Control the auto-adjustment of targetHits in ANN using post-filtering.

When searching the HNSW index in a post-filtering case,
targetHits is auto-adjusted in an effort to still expose targetHits hits to first-phase ranking after post-filtering.
The following formula is now used to ensure an upper bound of adjustedTargetHits,
avoiding that the search in the HNSW index takes too long.

adjustedTargetHits = min(targetHits / estimatedHitRatio, targetHits * targetHitsMaxAdjustmentFactor).

The target-hits-max-adjustment-factor can be set in a rank profile and overriden per query.
The value is in the range [1.0,inf], with the default being 20.0.

When setting this to 1.0, auto-adjustment of targetHits is effectively disabled.

1 files changed, 1 insertions, 0 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/query/properties/QueryProperties.java b/container-search/src/main/java/com/yahoo/search/query/properties/QueryProperties.java
index 800b3a1ba89..99d6959441a 100644
--- a/container-search/src/main/java/com/yahoo/search/query/properties/QueryProperties.java
+++ b/container-search/src/main/java/com/yahoo/search/query/properties/QueryProperties.java
@@ -91,6 +91,7 @@ public class QueryProperties extends Properties {
         addDualCasedRM(map, Matching.MINHITSPERTHREAD, GetterSetter.of(query -> query.getRanking().getMatching().getMinHitsPerThread(), (query, value) -> query.getRanking().getMatching().setMinHitsPerThread(asInteger(value, 0))));
         addDualCasedRM(map, Matching.POST_FILTER_THRESHOLD, GetterSetter.of(query -> query.getRanking().getMatching().getPostFilterThreshold(), (query, value) -> query.getRanking().getMatching().setPostFilterThreshold(asDouble(value, 1.0))));
         addDualCasedRM(map, Matching.APPROXIMATE_THRESHOLD, GetterSetter.of(query -> query.getRanking().getMatching().getApproximateThreshold(), (query, value) -> query.getRanking().getMatching().setApproximateThreshold(asDouble(value, 0.05))));
+        addDualCasedRM(map, Matching.TARGET_HITS_MAX_ADJUSTMENT_FACTOR, GetterSetter.of(query -> query.getRanking().getMatching().getTargetHitsMaxAdjustmentFactor(), (query, value) -> query.getRanking().getMatching().setTargetHitsMaxAdjustmentFactor(asDouble(value, 20.0))));
 
         map.put(CompoundName.fromComponents(Ranking.RANKING, Ranking.MATCH_PHASE, MatchPhase.ATTRIBUTE), GetterSetter.of(query -> query.getRanking().getMatchPhase().getAttribute(), (query, value) -> query.getRanking().getMatchPhase().setAttribute(asString(value, null))));
         map.put(CompoundName.fromComponents(Ranking.RANKING, Ranking.MATCH_PHASE, MatchPhase.ASCENDING), GetterSetter.of(query -> query.getRanking().getMatchPhase().getAscending(), (query, value) -> query.getRanking().getMatchPhase().setAscending(asBoolean(value, false))));