ES|QL: add MV_APPEND function (#107001)

Adding `MV_APPEND(value1, value2)` function, that appends two values
creating a single multi-value. If one or both the inputs are
multi-values, the result is the concatenation of all the values, eg.

```
MV_APPEND([a, b], [c, d]) -> [a, b, c, d]
```

~I think for this specific case it makes sense to consider `null` values
as empty arrays, so that~ ~MV_APPEND(value, null) -> value~ ~It is
pretty uncommon for ESQL (all the other functions, apart from
`COALESCE`, short-circuit to `null` when one of the values is null), so
let's discuss this behavior.~

[EDIT] considering the feedback from Andrei, I changed this logic and
made it consistent with the other functions: now if one of the
parameters is null, the function returns null

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

@@ -0,0 +1,5 @@
+// This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
+
+*Description*
+
+Concatenates values of two multi-value fields.

docs/reference/esql/functions/kibana/definition/mv_append.json

@@ -0,0 +1,242 @@
+{
+  "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
+  "type" : "eval",
+  "name" : "mv_append",
+  "description" : "Concatenates values of two multi-value fields.",
+  "signatures" : [
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "boolean",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "boolean",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "boolean"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "cartesian_point",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "cartesian_point",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "cartesian_point"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "cartesian_shape",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "cartesian_shape",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "cartesian_shape"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "datetime",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "datetime",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "datetime"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "double",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "double",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "double"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "geo_point",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "geo_point",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "geo_point"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "geo_shape",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "geo_shape",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "geo_shape"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "integer",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "integer",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "integer"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "ip",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "ip",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "ip"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "keyword",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "keyword",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "keyword"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "long",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "long",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "long"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "text",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "text",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "text"
+    },
+    {
+      "params" : [
+        {
+          "name" : "field1",
+          "type" : "version",
+          "optional" : false,
+          "description" : ""
+        },
+        {
+          "name" : "field2",
+          "type" : "version",
+          "optional" : false,
+          "description" : ""
+        }
+      ],
+      "variadic" : false,
+      "returnType" : "version"
+    }
+  ]
+}

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

@@ -0,0 +1,7 @@
+<!--
+This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
+-->
+
+### MV_APPEND
+Concatenates values of two multi-value fields.
+

docs/reference/esql/functions/layout/mv_append.asciidoc

@@ -0,0 +1,14 @@
+// This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
+
+[discrete]
+[[esql-mv_append]]
+=== `MV_APPEND`
+
+*Syntax*
+
+[.text-center]
+image::esql/functions/signature/mv_append.svg[Embedded,opts=inline]
+
+include::../parameters/mv_append.asciidoc[]
+include::../description/mv_append.asciidoc[]
+include::../types/mv_append.asciidoc[]

docs/reference/esql/functions/parameters/mv_append.asciidoc

@@ -0,0 +1,9 @@
+// This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
+
+*Parameters*
+
+`field1`::
+
+
+`field2`::
+

docs/reference/esql/functions/signature/mv_append.svg

@@ -0,0 +1 @@
+<svg version="1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" width="468" height="46" viewbox="0 0 468 46"><defs><style type="text/css">#guide .c{fill:none;stroke:#222222;}#guide .k{fill:#000000;font-family:Roboto Mono,Sans-serif;font-size:20px;}#guide .s{fill:#e4f4ff;stroke:#222222;}#guide .syn{fill:#8D8D8D;font-family:Roboto Mono,Sans-serif;font-size:20px;}</style></defs><path class="c" d="M0 31h5m128 0h10m32 0h10m92 0h10m32 0h10m92 0h10m32 0h5"/><rect class="s" x="5" y="5" width="128" height="36"/><text class="k" x="15" y="31">MV_APPEND</text><rect class="s" x="143" y="5" width="32" height="36" rx="7"/><text class="syn" x="153" y="31">(</text><rect class="s" x="185" y="5" width="92" height="36" rx="7"/><text class="k" x="195" y="31">field1</text><rect class="s" x="287" y="5" width="32" height="36" rx="7"/><text class="syn" x="297" y="31">,</text><rect class="s" x="329" y="5" width="92" height="36" rx="7"/><text class="k" x="339" y="31">field2</text><rect class="s" x="431" y="5" width="32" height="36" rx="7"/><text class="syn" x="441" y="31">)</text></svg>

docs/reference/esql/functions/types/mv_append.asciidoc

@@ -0,0 +1,21 @@
+// This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
+
+*Supported types*
+
+[%header.monospaced.styled,format=dsv,separator=|]
+|===
+field1 | field2 | result
+boolean | boolean | boolean
+cartesian_point | cartesian_point | cartesian_point
+cartesian_shape | cartesian_shape | cartesian_shape
+datetime | datetime | datetime
+double | double | double
+geo_point | geo_point | geo_point
+geo_shape | geo_shape | geo_shape
+integer | integer | integer
+ip | ip | ip
+keyword | keyword | keyword
+long | long | long
+text | text | text
+version | version | version
+|===

x-pack/plugin/esql-core/src/test/resources/mapping-multi-field-variation.json

@@ -8,6 +8,8 @@
         "keyword" : { "type" : "keyword" },
         "date" :  { "type" : "date" },
         "date_nanos": { "type" : "date_nanos" },
+        "long" :  { "type" : "long" },
+        "ip" :  { "type" : "ip" },
         "unsupported" : { "type" : "ip_range" },
         "some" : {
             "properties" : {

x-pack/plugin/esql/qa/testFixtures/src/main/resources/date.csv-spec

@@ -1076,6 +1076,23 @@ required_capability: agg_values
 [1955-01-21T00:00:00Z, 1957-05-23T00:00:00Z, 1959-12-03T00:00:00Z] | null
 ;
 
+
+mvAppendDates
+required_capability: fn_mv_append
+
+FROM employees
+| WHERE emp_no == 10039 OR emp_no == 10040
+| SORT emp_no
+| EVAL dates = mv_append(birth_date, hire_date)
+| KEEP emp_no, birth_date, hire_date, dates
+;
+
+emp_no:integer | birth_date:date      | hire_date:date       | dates:date
+10039          | 1959-10-01T00:00:00Z | 1988-01-19T00:00:00Z | [1959-10-01T00:00:00Z, 1988-01-19T00:00:00Z]
+10040          | null                 | 1993-02-14T00:00:00Z | null 
+;
+
+
 implicitCastingNotEqual
 required_capability: string_literal_auto_casting
 from employees | where birth_date != "1957-05-23T00:00:00Z" | keep emp_no, birth_date | sort emp_no | limit 3;

x-pack/plugin/esql/qa/testFixtures/src/main/resources/floats.csv-spec

@@ -523,6 +523,25 @@ required_capability: agg_values
 [1.7, 1.83, 2.05] | null
 ;
 
