This is for filtering results on how many times the term appears on the domain. The intent is to be beneficial in creating e.g. a domain search feature. It's also very helpful when tracking down spammy domains.
This is a system-wide change. The index used to have a lexicon, mapping words to wordIds using a large in-memory hash table. This made index-construction easier, but it
also added a fairly significant RAM penalty to both the index service and the loader.
The new design moves to 64 bit word identifiers calculated using the murmur hash of the keyword, and an index construction based on merging smaller indices.
It also became necessary half-way through to upgrade guice as its error reporting wasn't *quite* compatible with JDK20.
... where some terms may previously have been ignored. The latter bug was due to the handling of QueryHeads with AnyOf-style predicates interacting poorly with alreadyConsideredTerms in SearchIndex.java
* A deduplication filter step ran too early, and removed many good results on the basis that they partially, but did not fully fit another set of search terms.
* Altered the query creation process to prefer documents where multiple terms appear in the priority index.
