Mapping change on upgrade to 5.2.2

Elastic Stack Elasticsearch
1

The mapping for fields in ES 2.3.3 was like:

fieldname {
type: "string",
fields: {
raw: {
type: "string",
index: "not_analyzed"
}
}
}

Now after upgrade to 5.2.2, it has become like:

fieldname: {
type: "string",
fields: {
raw: {
type: "string",
index: "not_analyzed",
fielddata: false
}
}
}

fielddata:false doesn't seem to be a valid mapping. Valid mapping to disable fielddata would be "fielddata":{"format":"disabled"}.

I do see fielddata being used for fieldname.raw, however reason for that could be the ordinals' memory consumption which is shown in fielddata (https://github.com/elastic/elasticsearch/issues/17472).

I have been wondering if there is any specific reason for this change in mapping on upgrade, and what can be the possible implications on performance (if any).

2

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