Configure IndexSearcher.maxClauseCount() based on Node characteristics

docs/reference/migration/migrate_8_0/cluster-node-setting-changes.asciidoc

@@ -16,7 +16,7 @@ The default for the `action.destructive_requires_name` setting changes from `fal
 to `true` in {es} 8.0.0.
 
 Previously, defaulting to `false` allowed users to use wildcard
-patterns to delete, close, or change index blocks on indices. 
+patterns to delete, close, or change index blocks on indices.
 To prevent the accidental deletion of indices that happen to match a
 wildcard pattern, we now default to requiring that destructive
 operations explicitly name the indices to be modified.
@@ -44,19 +44,28 @@ non-frozen node will result in an error on startup.
 ====
 
 [[max_clause_count_change]]
-.The `indices.query.bool.max_clause_count` setting now limits all query clauses.
+.The `indices.query.bool.max_clause_count` setting has been deprecated, and no longer has any effect.
 [%collapsible]
 ====
 *Details* +
-Previously, the `indices.query.bool.max_clause_count` would apply to the number
-of clauses of a single `bool` query. It now applies to the total number of
-clauses of the rewritten query. To reduce chances of breaks, its
-default value has been bumped from 1024 to 4096.
+Elasticsearch will now dynamically set the maximum number of allowed clauses
+in a query, using a heuristic based on the size of the search thread pool and
+the size of the heap allocated to the JVM. This limit has a minimum value of
+1024 and will in most cases be larger (for example, a node with 30Gb RAM and
+48 CPUs will have a maximum clause count of around 27,000). Larger heaps lead
+to higher values, and larger thread pools result in lower values.
 
 *Impact* +
-Queries with many clauses should be avoided whenever possible. 
-If you previously bumped this setting to accommodate heavy queries, 
-you might need to increase it further. 
+Queries with many clauses should be avoided whenever possible.
+If you previously bumped this setting to accommodate heavy queries,
+you might need to increase the amount of memory available to Elasticsearch,
+or to reduce the size of your search thread pool so that more memory is
+available to each concurrent search.
+
+In previous versions of Lucene you could get around this limit by nesting
+boolean queries within each other, but the limit is now based on the total
+number of leaf queries within the query as a whole and this workaround will
+no longer help.
 ====
 
 [[ilm-poll-interval-limit]]
@@ -224,7 +233,7 @@ Remove the `http.content_type.required` setting from `elasticsearch.yml`. Specif
 The `http.tcp_no_delay` setting was deprecated in 7.x and has been removed in 8.0. Use`http.tcp.no_delay` instead.
 
 *Impact* +
-Replace the `http.tcp_no_delay` setting with `http.tcp.no_delay`.  
+Replace the `http.tcp_no_delay` setting with `http.tcp.no_delay`.
 Specifying  `http.tcp_no_delay` in `elasticsearch.yml` will
 result in an error on startup.
 ====
@@ -237,7 +246,7 @@ The `network.tcp.connect_timeout` setting was deprecated in 7.x and has been rem
 was a fallback setting for `transport.connect_timeout`.
 
 *Impact* +
-Remove the`network.tcp.connect_timeout` setting. 
+Remove the`network.tcp.connect_timeout` setting.
 Use the `transport.connect_timeout` setting to change the default connection
 timeout for client connections. Specifying
 `network.tcp.connect_timeout` in `elasticsearch.yml` will result in an
@@ -282,7 +291,7 @@ since the 5.2 release of {es}.
 
 *Impact* +
 Remove the `xpack.security.authz.store.roles.index.cache.max_size`
-and `xpack.security.authz.store.roles.index.cache.ttl` settings from `elasticsearch.yml` . 
+and `xpack.security.authz.store.roles.index.cache.ttl` settings from `elasticsearch.yml` .
 Specifying these settings will result in an error on startup.
 ====
 

server/src/internalClusterTest/java/org/elasticsearch/search/aggregations/bucket/AdjacencyMatrixIT.java

@@ -8,14 +8,13 @@
 
 package org.elasticsearch.search.aggregations.bucket;
 