+
+mvAppend
+required_capability: fn_mv_append
+
+FROM employees
+| WHERE emp_no == 10008 OR emp_no == 10021
+| EVAL d = mv_append(salary_change, salary_change),
+       i = mv_append(salary_change.int, salary_change.int),
+       i2 = mv_append(emp_no, salary_change.int),
+       i3 = mv_append(emp_no, emp_no),  
+       s = mv_append(salary_change.keyword, salary_change.keyword)
+| KEEP emp_no, salary_change, d, i, i2, i3, s;
+
+emp_no:integer | salary_change:double    | d:double                                       | i:integer              | i2:integer         | i3:integer     | s:keyword
+10008          | [-2.92,0.75,3.54,12.68] | [-2.92,0.75,3.54,12.68,-2.92,0.75,3.54,12.68]  | [-2,0,3,12,-2,0,3,12]  | [10008,-2,0,3,12]  | [10008, 10008] | [-2.92,0.75,12.68,3.54,-2.92,0.75,12.68,3.54]
+10021          | null                    | null                                           | null                   | null               | [10021, 10021] | null
+;
+
+
 signumOfPositiveDouble#[skip:-8.13.99,reason:new scalar function added in 8.14]
 row d = to_double(100) | eval s = signum(d);
 

x-pack/plugin/esql/qa/testFixtures/src/main/resources/meta.csv-spec

@@ -42,6 +42,7 @@ double e()
 "double|integer|long median(number:double|integer|long)"
 "double|integer|long median_absolute_deviation(number:double|integer|long)"
 "double|integer|long min(number:double|integer|long)"
+"boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version mv_append(field1:boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version, field2:boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version)"
 "double mv_avg(number:double|integer|long|unsigned_long)"
 "keyword mv_concat(string:text|keyword, delim:text|keyword)"
 "integer mv_count(field:boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|unsigned_long|version)"
@@ -157,6 +158,7 @@ max           |number                              |"double|integer|long"
 median        |number                              |"double|integer|long"                                                                                                             |[""]
 median_absolut|number                              |"double|integer|long"                                                                                                             |[""]
 min           |number                              |"double|integer|long"                                                                                                             |[""]
+mv_append     |[field1, field2]                    |["boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version", "boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version"]                 | ["", ""]
 mv_avg        |number                              |"double|integer|long|unsigned_long"                                                                                               |Multivalue expression.
 mv_concat     |[string, delim]                     |["text|keyword", "text|keyword"]                                                                                                  |[Multivalue expression., Delimiter.]
 mv_count      |field                               |"boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|unsigned_long|version"      |Multivalue expression.
@@ -273,6 +275,7 @@ max           |The maximum value of a numeric field.
 median        |The value that is greater than half of all values and less than half of all values.
 median_absolut|The median absolute deviation, a measure of variability.
 min           |The minimum value of a numeric field.
+mv_append     |Concatenates values of two multi-value fields.
 mv_avg        |Converts a multivalued field into a single valued field containing the average of all of the values.
 mv_concat     |Converts a multivalued string expression into a single valued column containing the concatenation of all values separated by a delimiter.
 mv_count      |Converts a multivalued expression into a single valued column containing a count of the number of values.
@@ -390,6 +393,7 @@ max           |"double|integer|long"
 median        |"double|integer|long"                                                                                                       |false                       |false           |true
 median_absolut|"double|integer|long"                                                                                                       |false                       |false           |true
 min           |"double|integer|long"                                                                                                       |false                       |false           |true
+mv_append     |"boolean|cartesian_point|cartesian_shape|date|double|geo_point|geo_shape|integer|ip|keyword|long|text|version"              |[false, false]              |false 		     |false
 mv_avg        |double                                                                                                                      |false                       |false           |false
 mv_concat     |keyword                                                                                                                     |[false, false]              |false           |false
 mv_count      |integer                                                                                                                     |false                       |false           |false
@@ -475,5 +479,5 @@ countFunctions#[skip:-8.14.99, reason:BIN added]
 meta functions |  stats  a = count(*), b = count(*), c = count(*) |  mv_expand c;
 
 a:long | b:long | c:long
-107    | 107    | 107
+108    | 108    | 108
 ;

x-pack/plugin/esql/qa/testFixtures/src/main/resources/string.csv-spec

@@ -1335,6 +1335,79 @@ l1:integer | l2:integer
 null       | 0
 ;
 
+
+mvAppend
+required_capability: fn_mv_append
+
+ROW a = "a", b = ["b", "c"], n = null
+| EVAL aa = mv_append(a, a), bb = mv_append(b, b), ab = mv_append(a, b), abb = mv_append(mv_append(a, b), b), na = mv_append(n, a), an = mv_append(a, n)
+;
+
+a:keyword | b:keyword | n:null | aa:keyword | bb:keyword   | ab:keyword | abb:keyword    | na:keyword | an:keyword
+a         | [b, c]    | null   |[a, a]     | [b, c, b, c] | [a, b, c]  | [a, b, c, b, c] | null       | null
+;
+
+
+mvAppendNull
+required_capability: fn_mv_append
+
+ROW a = "a", b = ["b", "c"], c = to_string(null)
+| EVAL a_null = mv_append(a, c),
+       null_a = mv_append(c, a),
+       b_null = mv_append(b, c),
+       null_b = mv_append(c, b),
+       null_null = mv_append(c, c)
+;
+
+a:keyword | b:keyword | c:keyword | a_null:keyword | null_a:keyword | b_null:keyword | null_b:keyword | null_null:keyword  
+a         | [b, c]    | null      | null           | null           | null           | null           | null
+;
+
+
+mvAppendStrings
+required_capability: fn_mv_append
+
+FROM employees
+| WHERE emp_no == 10004
+| EVAL names = mv_sort(mv_append(first_name, last_name)), 
+       two_jobs = mv_sort(mv_append(job_positions, job_positions)),
+       three_jobs = mv_sort(mv_append(job_positions, mv_append(job_positions, job_positions)))
+| KEEP emp_no, names, two_jobs, three_jobs
+;
+
+emp_no:integer | names:keyword    | two_jobs:keyword                                       | three_jobs:keyword
+10004          | ["Chirstian", "Koblick"] | ["Head Human Resources","Head Human Resources","Reporting Analyst","Reporting Analyst","Support Engineer","Support Engineer","Tech Lead","Tech Lead"]  | ["Head Human Resources","Head Human Resources","Head Human Resources","Reporting Analyst","Reporting Analyst","Reporting Analyst","Support Engineer","Support Engineer","Support Engineer","Tech Lead","Tech Lead","Tech Lead"] 
+;
+
+
+
+mvAppendStringsWhere
+required_capability: fn_mv_append
+
+FROM employees
+| EVAL two_jobs = mv_append(mv_sort(job_positions), mv_sort(job_positions)) 
+| WHERE emp_no == 10004 AND mv_slice(mv_append(mv_sort(job_positions), mv_sort(job_positions)), 6, 6) == "Support Engineer"
+| KEEP emp_no, two_jobs
+;
+
+emp_no:integer | two_jobs:keyword                       
+10004          | ["Head Human Resources","Reporting Analyst","Support Engineer","Tech Lead","Head Human Resources","Reporting Analyst","Support Engineer","Tech Lead"]   
+;
+
+mvAppendNullFields
+required_capability: fn_mv_append
+
+FROM employees
+| WHERE emp_no == 10005
+| EVAL x = mv_append(first_name, job_positions), y = mv_append(job_positions, first_name), z = mv_append(job_positions, job_positions)
+| keep emp_no, first_name, job_positions, x, y, z
+;
+
+emp_no:integer | first_name:keyword | job_positions:keyword | x:keyword | y:keyword | z:keyword
+10005          | Kyoichi            | null                  | null      | null      | null
+;         
+
+
 base64Encode#[skip:-8.13.99,reason:new base64 function added in 8.14]
 required_capability: base64_decode_encode
 

