Synthetic _source can't be retrieved with overlapping keys in flattened field #122936
Description
Elasticsearch Version
main
Installed Plugins
No response
Java Version
bundled
OS Version
macOS 15.3
Problem Description
When using flattened fields in a logsdb index, synthetic source is used to reconstruct the value of the flattened field. In case the key/value pairs in the flattened field have an object/scalar mismatch, the search request fails because the _source can't be constructed.
Steps to Reproduce
PUT my-index { "settings": { "mode": "logsdb" }, "mappings": { "properties": { "test": { "type": "flattened" } } } } POST my-index/_doc { "@timestamp": "2025", "test": { "nested.doublynested": 123, "nested": { "doublynested": { "gotcha": true } } } } GET my-index/_search // returns 500 Logs (if relevant)
failure encoding chunk com.fasterxml.jackson.core.JsonParseException: Duplicate field 'doublynested' │ at [Source: (org.elasticsearch.common.io.stream.ByteBufferStreamInput); line: 1, column: 112] │ at com.fasterxml.jackson.core@2.17.2/com.fasterxml.jackson.core.json.JsonReadContext._checkDup(JsonReadContext.java:250) │ at com.fasterxml.jackson.core@2.17.2/com.fasterxml.jackson.core.json.JsonReadContext.setCurrentName(JsonReadContext.java:244) │ at com.fasterxml.jackson.core@2.17.2/com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:758) │ at com.fasterxml.jackson.core@2.17.2/com.fasterxml.jackson.core.JsonGenerator._copyCurrentContents(JsonGenerator.java:2657) │ at com.fasterxml.jackson.core@2.17.2/com.fasterxml.jackson.core.JsonGenerator.copyCurrentStructure(JsonGenerator.java:2638) │ at org.elasticsearch.xcontent.impl@9.1.0-SNAPSHOT/org.elasticsearch.xcontent.provider.json.JsonXContentGenerator.copyCurrentStructure(JsonXContentGenerator.java:540) │ at org.elasticsearch.xcontent.impl@9.1.0-SNAPSHOT/org.elasticsearch.xcontent.provider.json.JsonXContentGenerator.writeRawField(JsonXContentGenerator.java:475) │ at org.elasticsearch.xcontent.impl@9.1.0-SNAPSHOT/org.elasticsearch.xcontent.provider.json.JsonXContentGenerator.writeRawField(JsonXContentGenerator.java:466) │ at org.elasticsearch.xcontent@9.1.0-SNAPSHOT/org.elasticsearch.xcontent.XContentBuilder.rawField(XContentBuilder.java:1205) │ at org.elasticsearch.server@9.1.0-SNAPSHOT/org.elasticsearch.common.xcontent.XContentHelper.writeRawField(XContentHelper.java:578) │ at org.elasticsearch.server@9.1.0-SNAPSHOT/org.elasticsearch.search.SearchHit.toInnerXContent(SearchHit.java:856) │ at org.elasticsearch.server@9.1.0-SNAPSHOT/org.elasticsearch.search.SearchHit.toXContent(SearchHit.java:801) │ at org.elasticsearch.server@9.1.0-SNAPSHOT/org.elasticsearch.rest.ChunkedRestResponseBodyPart$1.encodeChunk(ChunkedRestResponseBodyPart.java:161) │ at org.elasticsearch.server@9.1.0-SNAPSHOT/org.elasticsearch.rest.RestController$EncodedLengthTrackingChunkedRestResponseBodyPart.encodeChunk(RestController.java:1002) │ at org.elasticsearch.transport.netty4@9.1.0-SNAPSHOT/org.elasticsearch.http.netty4.Netty4HttpPipeliningHandler.writeChunk(Netty4HttpPipeliningHandler.java:440) │ at org.elasticsearch.transport.netty4@9.1.0-SNAPSHOT/org.elasticsearch.http.netty4.Netty4HttpPipeliningHandler.doWriteChunkedResponse(Netty4HttpPipeliningHandler.java:267) │ at org.elasticsearch.transport.netty4@9.1.0-SNAPSHOT/org.elasticsearch.http.netty4.Netty4HttpPipeliningHandler.doWrite(Netty4HttpPipeliningHandler.java:235) │ at org.elasticsearch.transport.netty4@9.1.0-SNAPSHOT/org.elasticsearch.http.netty4.Netty4HttpPipeliningHandler.write(Netty4HttpPipeliningHandler.java:188) │ at io.netty.transport@4.1.115.Final/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:891) │ at io.netty.transport@4.1.115.Final/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) │ at io.netty.transport@4.1.115.Final/io.netty.channel.AbstractChannelHandlerContext$WriteTask.run(AbstractChannelHandlerContext.java:1263) │ at io.netty.common@4.1.115.Final/io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:173) │ at io.netty.common@4.1.115.Final/io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:166) │ at io.netty.common@4.1.115.Final/io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472) │ at io.netty.transport@4.1.115.Final/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569) │ at io.netty.common@4.1.115.Final/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) │ at io.netty.common@4.1.115.Final/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) │ at java.base/java.lang.Thread.run(Thread.java:1575)