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This adds documentation for the supported metadata fields. --------- Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>
55 lines
1.6 KiB
Text
55 lines
1.6 KiB
Text
[[esql-metadata-fields]]
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== {esql} metadata fields
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++++
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<titleabbrev>Metadata fields</titleabbrev>
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++++
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{esql} can access <<mapping-fields, metadata fields>>. The currently
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supported ones are:
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* <<mapping-index-field,`_index`>>: the index to which the document belongs.
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The field is of the type <<keyword, keyword>>.
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* <<mapping-id-field,`_id`>>: the source document's ID. The field is of the
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type <<keyword, keyword>>.
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* `_version`: the source document's version. The field is of the type
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<<number,long>>.
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To enable the access to these fields, the <<esql-from,`FROM`>> source command needs
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to be provided with a dedicated directive:
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[source,esql]
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----
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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.
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Consequently, `FROM` is the only source commands that supports the `METADATA`
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directive.
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Once enabled, the fields are then available to subsequent processing commands, just
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like the other index fields:
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[source.merge.styled,esql]
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----
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include::{esql-specs}/metadata-ignoreCsvTests.csv-spec[tag=multipleIndices]
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----
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[%header.monospaced.styled,format=dsv,separator=|]
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|===
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include::{esql-specs}/metadata-ignoreCsvTests.csv-spec[tag=multipleIndices-result]
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|===
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Also, similar to the index fields, once an aggregation is performed, a
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metadata field will no longer be accessible to subsequent commands, unless
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used as grouping field:
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[source.merge.styled,esql]
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----
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include::{esql-specs}/metadata-ignoreCsvTests.csv-spec[tag=metaIndexInAggs]
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----
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[%header.monospaced.styled,format=dsv,separator=|]
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|===
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include::{esql-specs}/metadata-ignoreCsvTests.csv-spec[tag=metaIndexInAggs-result]
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|===
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