ARRAY_LAST

array_last

SinceVersion 2.0.0

Description

Finds the last element in the array that satisfies the lambda expression. Finds the last element that satisfies the condition and returns it.

Syntax

array_last(lambda, ARRAY<T> arr1, [ARRAY<T> arr2, ...])

Parameters

• lambda：lambda expression used to define search conditions
• arr1, arr2, ...：ARRAY type, arrays to search. Supports one or more array parameters.

Supported types for T:

• Numeric types: TINYINT, SMALLINT, INT, BIGINT, LARGEINT, FLOAT, DOUBLE, DECIMAL
• String types: CHAR, VARCHAR, STRING
• Date and time types: DATE, DATETIME, DATEV2, DATETIMEV2
• Boolean type: BOOLEAN
• IP types: IPV4, IPV6
• Complex types: ARRAY, MAP, STRUCT

Return Value

Return type: T

Return value meaning:

• Returns the last element in the array that satisfies the lambda expression
• NULL: if no element satisfies the condition, or if the input array is NULL

Usage notes:

• The number of parameters in the lambda expression must match the number of array parameters
• If no element satisfies the condition, returns NULL
• Does not support NULL input parameters
• When there are multiple array parameters, all arrays must have the same length
• Lambda can use any scalar expression, but cannot use aggregate functions
• Lambda expressions can call other higher-order functions, but the return types must be compatible
• For null values in array elements: null elements will be passed to the lambda expression for processing, and lambda can check for null values

Query Examples:

Find the last element greater than or equal to 3 in a floating-point array:

SELECT array_last(x -> x >= 3, [1.1, 2.2, 3.3, 4.4, 5.5]);
+----------------------------------------------------+
| array_last(x -> x >= 3, [1.1, 2.2, 3.3, 4.4, 5.5]) |
+----------------------------------------------------+
|                                                5.5 |
+----------------------------------------------------+

Find the last element with length greater than 2 in a string array:

SELECT array_last(x -> length(x) > 2, ['a', 'bb', 'ccc', 'dddd', 'eeeee']);
+---------------------------------------------------------------------+
| array_last(x -> length(x) > 2, ['a', 'bb', 'ccc', 'dddd', 'eeeee']) |
+---------------------------------------------------------------------+
| eeeee                                                               |
+---------------------------------------------------------------------+

Empty array returns NULL:

SELECT array_last(x -> x > 0, []);
+-------------------------------------+
| array_last(x -> x > 0, [])        |
+-------------------------------------+
| NULL                                |
+-------------------------------------+

NULL input parameter will error:

SELECT array_last(x -> x > 2, NULL);
ERROR 1105 (HY000): errCode = 2, detailMessage = lambda argument must be array but is NULL

SELECT array_last(NULL);
ERROR 1105 (HY000): errCode = 2, detailMessage = Can not build function: 'array_last', expression: array_last(NULL), The 1st arg of array_filter must be lambda but is NULL

Array containing null values, lambda can check for null:

SELECT array_last(x -> x is not null, [null, 1, null, 3, null, 5]);
+-------------------------------------------------------------+
| array_last(x -> x is not null, [null, 1, null, 3, null, 5]) |
+-------------------------------------------------------------+
|                                                           5 |
+-------------------------------------------------------------+

Multi-array search, find the last element where the first array is greater than the second array:

SELECT array_last((x, y) -> x > y, [1, 2, 3, 4, 5], [1.1, 2.2, 3.3, 4.4, 5.5]);
+-------------------------------------------------------------------------+
| array_last((x, y) -> x > y, [1, 2, 3, 4, 5], [1.1, 2.2, 3.3, 4.4, 5.5]) |
+-------------------------------------------------------------------------+
|                                                                    NULL |
+-------------------------------------------------------------------------+

Nested array search, find the last element where each sub-array length is greater than 2:

SELECT array_last(x -> size(x) > 2, [[1,2],[3,4,5],[6],[7,8,9,10]]);
+--------------------------------------------------------------+
| array_last(x -> size(x) > 2, [[1,2],[3,4,5],[6],[7,8,9,10]]) |
+--------------------------------------------------------------+
| [7, 8, 9, 10]                                                |
+--------------------------------------------------------------+

Error when parameter count is wrong:

SELECT array_last();
ERROR 1105 (HY000): errCode = 2, detailMessage = Can not found function 'array_last' which has 0 arity. Candidate functions are: [array_last(Expression, Expression...)]

Error when the number of parameters in lambda expression doesn't match the number of array parameters:

SELECT array_last(x -> x > 0, [1,2,3], [4,5,6], [7,8,9]);
ERROR 1105 (HY000): errCode = 2, detailMessage = lambda x -> (x > 0) arguments' size is not equal parameters' size

Error when passing non-array type:

SELECT array_last(x -> x > 0, 'not_an_array');
ERROR 1105 (HY000): errCode = 2, detailMessage = Can not find the compatibility function signature: array_last(Expression, VARCHAR(12))

Keywords

ARRAY, LAST, ARRAY_LAST