Remove too_many_fields upgrade check (#82809)

This check issues a warning if the cluster contains an index that has more
than 1024 fields, and no default_field set for searching. However, the 1024
boolean clause limit is no longer relevant with #81850, and in any case this
isn't something that would have prevented a successful upgrade from 7.17 to
8.0, so we can remove the check entirely.

Fixes #81539

Author: romseygeek

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -249,7 +249,6 @@ private static Set<Setting<Boolean>> getAllDeprecatedNodeRolesSettings() {
     static List<BiFunction<ClusterState, IndexMetadata, DeprecationIssue>> INDEX_SETTINGS_CHECKS = Collections.unmodifiableList(
         Arrays.asList(
             (clusterState, indexMetadata) -> IndexDeprecationChecks.oldIndicesCheck(indexMetadata),
-            (clusterState, indexMetadata) -> IndexDeprecationChecks.tooManyFieldsCheck(indexMetadata),
             (clusterState, indexMetadata) -> IndexDeprecationChecks.chainedMultiFieldsCheck(indexMetadata),
             (clusterState, indexMetadata) -> IndexDeprecationChecks.chainedMultiFieldsDynamicTemplateCheck(indexMetadata),
             (clusterState, indexMetadata) -> IndexDeprecationChecks.boostMappingCheck(indexMetadata),

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/IndexDeprecationChecks.java

@@ -34,7 +34,6 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Function;
@@ -193,38 +192,6 @@ static DeprecationIssue oldIndicesCheck(IndexMetadata indexMetadata) {
         return null;
     }
 
-    static DeprecationIssue tooManyFieldsCheck(IndexMetadata indexMetadata) {
-        if (indexMetadata.getSettings().get(IndexSettings.DEFAULT_FIELD_SETTING.getKey()) == null) {
-            AtomicInteger fieldCount = new AtomicInteger(0);
-
-            fieldLevelMappingIssue(
-                indexMetadata,
-                ((mappingMetadata, sourceAsMap) -> { fieldCount.addAndGet(countFieldsRecursively(mappingMetadata.type(), sourceAsMap)); })
-            );
-
-            // We can't get to the setting `indices.query.bool.max_clause_count` from here, so just check the default of that setting.
-            // It's also much better practice to set `index.query.default_field` than `indices.query.bool.max_clause_count` - there's a
-            // reason we introduced the limit.
-            if (fieldCount.get() > 1024) {
-                return new DeprecationIssue(
-                    DeprecationIssue.Level.WARNING,
-                    "Number of fields exceeds automatic field expansion limit",
-                    "https://ela.st/es-deprecation-7-number-of-auto-expanded-fields",
-                    "This index has "
-                        + fieldCount.get()
-                        + " fields, which exceeds the automatic field expansion limit (1024). Set "
-                        + IndexSettings.DEFAULT_FIELD_SETTING.getKey()
-                        + " to prevent queries that support automatic field expansion from "
-                        + "failing if no fields are specified. Otherwise, you must explicitly specify fields in all query_string, "
-                        + "simple_query_string, and multi_match queries.",
-                    false,
-                    null
-                );
-            }
-        }
-        return null;
-    }
-
     static DeprecationIssue deprecatedDateTimeFormat(IndexMetadata indexMetadata) {
         Version createdWith = indexMetadata.getCreationVersion();
         if (createdWith.before(Version.V_7_0_0)) {

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/IndexDeprecationChecksTests.java

@@ -12,7 +12,6 @@
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.cluster.metadata.MappingMetadata;
 import org.elasticsearch.cluster.routing.allocation.DataTier;
-import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.IndexModule;
@@ -41,7 +40,6 @@
 import java.util.stream.Stream;
 
 import static java.util.Collections.singletonList;
-import static org.elasticsearch.xcontent.XContentFactory.jsonBuilder;
 import static org.elasticsearch.xpack.cluster.routing.allocation.DataTierAllocationDecider.INDEX_ROUTING_EXCLUDE_SETTING;
 import static org.elasticsearch.xpack.cluster.routing.allocation.DataTierAllocationDecider.INDEX_ROUTING_INCLUDE_SETTING;
 import static org.elasticsearch.xpack.cluster.routing.allocation.DataTierAllocationDecider.INDEX_ROUTING_REQUIRE_SETTING;
@@ -83,87 +81,6 @@ public void testOldIndicesCheck() {
         assertEquals(singletonList(expected), issues);
     }
 
