public Context context() {
        return context;
    }
Returns the context of this execution, which contains various objects
which are looked up through a memory barrier at the point this is created
and which is guaranteed to be frozen during the execution of this query.
<p>
Note that the context itself can be changed. Such changes will be visible
to downstream searchers, but not after returning from the modifying
searcher. In other words, a change in the context will not be visible to
the preceding searchers when the result is returned from the searcher
which modified the context.
container-search/src/main/java/com/yahoo/search/searchchain/Execution.java