related: Add config option cardinalityThreshold

Fixes #10744

diff --git a/docs/content/en/content-management/related.md b/docs/content/en/content-management/related.md
index 98af0a36f8c857b730c1f5751784ee191f11160b..c25b0ed616fa7b3f63104f3ead4232299a04314e 100644 (file)
--- a/docs/content/en/content-management/related.md
+++ b/docs/content/en/content-management/related.md
@@ -160,6 +160,10 @@ applyFilter
 weight
 : An integer weight that indicates _how important_ this parameter is relative to the other parameters.  It can be 0, which has the effect of turning this index off, or even negative. Test with different values to see what fits your content best.
 
+
+cardinalityThreshold (default 0)
+: {{< new-in "0.111.0" >}}. A percentage (0-100) used to remove common keywords from the index. As an example, setting this to 50 will remove all keywords that are used in more than 50% of the documents in the index.
+
 pattern
 : This is currently only relevant for dates. When listing related content, we may want to list content that is also close in time. Setting "2006" (default value for date indexes) as the pattern for a date index will add weight to pages published in the same year. For busier blogs, "200601" (year and month) may be a better default.
 

diff --git a/related/inverted_index.go b/related/inverted_index.go
index eab97098ae01c895351700df3a25e5c3a81572b1..967855133dc8eb50cc8207f73443a53238f1fc87 100644 (file)
--- a/related/inverted_index.go
+++ b/related/inverted_index.go
@@ -135,9 +135,21 @@ type IndexConfig struct {
        // This field's weight when doing multi-index searches. Higher is "better".
        Weight int
 
+       // A percentage (0-100) used to remove common keywords from the index.
+       // As an example, setting this to 50 will remove all keywords that are
+       // used in more than 50% of the documents in the index.
+       CardinalityThreshold int
+
        // Will lower case all string values in and queries tothis index.
        // May get better accurate results, but at a slight performance cost.
        ToLower bool
+
+       // Counts the number of documents in the index.
+       numDocs int
+}
+
+func (cfg *IndexConfig) incrNumDocs() {
+       cfg.numDocs++
 }
 
 // Document is the interface an indexable document in Hugo must fulfill.
@@ -169,6 +181,9 @@ type InvertedIndex struct {
 
        minWeight int
        maxWeight int
+
+       // No modifications after this is set.
+       finalized bool
 }
 
 func (idx *InvertedIndex) getIndexCfg(name string) (IndexConfig, bool) {
@@ -202,8 +217,11 @@ func NewInvertedIndex(cfg Config) *InvertedIndex {
 // Add documents to the inverted index.
 // The value must support == and !=.
 func (idx *InvertedIndex) Add(ctx context.Context, docs ...Document) error {
+       if idx.finalized {
+               panic("index is finalized")
+       }
        var err error
-       for _, config := range idx.cfg.Indices {
+       for i, config := range idx.cfg.Indices {
                if config.Weight == 0 {
                        // Disabled
                        continue
@@ -211,6 +229,7 @@ func (idx *InvertedIndex) Add(ctx context.Context, docs ...Document) error {
                setm := idx.index[config.Name]
 
                for _, doc := range docs {
+                       var added bool
                        var words []Keyword
                        words, err = doc.RelatedKeywords(config)
                        if err != nil {
@@ -218,22 +237,60 @@ func (idx *InvertedIndex) Add(ctx context.Context, docs ...Document) error {
                        }
 
                        for _, keyword := range words {
+                               added = true
                                setm[keyword] = append(setm[keyword], doc)
                        }
 
                        if config.Type == TypeFragments {
                                if fp, ok := doc.(FragmentProvider); ok {
                                        for _, fragment := range fp.Fragments(ctx).Identifiers {
+                                               added = true
                                                setm[FragmentKeyword(fragment)] = append(setm[FragmentKeyword(fragment)], doc)
                                        }
                                }
                        }
+
+                       if added {
+                               c := &idx.cfg.Indices[i]
+                               (*c).incrNumDocs()
+                       }
                }
        }
 
