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
HLL function
The HLL function returns the HyperLogLog cardinality of the input expression values. The HLL function works with any data types except the HLLSKETCH data type. The HLL function ignores NULL values. When there are no rows in a table or all rows are NULL, the resulting cardinality is 0.
Syntax
HLL (aggregate_expression)
Argument
- aggregate_expression
-
Any valid expression that provides the value to an aggregate, such as a column name. This function supports any data type as input except HLLSKETCH, GEOMETRY, GEOGRAPHY, and VARBYTE.
Return type
The HLL function returns a BIGINT or INT8 value.
Examples
The following example returns the cardinality of column an_int in table
a_table.
CREATE TABLE a_table(an_int INT); INSERT INTO a_table VALUES (1), (2), (3), (4); SELECT hll(an_int) AS cardinality FROM a_table; cardinality ------------- 4
