Field names in FacetsConfig. State manager refreshes ok.

lucene/demo/src/java/org/apache/lucene/demo/facet/SimpleSortedSetFacetsExample.java

@@ -26,10 +26,10 @@ import org.apache.lucene.facet.FacetResult;
 import org.apache.lucene.facet.Facets;
 import org.apache.lucene.facet.FacetsCollector;
 import org.apache.lucene.facet.FacetsConfig;
-import org.apache.lucene.facet.sortedset.DefaultSortedSetDocValuesReaderState;
 import org.apache.lucene.facet.sortedset.SortedSetDocValuesFacetCounts;
 import org.apache.lucene.facet.sortedset.SortedSetDocValuesFacetField;
 import org.apache.lucene.facet.sortedset.SortedSetDocValuesReaderState;
+import org.apache.lucene.facet.sortedset.SsdvReaderStatesManager;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
@@ -88,8 +88,8 @@ public class SimpleSortedSetFacetsExample {
   private List<FacetResult> search() throws IOException {
     DirectoryReader indexReader = DirectoryReader.open(indexDir);
     IndexSearcher searcher = new IndexSearcher(indexReader);
-    SortedSetDocValuesReaderState state =
+    SsdvReaderStatesManager statesManager = new SsdvReaderStatesManager(config);
-        new DefaultSortedSetDocValuesReaderState(indexReader, config);
+    SortedSetDocValuesReaderState state = statesManager.getReaderState(indexReader);
 
     // Aggregatses the facet counts
     FacetsCollector fc = new FacetsCollector();
@@ -114,8 +114,8 @@ public class SimpleSortedSetFacetsExample {
   private FacetResult drillDown() throws IOException {
     DirectoryReader indexReader = DirectoryReader.open(indexDir);
     IndexSearcher searcher = new IndexSearcher(indexReader);
-    SortedSetDocValuesReaderState state =
+    SsdvReaderStatesManager statesManager = new SsdvReaderStatesManager(config);
-        new DefaultSortedSetDocValuesReaderState(indexReader, config);
+    SortedSetDocValuesReaderState state = statesManager.getReaderState(indexReader);
 
     // Now user drills down on Publish Year/2010:
     DrillDownQuery q = new DrillDownQuery(config);

lucene/facet/src/java/org/apache/lucene/facet/FacetsConfig.java

@@ -67,6 +67,9 @@ public class FacetsConfig {
   // int/float/bytes in a single indexed field:
   private final Map<String, String> assocDimTypes = new ConcurrentHashMap<>();
 
+  /** All the fields used for faceting. */
+  private final Set<String> fieldNames = new HashSet<>();
+
   /**
    * Drill down terms indexing option to control whether dimension and sub-path terms should be
    * indexed.
@@ -230,6 +233,14 @@ public class FacetsConfig {
     return fieldTypes;
   }
 
+  /**
+   * Return the names of all fields used for faceting. This is only populated for fields that are
+   * encountered by {@link #build(TaxonomyWriter, Document)}}.
+   */
+  public Set<String> getFieldNames() {
+    return fieldNames;
+  }
+
   private static void checkSeen(Set<String> seenDims, String dim) {
     if (seenDims.contains(dim)) {
       throw new IllegalArgumentException(
@@ -272,6 +283,7 @@ public class FacetsConfig {
       if (field.fieldType() == FacetField.TYPE) {
         FacetField facetField = (FacetField) field;
         FacetsConfig.DimConfig dimConfig = getDimConfig(facetField.dim);
+        fieldNames.add(dimConfig.indexFieldName);
         if (dimConfig.multiValued == false) {
           checkSeen(seenDims, facetField.dim);
         }
@@ -283,6 +295,7 @@ public class FacetsConfig {
       if (field.fieldType() == SortedSetDocValuesFacetField.TYPE) {
         SortedSetDocValuesFacetField facetField = (SortedSetDocValuesFacetField) field;
         FacetsConfig.DimConfig dimConfig = getDimConfig(facetField.dim);
+        fieldNames.add(dimConfig.indexFieldName);
         if (dimConfig.multiValued == false) {
           checkSeen(seenDims, facetField.dim);
         }
@@ -295,6 +308,7 @@ public class FacetsConfig {
       if (field.fieldType() == AssociationFacetField.TYPE) {
         AssociationFacetField facetField = (AssociationFacetField) field;
         FacetsConfig.DimConfig dimConfig = getDimConfig(facetField.dim);
+        fieldNames.add(dimConfig.indexFieldName);
         if (dimConfig.multiValued == false) {
           checkSeen(seenDims, facetField.dim);
         }

lucene/facet/src/java/org/apache/lucene/facet/sortedset/SsdvReaderStatesManager.java

@@ -17,11 +17,12 @@
 package org.apache.lucene.facet.sortedset;
 
 import java.io.IOException;
-import java.io.UncheckedIOException;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import org.apache.lucene.facet.FacetsConfig;
-import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.index.IndexReader;
 
