Add a simple JSON field mapper. (#33923)

* Add a simple JSON field type.
* Add support for ignore_above.
* Add support for null_value.
* Add support for split_queries_on_whitespace.
* Prevent norms from being enabled.
* Clarify the message around copy_to not being supported.
* Disallow wildcard queries.
* For now, disallow the field from being stored.

Author: jtibshirani

server/src/main/java/org/elasticsearch/index/mapper/JsonFieldMapper.java

@@ -0,0 +1,327 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.mapper;
+
+import org.apache.lucene.analysis.core.WhitespaceAnalyzer;
+import org.apache.lucene.index.IndexOptions;
+import org.apache.lucene.index.IndexableField;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.search.MultiTermQuery;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TermQuery;
+import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.common.lucene.Lucene;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.unit.Fuzziness;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.support.XContentMapValues;
+import org.elasticsearch.index.analysis.AnalyzerScope;
+import org.elasticsearch.index.analysis.NamedAnalyzer;
+import org.elasticsearch.index.query.QueryShardContext;
+
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import static org.elasticsearch.index.mapper.TypeParsers.parseField;
+
+/**
+ * A field mapper that accepts a JSON object and flattens it into a single field. This data type
+ * can be a useful alternative to an 'object' mapping when the object has a large, unknown set
+ * of keys.
+ *
+ * Currently the mapper extracts all leaf values of the JSON object, converts them to their text
+ * representations, and indexes each one as a keyword. As an example, given a json field called
+ * 'json_field' and the following input
+ *
+ * {
+ *   "json_field: {
+ *     "key1": "some value",
+ *     "key2": {
+ *       "key3": true
+ *     }
+ *   }
+ * }
+ *
+ * the mapper will produce untokenized string fields with the values "some value" and "true".
+ */
+public final class JsonFieldMapper extends FieldMapper {
+
+    public static final String CONTENT_TYPE = "json";
+    public static final NamedAnalyzer WHITESPACE_ANALYZER = new NamedAnalyzer(
+        "whitespace", AnalyzerScope.INDEX, new WhitespaceAnalyzer());
+
+    private static class Defaults {
+        public static final MappedFieldType FIELD_TYPE = new JsonFieldType();
+
+        static {
+            FIELD_TYPE.setTokenized(false);
+            FIELD_TYPE.setOmitNorms(true);
+            FIELD_TYPE.setStored(false);
+            FIELD_TYPE.setIndexOptions(IndexOptions.DOCS);
+            FIELD_TYPE.freeze();
+        }
+
+        public static final int IGNORE_ABOVE = Integer.MAX_VALUE;
+    }
+
+    public static class Builder extends FieldMapper.Builder<Builder, JsonFieldMapper> {
+        private int ignoreAbove = Defaults.IGNORE_ABOVE;
+
+        public Builder(String name) {
+            super(name, Defaults.FIELD_TYPE, Defaults.FIELD_TYPE);
+            builder = this;
+        }
+
+        @Override
+        public JsonFieldType fieldType() {
+            return (JsonFieldType) super.fieldType();
+        }
+
+        @Override
+        public Builder indexOptions(IndexOptions indexOptions) {
+            if (indexOptions.compareTo(IndexOptions.DOCS_AND_FREQS) > 0) {
+                throw new IllegalArgumentException("The [" + CONTENT_TYPE
+                    + "] field does not support positions, got [index_options]="
+                    + indexOptionToString(indexOptions));
+            }
+            return super.indexOptions(indexOptions);
+        }
+
+        public Builder ignoreAbove(int ignoreAbove) {
+            if (ignoreAbove < 0) {
+                throw new IllegalArgumentException("[ignore_above] must be positive, got " + ignoreAbove);
+            }
+            this.ignoreAbove = ignoreAbove;
+            return this;
+        }
+
+        public Builder splitQueriesOnWhitespace(boolean splitQueriesOnWhitespace) {
+            fieldType().setSplitQueriesOnWhitespace(splitQueriesOnWhitespace);
+            return builder;
+        }
+
+        @Override
+        public Builder addMultiField(Mapper.Builder mapperBuilder) {
+            throw new UnsupportedOperationException("[fields] is not supported for [" + CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public Builder copyTo(CopyTo copyTo) {
+            throw new UnsupportedOperationException("[copy_to] is not supported for [" + CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public Builder store(boolean store) {
+            throw new UnsupportedOperationException("[store] is not currently supported for [" +
+                CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public JsonFieldMapper build(BuilderContext context) {
+            setupFieldType(context);
+            if (fieldType().splitQueriesOnWhitespace()) {
+                fieldType().setSearchAnalyzer(WHITESPACE_ANALYZER);
+            }
+            return new JsonFieldMapper(name, fieldType, defaultFieldType,
+                ignoreAbove, context.indexSettings());
+        }
+    }
+
+    public static class TypeParser implements Mapper.TypeParser {
+        @Override
+        public Mapper.Builder<?,?> parse(String name, Map<String, Object> node, ParserContext parserContext) throws MapperParsingException {
+            JsonFieldMapper.Builder builder = new JsonFieldMapper.Builder(name);
+            parseField(builder, name, node, parserContext);
+            for (Iterator<Map.Entry<String, Object>> iterator = node.entrySet().iterator(); iterator.hasNext();) {
+                Map.Entry<String, Object> entry = iterator.next();
+                String propName = entry.getKey();
+                Object propNode = entry.getValue();
+                if (propName.equals("ignore_above")) {
+                    builder.ignoreAbove(XContentMapValues.nodeIntegerValue(propNode, -1));