+import org.apache.lucene.search.IndexSearcher;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.index.IndexRequestBuilder;
 import org.elasticsearch.action.search.SearchPhaseExecutionException;
 import org.elasticsearch.action.search.SearchResponse;
-import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.query.BoolQueryBuilder;
 import org.elasticsearch.index.query.QueryBuilder;
-import org.elasticsearch.search.SearchModule;
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.bucket.adjacency.AdjacencyMatrix;
 import org.elasticsearch.search.aggregations.bucket.adjacency.AdjacencyMatrix.Bucket;
@@ -276,20 +275,28 @@ public void testWithSubAggregation() throws Exception {
 
     }
 
-    public void testTooLargeMatrix() throws Exception {
+    public void testTooLargeMatrix() {
 
-        // Create more filters than is permitted by Lucene Bool clause settings.
-        MapBuilder filtersMap = new MapBuilder();
-        int maxFilters = SearchModule.INDICES_MAX_CLAUSE_COUNT_SETTING.get(Settings.EMPTY);
-        for (int i = 0; i <= maxFilters; i++) {
-            filtersMap.add("tag" + i, termQuery("tag", "tag" + i));
-        }
+        int originalMaxClauses = IndexSearcher.getMaxClauseCount();
 
         try {
-            client().prepareSearch("idx").addAggregation(adjacencyMatrix("tags", "\t", filtersMap)).get();
-            fail("SearchPhaseExecutionException should have been thrown");
-        } catch (SearchPhaseExecutionException ex) {
-            assertThat(ex.getCause().getMessage(), containsString("Number of filters is too large"));
+            // Create more filters than is permitted by Lucene Bool clause settings.
+            MapBuilder filtersMap = new MapBuilder();
+            int maxFilters = randomIntBetween(50, 100);
+            IndexSearcher.setMaxClauseCount(maxFilters);
+            for (int i = 0; i <= maxFilters; i++) {
+                filtersMap.add("tag" + i, termQuery("tag", "tag" + i));
+            }
+
+            try {
+                client().prepareSearch("idx").addAggregation(adjacencyMatrix("tags", "\t", filtersMap)).get();
+                fail("SearchPhaseExecutionException should have been thrown");
+            } catch (SearchPhaseExecutionException ex) {
+                assertThat(ex.getCause().getMessage(), containsString("Number of filters is too large"));
+            }
+
+        } finally {
+            IndexSearcher.setMaxClauseCount(originalMaxClauses);
         }
     }
 

server/src/internalClusterTest/java/org/elasticsearch/search/query/QueryStringIT.java

@@ -8,6 +8,7 @@
 
 package org.elasticsearch.search.query;
 
+import org.apache.lucene.search.IndexSearcher;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.index.IndexRequestBuilder;
 import org.elasticsearch.action.search.SearchResponse;
@@ -17,12 +18,10 @@
 import org.elasticsearch.index.query.QueryStringQueryBuilder;
 import org.elasticsearch.search.SearchHit;
 import org.elasticsearch.search.SearchHits;
-import org.elasticsearch.search.SearchModule;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentType;
 import org.junit.Before;
-import org.junit.BeforeClass;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -42,28 +41,13 @@
 
 public class QueryStringIT extends ESIntegTestCase {
 
-    private static int CLUSTER_MAX_CLAUSE_COUNT;
-
-    @BeforeClass
-    public static void createRandomClusterSetting() {
-        CLUSTER_MAX_CLAUSE_COUNT = randomIntBetween(50, 100);
-    }
-
     @Before
     public void setup() throws Exception {
         String indexBody = copyToStringFromClasspath("/org/elasticsearch/search/query/all-query-index.json");
         prepareCreate("test").setSource(indexBody, XContentType.JSON).get();
         ensureGreen("test");
     }
 
-    @Override
-    protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
-        return Settings.builder()
-            .put(super.nodeSettings(nodeOrdinal, otherSettings))
-            .put(SearchModule.INDICES_MAX_CLAUSE_COUNT_SETTING.getKey(), CLUSTER_MAX_CLAUSE_COUNT)
-            .build();
-    }
-
     public void testBasicAllQuery() throws Exception {
         List<IndexRequestBuilder> reqs = new ArrayList<>();
         reqs.add(client().prepareIndex("test").setId("1").setSource("f1", "foo bar baz"));
@@ -250,40 +234,18 @@ public void testAllFieldsWithSpecifiedLeniency() throws IOException {
         assertThat(e.getCause().getMessage(), containsString("unit [D] not supported for date math [-2D]"));
     }
 