 /**
  * This class demonstrates how Lucene could help a user build SSDV ordinal maps eagerly, on refresh.
@@ -29,48 +30,60 @@ import org.apache.lucene.search.IndexSearcher;
  *
  * <p>1. A centralized store of SSDV reader states.
  *
- * <p>2. A method to rebuild all reader states the user needs.
+ * <p>2. A mechanism to rebuild all reader states the user needs.
  */
 public class SsdvReaderStatesManager {
-  /**
+  /** Use the {@link FacetsConfig} to find out which fields are used for faceting. */
-   * The only attribute is a mapping of SSDV fields to reader states. Each reader state will be a
+  FacetsConfig facetsConfig;
-   * {@link DefaultSortedSetDocValuesReaderState} with an ordinal map for one of the fields.
-   */
-  private Map<String, SortedSetDocValuesReaderState> fieldToReaderState;
-
-  /** No arguments in the constructor. */
-  SsdvReaderStatesManager() {}
 
   /**
-   * The application code would have a set of fields the user wants to facet on. They pass this set
+   * The values in this map are mappings of fields to reader states. Each reader state will be a
-   * here once, on application start-up.
+   * {@link DefaultSortedSetDocValuesReaderState} with an ordinal map for the field. These mappings
+   * are keyed by {@link IndexReader} to account for multiple active index readers during refresh.
    */
-  public void registerFields(Set<String> fields) {
+  private final Map<IndexReader, Map<String, SortedSetDocValuesReaderState>> readerStates =
-    fields.forEach(field -> fieldToReaderState.put(field, null));
+      new HashMap<>();
+
+  /** Accept a {@link FacetsConfig}. */
+  public SsdvReaderStatesManager(FacetsConfig facetsConfig) {
+    this.facetsConfig = facetsConfig;
   }
 
   /**
-   * Here we create corresponding reader states for all the fields. Each time the user does a
+   * Retrieve and, if necessary, create reader states for all the fields in the {@link
-   * refresh, they would also call this method, which ensures they will be using up-to-date ordinal
+   * FacetsConfig}.
-   * maps until the next refresh.
    */
-  public void loadReaderStates(IndexSearcher searcher, FacetsConfig facetsConfig) {
+  public Set<SortedSetDocValuesReaderState> getReaderStates(IndexReader indexReader)
-    fieldToReaderState.replaceAll(
+      throws IOException {
-        (field, readerState) -> {
+    Set<SortedSetDocValuesReaderState> states = new HashSet<>();
-          try {
+    for (String field : facetsConfig.getFieldNames()) {
-            return new DefaultSortedSetDocValuesReaderState(
+      states.add(getReaderState(indexReader, field));
-                searcher.getIndexReader(), field, facetsConfig);
-          } catch (IOException e) {
-            throw new UncheckedIOException(e);
     }
-        });
+    return states;
+  }
+
+  /** Retrieve and, if necessary, create the reader state for the default field. */
+  public SortedSetDocValuesReaderState getReaderState(IndexReader indexReader) throws IOException {
+    return getReaderState(indexReader, FacetsConfig.DEFAULT_INDEX_FIELD_NAME);
   }
 
   /**
-   * When the user wants to facet on a field, they call getReaderState on that field and pass the
+   * Retrieve and, if necessary, create the reader state for a named field. Store the reader state
-   * resulting reader state to the {@link SortedSetDocValuesFacetCounts} constructor.
+   * for re-use.
    */
-  public SortedSetDocValuesReaderState getReaderState(String field) {
+  public SortedSetDocValuesReaderState getReaderState(IndexReader indexReader, String field)
-    return fieldToReaderState.get(field);
+      throws IOException {
+    Map<String, SortedSetDocValuesReaderState> states = readerStates.get(indexReader);
+    if (states == null) {
+      states = new HashMap<>();
+      readerStates.put(indexReader, states);
+    }
+
+    SortedSetDocValuesReaderState state = states.get(field);
+    if (state == null) {
+      state = new DefaultSortedSetDocValuesReaderState(indexReader, field, facetsConfig);
+      states.put(field, state);
+    }
+    return state;
   }
 }

lucene/facet/src/test/org/apache/lucene/facet/TestFacetsConfig.java

@@ -16,8 +16,11 @@
  */
 package org.apache.lucene.facet;
 
+import java.io.IOException;
 import java.util.Arrays;
+import java.util.Set;
 import org.apache.lucene.document.Document;
+import org.apache.lucene.facet.sortedset.SortedSetDocValuesFacetField;
 import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyReader;
 import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyWriter;
 import org.apache.lucene.index.DirectoryReader;
@@ -115,4 +118,21 @@ public class TestFacetsConfig extends FacetTestCase {
 
     assertTrue(config.getDimConfig("foobar").hierarchical);
   }
+
+  public void testGetFieldNames() throws IOException {
+    FacetsConfig config = new FacetsConfig();
+    config.setIndexFieldName("a", "not-$facets");
+    Document doc;
+
+    doc = new Document();
+    doc.add(new SortedSetDocValuesFacetField("a", "1"));
+    config.build(doc);
+    assertEquals(Set.of("not-$facets"), config.getFieldNames());
+
+    doc = new Document();
+    doc.add(new SortedSetDocValuesFacetField("b", "1"));
+    config.build(doc);
+    assertEquals(
+        Set.of("not-$facets", FacetsConfig.DEFAULT_INDEX_FIELD_NAME), config.getFieldNames());
+  }
 }