Result level caching is currently broken in master for all kind of queries.

Affected Version

Master

Description

During the query execution on the broker side, ClientQuerySegmentWalker wraps the CachingClusteredClient.run method in a chain of query runners. One of the participating runner is ResultLevelCachingQueryRunner which is responsible for populating result level cache. It assumes that when this chain is invoked, the responseContext is updated with the E-TAG. This E-TAG is used in ResultLevelCachingQueryRunner and if this E-TAG is null, result level cache is not populated. The flow is much better explained in #8713

The problem is that chain of query runners now include a RetryQueryRunner on top of CachingClusteredClient.run which similar to UnionQueryRunner in #8713, turns an eager load into a lazy load. Because of this, ResultLevelCachingQueryRunner never actually sees the E-TAG when it tries to access it. It's populated in the responseContext later on during the query execution. Because of this, result level cache is never populated.