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* Document nested expressions for stats * More docs * Apply suggestions from review - count-distinct.asciidoc - Content restructured, moving the section about approximate counts to end of doc. - count.asciidoc - Clarified that omitting the `expression` parameter in `COUNT` is equivalent to `COUNT(*)`, which counts the number of rows. - percentile.asciidoc - Moved the note about `PERCENTILE` being approximate and non-deterministic to end of doc. - stats.asciidoc - Clarified the `STATS` command - Added a note indicating that individual `null` values are skipped during aggregation * Comment out mentioning a buggy behavior * Update sum with inline function example, update test file * Fix typo * Delete line * Simplify wording * Fix conflict fix typo --------- Co-authored-by: Liam Thompson <leemthompo@gmail.com> Co-authored-by: Liam Thompson <32779855+leemthompo@users.noreply.github.com>
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1.6 KiB
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60 lines
No EOL
1.6 KiB
Text
[discrete]
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[[esql-agg-percentile]]
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=== `PERCENTILE`
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*Syntax*
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[source,esql]
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----
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PERCENTILE(expression, percentile)
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----
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*Parameters*
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`expression`::
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Expression from which to return a percentile.
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`percentile`::
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A constant numeric expression.
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*Description*
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Returns the value at which a certain percentage of observed values occur. For
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example, the 95th percentile is the value which is greater than 95% of the
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observed values and the 50th percentile is the <<esql-agg-median>>.
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*Example*
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[source.merge.styled,esql]
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----
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include::{esql-specs}/stats_percentile.csv-spec[tag=percentile]
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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}/stats_percentile.csv-spec[tag=percentile-result]
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|===
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The expression can use inline functions. For example, to calculate a percentile
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of the maximum values of a multivalued column, first use `MV_MAX` to get the
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maximum value per row, and use the result with the `PERCENTILE` function:
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[source.merge.styled,esql]
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----
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include::{esql-specs}/stats_percentile.csv-spec[tag=docsStatsPercentileNestedExpression]
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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}/stats_percentile.csv-spec[tag=docsStatsPercentileNestedExpression-result]
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|===
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[discrete]
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[[esql-agg-percentile-approximate]]
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==== `PERCENTILE` is (usually) approximate
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include::../../aggregations/metrics/percentile-aggregation.asciidoc[tag=approximate]
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[WARNING]
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====
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`PERCENTILE` is also {wikipedia}/Nondeterministic_algorithm[non-deterministic].
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This means you can get slightly different results using the same data.
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==== |