Add a cluster setting to disallow expensive queries

docs/reference/mapping/types/geo-shape.asciidoc

@@ -252,6 +252,10 @@ between index size and a reasonable level of precision of 50m at the
 equator. This allows for indexing tens of millions of shapes without
 overly bloating the resulting index too much relative to the input size.
 
+[NOTE]
+Geo-shape queries on geo-shapes implemented with PrefixTrees will not be executed if
+<<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>> is set to false.
+
 [[input-structure]]
 [float]
 ==== Input Structure

docs/reference/query-dsl.asciidoc

@@ -25,6 +25,27 @@ or to alter their behaviour (such as the
 
 Query clauses behave differently depending on whether they are used in
 <<query-filter-context,query context or filter context>>.
+
+[[query-dsl-allow-expensive-queries]]
+Allow expensive queries::
+Certain types of queries will generally execute slowly due to the way they are implemented, which can affect
+the stability of the cluster. Those queries can be categorised as follows:
+* Queries that need to do linear scans to identify matches:
+** <<query-dsl-script-query, `script queries`>>
+* Queries that have a high up-front cost:
+** <<query-dsl-fuzzy-query,`fuzzy queries`>>
+** <<query-dsl-regexp-query,`regexp queries`>>
+** <<query-dsl-prefix-query,`prefix queries`>> without <<index-prefixes, `index_prefixes`>>
+** <<query-dsl-wildcard-query, `wildcard queries`>>
+** <<query-dsl-range-query, `range queries>> on <<text, `text`>> and <<keyword, `keyword`>> fields
+* <<joining-queries, `Joining queries`>>
+* Queries on <<prefix-trees, deprecated geo shapes>>
+* Queries that may have a high per-document cost:
+** <<query-dsl-script-score-query, `script score queries`>>
+** <<query-dsl-percolate-query, `percolate queries`>>
+
+The execution of such queries can be prevented by setting the value of the `search.allow_expensive_queries`
+setting to `false` (defaults to `true`).
 --
 
 include::query-dsl/query_filter_context.asciidoc[]
@@ -51,4 +72,4 @@ include::query-dsl/minimum-should-match.asciidoc[]
 
 include::query-dsl/multi-term-rewrite.asciidoc[]
 
-include::query-dsl/regexp-syntax.asciidoc[]
+include::query-dsl/regexp-syntax.asciidoc[]

docs/reference/query-dsl/fuzzy-query.asciidoc

@@ -97,4 +97,8 @@ adjacent characters (ab → ba). Defaults to `true`.
 
 `rewrite`::
 (Optional, string) Method used to rewrite the query. For valid values and more
-information, see the <<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
+information, see the <<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
+
+==== Notes
+Fuzzy queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

docs/reference/query-dsl/geo-shape-query.asciidoc

@@ -161,3 +161,7 @@ and will not match any documents for this query. This can be useful when
 querying multiple indexes which might have different mappings. When set to
 `false` (the default value) the query will throw an exception if the field
 is not mapped.
+
+==== Notes
+Geo-shape queries on geo-shapes implemented with <<prefix-trees, `PrefixTrees`>> will not be executed if
+<<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>> is set to false.

docs/reference/query-dsl/joining-queries.asciidoc

@@ -29,4 +29,7 @@ include::has-parent-query.asciidoc[]
 
 include::parent-id-query.asciidoc[]
 
-
+=== Notes
+==== Allow expensive queries
+Joining queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

docs/reference/query-dsl/percolate-query.asciidoc

@@ -686,3 +686,8 @@ being percolated, as opposed to a single index as we do in examples. There are a
 allows for fields to be stored in a denser, more efficient way.
 - Percolate queries do not scale in the same way as other queries, so percolation performance may benefit from using
 a different index configuration, like the number of primary shards.
+
+=== Notes
+==== Allow expensive queries
+Percolate queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

docs/reference/query-dsl/prefix-query.asciidoc

@@ -64,4 +64,10 @@ GET /_search
 You can speed up prefix queries using the <<index-prefixes,`index_prefixes`>>
 mapping parameter. If enabled, {es} indexes prefixes between 2 and 5
 characters in a separate field. This lets {es} run prefix queries more
-efficiently at the cost of a larger index.
+efficiently at the cost of a larger index.
+
+[[prefix-query-allow-expensive-queries]]
+===== Allow expensive queries
+Prefix queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false. However, if <<index-prefixes, `index_prefixes`>> are enabled, an optimised query is built which
+is not considered slow, and will be executed in spite of this setting.