x-pack/plugin/esql/qa/testFixtures/src/main/resources/version.csv-spec

@@ -371,6 +371,21 @@ version:version | name:keyword
           5.2.9 | mmmmm
 ;
 
+
+mvAppend
+required_capability: fn_mv_append
+
+ROW a = to_version("1.2.0"), x1 = to_version("0.0.1"), x2 = to_version("1.0.0")
+| EVAL b = mv_append(x1, x2)
+| EVAL aa = mv_append(a, a), bb = mv_append(b, b), ab = mv_append(a, b), abb = mv_append(mv_append(a, b), b)
+| KEEP a, b, aa, bb, ab, abb
+;
+
+a:version | b:version       | aa:version         | bb:version                   | ab:version             | abb:version
+1.2.0     | [0.0.1, 1.0.0]  | [1.2.0, 1.2.0]     | [0.0.1, 1.0.0, 0.0.1, 1.0.0] | [1.2.0, 0.0.1, 1.0.0]  | [1.2.0, 0.0.1, 1.0.0, 0.0.1, 1.0.0]
+;
+
+
 implictCastingEqual
 required_capability: string_literal_auto_casting_extended
 from apps | where version == "1.2.3.4" | sort name | keep name, version;

x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendBooleanEvaluator.java

@@ -0,0 +1,102 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License
+// 2.0; you may not use this file except in compliance with the Elastic License
+// 2.0.
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import java.lang.Override;
+import java.lang.String;
+import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.BooleanBlock;
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.compute.operator.DriverContext;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.expression.function.Warnings;
+
+/**
+ * {@link EvalOperator.ExpressionEvaluator} implementation for {@link MvAppend}.
+ * This class is generated. Do not edit it.
+ */
+public final class MvAppendBooleanEvaluator implements EvalOperator.ExpressionEvaluator {
+  private final Warnings warnings;
+
+  private final EvalOperator.ExpressionEvaluator field1;
+
+  private final EvalOperator.ExpressionEvaluator field2;
+
+  private final DriverContext driverContext;
+
+  public MvAppendBooleanEvaluator(Source source, EvalOperator.ExpressionEvaluator field1,
+      EvalOperator.ExpressionEvaluator field2, DriverContext driverContext) {
+    this.warnings = new Warnings(source);
+    this.field1 = field1;
+    this.field2 = field2;
+    this.driverContext = driverContext;
+  }
+
+  @Override
+  public Block eval(Page page) {
+    try (BooleanBlock field1Block = (BooleanBlock) field1.eval(page)) {
+      try (BooleanBlock field2Block = (BooleanBlock) field2.eval(page)) {
+        return eval(page.getPositionCount(), field1Block, field2Block);
+      }
+    }
+  }
+
+  public BooleanBlock eval(int positionCount, BooleanBlock field1Block, BooleanBlock field2Block) {
+    try(BooleanBlock.Builder result = driverContext.blockFactory().newBooleanBlockBuilder(positionCount)) {
+      position: for (int p = 0; p < positionCount; p++) {
+        boolean allBlocksAreNulls = true;
+        if (!field1Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (!field2Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (allBlocksAreNulls) {
+          result.appendNull();
+          continue position;
+        }
+        MvAppend.process(result, p, field1Block, field2Block);
+      }
+      return result.build();
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "MvAppendBooleanEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+  }
+
+  @Override
+  public void close() {
+    Releasables.closeExpectNoException(field1, field2);
+  }
+
+  static class Factory implements EvalOperator.ExpressionEvaluator.Factory {
+    private final Source source;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field1;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field2;
+
+    public Factory(Source source, EvalOperator.ExpressionEvaluator.Factory field1,
+        EvalOperator.ExpressionEvaluator.Factory field2) {
+      this.source = source;
+      this.field1 = field1;
+      this.field2 = field2;
+    }
+
+    @Override
+    public MvAppendBooleanEvaluator get(DriverContext context) {
+      return new MvAppendBooleanEvaluator(source, field1.get(context), field2.get(context), context);
+    }
+
+    @Override
+    public String toString() {
+      return "MvAppendBooleanEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+    }
+  }
+}

x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendBytesRefEvaluator.java

@@ -0,0 +1,103 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License
+// 2.0; you may not use this file except in compliance with the Elastic License
+// 2.0.
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import java.lang.Override;
+import java.lang.String;
+import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.BytesRefBlock;
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.compute.operator.DriverContext;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.expression.function.Warnings;
+
+/**
+ * {@link EvalOperator.ExpressionEvaluator} implementation for {@link MvAppend}.
+ * This class is generated. Do not edit it.
+ */
+public final class MvAppendBytesRefEvaluator implements EvalOperator.ExpressionEvaluator {
+  private final Warnings warnings;
+
+  private final EvalOperator.ExpressionEvaluator field1;
+
+  private final EvalOperator.ExpressionEvaluator field2;
+
+  private final DriverContext driverContext;
+
+  public MvAppendBytesRefEvaluator(Source source, EvalOperator.ExpressionEvaluator field1,
+      EvalOperator.ExpressionEvaluator field2, DriverContext driverContext) {
+    this.warnings = new Warnings(source);
+    this.field1 = field1;
+    this.field2 = field2;
+    this.driverContext = driverContext;
+  }
+
+  @Override
+  public Block eval(Page page) {
+    try (BytesRefBlock field1Block = (BytesRefBlock) field1.eval(page)) {
+      try (BytesRefBlock field2Block = (BytesRefBlock) field2.eval(page)) {
+        return eval(page.getPositionCount(), field1Block, field2Block);
+      }
+    }
+  }
+
+  public BytesRefBlock eval(int positionCount, BytesRefBlock field1Block,
+      BytesRefBlock field2Block) {
+    try(BytesRefBlock.Builder result = driverContext.blockFactory().newBytesRefBlockBuilder(positionCount)) {
+      position: for (int p = 0; p < positionCount; p++) {
+        boolean allBlocksAreNulls = true;
+        if (!field1Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (!field2Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (allBlocksAreNulls) {
+          result.appendNull();
+          continue position;
+        }
+        MvAppend.process(result, p, field1Block, field2Block);
+      }
+      return result.build();
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "MvAppendBytesRefEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+  }
+
+  @Override
+  public void close() {
+    Releasables.closeExpectNoException(field1, field2);
+  }
+
+  static class Factory implements EvalOperator.ExpressionEvaluator.Factory {
+    private final Source source;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field1;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field2;
+
+    public Factory(Source source, EvalOperator.ExpressionEvaluator.Factory field1,
+        EvalOperator.ExpressionEvaluator.Factory field2) {
+      this.source = source;
+      this.field1 = field1;
+      this.field2 = field2;
+    }
+
+    @Override
+    public MvAppendBytesRefEvaluator get(DriverContext context) {
+      return new MvAppendBytesRefEvaluator(source, field1.get(context), field2.get(context), context);
+    }
+
+    @Override
+    public String toString() {
+      return "MvAppendBytesRefEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+    }
+  }
+}

