Add syntax for filter-threshold for a rank profile.

A number between 0 and 1 that specifies the threshold value
for when a query term is considered a filter in backend matching,
and cheaper bitvector posting lists can be used.
Is triggered when the hit estimate of the query term is larger than the threshold value.

Note: This functionality is not yet wired in the backend,
so only the schema syntax is available for now.

config-model/src/main/java/com/yahoo/schema/RankProfile.java

@@ -106,6 +106,7 @@ public class RankProfile implements Cloneable {
     private Double targetHitsMaxAdjustmentFactor = null;
     private Double weakandStopwordLimit = null;
     private Double weakandAdjustTarget = null;
+    private Double filterThreshold = null;
 
     /** The drop limit used to drop hits with rank score less than or equal to this value */
     private double rankScoreDropLimit = -Double.MAX_VALUE;
@@ -784,6 +785,7 @@ public int getNumSearchPartitions() {
     public void setTargetHitsMaxAdjustmentFactor(double factor) { this.targetHitsMaxAdjustmentFactor = factor; }
     public void setWeakandStopwordLimit(double limit) { this.weakandStopwordLimit = limit; }
     public void setWeakandAdjustTarget(double target) { this.weakandAdjustTarget = target; }
+    public void setFilterThreshold(double threshold) { this.filterThreshold = threshold; }
 
     public OptionalDouble getTermwiseLimit() {
         if (termwiseLimit != null) return OptionalDouble.of(termwiseLimit);
@@ -826,6 +828,13 @@ public OptionalDouble getWeakandAdjustTarget() {
         return uniquelyInherited(RankProfile::getWeakandAdjustTarget, OptionalDouble::isPresent, "weakand-adjust-target").orElse(OptionalDouble.empty());
     }
 
+    public OptionalDouble getFilterThreshold() {
+        if (filterThreshold != null) {
+            return OptionalDouble.of(filterThreshold);
+        }
+        return uniquelyInherited(RankProfile::getFilterThreshold, OptionalDouble::isPresent, "filter-threshold").orElse(OptionalDouble.empty());
+    }
+
     /** Whether we should ignore the default rank features. Set to null to use inherited */
     public void setIgnoreDefaultRankFeatures(Boolean ignoreDefaultRankFeatures) {
         this.ignoreDefaultRankFeatures = ignoreDefaultRankFeatures;

config-model/src/main/java/com/yahoo/schema/derived/RawRankProfile.java

@@ -171,6 +171,7 @@ private static class Deriver {
         private final OptionalDouble targetHitsMaxAdjustmentFactor;
         private final OptionalDouble weakandStopwordLimit;
         private final OptionalDouble weakandAdjustTarget;
+        private final OptionalDouble filterThreshold;
         private final double rankScoreDropLimit;
         private final double secondPhaseRankScoreDropLimit;
         private final boolean sortBlueprintsByCost;
@@ -224,6 +225,7 @@ private static class Deriver {
             targetHitsMaxAdjustmentFactor = compiled.getTargetHitsMaxAdjustmentFactor();
             weakandStopwordLimit = compiled.getWeakandStopwordLimit();
             weakandAdjustTarget = compiled.getWeakandAdjustTarget();
+            filterThreshold = compiled.getFilterThreshold();
             keepRankCount = compiled.getKeepRankCount();
             rankScoreDropLimit = compiled.getRankScoreDropLimit();
             secondPhaseRankScoreDropLimit = compiled.getSecondPhaseRankScoreDropLimit();
@@ -493,6 +495,9 @@ else if (RankingExpression.propertyName(RankProfile.GLOBAL_PHASE).equals(propert
             if (weakandAdjustTarget.isPresent()) {
                 properties.add(new Pair<>("vespa.matching.weakand.stop_word_adjust_limit", String.valueOf(weakandAdjustTarget.getAsDouble())));
             }
+            if (filterThreshold.isPresent()) {
+                properties.add(new Pair<>("vespa.matching.filter_threshold", String.valueOf(filterThreshold.getAsDouble())));
+            }
             if (matchPhaseSettings != null) {
                 properties.add(new Pair<>("vespa.matchphase.degradation.attribute", matchPhaseSettings.getAttribute()));
                 properties.add(new Pair<>("vespa.matchphase.degradation.ascendingorder", matchPhaseSettings.getAscending() + ""));

config-model/src/main/java/com/yahoo/schema/parser/ParsedRankProfile.java

@@ -50,6 +50,7 @@ public class ParsedRankProfile extends ParsedBlock {
     private Boolean useSignificanceModel = null;
     private Double weakandStopwordLimit = null;
     private Double weakandAdjustTarget = null;
+    private Double filterThreshold = null;
     private final List<MutateOperation> mutateOperations = new ArrayList<>();
     private final List<String> inherited = new ArrayList<>();
     private final Map<String, Boolean> fieldsRankFilter = new LinkedHashMap<>();
@@ -108,6 +109,7 @@ public ParsedRankProfile(String name) {
 
