The Dremio Blog

New Array Functions in Dremio

Albert Vernon Albert VernonSenior Product Manager, Dremio


Data types in Dremio fall into two categories: primitive types such as INT and VARCHAR that hold single values, and semi-structured types like LIST, STRUCT, and MAP that hold complex values.

Arrays are lists of arbitrary size of any single type, indexed by non-negative integers, and are useful for holding sparse data.

Note: LIST and ARRAY are synonyms in Dremio, so you will see references to both in documentation, error messages, and function names.

Dremo Cloud as of mid-September and Dremio Software version 24.2 provide a variety of functions for manipulating array data. 

The remainder of this article describes array functions in Dremio.

Dremio Array Functions

Creating Arrays

In Dremio Software v24.2+ and in Dremio Cloud, you create array literals with the ARRAY keyword like this:

SELECT ARRAY['apple', 'strawberry', 'banana']
-- ["apple","strawberry","banana"]

Dremio Software versions before v24.2 do not have array literals, but you can get the same result using CONVERT_FROM and JSON strings. For example:

SELECT CONVERT_FROM('["apple", "strawberry", "banana"]', 'json')
-- ["apple","strawberry","banana"]

You can also query array columns from tables and views in the usual manner. The Python 3 script below creates a file example.parquet that has array columns named fruits and numbers:

#!/usr/bin/env python3
import pyarrow as pa
import pyarrow.parquet as pq

table = pa.table(
        "fruits": [("apple", "strawberry", "banana")],
        "numbers": [(1, 2, 3,)],

pq.write_table(table, "example.parquet")

After uploading example.parquet you can query fruits and numbers through Dremio as you would any columns:

SELECT fruits FROM example;
-- ["apple","strawberry","banana"]
SELECT numbers FROM example;
-- [1, 2, 3]

Available Functions

The functions below are available in Dremio Software v24.2 and in Dremio Cloud:

array_avg(A)Returns the average of all non-null elements in A.
array_contains(A, V)Returns whether A contains V.
array_max(A)Returns the maximum value in A.
array_min(A)Returns the minimum value in A.
array_remove(A, V)Removes all elements that equal V in A.
array_sum(A)Returns the sum of all non-null elements in A.
cardinality(A)Returns the number of elements in A.
unnest(A)Converts elements in A into rows.


SELECT ARRAY_AVG(numbers) FROM example;
-- 2.000000
SELECT ARRAY_CONTAINS(fruits, 'banana') FROM example;
-- true
SELECT ARRAY_MAX(numbers) FROM example;
-- 3
SELECT ARRAY_MIN(numbers) FROM example;
-- 1
SELECT ARRAY_REMOVE(fruits, 'strawberry') FROM example;
-- ["apple","banana"]
SELECT ARRAY_SUM(numbers) FROM example;
-- 6
-- 3
SELECT fruit FROM example, UNNEST(fruits) as t(fruit);
-- apple
-- strawberry
-- banana

Coming Soon

The functions below are planned for Dremio Software v24.3 and the November 2023 update of Dremio Cloud:

array_agg(expr)Returns an array consisting of all values in expr.
array_append(A, E)Returns a new array with E at the end of A.
array_distinct(A)Returns a new array with only the distinct elements from A.
array_frequency(A)Returns a map where the keys are the unique elements in A, and the values are how many times the key appears.
array_prepend(A, E)Returns a new array with E at the beginning of A.
arrays_overlap(X, Y)Returns whether X and Y have any elements in common.
set_union(X, Y, ...)Returns an array of all the distinct values contained in each array of the input.

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