Revert "Revert "[8.19] Backport ES|QL sample processing command (elastic#129617)" (elastic#129797)"

This reverts commit 8e019be.

Author: jan-elastic

docs/changelog/125570.yaml

@@ -0,0 +1,5 @@
+pr: 125570
+summary: ES|QL random sampling
+area: Machine Learning
+type: feature
+issues: []

docs/changelog/129797.yaml

@@ -46,6 +46,7 @@ endif::[]
 * experimental:[] <<esql-lookup-join>>
 * experimental:[] <<esql-mv_expand>>
 * <<esql-rename>>
+* experimental:[] <<esql-sample>>
 * <<esql-sort>>
 * <<esql-stats-by>>
 * <<esql-where>>
@@ -70,6 +71,7 @@ include::processing-commands/limit.asciidoc[]
 include::processing-commands/lookup.asciidoc[]
 include::processing-commands/mv_expand.asciidoc[]
 include::processing-commands/rename.asciidoc[]
+include::processing-commands/sample.asciidoc[]
 include::processing-commands/sort.asciidoc[]
 include::processing-commands/stats.asciidoc[]
 include::processing-commands/where.asciidoc[]

docs/reference/esql/esql-commands.asciidoc

@@ -0,0 +1,30 @@
+[discrete]
+[[esql-sample]]
+=== `SAMPLE`
+
+preview::[]
+
+The `SAMPLE` command samples a fraction of the table rows.
+
+**Syntax**
+
+[source,esql]
+----
+SAMPLE probability
+----
+
+*Parameters*
+
+`probability`::
+The probability that a row is included in the sample. The value must be between 0 and 1, exclusive.
+
+*Example*
+
+[source.merge.styled,esql]
+----
+include::{esql-specs}/sample.csv-spec[tag=sampleForDocs]
+----
+[%header.monospaced.styled,format=dsv,separator=|]
+|===
+include::{esql-specs}/sample.csv-spec[tag=sampleForDocs-result]
+|===

docs/reference/esql/functions/description/date_trunc.asciidoc

@@ -249,7 +249,8 @@ GET /_xpack/usage
       "lookup_join" : 0,
       "change_point" : 0,
       "completion": 0,
-      "rerank": 0
+      "rerank": 0,
+      "sample": 0
     },
     "queries" : {
       "rest" : {

docs/reference/esql/functions/kibana/docs/date_trunc.md

@@ -244,6 +244,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion SETTINGS_IN_DATA_STREAMS_8_19 = def(8_841_0_51);
     public static final TransportVersion ML_INFERENCE_CUSTOM_SERVICE_REMOVE_ERROR_PARSING_8_19 = def(8_841_0_52);
     public static final TransportVersion ML_INFERENCE_CUSTOM_SERVICE_EMBEDDING_BATCH_SIZE_8_19 = def(8_841_0_53);
+    public static final TransportVersion RANDOM_SAMPLER_QUERY_BUILDER_8_19 = def(8_841_0_54);
 
     /*
      * STOP! READ THIS FIRST! No, really,