elastic/elasticsearch

Dynamic mappings fail when a single document generates inconsistent mapping updates

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#15,377 opened on Dec 10, 2015

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Description

For instance indexing the following document would fail if the foo.bar field is not mapped explicitly:

{
  "foo": [
    {
      "bar": "baz"
    },
    {
      "bar": 42
    }
  ]
}

The reason is that mapping updates for the 2 sub documents are generated independently (one triggers the creation of a string field and the other one of a long field) but they can't be reconciliated in order to generate the mapping update that will be sent to the master node.

Bug report courtesy of Benjamin Gathmann at https://discuss.elastic.co/t/coerce-long-to-double-not-working/36882.

Contributor guide

Research direction
Reproduce the issue by indexing a document with mixed types in an array field without explicit mapping. Examine the mapping update generation logic in Elasticsearch's dynamic mapping code (likely in `DocumentMapper` or related classes). Trace how individual field updates are collected and merged, and identify where reconciliation fails for array elements with different types.
Tech stack
java
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaElasticsearch mapping concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45