Remove use_field_mapping format option for docvalue fields. (#55622)

In 7.0, we began formatting `docvalue_fields` by default using each field's
mapping definition. To ease the transition from 6.x, we added the format
option `use_field_mapping`. This parameter was deprecated in 7.0, and we can
remove it in 8.0.

docs/reference/migration/migrate_8_0/search.asciidoc

@@ -63,3 +63,10 @@ deprecated in 7.6, and are now removed in 8.x. The form
 The `indices_boost` option in the search request used to accept the boosts
 both as an object and as an array. The object format has been deprecated since
 5.2 and is now removed in 8.0.
+
+[float]
+==== Removal of `use_field_mapping` for docvalues fields
+In 7.0, we began formatting `docvalue_fields` by default using each field's
+mapping definition. To ease the transition from 6.x, we added the format
+option `use_field_mapping`. This parameter was deprecated in 7.0, and is now
+removed in 8.0.

server/src/main/java/org/elasticsearch/search/fetch/subphase/FetchDocValuesPhase.java

@@ -18,16 +18,14 @@
  */
 package org.elasticsearch.search.fetch.subphase;
 
-import org.apache.logging.log4j.LogManager;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.ReaderUtil;
 import org.apache.lucene.index.SortedNumericDocValues;
 import org.elasticsearch.common.document.DocumentField;
-import org.elasticsearch.common.logging.DeprecationLogger;
-import org.elasticsearch.index.fielddata.LeafFieldData;
-import org.elasticsearch.index.fielddata.LeafNumericFieldData;
 import org.elasticsearch.index.fielddata.IndexFieldData;
 import org.elasticsearch.index.fielddata.IndexNumericFieldData;
+import org.elasticsearch.index.fielddata.LeafFieldData;
+import org.elasticsearch.index.fielddata.LeafNumericFieldData;
 import org.elasticsearch.index.fielddata.SortedBinaryDocValues;
 import org.elasticsearch.index.fielddata.SortedNumericDoubleValues;
 import org.elasticsearch.index.fielddata.plain.SortedNumericDVIndexFieldData;
@@ -45,7 +43,6 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
-import java.util.Objects;
 
 import static org.elasticsearch.index.fielddata.IndexNumericFieldData.NumericType;
 import static org.elasticsearch.search.DocValueFormat.withNanosecondResolution;
@@ -57,10 +54,6 @@ import static org.elasticsearch.search.DocValueFormat.withNanosecondResolution;
  */
 public final class FetchDocValuesPhase implements FetchSubPhase {
 
-    private static final String USE_DEFAULT_FORMAT = "use_field_mapping";
-    private static final DeprecationLogger DEPRECATION_LOGGER = new DeprecationLogger(
-            LogManager.getLogger(FetchDocValuesPhase.class));
-
     @Override
     public void hitsExecute(SearchContext context, SearchHit[] hits) throws IOException {
 
@@ -82,16 +75,6 @@ public final class FetchDocValuesPhase implements FetchSubPhase {
         hits = hits.clone(); // don't modify the incoming hits
         Arrays.sort(hits, Comparator.comparingInt(SearchHit::docId));
 
-        if (context.docValuesContext().fields().stream()
-                .map(f -> f.format)
-                .filter(USE_DEFAULT_FORMAT::equals)
-                .findAny()
-                .isPresent()) {
-            DEPRECATION_LOGGER.deprecatedAndMaybeLog("explicit_default_format",
-                    "[" + USE_DEFAULT_FORMAT + "] is a special format that was only used to " +
-                    "ease the transition to 7.x. It has become the default and shouldn't be set explicitly anymore.");
-        }
-
         for (FieldAndFormat fieldAndFormat : context.docValuesContext().fields()) {
             String field = fieldAndFormat.field;
             MappedFieldType fieldType = context.mapperService().fieldType(field);
@@ -105,10 +88,6 @@ public final class FetchDocValuesPhase implements FetchSubPhase {
                 }
                 final DocValueFormat format;
                 String formatDesc = fieldAndFormat.format;
-                if (Objects.equals(formatDesc, USE_DEFAULT_FORMAT)) {
-                    // TODO: Remove in 8.x
-                    formatDesc = null;
-                }
                 if (isNanosecond) {
                     format = withNanosecondResolution(fieldType.docValueFormat(formatDesc, null));
                 } else {

