[FEATURE] New Doc Collector for Normalization and Score Combination Query

[martin-gaievski]

Description

For Normalization and Score Combination feature, we need to collect results of different sub-queries and pass those results for actual post processing (normalization and score combination) before the Fetch phase.

Solution

Solution we are proposing is to create new implementation of a Collector for results.

Because new collector cannot be plugged to OpenSearch directly (there no suitable extension points) we also need a new implementation of QueryPhaseSearcher. Plugin can register new QueryPhaseSearcher (with certain limitations), and that searcher will be executing new collector.

Tasks

• Create RFC for new Document Collector: [RFC] Low Level Design for Normalization and Score Combination Query Phase Searcher #193
• Implementation of a Query clause
• Testing

Reference Links

1. [RFC] High Level Approach and Design For Normalization and Score Combination #126
2. [RFC] Low Level Design for Normalization and Score Combination Query #174
3. [RFC] Low Level Design for Normalization and Score Combination Query Phase Searcher #193