Array Functions and Operators#

Subscript Operator: []#

The [] operator is used to access an element of an array and is indexed starting from one:

SELECT my_array[1] AS first_element

Concatenation Operator: ||#

The || operator is used to concatenate an array with an array or an element of the same type:

SELECT ARRAY [1] || ARRAY [2]; -- [1, 2]
SELECT ARRAY [1] || 2; -- [1, 2]
SELECT 2 || ARRAY [1]; -- [2, 1]

Array Functions#

all_match(array(T), function(T, boolean)) → boolean#: Returns whether all elements of an array match the given predicate. Returns true if all the elements match the predicate (a special case is when the array is empty); false if one or more elements don’t match; NULL if the predicate function returns NULL for one or more elements and true for all other elements.

any_match(array(T), function(T, boolean)) → boolean#: Returns whether any elements of an array match the given predicate. Returns true if one or more elements match the predicate; false if none of the elements matches (a special case is when the array is empty); NULL if the predicate function returns NULL for one or more elements and false for all other elements.

array_average(array(double)) → double#: Returns the average of all non-null elements of the array. If there is no non-null elements, returns null.

array_distinct(x) → array#: Remove duplicate values from the array x.

array_duplicates(array(T)) -> array(bigint/varchar)#

Returns a set of elements that occur more than once in array.

T must be coercible to bigint or varchar.

array_except(x, y) → array#: Returns an array of elements in x but not in y, without duplicates.

array_frequency(array(bigint)) -> map(bigint, int)#: Returns a map: keys are the unique elements in the array, values are how many times the key appears. Ignores null elements. Empty array returns empty map.

array_frequency(array(varchar)) -> map(varchar, int)#: Returns a map: keys are the unique elements in the array, values are how many times the key appears. Ignores null elements. Empty array returns empty map.

array_has_duplicates(array(T)) → boolean#

Returns a boolean: whether array has any elements that occur more than once.

T must be coercible to bigint or varchar.

array_intersect(x, y) → array#: Returns an array of the elements in the intersection of x and y, without duplicates.

array_intersect(array(array(E))) -> array(bigint/double)#: Returns an array of the elements in the intersection of all arrays in the given array, without duplicates. E must be coercible to double. Returns bigint if T is coercible to bigint. Otherwise, returns double.

array_join(x, delimiter, null_replacement) → varchar#: Concatenates the elements of the given array using the delimiter and an optional string to replace nulls.

array_max(x) → x#: Returns the maximum value of input array.

array_min(x) → x#: Returns the minimum value of input array.

array_normalize(x, p) → array#: Normalizes array x by dividing each element by the p-norm of the array. It is equivalent to TRANSFORM(array, v -> v / REDUCE(array, 0, (a, v) -> a + POW(ABS(v), p), a -> POW(a, 1 / p)), but the reduce part is only executed once. Returns null if the array is null or there are null array elements.

array_position(x, element) → bigint#: Returns the position of the first occurrence of the element in array x (or 0 if not found).

array_position(x, element, instance) → bigint#: If instance > 0, returns the position of the instance-th occurrence of the element in array x. If instance < 0, returns the position of the instance-to-last occurrence of the element in array x. If no matching element instance is found, 0 is returned.

array_remove(x, element) → array#: Remove all elements that equal element from array x.

array_sort(x) → array#: Sorts and returns the array x. The elements of x must be orderable. Null elements will be placed at the end of the returned array.

array_sort(array(T), function(T, T, int)) -> array(T)#

Sorts and returns the array based on the given comparator function. The comparator will take two nullable arguments representing two nullable elements of the array. It returns -1, 0, or 1 as the first nullable element is less than, equal to, or greater than the second nullable element. If the comparator function returns other values (including NULL), the query will fail and raise an error

