Introduce index option named 'index.percolator.map_unmapped_fields_as_string', that handles unmapped fields in percolator queries as type string.

Closes #9053
Closes #9054

docs/reference/search/percolate.asciidoc

@@ -472,3 +472,14 @@ achieve the same result (with way less memory being used).
 
 The delete-by-query api doesn't work to unregister a query, it only deletes the percolate documents from disk. In order
 to update the registered queries in memory the index needs be closed and opened.
+
+[float]
+=== Forcing unmapped fields to be handled as string
+
+In certain cases it is unknown what kind of percolator queries do get registered and if no field mapping exist for fields
+that are referred by percolator queries then adding a percolator query fails. This means the mapping needs to be updated
+to have the field with the appropriate settings and then the percolator query can be added. But sometimes it is sufficient
+if all unmapped fields are handled as if these were default string fields. In those cases one can configure the
+`index.percolator.map_unmapped_fields_as_string` setting to `true` (default to `false`) and then if a field referred in
+a percolator query does not exist, it will be handled as a default string field, so adding the percolator query doesn't
+fail.

src/main/java/org/elasticsearch/index/percolator/PercolatorQueriesRegistry.java

@@ -69,6 +69,8 @@ import java.util.concurrent.atomic.AtomicBoolean;
  */
 public class PercolatorQueriesRegistry extends AbstractIndexShardComponent implements Closeable{
 
+    public final String MAP_UNMAPPED_FIELDS_AS_STRING = "index.percolator.map_unmapped_fields_as_string";
+
     // This is a shard level service, but these below are index level service:
     private final IndexQueryParserService queryParserService;
     private final MapperService mapperService;
@@ -85,6 +87,8 @@ public class PercolatorQueriesRegistry extends AbstractIndexShardComponent imple
     private final PercolateTypeListener percolateTypeListener = new PercolateTypeListener();
     private final AtomicBoolean realTimePercolatorEnabled = new AtomicBoolean(false);
 
+    private boolean mapUnmappedFieldsAsString;
+
     private CloseableThreadLocal<QueryParseContext> cache = new CloseableThreadLocal<QueryParseContext>() {
         @Override
         protected QueryParseContext initialValue() {
@@ -104,6 +108,7 @@ public class PercolatorQueriesRegistry extends AbstractIndexShardComponent imple
         this.indexCache = indexCache;
         this.indexFieldDataService = indexFieldDataService;
         this.shardPercolateService = shardPercolateService;
+        this.mapUnmappedFieldsAsString = indexSettings.getAsBoolean(MAP_UNMAPPED_FIELDS_AS_STRING, false);
 
         indicesLifecycle.addListener(shardLifecycleListener);
         mapperService.addTypeListener(percolateTypeListener);
@@ -209,7 +214,11 @@ public class PercolatorQueriesRegistry extends AbstractIndexShardComponent imple
             // Query parsing can't introduce new fields in mappings (which happens when registering a percolator query),
             // because field type can't be inferred from queries (like document do) so the best option here is to disallow
             // the usage of unmapped fields in percolator queries to avoid unexpected behaviour
+            //
+            // if index.percolator.map_unmapped_fields_as_string is set to true, query can contain unmapped fields which will be mapped
+            // as an analyzed string.
             context.setAllowUnmappedFields(false);
+            context.setMapUnmappedFieldAsString(mapUnmappedFieldsAsString ? true : false);
             return queryParserService.parseInnerQuery(context);
         } catch (IOException e) {
             throw new QueryParsingException(queryParserService.index(), "Failed to parse", e);

src/main/java/org/elasticsearch/index/query/QueryParseContext.java

@@ -39,6 +39,7 @@ import org.elasticsearch.common.lucene.search.NoCacheFilter;
 import org.elasticsearch.common.lucene.search.NoCacheQuery;
 import org.elasticsearch.common.lucene.search.Queries;
 import org.elasticsearch.common.lucene.search.ResolvableFilter;
+import org.elasticsearch.common.settings.ImmutableSettings;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.analysis.AnalysisService;
@@ -46,7 +47,11 @@ import org.elasticsearch.index.cache.query.parser.QueryParserCache;
 import org.elasticsearch.index.fielddata.IndexFieldData;
 import org.elasticsearch.index.mapper.FieldMapper;
 import org.elasticsearch.index.mapper.FieldMappers;
+import org.elasticsearch.index.mapper.Mapper;
 import org.elasticsearch.index.mapper.MapperService;
+import org.elasticsearch.index.mapper.MapperBuilders;
+import org.elasticsearch.index.mapper.ContentPath;
+import org.elasticsearch.index.mapper.core.StringFieldMapper;
 import org.elasticsearch.index.search.child.CustomQueryWrappingFilter;
 import org.elasticsearch.index.similarity.SimilarityService;
 import org.elasticsearch.script.ScriptService;
@@ -102,6 +107,8 @@ public class QueryParseContext {
 