-    // The only expectation for this test is to not throw exception
-    public void testLimitOnExpandedFieldsButIgnoreUnmappedFields() throws Exception {
-        XContentBuilder builder = jsonBuilder();
-        builder.startObject();
-        builder.startObject("_doc");
-        builder.startObject("properties");
-        for (int i = 0; i < CLUSTER_MAX_CLAUSE_COUNT; i++) {
-            builder.startObject("field" + i).field("type", "text").endObject();
-        }
-        builder.endObject(); // properties
-        builder.endObject(); // type1
-        builder.endObject();
-
-        assertAcked(prepareCreate("ignoreunmappedfields").setMapping(builder));
-
-        client().prepareIndex("ignoreunmappedfields").setId("1").setSource("field1", "foo bar baz").get();
-        refresh();
+    public void testLimitOnExpandedFields() throws Exception {
 
-        QueryStringQueryBuilder qb = queryStringQuery("bar");
-        if (randomBoolean()) {
-            qb.field("*").field("unmappedField1").field("unmappedField2").field("unmappedField3").field("unmappedField4");
-        }
-        client().prepareSearch("ignoreunmappedfields").setQuery(qb).get();
-    }
+        final int maxClauseCount = randomIntBetween(50, 100);
 
-    public void testLimitOnExpandedFields() throws Exception {
         XContentBuilder builder = jsonBuilder();
         builder.startObject();
         {
             builder.startObject("_doc");
             {
                 builder.startObject("properties");
                 {
-                    for (int i = 0; i < CLUSTER_MAX_CLAUSE_COUNT; i++) {
+                    for (int i = 0; i < maxClauseCount; i++) {
                         builder.startObject("field_A" + i).field("type", "text").endObject();
                         builder.startObject("field_B" + i).field("type", "text").endObject();
                     }
@@ -296,25 +258,34 @@ public void testLimitOnExpandedFields() throws Exception {
 
         assertAcked(
             prepareCreate("testindex").setSettings(
-                Settings.builder().put(MapperService.INDEX_MAPPING_TOTAL_FIELDS_LIMIT_SETTING.getKey(), CLUSTER_MAX_CLAUSE_COUNT + 100)
+                Settings.builder().put(MapperService.INDEX_MAPPING_TOTAL_FIELDS_LIMIT_SETTING.getKey(), maxClauseCount + 100)
             ).setMapping(builder)
         );
 
         client().prepareIndex("testindex").setId("1").setSource("field_A0", "foo bar baz").get();
         refresh();
 
-        // single field shouldn't trigger the limit
-        doAssertOneHitForQueryString("field_A0:foo");
-        // expanding to the limit should work
-        doAssertOneHitForQueryString("field_A\\*:foo");
+        int originalMaxClauses = IndexSearcher.getMaxClauseCount();
+        try {
+
+            IndexSearcher.setMaxClauseCount(maxClauseCount);
+
+            // single field shouldn't trigger the limit
+            doAssertOneHitForQueryString("field_A0:foo");
+            // expanding to the limit should work
+            doAssertOneHitForQueryString("field_A\\*:foo");
 
-        // adding a non-existing field on top shouldn't overshoot the limit
-        doAssertOneHitForQueryString("field_A\\*:foo unmapped:something");
+            // adding a non-existing field on top shouldn't overshoot the limit
+            doAssertOneHitForQueryString("field_A\\*:foo unmapped:something");
 
-        // the following should exceed the limit
-        doAssertLimitExceededException("foo", CLUSTER_MAX_CLAUSE_COUNT * 2, "*");
-        doAssertLimitExceededException("*:foo", CLUSTER_MAX_CLAUSE_COUNT * 2, "*");
-        doAssertLimitExceededException("field_\\*:foo", CLUSTER_MAX_CLAUSE_COUNT * 2, "field_*");
+            // the following should exceed the limit
+            doAssertLimitExceededException("foo", IndexSearcher.getMaxClauseCount() * 2, "*");
+            doAssertLimitExceededException("*:foo", IndexSearcher.getMaxClauseCount() * 2, "*");
+            doAssertLimitExceededException("field_\\*:foo", IndexSearcher.getMaxClauseCount() * 2, "field_*");
+
+        } finally {
+            IndexSearcher.setMaxClauseCount(originalMaxClauses);
+        }
     }
 
     private void doAssertOneHitForQueryString(String queryString) {
@@ -340,7 +311,7 @@ private void doAssertLimitExceededException(String queryString, int exceedingFie
                 "field expansion for ["
                     + inputFieldPattern
                     + "] matches too many fields, limit: "
-                    + CLUSTER_MAX_CLAUSE_COUNT
+                    + IndexSearcher.getMaxClauseCount()
                     + ", got: "
                     + exceedingFieldCount
             )

server/src/internalClusterTest/java/org/elasticsearch/search/query/SimpleQueryStringIT.java

