elasticsearch/docs/reference/esql/functions/description/mv_first.asciidoc

// This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.

*Description*

Converts a multivalued expression into a single valued column containing the first value. This is most useful when reading from a function that emits multivalued columns in a known order like <<esql-split>>.

The order that <<esql-multivalued-fields, multivalued fields>> are read from
underlying storage is not guaranteed. It is *frequently* ascending, but don't
rely on that. If you need the minimum value use <<esql-mv_min>> instead of
`MV_FIRST`. `MV_MIN` has optimizations for sorted values so there isn't a
performance benefit to `MV_FIRST`.