-    public void testTooManyFieldsCheck() throws IOException {
-        String simpleMapping = "{\n"
-            + "  \"properties\": {\n"
-            + "    \"some_field\": {\n"
-            + "      \"type\": \"text\"\n"
-            + "    },\n"
-            + "    \"other_field\": {\n"
-            + "      \"type\": \"text\",\n"
-            + "      \"properties\": {\n"
-            + "        \"raw\": {\"type\": \"keyword\"}\n"
-            + "      }\n"
-            + "    }\n"
-            + "  }\n"
-            + "}";
-
-        IndexMetadata simpleIndex = IndexMetadata.builder(randomAlphaOfLengthBetween(5, 10))
-            .settings(settings(Version.V_7_0_0))
-            .numberOfShards(randomIntBetween(1, 100))
-            .numberOfReplicas(randomIntBetween(1, 100))
-            .putMapping("_doc", simpleMapping)
-            .build();
-        List<DeprecationIssue> noIssues = DeprecationChecks.filterChecks(
-            INDEX_SETTINGS_CHECKS,
-            c -> c.apply(ClusterState.EMPTY_STATE, simpleIndex)
-        );
-        assertEquals(0, noIssues.size());
-
-        // Test that it catches having too many fields
-        int fieldCount = randomIntBetween(1025, 10_000); // 10_000 is arbitrary
-
-        XContentBuilder mappingBuilder = jsonBuilder();
-        mappingBuilder.startObject();
-        {
-            mappingBuilder.startObject("properties");
-            {
-                addRandomFields(fieldCount, mappingBuilder);
-            }
-            mappingBuilder.endObject();
-        }
-        mappingBuilder.endObject();
-
-        IndexMetadata tooManyFieldsIndex = IndexMetadata.builder(randomAlphaOfLengthBetween(5, 10))
-            .settings(settings(Version.V_7_0_0))
-            .numberOfShards(randomIntBetween(1, 100))
-            .numberOfReplicas(randomIntBetween(1, 100))
-            .putMapping("_doc", Strings.toString(mappingBuilder))
-            .build();
-        DeprecationIssue expected = new DeprecationIssue(
-            DeprecationIssue.Level.WARNING,
-            "Number of fields exceeds automatic field expansion limit",
-            "https://ela.st/es-deprecation-7-number-of-auto-expanded-fields",
-            "This index has "
-                + fieldCount
-                + " fields, which exceeds the automatic field expansion limit (1024). Set "
-                + IndexSettings.DEFAULT_FIELD_SETTING.getKey()
-                + " to prevent queries that support automatic field expansion from failing "
-                + "if no fields are specified. Otherwise, you must explicitly specify fields in all query_string, simple_query_string, and "
-                + "multi_match queries.",
-            false,
-            null
-        );
-        List<DeprecationIssue> issues = DeprecationChecks.filterChecks(
-            INDEX_SETTINGS_CHECKS,
-            c -> c.apply(ClusterState.EMPTY_STATE, tooManyFieldsIndex)
-        );
-        assertEquals(singletonList(expected), issues);
-
-        // Check that it's okay to have too many fields as long as `index.query.default_field` is set
-        IndexMetadata tooManyFieldsOk = IndexMetadata.builder(randomAlphaOfLengthBetween(5, 10))
-            .settings(settings(Version.V_7_0_0).put(IndexSettings.DEFAULT_FIELD_SETTING.getKey(), randomAlphaOfLength(5)))
-            .numberOfShards(randomIntBetween(1, 100))
-            .numberOfReplicas(randomIntBetween(1, 100))
-            .putMapping("_doc", Strings.toString(mappingBuilder))
-            .build();
-        List<DeprecationIssue> withDefaultFieldIssues = DeprecationChecks.filterChecks(
-            INDEX_SETTINGS_CHECKS,
-            c -> c.apply(ClusterState.EMPTY_STATE, tooManyFieldsOk)
-        );
-        assertEquals(0, withDefaultFieldIssues.size());
-    }
-
     public void testChainedMultiFields() throws IOException {
         XContentBuilder xContent = XContentFactory.jsonBuilder();
         xContent.startObject();