at the core, the Next() method moves another searcher forward
and checks each hit to see if it also satisfies the phrase
constraints. the current implementation has 4 nested for loops.
these nested loops make it harder read (indentation) and harder
to reason about (complexity).
this refactor does not remove any loops, it simply moves some
of the inner loops into separate methods so that one can
more easily reason about the parts separately.
While researching an observed performance issue with wildcard
queries, it was observed that the LiteralPrefix() method on
the regexp.Regexp struct did not always behave as expected.
In particular, when the pattern starts with ^, AND involves
some backtracking, the LiteralPrefix() seems to always be the
empty string.
The side-effect of this is that we rely on having a helpful
prefix, to reduce the number of terms in the term dictionary
that need to be visited.
This change now makes the searcher enforce start/end on the term
directly, by using FindStringIndex() instead of Match().
Next, we also modified WildcardQuery and RegexpQuery to no
longer include the ^ and $ modifiers.
Documentation was also udpated to instruct users that they should
not include the ^ and $ modifiers in their patterns.
This is a change in search result behavior in that location
information is no longer provided by default with search results.
Although this looks like a wide-ranging change, it's mostly a
mechanical replacement of the explain bool flag with a new
search.SearcherOptions struct, which holds both the Explain bool flag
and the IncludeTermVectors bool flag.
This commit reverts a previous optimization attempt 3f588cd4a that
tried to trim or shrink the array of child searchers in a
search-disjunction.
Although I am not sure why at the moment, that optimization
incorrectly broke higher level boolean queries, but reverting so that
functionality is restored.
Disjunction searchers are used heavily by higher-level searchers, like
prefix searchers. In that case, a disjunction searcher might have
many thousands of child searchers.
This commit adds an optimization to close each child term searcher as
soon as a child searcher is finished and remove it from the
disjunction searcher's children.
