/// <summary>
/// An instance of `MatchData` will be created for every term that matches a
/// document. However only one instance is required in an index result. This
/// method combines metadata from another instance of `MatchData` with this
/// object's metadata.
/// </summary>
/// <param name="otherMatchData">Another instance of match data to merge with this one.</param>
public void Combine(MatchData otherMatchData)
{
IEnumerable <string> terms = otherMatchData.Posting.Keys;
foreach (string term in terms)
{
IEnumerable <string> fields = otherMatchData.Posting[term].Keys;
if (!Posting.ContainsKey(term))
{
Posting.Add(term, new FieldMatches());
}
Dictionary <string, FieldMatchMetadata> thisTermEntry = Posting[term];
foreach (string field in fields)
{
IEnumerable <string> keys = otherMatchData.Posting[term][field].Keys;
if (!thisTermEntry.ContainsKey(field))
{
thisTermEntry.Add(field, new FieldMatchMetadata(capacity: otherMatchData.Posting[term][field].Keys.Count));
}
FieldMatchMetadata thisFieldEntry = thisTermEntry[field];
foreach (string key in keys)
{
IList <object?> otherData = otherMatchData.Posting[term][field][key];
if (!thisFieldEntry.ContainsKey(key))
{
thisFieldEntry.Add(key, new List <object?>(otherData));
}
else
{
thisFieldEntry[key] = thisFieldEntry[key].Concat(otherData).ToList();
}
}
}
}
}
/// <summary>
/// Add metadata for a term/field pair to this instance of match data.
/// </summary>
/// <param name="term">The term this match data is associated with.</param>
/// <param name="field">The field in which the term was found.</param>
/// <param name="metadata">The metadata recorded about this term in this field.</param>
public void Add(string term, string field, FieldMatchMetadata metadata)
{
if (!Posting.ContainsKey(term))
{
Posting.Add(term, new FieldMatches
{
{
field,
metadata
}
});
return;
}
FieldMatches termMetadata = Posting[term];
if (!termMetadata.ContainsKey(field))
{
termMetadata.Add(field, metadata);
return;
}
foreach (string key in metadata.Keys)
{
FieldMatchMetadata fieldMetadata = termMetadata[field];
if (fieldMetadata.ContainsKey(key))
{
fieldMetadata[key] = fieldMetadata[key].Concat(metadata[key]).ToList();
}
else
{
fieldMetadata[key] = metadata[key];
}
}
}
/// <summary>Constructs a `MatchData`.</summary>
/// <param name="term">The term this match data is associated with.</param>
/// <param name="field">The field in which the term was found.</param>
/// <param name="metadata">The metadata recorded about this term in this field.</param>
public MatchData(
string term,
string field,
FieldMatchMetadata metadata)
{
Term = term;
Field = field;
// Cloning the metadata to prevent the original being mutated during match data combination.
// Metadata is kept in an array within the inverted index.
var clonedMetadata = new FieldMatchMetadata(capacity: metadata.Count);
foreach ((string key, IEnumerable <object?> value) in metadata)
{
clonedMetadata.Add(key, new List <object?>(value));
}
Posting = new InvertedIndexEntry
{
{
term,
new FieldMatches
{
{ field, clonedMetadata }
}
}
};
}
/// <summary>
/// Performs a query against the index using the `Query` object built
/// by the provided factory.
///
/// If performing programmatic queries against the index, this method is preferred
/// over `Index.Search` so as to avoid the additional query parsing overhead.
///
/// A query object is yielded to the supplied function which should be used to
/// express the query to be run against the index.