     Optional<Double> getWeakandStopwordLimit() { return Optional.ofNullable(this.weakandStopwordLimit); }
     Optional<Double> getWeakandAdjustTarget() { return Optional.ofNullable(this.weakandAdjustTarget); }
+    Optional<Double> getFilterThreshold() { return Optional.ofNullable(this.filterThreshold); }
 
     public void addSummaryFeatures(FeatureList features) { this.summaryFeatures.add(features); }
     public void addMatchFeatures(FeatureList features) { this.matchFeatures.add(features); }
@@ -255,6 +257,11 @@ public void setWeakandAdjustTarget(double target) {
         this.weakandAdjustTarget = target;
     }
 
+    public void setFilterThreshold(double threshold) {
+        verifyThat(this.filterThreshold == null, "already has filter-threshold");
+        this.filterThreshold = threshold;
+    }
+
     public void setTermwiseLimit(double limit) {
         verifyThat(termwiseLimit == null, "already has termwise-limit");
         this.termwiseLimit = limit;

config-model/src/main/java/com/yahoo/schema/parser/ParsedRankingConverter.java

@@ -66,6 +66,7 @@ private void populateFrom(ParsedRankProfile parsed, RankProfile profile) {
         parsed.getTargetHitsMaxAdjustmentFactor().ifPresent(profile::setTargetHitsMaxAdjustmentFactor);
         parsed.getWeakandStopwordLimit().ifPresent(profile::setWeakandStopwordLimit);
         parsed.getWeakandAdjustTarget().ifPresent(profile::setWeakandAdjustTarget);
+        parsed.getFilterThreshold().ifPresent(profile::setFilterThreshold);
         parsed.getKeepRankCount().ifPresent(profile::setKeepRankCount);
         parsed.getMinHitsPerThread().ifPresent(profile::setMinHitsPerThread);
         parsed.getNumSearchPartitions().ifPresent(profile::setNumSearchPartitions);

config-model/src/main/javacc/SchemaParser.jj

@@ -193,6 +193,7 @@ TOKEN :
 | < WEAKAND: "weakand">
 | < STOPWORD_LIMIT: "stopword-limit">
 | < ADJUST_TARGET: "adjust-target">
+| < FILTER_THRESHOLD: "filter-threshold">
 | < INTRAOP_THREADS: "intraop-threads">
 | < INTEROP_THREADS: "interop-threads">
 | < GPU_DEVICE: "gpu-device">
@@ -1780,7 +1781,8 @@ void rankProfileItem(ParsedSchema schema, ParsedRankProfile profile) : { }
       | onnxModelInProfile(profile)
       | strict(profile)
       | significance(profile)
-      | weakand(profile))
+      | weakand(profile)
+      | filterThreshold(profile))
 }
 
 /**
@@ -2194,6 +2196,14 @@ void weakandAdjustTarget(ParsedRankProfile profile) :
     (<ADJUST_TARGET> <COLON> target = floatValue()) { profile.setWeakandAdjustTarget(target); }
 }
 
+void filterThreshold(ParsedRankProfile profile) :
+{
+    double threshold;
+}
+{
+    (<FILTER_THRESHOLD> <COLON> threshold = floatValue()) { profile.setFilterThreshold(threshold); }
+}
+
 /**
  * Consumes a match-features block of a rank profile.
  *
@@ -2745,6 +2755,7 @@ String identifierWithDash() :
     | <FAST_ACCESS>
     | <FAST_RANK>
     | <FAST_SEARCH>
+    | <FILTER_THRESHOLD>
     | <FIRST_PHASE>
     | <FROM_DISK>
     | <GLOBAL_PHASE>

config-model/src/test/java/com/yahoo/schema/RankProfileTestCase.java

@@ -570,6 +570,18 @@ private void verifyWeakandAdjustTarget(Double adjustTarget) throws ParseExceptio
                                  adjustTarget, "vespa.matching.weakand.stop_word_adjust_limit");
     }
 
+    @Test
+    void filter_threshold_is_configurable() throws ParseException {
+        verifyFilterThreshold(null);
+        verifyFilterThreshold(0.05);
+    }
+
+    private void verifyFilterThreshold(Double threshold) throws ParseException {
+        var rp = createRankProfile(createSDWithRankProfile(null, null, null, null, null, threshold));
+        verifyRankProfileSetting(rp.getFirst(), rp.getSecond(), RankProfile::getFilterThreshold,
+                threshold, "vespa.matching.filter_threshold");
+    }
+
     private void verifyRankProfileSetting(RankProfile rankProfile, RawRankProfile rawRankProfile, Function<RankProfile, OptionalDouble> func,
                                           Double expValue, String expPropertyName) {
         if (expValue != null) {
@@ -584,12 +596,12 @@ private void verifyRankProfileSetting(RankProfile rankProfile, RawRankProfile ra
     private Pair<RankProfile, RawRankProfile> createRankProfile(Double postFilterThreshold,
                                                                 Double approximateThreshold,
                                                                 Double targetHitsMaxAdjustmentFactor) throws ParseException {
-        return createRankProfile(createSDWithRankProfile(postFilterThreshold, approximateThreshold, targetHitsMaxAdjustmentFactor, null, null));
+        return createRankProfile(createSDWithRankProfile(postFilterThreshold, approximateThreshold, targetHitsMaxAdjustmentFactor, null, null, null));
     }
 