@@ -11,6 +11,7 @@
 import org.apache.lucene.analysis.TokenFilter;
 import org.apache.lucene.analysis.TokenStream;
 import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
+import org.apache.lucene.search.IndexSearcher;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.admin.indices.create.CreateIndexRequestBuilder;
 import org.elasticsearch.action.index.IndexRequestBuilder;
@@ -29,13 +30,11 @@
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.search.SearchHit;
 import org.elasticsearch.search.SearchHits;
-import org.elasticsearch.search.SearchModule;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
 import org.elasticsearch.xcontent.XContentType;
-import org.junit.BeforeClass;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -69,21 +68,6 @@
  */
 public class SimpleQueryStringIT extends ESIntegTestCase {
 
-    private static int CLUSTER_MAX_CLAUSE_COUNT;
-
-    @BeforeClass
-    public static void createRandomClusterSetting() {
-        CLUSTER_MAX_CLAUSE_COUNT = randomIntBetween(60, 100);
-    }
-
-    @Override
-    protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
-        return Settings.builder()
-            .put(super.nodeSettings(nodeOrdinal, otherSettings))
-            .put(SearchModule.INDICES_MAX_CLAUSE_COUNT_SETTING.getKey(), CLUSTER_MAX_CLAUSE_COUNT)
-            .build();
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Collections.singletonList(MockAnalysisPlugin.class);
@@ -578,11 +562,14 @@ public void testAllFieldsWithSpecifiedLeniency() throws IOException {
     }
 
     public void testLimitOnExpandedFields() throws Exception {
+
+        final int maxClauseCount = randomIntBetween(50, 100);
+
         XContentBuilder builder = jsonBuilder();
         builder.startObject();
         builder.startObject("_doc");
         builder.startObject("properties");
-        for (int i = 0; i < CLUSTER_MAX_CLAUSE_COUNT + 1; i++) {
+        for (int i = 0; i < maxClauseCount + 1; i++) {
             builder.startObject("field" + i).field("type", "text").endObject();
         }
         builder.endObject(); // properties
@@ -591,15 +578,21 @@ public void testLimitOnExpandedFields() throws Exception {
 
         assertAcked(
             prepareCreate("toomanyfields").setSettings(
-                Settings.builder().put(MapperService.INDEX_MAPPING_TOTAL_FIELDS_LIMIT_SETTING.getKey(), CLUSTER_MAX_CLAUSE_COUNT + 100)
+                Settings.builder().put(MapperService.INDEX_MAPPING_TOTAL_FIELDS_LIMIT_SETTING.getKey(), maxClauseCount + 100)
             ).setMapping(builder)
         );
 
         client().prepareIndex("toomanyfields").setId("1").setSource("field1", "foo bar baz").get();
         refresh();
 
-        doAssertLimitExceededException("*", CLUSTER_MAX_CLAUSE_COUNT + 1);
-        doAssertLimitExceededException("field*", CLUSTER_MAX_CLAUSE_COUNT + 1);
+        int originalMaxClauses = IndexSearcher.getMaxClauseCount();
+        try {
+            IndexSearcher.setMaxClauseCount(maxClauseCount);
+            doAssertLimitExceededException("*", maxClauseCount + 1);
+            doAssertLimitExceededException("field*", maxClauseCount + 1);
+        } finally {
+            IndexSearcher.setMaxClauseCount(originalMaxClauses);
+        }
     }
 
     private void doAssertLimitExceededException(String field, int exceedingFieldCount) {
@@ -610,7 +603,9 @@ private void doAssertLimitExceededException(String field, int exceedingFieldCoun
         });
         assertThat(
             ExceptionsHelper.unwrap(e, IllegalArgumentException.class).getMessage(),
-            containsString("field expansion matches too many fields, limit: " + CLUSTER_MAX_CLAUSE_COUNT + ", got: " + exceedingFieldCount)
+            containsString(
+                "field expansion matches too many fields, limit: " + IndexSearcher.getMaxClauseCount() + ", got: " + exceedingFieldCount
+            )
         );
     }