Amazon Redshift will no longer support the use of Python UDFs after June 30, 2026. We will start enforcing it in phases. For more information on the details of Python end of life and migration options, see the [ blog post ](https://aws.amazon.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/) that was published on June 30, 2025. 

# HLL\_CARDINALITY function
<a name="r_HLL_CARDINALITY"></a>

The HLL\_CARDINALITY function returns the cardinality of the input HLLSKETCH data type.

## Syntax
<a name="r_HLL_CARDINALITY-synopsis"></a>

```
HLL_CARDINALITY (hllsketch_expression)
```

## Argument
<a name="r_HLL_CARDINALITY-argument"></a>

 *hllsketch\_expression*   
Any valid expression that evaluates to an HLLSKETCH type, such as a column name. The input value is the HLLSKETCH data type.

## Return type
<a name="r_HLL_CARDINALITY-return-type"></a>

The HLL\_CARDINALITY function returns a BIGINT or INT8 value.

## Examples
<a name="r_HLL_CARDINALITY-examples"></a>

The following example returns the cardinality of column `sketch` in table `hll_table`.

```
CREATE TABLE a_table(an_int INT, b_int INT);
INSERT INTO a_table VALUES (1,1), (2,1), (3,1), (4,1), (1,2), (2,2), (3,2), (4,2), (5,2), (6,2);

CREATE TABLE hll_table (sketch HLLSKETCH);
INSERT INTO hll_table select hll_create_sketch(an_int) from a_table group by b_int;

SELECT hll_cardinality(sketch) AS cardinality FROM hll_table;
cardinality
-------------
6
4
(2 rows)
```