     private Pair<RankProfile, RawRankProfile> createWeakandRankProfile(Double weakAndStopwordLimit,
                                                                        Double weakAndAdjustTarget) throws ParseException {
-        return createRankProfile(createSDWithRankProfile(null, null, null,  weakAndStopwordLimit, weakAndAdjustTarget));
+        return createRankProfile(createSDWithRankProfile(null, null, null,  weakAndStopwordLimit, weakAndAdjustTarget, null));
     }
 
     private Pair<RankProfile, RawRankProfile> createRankProfile(String schemaContent) throws ParseException {
@@ -611,7 +623,8 @@ private String createSDWithRankProfile(Double postFilterThreshold,
                                            Double approximateThreshold,
                                            Double targetHitsMaxAdjustmentFactor,
                                            Double weakandStopwordLimit,
-                                           Double weakandAdjustTarget) {
+                                           Double weakandAdjustTarget,
+                                           Double filterThreshold) {
         return joinLines(
                 "search test {",
                 "    document test {}",
@@ -621,6 +634,7 @@ private String createSDWithRankProfile(Double postFilterThreshold,
                 (targetHitsMaxAdjustmentFactor != null ? ("        target-hits-max-adjustment-factor: " + targetHitsMaxAdjustmentFactor) : ""),
                 (weakandStopwordLimit != null ?          ("        weakand { stopword-limit: " + weakandStopwordLimit + "}") : ""),
                 (weakandAdjustTarget != null ?           ("        weakand { adjust-target: " + weakandAdjustTarget + "}") : ""),
+                (filterThreshold != null ?               ("        filter-threshold: " + filterThreshold) : ""),
                 "    }",
                 "}");
     }

config-model/src/test/java/com/yahoo/schema/parser/SchemaParserTestCase.java

@@ -183,6 +183,20 @@ void weakand_adjust_target_can_be_parsed() throws Exception {
         assertEquals(0.01, target.get());
     }
 
+
+    @Test
+    void filter_threshold_can_be_parsed() throws Exception {
+        String input = joinLines("schema foo {",
+                "rank-profile rp {",
+                "filter-threshold: 0.05",
+                "}",
+                "}");
+        var schema = parseString(input);
+        var target = schema.getRankProfiles().get(0).getFilterThreshold();
+        assertTrue(target.isPresent());
+        assertEquals(0.05, target.get());
+    }
+
     @Test
     void maxOccurrencesCanBeParsed() throws Exception {
         String input = joinLines

integration/schema-language-server/language-server/src/main/ccc/SchemaParser.ccc

@@ -383,6 +383,7 @@ TOKEN :
 | < WEAKAND: "weakand">
 | < STOPWORD_LIMIT: "stopword-limit">
 | < ADJUST_TARGET: "adjust-target">
+| < FILTER_THRESHOLD: "filter-threshold">
 | < INTRAOP_THREADS: "intraop-threads">
 | < INTEROP_THREADS: "interop-threads">
 | < GPU_DEVICE: "gpu-device">
@@ -2076,6 +2077,7 @@ void rankProfileItem(ParsedSchema schema, ParsedRankProfile profile) : { }
        | strictElm(profile)
        | significanceElm(profile)
        | weakandElm(profile)
+       | filterThreshold(profile)
     )
 ;
 
@@ -2512,6 +2514,14 @@ void weakandAdjustTarget(ParsedRankProfile profile) :
     (<ADJUST_TARGET> <COLON> target = floatValue()) { profile.setWeakandAdjustTarget(target); }
 ;
 
+void filterThreshold(ParsedRankProfile profile) :
+{
+    double threshold;
+}
+
+    (<FILTER_THRESHOLD> <COLON> threshold = floatValue()) { profile.setFilterThreshold(threshold); }
+;
+
 /**
  * Consumes a match-features block of a rank profile.
  *
@@ -3079,6 +3089,7 @@ String identifierWithDashStr :
     | <FAST_ACCESS>
     | <FAST_RANK>
     | <FAST_SEARCH>
+    | <FILTER_THRESHOLD>
     | <FIRST_PHASE>
     | <FROM_DISK>
     | <GLOBAL_PHASE>