropriately transform between primitive types. Meaning, for comparing float and double, the objects are casted appropriately.

Second, SearchPhaseController needs to have updated logic for checkSameSortTypes and how it builds the corresponding sort object. Instead of blindly taking the first docs group and using those sorts (since they might be of Float, but you also have Double), it should return one of the new SortField objects if we determine we have many different, but compatible types.

Third, IndexNumericFieldData.NumericType needs updated so that the appropriate primitive type is provided.

There are probably other refactors required, but these are what I found so far.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)