/// </summary>
/// <param name="queryFactory">A function that builds the query object that gets passed to it.</param>
/// <param name="cancellationToken">A cancellation token.</param>
/// <returns>The results of the query.</returns>
public async IAsyncEnumerable <Result> Query(
Action <Query> queryFactory,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
var results = new List <Result>();
var query = new Query(Fields);
var matchingFields = new Dictionary <FieldReference, MatchData>();
var termFieldCache = new HashSet <string>();
var requiredMatches = new Dictionary <string, ISet <string> >();
var prohibitedMatches = new Dictionary <string, ISet <string> >();
// To support field level boosts a query vector is created per
// field. An empty vector is eagerly created to support negated
// queries.
var queryVectors = new Dictionary <string, Vector>();
foreach (string field in Fields)
{
queryVectors[field] = new Vector();
}
queryFactory(query);
for (int i = 0; i < query.Clauses.Count; i++)
{
Clause clause = query.Clauses[i];
ISet <string> clauseMatches = Set <string> .Empty;
// Unless the pipeline has been disabled for this term, which is
// the case for terms with wildcards, we need to pass the clause
// term through the search pipeline. A pipeline returns an array
// of processed terms. Pipeline functions may expand the passed
// term, which means we may end up performing multiple index lookups
// for a single query term.
await foreach (string term in clause.UsePipeline
? Pipeline.RunString(
clause.Term,
new TokenMetadata
{
{ "fields", clause.Fields }
},
cancellationToken)
: new[] { clause.Term }.ToAsyncEnumerable(cancellationToken))
{
// Each term returned from the pipeline needs to use the same query
// clause object, e.g. the same boost and or edit distance. The
// simplest way to do this is to re-use the clause object but mutate
// its term property.
clause = clause.WithTerm(term);
// From the term in the clause we create a token set which will then
// be used to intersect the indexes token set to get a list of terms
// to lookup in the inverted index.
var termTokenSet = TokenSet.FromClause(clause);
IEnumerable <string> expandedTerms = TokenSet.Intersect(termTokenSet).ToEnumeration();
// If a term marked as required does not exist in the tokenSet it is
// impossible for the search to return any matches.We set all the field
// scoped required matches set to empty and stop examining any further
// clauses.
if (!expandedTerms.Any() && clause.Presence == QueryPresence.Required)
{
foreach (string field in clause.Fields)
{
requiredMatches.Add(field, Set <string> .Empty);
}
break;
}
foreach (string expandedTerm in expandedTerms)
{
// For each term get the posting and termIndex, this is required for building the query vector.
InvertedIndexEntry posting = InvertedIndex[expandedTerm];
int termIndex = posting.Index;
foreach (string field in clause.Fields)
{
// For each field that this query term is scoped by (by default
// all fields are in scope) we need to get all the document refs
// that have this term in that field.
//
// The posting is the entry in the invertedIndex for the matching
// term from above.
// For each field that this query term is scoped by (by default
// all fields are in scope) we need to get all the document refs
// that have this term in that field.
//
// The posting is the entry in the invertedIndex for the matching
// term from above.
FieldMatches fieldPosting = posting[field];
ICollection <string> matchingDocumentRefs = fieldPosting.Keys;
string termField = expandedTerm + '/' + field;
var matchingDocumentSet = new Set <string>(matchingDocumentRefs);
// if the presence of this term is required ensure that the matching
// documents are added to the set of required matches for this clause.
if (clause.Presence == QueryPresence.Required)
{
clauseMatches = clauseMatches.Union(matchingDocumentSet);
if (!requiredMatches.ContainsKey(field))
{
requiredMatches.Add(field, Set <string> .Complete);
}
}
// if the presence of this term is prohibited ensure that the matching
// documents are added to the set of prohibited matches for this field,
// creating that set if it does not yet exist.
if (clause.Presence == QueryPresence.Prohibited)
{
if (!prohibitedMatches.ContainsKey(field))
{
prohibitedMatches.Add(field, Set <string> .Empty);
}
prohibitedMatches[field] = prohibitedMatches[field].Union(matchingDocumentSet);
// Prohibited matches should not be part of the query vector used for
// similarity scoring and no metadata should be extracted so we continue
// to the next field.
continue;
}
// The query field vector is populated using the termIndex found for
// the term and a unit value with the appropriate boost applied.