        return err
 }
 
+func (idx *InvertedIndex) Finalize(ctx context.Context) error {
+       if idx.finalized {
+               return nil
+       }
+
+       for _, config := range idx.cfg.Indices {
+               if config.CardinalityThreshold == 0 {
+                       continue
+               }
+               setm := idx.index[config.Name]
+               numDocs := config.numDocs
+               if numDocs == 0 {
+                       continue
+               }
+
+               // Remove high cardinality terms.
+               for k, v := range setm {
+                       percentageWithKeyword := int(math.Ceil(float64(len(v)) / float64(numDocs) * 100))
+                       if percentageWithKeyword > config.CardinalityThreshold {
+                               delete(setm, k)
+                       }
+               }
+
+       }
+
+       idx.finalized = true
+
+       return nil
+
+}
+
 // queryElement holds the index name and keywords that can be used to compose a
 // search for related content.
 type queryElement struct {
@@ -548,12 +605,16 @@ func DecodeConfig(m maps.Params) (Config, error) {
                }
        }
        for i := range c.Indices {
-               if c.Indices[i].Type == "" {
+               icfg := c.Indices[i]
+               if icfg.Type == "" {
                        c.Indices[i].Type = TypeBasic
                }
                if !validTypes[c.Indices[i].Type] {
                        return c, fmt.Errorf("invalid index type %q. Must be one of %v", c.Indices[i].Type, xmaps.Keys(validTypes))
                }
+               if icfg.CardinalityThreshold < 0 || icfg.CardinalityThreshold > 100 {
+                       return Config{}, errors.New("cardinalityThreshold threshold must be between 0 and 100")
+               }
        }
 
        return c, nil

diff --git a/related/inverted_index_test.go b/related/inverted_index_test.go
index d38a7f6eb183efc0daa75b6bad86201fc0c86dc0..c7348e0889897dfeb5469d39847b16c99371c663 100644 (file)
--- a/related/inverted_index_test.go
+++ b/related/inverted_index_test.go
@@ -86,6 +86,41 @@ func (d *testDoc) PublishDate() time.Time {
        return d.date
 }
 
+func TestCardinalityThreshold(t *testing.T) {
+       c := qt.New(t)
+       config := Config{
+               Threshold:    90,
+               IncludeNewer: false,
+               Indices: IndexConfigs{
+                       IndexConfig{Name: "tags", Weight: 50, CardinalityThreshold: 79},
+                       IndexConfig{Name: "keywords", Weight: 65, CardinalityThreshold: 90},
+               },
+       }
+
+       idx := NewInvertedIndex(config)
+       hasKeyword := func(index, keyword string) bool {
+               _, found := idx.index[index][StringKeyword(keyword)]
+               return found
+       }
+
+       docs := []Document{
+               newTestDoc("tags", "a", "b", "c", "d"),
+               newTestDoc("tags", "b", "d", "g"),
+               newTestDoc("tags", "b", "d", "g"),
+               newTestDoc("tags", "b", "h").addKeywords("keywords", "a"),
+               newTestDoc("tags", "g", "h").addKeywords("keywords", "a", "b", "z"),
+       }
+
+       idx.Add(context.Background(), docs...)
+       c.Assert(idx.Finalize(context.Background()), qt.IsNil)
+       // Only tags=b should be removed.
+       c.Assert(hasKeyword("tags", "a"), qt.Equals, true)
+       c.Assert(hasKeyword("tags", "b"), qt.Equals, false)
+       c.Assert(hasKeyword("tags", "d"), qt.Equals, true)
+       c.Assert(hasKeyword("keywords", "b"), qt.Equals, true)
+
+}
+
 func TestSearch(t *testing.T) {
        config := Config{
                Threshold:    90,

diff --git a/resources/page/pages_related.go b/resources/page/pages_related.go
index 327369603c205236d8014ff0acd52dbbdb0e7a4b..217aced47796ac2645c4dd3e58c8f834a289035d 100644 (file)
--- a/resources/page/pages_related.go
+++ b/resources/page/pages_related.go
@@ -236,5 +236,9 @@ func (s *RelatedDocsHandler) getOrCreateIndex(ctx context.Context, p Pages) (*re
 
        s.postingLists = append(s.postingLists, &cachedPostingList{p: p, postingList: searchIndex})
 
+       if err := searchIndex.Finalize(ctx); err != nil {
+               return nil, err
+       }
+
        return searchIndex, nil
 }