docs/reference/query-dsl/query-string-query.asciidoc

@@ -537,3 +537,9 @@ The example above creates a boolean query:
 `(blended(terms:[field2:this, field1:this]) blended(terms:[field2:that, field1:that]) blended(terms:[field2:thus, field1:thus]))~2`
 
 that matches documents with at least two of the three per-term blended queries.
+
+==== Notes
+===== Allow expensive queries
+Query string query can be internally be transformed to a <<query-dsl-prefix-query, `prefix query`>> which means
+that if the prefix queries are disabled as explained <<prefix-query-allow-expensive-queries, here>> the query will not be
+executed and an exception will be thrown.

docs/reference/query-dsl/range-query.asciidoc

@@ -134,6 +134,11 @@ increases the relevance score.
 [[range-query-notes]]
 ==== Notes
 
+[[ranges-on-text-and-keyword]]
+===== Using the `range` query with `text` and `keyword` fields
+Range queries on <<text, `text`>> or <<keyword, `keyword`>> files will not be executed if
+<<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>> is set to false.
+
 [[ranges-on-dates]]
 ===== Using the `range` query with `date` fields
 

docs/reference/query-dsl/regexp-query.asciidoc

@@ -86,3 +86,8 @@ regular expressions.
 `rewrite`::
 (Optional, string) Method used to rewrite the query. For valid values and more
 information, see the <<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
+
+==== Notes
+===== Allow expensive queries
+Regexp queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

docs/reference/query-dsl/script-query.asciidoc

@@ -69,3 +69,7 @@ GET /_search
     }
 }
 ----
+
+===== Allow expensive queries
+Script queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

docs/reference/query-dsl/script-score-query.asciidoc

@@ -221,6 +221,10 @@ and default time zone. Also calculations with `now` are not supported.
 <<vector-functions, Functions for vector fields>> are accessible through
 `script_score` query.
 
+===== Allow expensive queries
+Script score queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.
+
 [[script-score-faster-alt]]
 ===== Faster alternatives
 The `script_score` query calculates the score for

docs/reference/query-dsl/wildcard-query.asciidoc

@@ -67,4 +67,9 @@ increases the relevance score.
 
 `rewrite`::
 (Optional, string) Method used to rewrite the query. For valid values and more information, see the
-<<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
+<<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
+
+==== Notes
+===== Allow expensive queries
+Wildcard queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
+is set to false.

modules/mapper-extras/src/test/java/org/elasticsearch/index/mapper/SearchAsYouTypeFieldTypeTests.java

@@ -26,6 +26,7 @@
 import org.apache.lucene.search.TermInSetQuery;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.index.mapper.SearchAsYouTypeFieldMapper.Defaults;
 import org.elasticsearch.index.mapper.SearchAsYouTypeFieldMapper.PrefixFieldType;
 import org.elasticsearch.index.mapper.SearchAsYouTypeFieldMapper.SearchAsYouTypeFieldType;
@@ -100,14 +101,19 @@ public void testPrefixQuery() {
 
         // this term should be a length that can be rewriteable to a term query on the prefix field
         final String withinBoundsTerm = "foo";
-        assertThat(fieldType.prefixQuery(withinBoundsTerm, CONSTANT_SCORE_REWRITE, null),
+        assertThat(fieldType.prefixQuery(withinBoundsTerm, CONSTANT_SCORE_REWRITE, randomMockShardContext()),
             equalTo(new ConstantScoreQuery(new TermQuery(new Term(PREFIX_NAME, withinBoundsTerm)))));
 