// Using upsert because there could already be an entry in the vector
// for the term we are working with.In that case we just add the scores
// together.
queryVectors[field].Upsert(
termIndex,
clause.Boost,
(a, b) => a + b);
// If we've already seen this term, field combo then we've already collected
// the matching documents and metadata, no need to go through all that again.
if (termFieldCache.Contains(termField))
{
continue;
}
foreach (string matchingDocumentRef in matchingDocumentRefs)
{
// All metadata for this term/field/document triple
// are then extracted and collected into an instance
// of lunr.MatchData ready to be returned in the query
// results.
var matchingFieldRef = new FieldReference(matchingDocumentRef, field);
FieldMatchMetadata metadata = fieldPosting[matchingDocumentRef];
if (!matchingFields.TryGetValue(matchingFieldRef, out MatchData? fieldMatch))
{
matchingFields.Add(
matchingFieldRef,
new MatchData(expandedTerm, field, metadata));
}
else
{
fieldMatch.Add(expandedTerm, field, metadata);
}
}
termFieldCache.Add(termField);
}
}
}
// If the presence was required we need to update the requiredMatches field sets.
// We do this after all fields for the term have collected their matches because
// the clause terms presence is required in _any_ of the fields not _all_ of the
// fields.
if (clause.Presence == QueryPresence.Required)
{
foreach (string field in clause.Fields)
{
requiredMatches[field] = requiredMatches[field].Intersect(clauseMatches);
}
}
}
// Need to combine the field scoped required and prohibited
// matching documents into a global set of required and prohibited
// matches.
ISet <string> allRequiredMatches = Set <string> .Complete;
ISet <string> allProhibitedMatches = Set <string> .Empty;
foreach (string field in Fields)
{
if (requiredMatches.ContainsKey(field))
{
allRequiredMatches = allRequiredMatches.Intersect(requiredMatches[field]);
}
if (prohibitedMatches.ContainsKey(field))
{
allProhibitedMatches = allProhibitedMatches.Union(prohibitedMatches[field]);
}
}
IEnumerable <string> matchingFieldRefs
= matchingFields.Keys.Select(k => k.ToString());
var matches = new Dictionary <string, Result>();
// If the query is negated (contains only prohibited terms)
// we need to get _all_ fieldRefs currently existing in the
// index. This is only done when we know that the query is
// entirely prohibited terms to avoid any cost of getting all
// fieldRefs unnecessarily.
//
// Additionally, blank MatchData must be created to correctly
// populate the results.
if (query.IsNegated)
{
matchingFieldRefs = FieldVectors.Keys;
foreach (string matchingFieldRef in matchingFieldRefs)
{
var fieldRef = FieldReference.FromString(matchingFieldRef);
matchingFields.Add(fieldRef, MatchData.Empty);
}
}
foreach (string fieldRefString in matchingFieldRefs)
{
// Currently we have document fields that match the query, but we
// need to return documents.The matchData and scores are combined
// from multiple fields belonging to the same document.
//
// Scores are calculated by field, using the query vectors created
// above, and combined into a final document score using addition.
var fieldRef = FieldReference.FromString(fieldRefString);
string docRef = fieldRef.DocumentReference;
if (!allRequiredMatches.Contains(docRef))
{
continue;
}
if (allProhibitedMatches.Contains(docRef))
{
continue;
}
Vector fieldVector = FieldVectors[fieldRefString];
double score = queryVectors[fieldRef.FieldName].Similarity(fieldVector);
if (matches.TryGetValue(docRef, out Result? docMatch))
{
docMatch.Score += score;
docMatch.MatchData.Combine(matchingFields[fieldRef]);
}
else
{
var match = new Result(
documentReference: docRef,
score,
matchData: matchingFields[fieldRef]
);
matches.Add(docRef, match);
if (cancellationToken.IsCancellationRequested)
{
yield break;
}
results.Add(match);
}
}
foreach (Result match in results.OrderByDescending(r => r.Score))
{
yield return(match);
}
}
