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* delete asciidoc files
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* Clarify release notes page titles
* Revert "Clarify release notes page titles"
This reverts commit 8be688648d.
* Comment out edternal URI images
* Clean up query languages landing pages, link to conceptual docs
* Add .md to url
* Fixes inference processor nesting.
---------
Co-authored-by: Liam Thompson <32779855+leemthompo@users.noreply.github.com>
Co-authored-by: Liam Thompson <leemthompo@gmail.com>
Co-authored-by: Martijn Laarman <Mpdreamz@gmail.com>
Co-authored-by: István Zoltán Szabó <szabosteve@gmail.com>
53 lines
2.5 KiB
Markdown
53 lines
2.5 KiB
Markdown
---
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navigation_title: "Metadata fields"
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mapped_pages:
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- https://www.elastic.co/guide/en/elasticsearch/reference/current/esql-metadata-fields.html
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---
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# {{esql}} metadata fields [esql-metadata-fields]
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{{esql}} can access [metadata fields](/reference/elasticsearch/mapping-reference/document-metadata-fields.md). The currently supported ones are:
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* [`_index`](/reference/elasticsearch/mapping-reference/mapping-index-field.md): the index to which the document belongs. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
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* [`_id`](/reference/elasticsearch/mapping-reference/mapping-id-field.md): the source document’s ID. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
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* `_version`: the source document’s version. The field is of the type [long](/reference/elasticsearch/mapping-reference/number.md).
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* [`_ignored`](/reference/elasticsearch/mapping-reference/mapping-ignored-field.md): the ignored source document fields. The field is of the type [keyword](/reference/elasticsearch/mapping-reference/keyword.md).
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* `_score`: when enabled, the final score assigned to each row matching an ES|QL query. Scoring will be updated when using [full text search functions](/reference/query-languages/esql/esql-functions-operators.md#esql-search-functions).
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To enable the access to these fields, the [`FROM`](/reference/query-languages/esql/esql-commands.md#esql-from) source command needs to be provided with a dedicated directive:
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```esql
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FROM index METADATA _index, _id
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```
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Metadata fields are only available if the source of the data is an index. Consequently, `FROM` is the only source commands that supports the `METADATA` directive.
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Once enabled, these fields will be available to subsequent processing commands, just like other index fields:
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```esql
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FROM ul_logs, apps METADATA _index, _version
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| WHERE id IN (13, 14) AND _version == 1
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| EVAL key = CONCAT(_index, "_", TO_STR(id))
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| SORT id, _index
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| KEEP id, _index, _version, key
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```
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| id:long | _index:keyword | _version:long | key:keyword |
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| --- | --- | --- | --- |
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| 13 | apps | 1 | apps_13 |
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| 13 | ul_logs | 1 | ul_logs_13 |
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| 14 | apps | 1 | apps_14 |
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| 14 | ul_logs | 1 | ul_logs_14 |
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Similar to index fields, once an aggregation is performed, a metadata field will no longer be accessible to subsequent commands, unless used as a grouping field:
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```esql
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FROM employees METADATA _index, _id
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| STATS max = MAX(emp_no) BY _index
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```
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| max:integer | _index:keyword |
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| --- | --- |
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| 10100 | employees |
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