x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendDoubleEvaluator.java

@@ -0,0 +1,102 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License
+// 2.0; you may not use this file except in compliance with the Elastic License
+// 2.0.
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import java.lang.Override;
+import java.lang.String;
+import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.DoubleBlock;
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.compute.operator.DriverContext;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.expression.function.Warnings;
+
+/**
+ * {@link EvalOperator.ExpressionEvaluator} implementation for {@link MvAppend}.
+ * This class is generated. Do not edit it.
+ */
+public final class MvAppendDoubleEvaluator implements EvalOperator.ExpressionEvaluator {
+  private final Warnings warnings;
+
+  private final EvalOperator.ExpressionEvaluator field1;
+
+  private final EvalOperator.ExpressionEvaluator field2;
+
+  private final DriverContext driverContext;
+
+  public MvAppendDoubleEvaluator(Source source, EvalOperator.ExpressionEvaluator field1,
+      EvalOperator.ExpressionEvaluator field2, DriverContext driverContext) {
+    this.warnings = new Warnings(source);
+    this.field1 = field1;
+    this.field2 = field2;
+    this.driverContext = driverContext;
+  }
+
+  @Override
+  public Block eval(Page page) {
+    try (DoubleBlock field1Block = (DoubleBlock) field1.eval(page)) {
+      try (DoubleBlock field2Block = (DoubleBlock) field2.eval(page)) {
+        return eval(page.getPositionCount(), field1Block, field2Block);
+      }
+    }
+  }
+
+  public DoubleBlock eval(int positionCount, DoubleBlock field1Block, DoubleBlock field2Block) {
+    try(DoubleBlock.Builder result = driverContext.blockFactory().newDoubleBlockBuilder(positionCount)) {
+      position: for (int p = 0; p < positionCount; p++) {
+        boolean allBlocksAreNulls = true;
+        if (!field1Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (!field2Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (allBlocksAreNulls) {
+          result.appendNull();
+          continue position;
+        }
+        MvAppend.process(result, p, field1Block, field2Block);
+      }
+      return result.build();
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "MvAppendDoubleEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+  }
+
+  @Override
+  public void close() {
+    Releasables.closeExpectNoException(field1, field2);
+  }
+
+  static class Factory implements EvalOperator.ExpressionEvaluator.Factory {
+    private final Source source;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field1;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field2;
+
+    public Factory(Source source, EvalOperator.ExpressionEvaluator.Factory field1,
+        EvalOperator.ExpressionEvaluator.Factory field2) {
+      this.source = source;
+      this.field1 = field1;
+      this.field2 = field2;
+    }
+
+    @Override
+    public MvAppendDoubleEvaluator get(DriverContext context) {
+      return new MvAppendDoubleEvaluator(source, field1.get(context), field2.get(context), context);
+    }
+
+    @Override
+    public String toString() {
+      return "MvAppendDoubleEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+    }
+  }
+}

x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendIntEvaluator.java

@@ -0,0 +1,102 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License
+// 2.0; you may not use this file except in compliance with the Elastic License
+// 2.0.
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import java.lang.Override;
+import java.lang.String;
+import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.IntBlock;
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.compute.operator.DriverContext;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.expression.function.Warnings;
+
+/**
+ * {@link EvalOperator.ExpressionEvaluator} implementation for {@link MvAppend}.
+ * This class is generated. Do not edit it.
+ */
+public final class MvAppendIntEvaluator implements EvalOperator.ExpressionEvaluator {
+  private final Warnings warnings;
+
+  private final EvalOperator.ExpressionEvaluator field1;
+
+  private final EvalOperator.ExpressionEvaluator field2;
+
+  private final DriverContext driverContext;
+
+  public MvAppendIntEvaluator(Source source, EvalOperator.ExpressionEvaluator field1,
+      EvalOperator.ExpressionEvaluator field2, DriverContext driverContext) {
+    this.warnings = new Warnings(source);
+    this.field1 = field1;
+    this.field2 = field2;
+    this.driverContext = driverContext;
+  }
+
+  @Override
+  public Block eval(Page page) {
+    try (IntBlock field1Block = (IntBlock) field1.eval(page)) {
+      try (IntBlock field2Block = (IntBlock) field2.eval(page)) {
+        return eval(page.getPositionCount(), field1Block, field2Block);
+      }
+    }
+  }
+
+  public IntBlock eval(int positionCount, IntBlock field1Block, IntBlock field2Block) {
+    try(IntBlock.Builder result = driverContext.blockFactory().newIntBlockBuilder(positionCount)) {
+      position: for (int p = 0; p < positionCount; p++) {
+        boolean allBlocksAreNulls = true;
+        if (!field1Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (!field2Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (allBlocksAreNulls) {
+          result.appendNull();
+          continue position;
+        }
+        MvAppend.process(result, p, field1Block, field2Block);
+      }
+      return result.build();
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "MvAppendIntEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+  }
+
+  @Override
+  public void close() {
+    Releasables.closeExpectNoException(field1, field2);
+  }
+
+  static class Factory implements EvalOperator.ExpressionEvaluator.Factory {
+    private final Source source;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field1;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field2;
+
+    public Factory(Source source, EvalOperator.ExpressionEvaluator.Factory field1,
+        EvalOperator.ExpressionEvaluator.Factory field2) {
+      this.source = source;
+      this.field1 = field1;
+      this.field2 = field2;
+    }
+
+    @Override
+    public MvAppendIntEvaluator get(DriverContext context) {
+      return new MvAppendIntEvaluator(source, field1.get(context), field2.get(context), context);
+    }
+
+    @Override
+    public String toString() {
+      return "MvAppendIntEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+    }
+  }
+}