         // our defaults don't allow a situation where a term can be too small
 
         // this term should be too long to be rewriteable to a term query on the prefix field
         final String longTerm = "toolongforourprefixfieldthistermis";
-        assertThat(fieldType.prefixQuery(longTerm, CONSTANT_SCORE_REWRITE, null),
+        assertThat(fieldType.prefixQuery(longTerm, CONSTANT_SCORE_REWRITE, MOCK_QSC),
             equalTo(new PrefixQuery(new Term(NAME, longTerm))));
+
+        ElasticsearchException ee = expectThrows(ElasticsearchException.class,
+                () -> fieldType.prefixQuery(longTerm, CONSTANT_SCORE_REWRITE, MOCK_QSC_DISALLOW_EXPENSIVE));
+        assertEquals("[prefix] queries cannot be executed when 'search.allow_expensive_queries' is set to false. " +
+                "For optimised prefix queries on text fields please enable [index_prefixes].", ee.getMessage());
     }
 }

modules/parent-join/src/main/java/org/elasticsearch/join/query/HasChildQueryBuilder.java

@@ -27,6 +27,7 @@
 import org.apache.lucene.search.join.JoinUtil;
 import org.apache.lucene.search.join.ScoreMode;
 import org.apache.lucene.search.similarities.Similarity;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -53,6 +54,8 @@
 import java.util.Map;
 import java.util.Objects;
 
+import static org.elasticsearch.search.SearchService.ALLOW_EXPENSIVE_QUERIES;
+
 /**
  * A query builder for {@code has_child} query.
  */
@@ -295,6 +298,11 @@ public String getWriteableName() {
 
     @Override
     protected Query doToQuery(QueryShardContext context) throws IOException {
+        if (context.allowExpensiveQueries() == false) {
+            throw new ElasticsearchException("[joining] queries cannot be executed when '" +
+                    ALLOW_EXPENSIVE_QUERIES.getKey() + "' is set to false.");
+        }
+
         ParentJoinFieldMapper joinFieldMapper = ParentJoinFieldMapper.getMapper(context.getMapperService());
         if (joinFieldMapper == null) {
             if (ignoreUnmapped) {

modules/parent-join/src/main/java/org/elasticsearch/join/query/HasParentQueryBuilder.java

@@ -21,6 +21,7 @@
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.join.ScoreMode;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -45,6 +46,8 @@
 import java.util.Map;
 import java.util.Objects;
 
+import static org.elasticsearch.search.SearchService.ALLOW_EXPENSIVE_QUERIES;
+
 /**
  * Builder for the 'has_parent' query.
  */
@@ -158,6 +161,11 @@ public boolean ignoreUnmapped() {
 
     @Override
     protected Query doToQuery(QueryShardContext context) throws IOException {
+        if (context.allowExpensiveQueries() == false) {
+            throw new ElasticsearchException("[joining] queries cannot be executed when '" +
+                    ALLOW_EXPENSIVE_QUERIES.getKey() + "' is set to false.");
+        }
+
         ParentJoinFieldMapper joinFieldMapper = ParentJoinFieldMapper.getMapper(context.getMapperService());
         if (joinFieldMapper == null) {
             if (ignoreUnmapped) {

modules/parent-join/src/main/java/org/elasticsearch/join/query/ParentIdQueryBuilder.java

@@ -23,6 +23,7 @@
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -38,6 +39,8 @@
 import java.io.IOException;
 import java.util.Objects;
 
+import static org.elasticsearch.search.SearchService.ALLOW_EXPENSIVE_QUERIES;
+
 public final class ParentIdQueryBuilder extends AbstractQueryBuilder<ParentIdQueryBuilder> {
     public static final String NAME = "parent_id";
 
@@ -153,6 +156,11 @@ public static ParentIdQueryBuilder fromXContent(XContentParser parser) throws IO
 
     @Override
     protected Query doToQuery(QueryShardContext context) throws IOException {
+        if (context.allowExpensiveQueries() == false) {
+            throw new ElasticsearchException("[joining] queries cannot be executed when '" +
+                    ALLOW_EXPENSIVE_QUERIES.getKey() + "' is set to false.");
+        }
+
         ParentJoinFieldMapper joinFieldMapper = ParentJoinFieldMapper.getMapper(context.getMapperService());
         if (joinFieldMapper == null) {
             if (ignoreUnmapped) {

modules/parent-join/src/test/java/org/elasticsearch/join/query/HasChildQueryBuilderTests.java

