Flattened field with synthetic _source produces incorrect _source if different object paths share same leaf name #129508
Description
Elasticsearch Version
main
Installed Plugins
none
Java Version
bundled
OS Version
Linux anduril 6.8.0-60-generic #63~22.04.1-Ubuntu
Problem Description
If an index has synthetic source and a flattened field, the source will be reconstructed from key/value doc_values. Where the keys are the flattened paths with a . character between each key in the path. If two paths share the same leaf name, and the paths are adjacent when all paths are sorted, the value for the first path will be attributed to the second path, and put in that object.
Steps to Reproduce
PUT my-index
{
"settings": {
"mode": "logsdb"
},
"mappings": {
"properties": {
"test": {
"type": "flattened"
}
}
}
}
POST my-index/_doc
{
"@timestamp": "2025",
"test": {
"a.x": 123,
"b.x": 456
}
}
GET my-index/_search
Returns:
"test": {
"a": {},
"b": {
"x": [
"10",
"20"
]
}
}
The value for a.x was added to b.x incorrectly. So a is empty, and b.x is an array with two values.
Logs (if relevant)
No response