+                    iterator.remove();
+                } else if (propName.equals("null_value")) {
+                    if (propNode == null) {
+                        throw new MapperParsingException("Property [null_value] cannot be null.");
+                    }
+                    builder.nullValue(propNode.toString());
+                    iterator.remove();
+                } else if (propName.equals("split_queries_on_whitespace")) {
+                    builder.splitQueriesOnWhitespace
+                        (XContentMapValues.nodeBooleanValue(propNode, "split_queries_on_whitespace"));
+                    iterator.remove();
+                }
+            }
+            return builder;
+        }
+    }
+
+    public static final class JsonFieldType extends StringFieldType {
+        private boolean splitQueriesOnWhitespace;
+
+        public JsonFieldType() {
+            setIndexAnalyzer(Lucene.KEYWORD_ANALYZER);
+            setSearchAnalyzer(Lucene.KEYWORD_ANALYZER);
+        }
+
+        private JsonFieldType(JsonFieldType ref) {
+            super(ref);
+            this.splitQueriesOnWhitespace = ref.splitQueriesOnWhitespace;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            if (!super.equals(o)) return false;
+            JsonFieldType that = (JsonFieldType) o;
+            return splitQueriesOnWhitespace == that.splitQueriesOnWhitespace;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(super.hashCode(), splitQueriesOnWhitespace);
+        }
+
+        public JsonFieldType clone() {
+            return new JsonFieldType(this);
+        }
+
+        @Override
+        public String typeName() {
+            return CONTENT_TYPE;
+        }
+
+        public boolean splitQueriesOnWhitespace() {
+            return splitQueriesOnWhitespace;
+        }
+
+        public void setSplitQueriesOnWhitespace(boolean splitQueriesOnWhitespace) {
+            checkIfFrozen();
+            this.splitQueriesOnWhitespace = splitQueriesOnWhitespace;
+        }
+
+        @Override
+        public Query existsQuery(QueryShardContext context) {
+            return new TermQuery(new Term(FieldNamesFieldMapper.NAME, name()));
+        }
+
+        @Override
+        public Query fuzzyQuery(Object value, Fuzziness fuzziness, int prefixLength, int maxExpansions,
+                                boolean transpositions) {
+            throw new UnsupportedOperationException("[fuzzy] queries are not currently supported on [" +
+                CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public Query regexpQuery(String value, int flags, int maxDeterminizedStates,
+                                 MultiTermQuery.RewriteMethod method, QueryShardContext context) {
+            throw new UnsupportedOperationException("[regexp] queries are not currently supported on [" +
+                CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public Query wildcardQuery(String value,
+                                   MultiTermQuery.RewriteMethod method,
+                                   QueryShardContext context) {
+            throw new UnsupportedOperationException("[wildcard] queries are not currently supported on [" +
+                CONTENT_TYPE + "] fields.");
+        }
+
+        @Override
+        public Object valueForDisplay(Object value) {
+            if (value == null) {
+                return null;
+            }
+            BytesRef binaryValue = (BytesRef) value;
+            return binaryValue.utf8ToString();
+        }
+    }
+
+    private final JsonFieldParser fieldParser;
+    private int ignoreAbove;
+
+    private JsonFieldMapper(String simpleName,
+                            MappedFieldType fieldType,
+                            MappedFieldType defaultFieldType,
+                            int ignoreAbove,
+                            Settings indexSettings) {
+        super(simpleName, fieldType, defaultFieldType, indexSettings, MultiFields.empty(), CopyTo.empty());
+        assert fieldType.indexOptions().compareTo(IndexOptions.DOCS_AND_FREQS) <= 0;
+
+        this.ignoreAbove = ignoreAbove;
+        this.fieldParser = new JsonFieldParser(fieldType, ignoreAbove);
+    }
+
+    @Override
+    protected String contentType() {
+        return CONTENT_TYPE;
+    }
+
+    @Override
+    protected void doMerge(Mapper mergeWith) {
+        super.doMerge(mergeWith);
+        this.ignoreAbove = ((JsonFieldMapper) mergeWith).ignoreAbove;
+    }
+
+    @Override
+    protected JsonFieldMapper clone() {
+        return (JsonFieldMapper) super.clone();
+    }
+
+    @Override
+    public JsonFieldType fieldType() {
+        return (JsonFieldType) super.fieldType();
+    }
+
+    @Override
+    protected void parseCreateField(ParseContext context, List<IndexableField> fields) throws IOException {
+        if (context.parser().currentToken() == XContentParser.Token.VALUE_NULL) {
+            return;
+        }
+
+        if (fieldType().indexOptions() != IndexOptions.NONE || fieldType().stored()) {
+            fields.addAll(fieldParser.parse(context.parser()));
+            createFieldNamesField(context, fields);
+        } else {
+            context.parser().skipChildren();
+        }
+    }
+
+    @Override
+    protected void doXContentBody(XContentBuilder builder, boolean includeDefaults, Params params) throws IOException {
+        super.doXContentBody(builder, includeDefaults, params);
+
+        if (includeDefaults || fieldType().nullValue() != null) {
+            builder.field("null_value", fieldType().nullValue());
+        }
+
+        if (includeDefaults || ignoreAbove != Defaults.IGNORE_ABOVE) {
+            builder.field("ignore_above", ignoreAbove);
+        }
+
+        if (includeDefaults || fieldType().splitQueriesOnWhitespace()) {
+            builder.field("split_queries_on_whitespace", fieldType().splitQueriesOnWhitespace());
+        }
+    }
+}