@@ -20,7 +20,6 @@
 package org.elasticsearch.join.query;
 
 import com.carrotsearch.randomizedtesting.generators.RandomPicks;
-
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
@@ -32,6 +31,7 @@
 import org.apache.lucene.search.join.ScoreMode;
 import org.apache.lucene.search.similarities.PerFieldSimilarityWrapper;
 import org.apache.lucene.search.similarities.Similarity;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.common.Strings;
@@ -70,6 +70,8 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class HasChildQueryBuilderTests extends AbstractQueryTestCase<HasChildQueryBuilder> {
 
@@ -361,5 +363,18 @@ public void testExtractInnerHitBuildersWithDuplicate() {
         queryBuilder.innerHit(new InnerHitBuilder("some_name"));
         IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
             () -> InnerHitContextBuilder.extractInnerHits(queryBuilder, Collections.singletonMap("some_name", null)));
+        assertEquals("[inner_hits] already contains an entry for key [some_name]", e.getMessage());
+    }
+
+    public void testDisallowExpensiveQueries() {
+        QueryShardContext queryShardContext = mock(QueryShardContext.class);
+        when(queryShardContext.allowExpensiveQueries()).thenReturn(false);
+
+        HasChildQueryBuilder queryBuilder =
+                hasChildQuery(CHILD_DOC, new TermQueryBuilder("custom_string", "value"), ScoreMode.None);
+        ElasticsearchException e = expectThrows(ElasticsearchException.class,
+                () -> queryBuilder.toQuery(queryShardContext));
+        assertEquals("[joining] queries cannot be executed when 'search.allow_expensive_queries' is set to false.",
+                e.getMessage());
     }
 }

modules/parent-join/src/test/java/org/elasticsearch/join/query/HasParentQueryBuilderTests.java

@@ -22,6 +22,7 @@
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.join.ScoreMode;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.common.Strings;
@@ -57,6 +58,8 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class HasParentQueryBuilderTests extends AbstractQueryTestCase<HasParentQueryBuilder> {
     private static final String TYPE = "_doc";
@@ -261,5 +264,18 @@ public void testExtractInnerHitBuildersWithDuplicate() {
         queryBuilder.innerHit(new InnerHitBuilder("some_name"));
         IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
             () -> InnerHitContextBuilder.extractInnerHits(queryBuilder, Collections.singletonMap("some_name", null)));
+        assertEquals("[inner_hits] already contains an entry for key [some_name]", e.getMessage());
+    }
+
+    public void testDisallowExpensiveQueries() {
+        QueryShardContext queryShardContext = mock(QueryShardContext.class);
+        when(queryShardContext.allowExpensiveQueries()).thenReturn(false);
+
+        HasParentQueryBuilder queryBuilder = new HasParentQueryBuilder(
+                CHILD_DOC, new WrapperQueryBuilder(new MatchAllQueryBuilder().toString()), false);
+        ElasticsearchException e = expectThrows(ElasticsearchException.class,
+                () -> queryBuilder.toQuery(queryShardContext));
+        assertEquals("[joining] queries cannot be executed when 'search.allow_expensive_queries' is set to false.",
+                e.getMessage());
     }
 }

modules/parent-join/src/test/java/org/elasticsearch/join/query/ParentIdQueryBuilderTests.java

@@ -25,6 +25,7 @@
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.common.Strings;
@@ -48,6 +49,8 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class ParentIdQueryBuilderTests extends AbstractQueryTestCase<ParentIdQueryBuilder> {
 
@@ -154,4 +157,14 @@ public void testIgnoreUnmapped() throws IOException {
         assertThat(e.getMessage(), containsString("[" + ParentIdQueryBuilder.NAME + "] no relation found for child [unmapped]"));
     }
 
+    public void testDisallowExpensiveQueries() {
+        QueryShardContext queryShardContext = mock(QueryShardContext.class);
+        when(queryShardContext.allowExpensiveQueries()).thenReturn(false);
+
+        ParentIdQueryBuilder queryBuilder = doCreateTestQueryBuilder();
+        ElasticsearchException e = expectThrows(ElasticsearchException.class,
+                () -> queryBuilder.toQuery(queryShardContext));
+        assertEquals("[joining] queries cannot be executed when 'search.allow_expensive_queries' is set to false.",
+                e.getMessage());
+    }
 }