# \#synthetic-source

**URL:** https://discuss.elastic.co/tag/synthetic-source/122.md

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## [Where is Elasticsearch storing unmapped field](https://discuss.elastic.co/t/where-is-elasticsearch-storing-unmapped-field/388701)

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**Author:** [@ddoroshenko](https://discuss.elastic.co/u/ddoroshenko)\
**Replies:** 7\
**Last updated:** [July 24, 2026, 5:51am UTC](https://discuss.elastic.co/t/where-is-elasticsearch-storing-unmapped-field/388701 "2026-07-24T05:51:26Z")

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I have an index created with index.mode=logsdb and index.mapping.source.mode=synthetic. The mapping also has dynamic: false. If I index a document containing an unmapped field, for example: { "@timestamp": "2026-07-2…

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## [Moving from source to synthetic\_source](https://discuss.elastic.co/t/moving-from-source-to-synthetic-source/358107)

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**Author:** [@Aditya\_Teltia](https://discuss.elastic.co/u/Aditya_Teltia)\
**Replies:** 4\
**Last updated:** [January 27, 2025, 11:16am UTC](https://discuss.elastic.co/t/moving-from-source-to-synthetic-source/358107 "2025-01-27T11:16:26Z")

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Hi everyone, I am moving set of indices from ES7 to ES8 with synthetic source. I added "mappings": { "\_source": { "mode": "synthetic" } } this in the mappings. But now I am getting following error - o…

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## [Return date fields as long numbers when using synthetic \_source and having format of date as epoch\_millis](https://discuss.elastic.co/t/return-date-fields-as-long-numbers-when-using-synthetic-source-and-having-format-of-date-as-epoch-millis/369383)

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**Author:** [@dbenesj](https://discuss.elastic.co/u/dbenesj)\
**Replies:** 0\
**Last updated:** [October 24, 2024, 6:57pm UTC](https://discuss.elastic.co/t/return-date-fields-as-long-numbers-when-using-synthetic-source-and-having-format-of-date-as-epoch-millis/369383 "2024-10-24T18:57:11Z")

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We are using synthetic \_source and date fields with format defined as epoch\_millis. Our expectation would be to get such fields as long number but we get them as strings. As we understand it might be necessary when date…

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## [Dense vector doesn't support synthetic source](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321)

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**Author:** [@ruslaniv](https://discuss.elastic.co/u/ruslaniv)\
**Replies:** 4\
**Last updated:** [December 2, 2022, 6:42am UTC](https://discuss.elastic.co/t/dense-vector-doesnt-support-synthetic-source/320321 "2022-12-02T06:42:59Z")

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According to this: Dense vector field type | Elasticsearch Guide \[8.5\] | Elastic dense\_vector field is supposed to support synthetic source. I just tried to create an index with the mapping like this: "mappings": { …