     private boolean allowUnmappedFields;
 
+    private boolean mapUnmappedFieldAsString;
+
     public QueryParseContext(Index index, IndexQueryParserService indexQueryParser) {
         this(index, indexQueryParser, false);
     }
@@ -389,10 +396,6 @@ public class QueryParseContext {
         return failIfFieldMappingNotFound(name, indexQueryParser.mapperService.smartName(name, getTypes()));
     }
 
-    public FieldMapper smartNameFieldMapper(String name) {
-        return failIfFieldMappingNotFound(name, indexQueryParser.mapperService.smartNameFieldMapper(name, getTypes()));
-    }
-
     public MapperService.SmartNameObjectMapper smartObjectMapper(String name) {
         return indexQueryParser.mapperService.smartNameObjectMapper(name, getTypes());
     }
@@ -401,9 +404,17 @@ public class QueryParseContext {
         this.allowUnmappedFields = allowUnmappedFields;
     }
 
-    private <T> T failIfFieldMappingNotFound(String name, T fieldMapping) {
+    public void setMapUnmappedFieldAsString(boolean mapUnmappedFieldAsString) {
+        this.mapUnmappedFieldAsString = mapUnmappedFieldAsString;
+    }
+
+    private MapperService.SmartNameFieldMappers failIfFieldMappingNotFound(String name, MapperService.SmartNameFieldMappers fieldMapping) {
         if (allowUnmappedFields) {
             return fieldMapping;
+        } else if (mapUnmappedFieldAsString){
+            StringFieldMapper.Builder builder = MapperBuilders.stringField(name);
+            StringFieldMapper stringFieldMapper = builder.build(new Mapper.BuilderContext(ImmutableSettings.EMPTY, new ContentPath(1)));
+            return new MapperService.SmartNameFieldMappers(mapperService(), new FieldMappers(stringFieldMapper), null, false);
         } else {
             Version indexCreatedVersion = indexQueryParser.getIndexCreatedVersion();
             if (fieldMapping == null && indexCreatedVersion.onOrAfter(Version.V_1_4_0_Beta1)) {

src/test/java/org/elasticsearch/percolator/PercolatorTests.java

@@ -33,6 +33,7 @@ import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.client.Requests;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.settings.ImmutableSettings;
 import org.elasticsearch.common.settings.ImmutableSettings.Builder;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentBuilder;
@@ -2034,5 +2035,25 @@ public class PercolatorTests extends ElasticsearchIntegrationTest {
                 .get();
         assertMatchCount(response, 3l);
     }
+
+    @Test
+    public void testMapUnmappedFieldAsString() throws IOException{
+        // If index.percolator.map_unmapped_fields_as_string is set to true, unmapped field is mapped as an analyzed string.
+        ImmutableSettings.Builder settings = ImmutableSettings.settingsBuilder()
+                .put(indexSettings())
+                .put("index.percolator.map_unmapped_fields_as_string", true);
+        assertAcked(prepareCreate("test")
+                .setSettings(settings));
+        client().prepareIndex("test", PercolatorService.TYPE_NAME)
+                .setSource(jsonBuilder().startObject().field("query", matchQuery("field1", "value")).endObject()).get();
+        logger.info("--> Percolate doc with field1=value");
+        PercolateResponse response1 = client().preparePercolate()
+                .setIndices("test").setDocumentType("type")
+                .setPercolateDoc(docBuilder().setDoc(jsonBuilder().startObject().field("field1", "value").endObject()))
+                .execute().actionGet();
+        assertMatchCount(response1, 1l);
+        assertThat(response1.getMatches(), arrayWithSize(1));
+
+    }
 }