x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendLongEvaluator.java

@@ -0,0 +1,102 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License
+// 2.0; you may not use this file except in compliance with the Elastic License
+// 2.0.
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import java.lang.Override;
+import java.lang.String;
+import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.LongBlock;
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.compute.operator.DriverContext;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.expression.function.Warnings;
+
+/**
+ * {@link EvalOperator.ExpressionEvaluator} implementation for {@link MvAppend}.
+ * This class is generated. Do not edit it.
+ */
+public final class MvAppendLongEvaluator implements EvalOperator.ExpressionEvaluator {
+  private final Warnings warnings;
+
+  private final EvalOperator.ExpressionEvaluator field1;
+
+  private final EvalOperator.ExpressionEvaluator field2;
+
+  private final DriverContext driverContext;
+
+  public MvAppendLongEvaluator(Source source, EvalOperator.ExpressionEvaluator field1,
+      EvalOperator.ExpressionEvaluator field2, DriverContext driverContext) {
+    this.warnings = new Warnings(source);
+    this.field1 = field1;
+    this.field2 = field2;
+    this.driverContext = driverContext;
+  }
+
+  @Override
+  public Block eval(Page page) {
+    try (LongBlock field1Block = (LongBlock) field1.eval(page)) {
+      try (LongBlock field2Block = (LongBlock) field2.eval(page)) {
+        return eval(page.getPositionCount(), field1Block, field2Block);
+      }
+    }
+  }
+
+  public LongBlock eval(int positionCount, LongBlock field1Block, LongBlock field2Block) {
+    try(LongBlock.Builder result = driverContext.blockFactory().newLongBlockBuilder(positionCount)) {
+      position: for (int p = 0; p < positionCount; p++) {
+        boolean allBlocksAreNulls = true;
+        if (!field1Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (!field2Block.isNull(p)) {
+          allBlocksAreNulls = false;
+        }
+        if (allBlocksAreNulls) {
+          result.appendNull();
+          continue position;
+        }
+        MvAppend.process(result, p, field1Block, field2Block);
+      }
+      return result.build();
+    }
+  }
+
+  @Override
+  public String toString() {
+    return "MvAppendLongEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+  }
+
+  @Override
+  public void close() {
+    Releasables.closeExpectNoException(field1, field2);
+  }
+
+  static class Factory implements EvalOperator.ExpressionEvaluator.Factory {
+    private final Source source;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field1;
+
+    private final EvalOperator.ExpressionEvaluator.Factory field2;
+
+    public Factory(Source source, EvalOperator.ExpressionEvaluator.Factory field1,
+        EvalOperator.ExpressionEvaluator.Factory field2) {
+      this.source = source;
+      this.field1 = field1;
+      this.field2 = field2;
+    }
+
+    @Override
+    public MvAppendLongEvaluator get(DriverContext context) {
+      return new MvAppendLongEvaluator(source, field1.get(context), field2.get(context), context);
+    }
+
+    @Override
+    public String toString() {
+      return "MvAppendLongEvaluator[" + "field1=" + field1 + ", field2=" + field2 + "]";
+    }
+  }
+}

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -27,6 +27,11 @@ public class EsqlCapabilities {
      */
     private static final String FN_CBRT = "fn_cbrt";
 
+    /**
+     * Support for {@code MV_APPEND} function. #107001
+     */
+    private static final String FN_MV_APPEND = "fn_mv_append";
+
     /**
      * Support for function {@code IP_PREFIX}.
      */
@@ -61,6 +66,7 @@ public class EsqlCapabilities {
         caps.add(FN_SUBSTRING_EMPTY_NULL);
         caps.add(ST_CENTROID_AGG_OPTIMIZED);
         caps.add(METADATA_IGNORED_FIELD);
+        caps.add(FN_MV_APPEND);
 
         if (Build.current().isSnapshot()) {
             caps.add(LOOKUP);

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/EsqlFunctionRegistry.java

@@ -76,6 +76,7 @@ import org.elasticsearch.xpack.esql.expression.function.scalar.math.Sqrt;
 import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tan;
 import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tanh;
 import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tau;
+import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvAppend;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvAvg;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcat;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvCount;
@@ -280,6 +281,7 @@ public final class EsqlFunctionRegistry extends FunctionRegistry {
                 def(ToVersion.class, ToVersion::new, "to_version", "to_ver"), },
             // multivalue functions
             new FunctionDefinition[] {
+                def(MvAppend.class, MvAppend::new, "mv_append"),
                 def(MvAvg.class, MvAvg::new, "mv_avg"),
                 def(MvConcat.class, MvConcat::new, "mv_concat"),
                 def(MvCount.class, MvCount::new, "mv_count"),