server/src/test/java/org/elasticsearch/search/fields/SearchFieldsIT.java

@@ -889,42 +889,6 @@ public class SearchFieldsIT extends ESIntegTestCase {
         assertThat(searchResponse.getHits().getAt(0).getFields().get("binary_field").getValue(), equalTo("KmQ"));
         assertThat(searchResponse.getHits().getAt(0).getFields().get("ip_field").getValue(), equalTo("::1"));
 
-        builder = client().prepareSearch().setQuery(matchAllQuery())
-                .addDocValueField("text_field", "use_field_mapping")
-                .addDocValueField("keyword_field", "use_field_mapping")
-                .addDocValueField("byte_field", "use_field_mapping")
-                .addDocValueField("short_field", "use_field_mapping")
-                .addDocValueField("integer_field", "use_field_mapping")
-                .addDocValueField("long_field", "use_field_mapping")
-                .addDocValueField("float_field", "use_field_mapping")
-                .addDocValueField("double_field", "use_field_mapping")
-                .addDocValueField("date_field", "use_field_mapping")
-                .addDocValueField("boolean_field", "use_field_mapping")
-                .addDocValueField("binary_field", "use_field_mapping")
-                .addDocValueField("ip_field", "use_field_mapping");
-        searchResponse = builder.get();
-
-        assertThat(searchResponse.getHits().getTotalHits().value, equalTo(1L));
-        assertThat(searchResponse.getHits().getHits().length, equalTo(1));
-        fields = new HashSet<>(searchResponse.getHits().getAt(0).getFields().keySet());
-        assertThat(fields, equalTo(newHashSet("byte_field", "short_field", "integer_field", "long_field",
-                "float_field", "double_field", "date_field", "boolean_field", "text_field", "keyword_field",
-                "binary_field", "ip_field")));
-
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("byte_field").getValue().toString(), equalTo("1"));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("short_field").getValue().toString(), equalTo("2"));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("integer_field").getValue(), equalTo((Object) 3L));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("long_field").getValue(), equalTo((Object) 4L));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("float_field").getValue(), equalTo((Object) 5.0));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("double_field").getValue(), equalTo((Object) 6.0d));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("date_field").getValue(),
-                equalTo(DateFormatter.forPattern("dateOptionalTime").format(date)));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("boolean_field").getValue(), equalTo((Object) true));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("text_field").getValue(), equalTo("foo"));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("keyword_field").getValue(), equalTo("foo"));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("binary_field").getValue(), equalTo("KmQ"));
-        assertThat(searchResponse.getHits().getAt(0).getFields().get("ip_field").getValue(), equalTo("::1"));
-
         builder = client().prepareSearch().setQuery(matchAllQuery())
                 .addDocValueField("byte_field", "#.0")
                 .addDocValueField("short_field", "#.0")
@@ -1029,7 +993,7 @@ public class SearchFieldsIT extends ESIntegTestCase {
 
         SearchRequestBuilder builder = client().prepareSearch().setQuery(matchAllQuery())
                 .addDocValueField("text_field_alias")
-                .addDocValueField("date_field_alias", "use_field_mapping")
+                .addDocValueField("date_field_alias")
                 .addDocValueField("date_field");
         SearchResponse searchResponse = builder.get();
 
@@ -1091,7 +1055,7 @@ public class SearchFieldsIT extends ESIntegTestCase {
         refresh("test");
 
         SearchRequestBuilder builder = client().prepareSearch().setQuery(matchAllQuery())
-            .addDocValueField("*alias", "use_field_mapping")
+            .addDocValueField("*alias")
             .addDocValueField("date_field");
         SearchResponse searchResponse = builder.get();