# Dense vector doesn't support synthetic source

**URL:** <https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321>\
**Category:** Elasticsearch\
**Tags:** vector-search, synthetic-source\
**Created:** [December 2, 2022, 5:26am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321 "2022-12-02T05:26:21Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ruslaniv](https://avatars.discourse-cdn.com/v4/letter/r/9de053/32.png) [@ruslaniv](https://discuss.elastic.co/u/ruslaniv)\
**Post date:** [December 2, 2022, 5:26am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/1 "2022-12-02T05:26:21Z")

</div>

According to this: [Dense vector field type | Elasticsearch Guide [8.5] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/current/dense-vector.html#dense-vector-synthetic-source)  
`dense_vector` field is supposed to support synthetic source.  
I just tried to create an index with the mapping like this:

```auto
"mappings": {
        "_source": {"mode": "synthetic"},
        "title_vector": {
                "type": "dense_vector",
                "dims": 1024,
                "index": true,
                "similarity": "dot_product"
            },

```

and got an error:

```auto
{
    "error": {
        "root_cause": [
            {
                "type": "illegal_argument_exception",
                "reason": "field [title_vector] of type [dense_vector] doesn't support synthetic source"
            }
        ],
        "type": "illegal_argument_exception",
        "reason": "field [title_vector] of type [dense_vector] doesn't support synthetic source"
    },
    "status": 400
}

```

So does dense\_vector support synthetic source or not?

---

<div class="post-metadata">

**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [December 2, 2022, 6:11am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/2 "2022-12-02T06:11:32Z")

</div>

Which version of Elasticsearch are you running?

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<div class="post-metadata">

**Author:** ![ruslaniv](https://avatars.discourse-cdn.com/v4/letter/r/9de053/32.png) [@ruslaniv](https://discuss.elastic.co/u/ruslaniv)\
**Post date:** [December 2, 2022, 6:30am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/3 "2022-12-02T06:30:32Z")

</div>

```auto
"version": {
        "number": "8.4.1",
        "build_flavor": "default",
        "build_type": "docker",
        "build_hash": "2bd229c8e56650b42e40992322a76e7914258f0c",
        "build_date": "2022-08-26T12:11:43.232597118Z",
        "build_snapshot": false,
        "lucene_version": "9.3.0",
        "minimum_wire_compatibility_version": "7.17.0",
        "minimum_index_compatibility_version": "7.0.0"
    },

```

---

<div class="post-metadata">

**Author:** ![ruslaniv](https://avatars.discourse-cdn.com/v4/letter/r/9de053/32.png) [@ruslaniv](https://discuss.elastic.co/u/ruslaniv)\
**Post date:** [December 2, 2022, 6:41am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/4 "2022-12-02T06:41:52Z")

</div>

Yes, it looks like 8.4 does not support `dense_vector` with synthetic source:

> **[\_source field | Elasticsearch Guide \[8.4\] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/8.4/mapping-source-field.html#synthetic-source)**

---

<div class="post-metadata">

**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [December 2, 2022, 6:42am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/5 "2022-12-02T06:42:59Z")

</div>

Exactly. It is important to always look at the correct version of the docs, especially for new and evolving features.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [December 30, 2022, 6:43am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321/6 "2022-12-30T06:43:09Z")

</div>

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