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppend.java

@@ -0,0 +1,285 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.compute.ann.Evaluator;
+import org.elasticsearch.compute.data.BooleanBlock;
+import org.elasticsearch.compute.data.BytesRefBlock;
+import org.elasticsearch.compute.data.DoubleBlock;
+import org.elasticsearch.compute.data.IntBlock;
+import org.elasticsearch.compute.data.LongBlock;
+import org.elasticsearch.compute.operator.EvalOperator;
+import org.elasticsearch.xpack.esql.EsqlIllegalArgumentException;
+import org.elasticsearch.xpack.esql.core.expression.Expression;
+import org.elasticsearch.xpack.esql.core.expression.Nullability;
+import org.elasticsearch.xpack.esql.core.tree.NodeInfo;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.core.type.DataType;
+import org.elasticsearch.xpack.esql.core.type.DataTypes;
+import org.elasticsearch.xpack.esql.evaluator.mapper.EvaluatorMapper;
+import org.elasticsearch.xpack.esql.expression.function.FunctionInfo;
+import org.elasticsearch.xpack.esql.expression.function.Param;
+import org.elasticsearch.xpack.esql.expression.function.scalar.EsqlScalarFunction;
+import org.elasticsearch.xpack.esql.planner.PlannerUtils;
+import org.elasticsearch.xpack.esql.type.EsqlDataTypes;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.function.Function;
+
+import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.FIRST;
+import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.SECOND;
+import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isType;
+
+/**
+ * Appends values to a multi-value
+ */
+public class MvAppend extends EsqlScalarFunction implements EvaluatorMapper {
+    private final Expression field1, field2;
+    private DataType dataType;
+
+    @FunctionInfo(
+        returnType = {
+            "boolean",
+            "cartesian_point",
+            "cartesian_shape",
+            "date",
+            "double",
+            "geo_point",
+            "geo_shape",
+            "integer",
+            "ip",
+            "keyword",
+            "long",
+            "text",
+            "version" },
+        description = "Concatenates values of two multi-value fields."
+    )
+    public MvAppend(
+        Source source,
+        @Param(
+            name = "field1",
+            type = {
+                "boolean",
+                "cartesian_point",
+                "cartesian_shape",
+                "date",
+                "double",
+                "geo_point",
+                "geo_shape",
+                "integer",
+                "ip",
+                "keyword",
+                "long",
+                "text",
+                "version" }
+        ) Expression field1,
+        @Param(
+            name = "field2",
+            type = {
+                "boolean",
+                "cartesian_point",
+                "cartesian_shape",
+                "date",
+                "double",
+                "geo_point",
+                "geo_shape",
+                "integer",
+                "ip",
+                "keyword",
+                "long",
+                "text",
+                "version" }
+        ) Expression field2
+    ) {
+        super(source, Arrays.asList(field1, field2));
+        this.field1 = field1;
+        this.field2 = field2;
+    }
+
+    @Override
+    protected TypeResolution resolveType() {
+        if (childrenResolved() == false) {
+            return new TypeResolution("Unresolved children");
+        }
+
+        TypeResolution resolution = isType(field1, EsqlDataTypes::isRepresentable, sourceText(), FIRST, "representable");
+        if (resolution.unresolved()) {
+            return resolution;
+        }
+        dataType = field1.dataType();
+        if (dataType == DataTypes.NULL) {
+            dataType = field2.dataType();
+            return isType(field2, EsqlDataTypes::isRepresentable, sourceText(), SECOND, "representable");
+        }
+        return isType(field2, t -> t == dataType, sourceText(), SECOND, dataType.typeName());
+    }
+
+    @Override
+    public boolean foldable() {
+        return field1.foldable() && field2.foldable();
+    }
+
+    @Override
+    public EvalOperator.ExpressionEvaluator.Factory toEvaluator(
+        Function<Expression, EvalOperator.ExpressionEvaluator.Factory> toEvaluator
+    ) {
+        return switch (PlannerUtils.toElementType(dataType())) {
+            case BOOLEAN -> new MvAppendBooleanEvaluator.Factory(source(), toEvaluator.apply(field1), toEvaluator.apply(field2));
+            case BYTES_REF -> new MvAppendBytesRefEvaluator.Factory(source(), toEvaluator.apply(field1), toEvaluator.apply(field2));
+            case DOUBLE -> new MvAppendDoubleEvaluator.Factory(source(), toEvaluator.apply(field1), toEvaluator.apply(field2));
+            case INT -> new MvAppendIntEvaluator.Factory(source(), toEvaluator.apply(field1), toEvaluator.apply(field2));
+            case LONG -> new MvAppendLongEvaluator.Factory(source(), toEvaluator.apply(field1), toEvaluator.apply(field2));
+            case NULL -> EvalOperator.CONSTANT_NULL_FACTORY;
+            default -> throw EsqlIllegalArgumentException.illegalDataType(dataType);
+        };
+    }
+
+    @Override
+    public Expression replaceChildren(List<Expression> newChildren) {
+        return new MvAppend(source(), newChildren.get(0), newChildren.get(1));
+    }
+
+    @Override
+    protected NodeInfo<? extends Expression> info() {
+        return NodeInfo.create(this, MvAppend::new, field1, field2);
+    }
+
+    @Override
+    public DataType dataType() {
+        if (dataType == null) {
+            resolveType();
+        }
+        return dataType;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(field1, field2);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null || obj.getClass() != getClass()) {
+            return false;
+        }
+        MvAppend other = (MvAppend) obj;
+        return Objects.equals(other.field1, field1) && Objects.equals(other.field2, field2);
+    }
+
+    @Evaluator(extraName = "Int")
+    static void process(IntBlock.Builder builder, int position, IntBlock field1, IntBlock field2) {
+        int count1 = field1.getValueCount(position);
+        int count2 = field2.getValueCount(position);
+        if (count1 == 0 || count2 == 0) {
+            builder.appendNull();
+        } else {
+            builder.beginPositionEntry();
+            int first1 = field1.getFirstValueIndex(position);
+            int first2 = field2.getFirstValueIndex(position);
+            for (int i = 0; i < count1; i++) {
+                builder.appendInt(field1.getInt(first1 + i));
+            }
+            for (int i = 0; i < count2; i++) {
+                builder.appendInt(field2.getInt(first2 + i));
+            }
+            builder.endPositionEntry();
+        }
+
+    }
+
+    @Evaluator(extraName = "Boolean")
+    static void process(BooleanBlock.Builder builder, int position, BooleanBlock field1, BooleanBlock field2) {
+        int count1 = field1.getValueCount(position);
+        int count2 = field2.getValueCount(position);
+        if (count1 == 0 || count2 == 0) {
+            builder.appendNull();
+        } else {
+            int first1 = field1.getFirstValueIndex(position);
+            int first2 = field2.getFirstValueIndex(position);
+            builder.beginPositionEntry();
+            for (int i = 0; i < count1; i++) {
+                builder.appendBoolean(field1.getBoolean(first1 + i));
+            }
+            for (int i = 0; i < count2; i++) {
+                builder.appendBoolean(field2.getBoolean(first2 + i));
+            }
+            builder.endPositionEntry();
+        }
+
+    }
+
+    @Evaluator(extraName = "Long")
+    static void process(LongBlock.Builder builder, int position, LongBlock field1, LongBlock field2) {
+        int count1 = field1.getValueCount(position);
+        int count2 = field2.getValueCount(position);
+        if (count1 == 0 || count2 == 0) {
+            builder.appendNull();
+        } else {
+            int first1 = field1.getFirstValueIndex(position);
+            int first2 = field2.getFirstValueIndex(position);
+            builder.beginPositionEntry();
+            for (int i = 0; i < count1; i++) {
+                builder.appendLong(field1.getLong(first1 + i));
+            }
+            for (int i = 0; i < count2; i++) {
+                builder.appendLong(field2.getLong(first2 + i));
+            }
+            builder.endPositionEntry();
+        }
+    }
+
+    @Evaluator(extraName = "Double")
+    static void process(DoubleBlock.Builder builder, int position, DoubleBlock field1, DoubleBlock field2) {
+        int count1 = field1.getValueCount(position);
+        int count2 = field2.getValueCount(position);
+        if (count1 == 0 || count2 == 0) {
+            builder.appendNull();
+        } else {
+            int first1 = field1.getFirstValueIndex(position);
+            int first2 = field2.getFirstValueIndex(position);
+            builder.beginPositionEntry();
+            for (int i = 0; i < count1; i++) {
+                builder.appendDouble(field1.getDouble(first1 + i));
+            }
+            for (int i = 0; i < count2; i++) {
+                builder.appendDouble(field2.getDouble(first2 + i));
+            }
+            builder.endPositionEntry();
+        }
+
+    }
+
+    @Evaluator(extraName = "BytesRef")
+    static void process(BytesRefBlock.Builder builder, int position, BytesRefBlock field1, BytesRefBlock field2) {
+        int count1 = field1.getValueCount(position);
+        int count2 = field2.getValueCount(position);
+        if (count1 == 0 || count2 == 0) {
+            builder.appendNull();
+        } else {
+            int first1 = field1.getFirstValueIndex(position);
+            int first2 = field2.getFirstValueIndex(position);
+            builder.beginPositionEntry();
+            BytesRef spare = new BytesRef();
+            for (int i = 0; i < count1; i++) {
+                builder.appendBytesRef(field1.getBytesRef(first1 + i, spare));
+            }
+            for (int i = 0; i < count2; i++) {
+                builder.appendBytesRef(field2.getBytesRef(first2 + i, spare));
+            }
+            builder.endPositionEntry();
+        }
+    }
+
+    @Override
+    public Nullability nullable() {
+        return Nullability.TRUE;
+    }
+}

