How to change the field type in an ElasticSearch Index?

I have index_A, which includes a number field "foo".

I copy the mapping for index_A, and make a dev tools call PUT /index_B with the field foo changed to text, so the mapping portion of that is:

  "foo": {
    "type": "text",
    "fields": {
      "keyword": {
        "type": "keyword"

I then reindex index_A to index_B with:

POST _reindex
  "source": {
    "index": "index_A"
  "dest": {
    "index": "index_B"

When I go to view any document for index_B, the entry for the "foo" field is still a number. (I was expecting for example: "foo": 30 to become "foo" : "30" in the new document's source).

As much as I've read on Mappings and reindexing, I'm still at a loss on how to accomplish this. What specifically do I need to run in order to get this new index with "foo" as a text field, and all number entries for foo in the original index changed to text entries in the new index?

hi @devbot,

you'll probably have more luck in the Elasticearch channel with this question.

A re-index will not cast your value automatically I believe. If you want to do an explicit conversion to string, you can do this with a pipeline with the "convert-processor":

Then use this pipeline when reindexing:

Hope that helps

You need to use an index template to set the mapping ahead of time, or explicitly create the index with the mapping.

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