# Summary index transform reference

**URL:** <https://discuss.elastic.co/t/summary-index-transform-reference/381800>\
**Category:** Elasticsearch\
**Tags:** transforms\
**Created:** [September 9, 2025, 1:26pm UTC](https://discuss.elastic.co/t/summary-index-transform-reference/381800 "2025-09-09T13:26:21Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![bigsby](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/bigsby/32/144961_2.png) [@bigsby](https://discuss.elastic.co/u/bigsby)\
**Post date:** [September 9, 2025, 1:26pm UTC](https://discuss.elastic.co/t/summary-index-transform-reference/381800/1 "2025-09-09T13:26:21Z")

</div>

I have a bunch of indices I’d like _merge_ into a single summary index. From what I read, ["Transforming data | Elastic Docs"](https://www.elastic.co/docs/explore-analyze/transforms) is the way to go but I’m not find the way to do this. Here it goes.

The indices I have are something like this…  
Index: accounts  
Sample documents:

```json
{
   "id": "1",
   "name": "account 1",
   "some_prop": "account 1 some_prop"
},
{
   "id": "2",
   "name": "account 2",
   "some_prop": "account 2 some_prop"
}

```

Index: account\_survey\_answer  
Sample documents:

```json
{
   "account_id": "1",
   "question_id": "a",
   "answer": "account 1 answer a"
},
{
   "account_id": "1",
   "question_id": "b",
   "answer": "account 1 answer b"
},
{
   "account_id": "2",
   "question_id": "a",
   "answer": "account 2 answer a"
},
{
   "account_id": "2",
   "question_id": "b",
   "answer": "account 2 answer b"
}

```

The wish is that the destination index of the transform looks something like this:

```json
{
   "account_id": "1",
   "name": "account 1",
   "some_prop": "account 1 some_prop",
   "answer_a": "account 1 answer a",
   "answer_b": "account 1 answer b"
},
{
   "account_id": "2",
   "name": "account 2",
   "some_prop": "account 2 some_prop",
   "answer_a": "account 2 answer a",
   "answer_b": "account 2 answer b"
}

```

Is this possible and, if so, I may I achieve it?  
Thank you, in advance for any help.

---

<div class="post-metadata">

**Author:** ![carly.richmond](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/carly.richmond/32/104935_2.png) [@carly.richmond](https://discuss.elastic.co/u/carly.richmond)\
**Post date:** [September 11, 2025, 12:45pm UTC](https://discuss.elastic.co/t/summary-index-transform-reference/381800/2 "2025-09-11T12:45:54Z")

</div>

Welcome @bigsby!

To confirm you want to merge the documents based on the `account_id` attribute? You should be able to use an [enrich processor](https://www.elastic.co/docs/reference/enrich-processor/enrich-processor) in an ingest pipeline. The below example should help you get started.

> **[Example: Enrich your data based on exact values | Elastic Docs](https://www.elastic.co/docs/manage-data/ingest/transform-enrich/example-enrich-data-based-on-exact-values)**
>
> match enrich policies match enrich data to incoming documents based on an exact value, such as a email address or ID, using a term query. The following...

Alternatively if you want to join the results without creating a new index, and are on a later version you could try using a [`LOOKUP JOIN`](https://www.elastic.co/docs/reference/query-languages/esql/esql-lookup-join) or [`ENRICH` operation](https://www.elastic.co/docs/reference/query-languages/esql/esql-enrich-data).

Hope that helps!