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/io/stream/PlanNamedTypes.java

@@ -118,6 +118,7 @@ import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tan;
 import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tanh;
 import org.elasticsearch.xpack.esql.expression.function.scalar.math.Tau;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.AbstractMultivalueFunction;
+import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvAppend;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvAvg;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcat;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvCount;
@@ -425,6 +426,7 @@ public final class PlanNamedTypes {
             of(AggregateFunction.class, Sum.class, PlanNamedTypes::writeAggFunction, PlanNamedTypes::readAggFunction),
             of(AggregateFunction.class, Values.class, PlanNamedTypes::writeAggFunction, PlanNamedTypes::readAggFunction),
             // Multivalue functions
+            of(ScalarFunction.class, MvAppend.class, PlanNamedTypes::writeMvAppend, PlanNamedTypes::readMvAppend),
             of(ScalarFunction.class, MvAvg.class, PlanNamedTypes::writeMvFunction, PlanNamedTypes::readMvFunction),
             of(ScalarFunction.class, MvCount.class, PlanNamedTypes::writeMvFunction, PlanNamedTypes::readMvFunction),
             of(ScalarFunction.class, MvConcat.class, PlanNamedTypes::writeMvConcat, PlanNamedTypes::readMvConcat),
@@ -1857,4 +1859,16 @@ public final class PlanNamedTypes {
         out.writeExpression(fields.get(1));
         out.writeOptionalWriteable(fields.size() == 3 ? o -> out.writeExpression(fields.get(2)) : null);
     }
+
+    static MvAppend readMvAppend(PlanStreamInput in) throws IOException {
+        return new MvAppend(Source.readFrom(in), in.readExpression(), in.readExpression());
+    }
+
+    static void writeMvAppend(PlanStreamOutput out, MvAppend fn) throws IOException {
+        Source.EMPTY.writeTo(out);
+        List<Expression> fields = fn.children();
+        assert fields.size() == 2;
+        out.writeExpression(fields.get(0));
+        out.writeExpression(fields.get(1));
+    }
 }

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/AnalyzerTests.java

@@ -62,6 +62,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
@@ -522,7 +523,9 @@ public class AnalyzerTests extends ESTestCase {
             "float",
             "foo_type",
             "int",
+            "ip",
             "keyword",
+            "long",
             "point",
             "shape",
             "some.ambiguous",
@@ -566,7 +569,9 @@ public class AnalyzerTests extends ESTestCase {
             "float",
             "foo_type",
             "int",
+            "ip",
             "keyword",
+            "long",
             "point",
             "shape",
             "some.ambiguous",
@@ -779,7 +784,9 @@ public class AnalyzerTests extends ESTestCase {
             "float",
             "foo_type",
             "int",
+            "ip",
             "keyword",
+            "long",
             "point",
             "shape",
             "some.ambiguous",
@@ -1878,6 +1885,40 @@ public class AnalyzerTests extends ESTestCase {
             """, "mapping-multi-field-variation.json", "text");
     }
 
+    public void testMvAppendValidation() {
+        String[][] fields = {
+            { "bool", "boolean" },
+            { "int", "integer" },
+            { "unsigned_long", "unsigned_long" },
+            { "float", "double" },
+            { "text", "text" },
+            { "keyword", "keyword" },
+            { "date", "datetime" },
+            { "point", "geo_point" },
+            { "shape", "geo_shape" },
+            { "long", "long" },
+            { "ip", "ip" },
+            { "version", "version" } };
+
+        Supplier<Integer> supplier = () -> randomInt(fields.length - 1);
+        int first = supplier.get();
+        int second = randomValueOtherThan(first, supplier);
+
+        String signature = "mv_append(" + fields[first][0] + ", " + fields[second][0] + ")";
+        verifyUnsupported(
+            " from test | eval " + signature,
+            "second argument of ["
+                + signature
+                + "] must be ["
+                + fields[first][1]
+                + "], found value ["
+                + fields[second][0]
+                + "] type ["
+                + fields[second][1]
+                + "]"
+        );
+    }
+
     public void testLookup() {
         var e = expectThrows(ParsingException.class, () -> analyze("""
               FROM test

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/function/scalar/multivalue/MvAppendTests.java

