gsmiller commented on code in PR #12089:
URL: https://github.com/apache/lucene/pull/12089#discussion_r1097623311
##########
lucene/core/src/java/org/apache/lucene/search/TermInSetQuery.java:
##########
@@ -258,13 +271,41 @@ public Matches matches(LeafReaderContext context, int
doc) throws IOException {
* On the given leaf context, try to either rewrite to a disjunction if
there are few matching
* terms, or build a bitset containing matching docs.
*/
- private WeightOrDocIdSet rewrite(LeafReaderContext context) throws
IOException {
+ private WeightOrDocIdSet rewrite(
+ LeafReaderContext context, long leadCost, boolean isPrimaryKeyField,
DocValuesType dvType)
+ throws IOException {
final LeafReader reader = context.reader();
Terms terms = reader.terms(field);
if (terms == null) {
return null;
}
+
+ long costThreshold = Long.MAX_VALUE;
+ if (dvType == DocValuesType.SORTED || dvType ==
DocValuesType.SORTED_SET) {
+ // Establish a threshold for switching to doc values. Give postings
a significant
+ // advantage for the primary-key case, since many of the primary-key
terms may not
+ // actually be in this segment. The 8x factor is arbitrary, based on
IndexOrDVQuery,
+ // but has performed well in benchmarks:
+ costThreshold = isPrimaryKeyField ? leadCost << 3 : leadCost;
+
+ if (termData.size() > costThreshold) {
+ // If the number of terms is > the number of candidates, DV should
perform better.
Review Comment:
I'm not sure actually. The up-front term-seeking you refer to is certainly a
cost, but it doesn't scale with the number of lead hits. So this can still be
cheaper. But also, +1 to the idea of trying out on-demand term seeking for
these situations!
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