@@ -0,0 +1,296 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql.expression.function.scalar.multivalue;
+
+import com.carrotsearch.randomizedtesting.annotations.Name;
+import com.carrotsearch.randomizedtesting.annotations.ParametersFactory;
+
+import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.geo.GeometryTestUtils;
+import org.elasticsearch.geo.ShapeTestUtils;
+import org.elasticsearch.xpack.esql.core.expression.Expression;
+import org.elasticsearch.xpack.esql.core.tree.Source;
+import org.elasticsearch.xpack.esql.core.type.DataTypes;
+import org.elasticsearch.xpack.esql.expression.function.AbstractFunctionTestCase;
+import org.elasticsearch.xpack.esql.expression.function.TestCaseSupplier;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+import static org.elasticsearch.xpack.esql.core.util.SpatialCoordinateTypes.CARTESIAN;
+import static org.elasticsearch.xpack.esql.core.util.SpatialCoordinateTypes.GEO;
+import static org.hamcrest.Matchers.equalTo;
+
+public class MvAppendTests extends AbstractFunctionTestCase {
+    public MvAppendTests(@Name("TestCase") Supplier<TestCaseSupplier.TestCase> testCaseSupplier) {
+        this.testCase = testCaseSupplier.get();
+    }
+
+    @ParametersFactory
+    public static Iterable<Object[]> parameters() {
+        List<TestCaseSupplier> suppliers = new ArrayList<>();
+        booleans(suppliers);
+        ints(suppliers);
+        longs(suppliers);
+        doubles(suppliers);
+        bytesRefs(suppliers);
+        nulls(suppliers);
+        return parameterSuppliersFromTypedData(suppliers);
+    }
+
+    @Override
+    protected Expression build(Source source, List<Expression> args) {
+        return new MvAppend(source, args.get(0), args.get(1));
+    }
+
+    private static void booleans(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.BOOLEAN, DataTypes.BOOLEAN), () -> {
+            List<Boolean> field1 = randomList(1, 10, () -> randomBoolean());
+            List<Boolean> field2 = randomList(1, 10, () -> randomBoolean());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.BOOLEAN, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.BOOLEAN, "field2")
+                ),
+                "MvAppendBooleanEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.BOOLEAN,
+                equalTo(result)
+            );
+        }));
+    }
+
+    private static void ints(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.INTEGER, DataTypes.INTEGER), () -> {
+            List<Integer> field1 = randomList(1, 10, () -> randomInt());
+            List<Integer> field2 = randomList(1, 10, () -> randomInt());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.INTEGER, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.INTEGER, "field2")
+                ),
+                "MvAppendIntEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.INTEGER,
+                equalTo(result)
+            );
+        }));
+    }
+
+    private static void longs(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.LONG, DataTypes.LONG), () -> {
+            List<Long> field1 = randomList(1, 10, () -> randomLong());
+            List<Long> field2 = randomList(1, 10, () -> randomLong());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.LONG, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.LONG, "field2")
+                ),
+                "MvAppendLongEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.LONG,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.DATETIME, DataTypes.DATETIME), () -> {
+            List<Long> field1 = randomList(1, 10, () -> randomLong());
+            List<Long> field2 = randomList(1, 10, () -> randomLong());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.DATETIME, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.DATETIME, "field2")
+                ),
+                "MvAppendLongEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.DATETIME,
+                equalTo(result)
+            );
+        }));
+    }
+
+    private static void doubles(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.DOUBLE, DataTypes.DOUBLE), () -> {
+            List<Double> field1 = randomList(1, 10, () -> randomDouble());
+            List<Double> field2 = randomList(1, 10, () -> randomDouble());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.DOUBLE, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.DOUBLE, "field2")
+                ),
+                "MvAppendDoubleEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.DOUBLE,
+                equalTo(result)
+            );
+        }));
+    }
+
+    private static void bytesRefs(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.KEYWORD, DataTypes.KEYWORD), () -> {
+            List<Object> field1 = randomList(1, 10, () -> randomLiteral(DataTypes.KEYWORD).value());
+            List<Object> field2 = randomList(1, 10, () -> randomLiteral(DataTypes.KEYWORD).value());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.KEYWORD, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.KEYWORD, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.KEYWORD,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.TEXT, DataTypes.TEXT), () -> {
+            List<Object> field1 = randomList(1, 10, () -> randomLiteral(DataTypes.TEXT).value());
+            List<Object> field2 = randomList(1, 10, () -> randomLiteral(DataTypes.TEXT).value());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.TEXT, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.TEXT, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.TEXT,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.IP, DataTypes.IP), () -> {
+            List<Object> field1 = randomList(1, 10, () -> randomLiteral(DataTypes.IP).value());
+            List<Object> field2 = randomList(1, 10, () -> randomLiteral(DataTypes.IP).value());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.IP, "field"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.IP, "field")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.IP,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.VERSION, DataTypes.VERSION), () -> {
+            List<Object> field1 = randomList(1, 10, () -> randomLiteral(DataTypes.VERSION).value());
+            List<Object> field2 = randomList(1, 10, () -> randomLiteral(DataTypes.VERSION).value());
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.VERSION, "field"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.VERSION, "field")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.VERSION,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.GEO_POINT, DataTypes.GEO_POINT), () -> {
+            List<Object> field1 = randomList(1, 10, () -> new BytesRef(GEO.asWkt(GeometryTestUtils.randomPoint())));
+            List<Object> field2 = randomList(1, 10, () -> new BytesRef(GEO.asWkt(GeometryTestUtils.randomPoint())));
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.GEO_POINT, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.GEO_POINT, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.GEO_POINT,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.CARTESIAN_POINT, DataTypes.CARTESIAN_POINT), () -> {
+            List<Object> field1 = randomList(1, 10, () -> new BytesRef(CARTESIAN.asWkt(ShapeTestUtils.randomPoint())));
+            List<Object> field2 = randomList(1, 10, () -> new BytesRef(CARTESIAN.asWkt(ShapeTestUtils.randomPoint())));
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.CARTESIAN_POINT, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.CARTESIAN_POINT, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.CARTESIAN_POINT,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.GEO_SHAPE, DataTypes.GEO_SHAPE), () -> {
+            List<Object> field1 = randomList(1, 10, () -> new BytesRef(GEO.asWkt(GeometryTestUtils.randomGeometry(randomBoolean()))));
+            List<Object> field2 = randomList(1, 10, () -> new BytesRef(GEO.asWkt(GeometryTestUtils.randomGeometry(randomBoolean()))));
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.GEO_SHAPE, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.GEO_SHAPE, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.GEO_SHAPE,
+                equalTo(result)
+            );
+        }));
+
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.CARTESIAN_SHAPE, DataTypes.CARTESIAN_SHAPE), () -> {
+            List<Object> field1 = randomList(1, 10, () -> new BytesRef(CARTESIAN.asWkt(ShapeTestUtils.randomGeometry(randomBoolean()))));
+            List<Object> field2 = randomList(1, 10, () -> new BytesRef(CARTESIAN.asWkt(ShapeTestUtils.randomGeometry(randomBoolean()))));
+            var result = new ArrayList<>(field1);
+            result.addAll(field2);
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.CARTESIAN_SHAPE, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.CARTESIAN_SHAPE, "field2")
+                ),
+                "MvAppendBytesRefEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.CARTESIAN_SHAPE,
+                equalTo(result)
+            );
+        }));
+    }
+
+    private static void nulls(List<TestCaseSupplier> suppliers) {
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.INTEGER, DataTypes.INTEGER), () -> {
+            List<Integer> field2 = randomList(2, 10, () -> randomInt());
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(null, DataTypes.INTEGER, "field1"),
+                    new TestCaseSupplier.TypedData(field2, DataTypes.INTEGER, "field2")
+                ),
+                "MvAppendIntEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.INTEGER,
+                equalTo(null)
+            );
+        }));
+        suppliers.add(new TestCaseSupplier(List.of(DataTypes.INTEGER, DataTypes.INTEGER), () -> {
+            List<Integer> field1 = randomList(2, 10, () -> randomInt());
+            return new TestCaseSupplier.TestCase(
+                List.of(
+                    new TestCaseSupplier.TypedData(field1, DataTypes.INTEGER, "field1"),
+                    new TestCaseSupplier.TypedData(null, DataTypes.INTEGER, "field2")
+                ),
+                "MvAppendIntEvaluator[field1=Attribute[channel=0], field2=Attribute[channel=1]]",
+                DataTypes.INTEGER,
+                equalTo(null)
+            );
+        }));
+    }
+}