SELECT array_sort(ARRAY [3, 2, 5, 1, 2], (x, y) -> IF(x < y, 1, IF(x = y, 0, -1))); -- [5, 3, 2, 2, 1]
SELECT array_sort(ARRAY ['bc', 'ab', 'dc'], (x, y) -> IF(x < y, 1, IF(x = y, 0, -1))); -- ['dc', 'bc', 'ab']
SELECT array_sort(ARRAY [3, 2, null, 5, null, 1, 2], -- sort null first with descending order
                  (x, y) -> CASE WHEN x IS NULL THEN -1
                                 WHEN y IS NULL THEN 1
                                 WHEN x < y THEN 1
                                 WHEN x = y THEN 0
                                 ELSE -1 END); -- [null, null, 5, 3, 2, 2, 1]
SELECT array_sort(ARRAY [3, 2, null, 5, null, 1, 2], -- sort null last with descending order
                  (x, y) -> CASE WHEN x IS NULL THEN 1
                                 WHEN y IS NULL THEN -1
                                 WHEN x < y THEN 1
                                 WHEN x = y THEN 0
                                 ELSE -1 END); -- [5, 3, 2, 2, 1, null, null]
SELECT array_sort(ARRAY ['a', 'abcd', 'abc'], -- sort by string length
                  (x, y) -> IF(length(x) < length(y),
                               -1,
                               IF(length(x) = length(y), 0, 1))); -- ['a', 'abc', 'abcd']
SELECT array_sort(ARRAY [ARRAY[2, 3, 1], ARRAY[4, 2, 1, 4], ARRAY[1, 2]], -- sort by array length
                  (x, y) -> IF(cardinality(x) < cardinality(y),
                               -1,
                               IF(cardinality(x) = cardinality(y), 0, 1))); -- [[1, 2], [2, 3, 1], [4, 2, 1, 4]]

array_sum(array(T)) → bigint/double#

Returns the sum of all non-null elements of the array. If there is no non-null elements, returns 0. The behavior is similar to aggregation function sum().

T must be coercible to double. Returns bigint if T is coercible to bigint. Otherwise, returns double.

arrays_overlap(x, y) → boolean#: Tests if arrays x and y have any non-null elements in common. Returns null if there are no non-null elements in common but either array contains null.

array_union(x, y) → array#: Returns an array of the elements in the union of x and y, without duplicates.

cardinality(x) → bigint#: Returns the cardinality (size) of the array x.

concat(array1, array2, ..., arrayN) → array: Concatenates the arrays array1, array2, ..., arrayN. This function provides the same functionality as the SQL-standard concatenation operator (||).

combinations(array(T), n) -> array(array(T))#

Returns n-element combinations of the input array. If the input array has no duplicates, combinations returns n-element subsets. Order of subgroup is deterministic but unspecified. Order of elements within a subgroup are deterministic but unspecified. n must not be greater than 5, and the total size of subgroups generated must be smaller than 100000:

SELECT combinations(ARRAY['foo', 'bar', 'boo'],2); --[['foo', 'bar'], ['foo', 'boo']['bar', 'boo']]
SELECT combinations(ARRAY[1,2,3,4,5],3); --[[1,2,3], [1,2,4], [1,3,4], [2,3,4]]
SELECT combinations(ARRAY[1,2,2],2); --[[1,2],[1,2],[2,2]]

contains(x, element) → boolean#: Returns true if the array x contains the element.

element_at(array(E), index) → E#: Returns element of array at given index. If index > 0, this function provides the same functionality as the SQL-standard subscript operator ([]). If index < 0, element_at accesses elements from the last to the first.

filter(array(T), function(T, boolean)) -> array(T)#

Constructs an array from those elements of array for which function returns true:

SELECT filter(ARRAY [], x -> true); -- []
SELECT filter(ARRAY [5, -6, NULL, 7], x -> x > 0); -- [5, 7]
SELECT filter(ARRAY [5, NULL, 7, NULL], x -> x IS NOT NULL); -- [5, 7]

flatten(x) → array#: Flattens an array(array(T)) to an array(T) by concatenating the contained arrays.

ngrams(array(T), n) -> array(array(T))#

Returns n-grams for the array:

SELECT ngrams(ARRAY['foo', 'bar', 'baz', 'foo'], 2); -- [['foo', 'bar'], ['bar', 'baz'], ['baz', 'foo']]
SELECT ngrams(ARRAY['foo', 'bar', 'baz', 'foo'], 3); -- [['foo', 'bar', 'baz'], ['bar', 'baz', 'foo']]
SELECT ngrams(ARRAY['foo', 'bar', 'baz', 'foo'], 4); -- [['foo', 'bar', 'baz', 'foo']]
SELECT ngrams(ARRAY['foo', 'bar', 'baz', 'foo'], 5); -- [['foo', 'bar', 'baz', 'foo']]
SELECT ngrams(ARRAY[1, 2, 3, 4], 2); -- [[1, 2], [2, 3], [3, 4]]

none_match(array(T), function(T, boolean)) → boolean#: Returns whether no elements of an array match the given predicate. Returns true if none of the elements matches the predicate (a special case is when the array is empty); false if one or more elements match; NULL if the predicate function returns NULL for one or more elements and false for all other elements.

reduce(array(T), initialState S, inputFunction(S, T, S), outputFunction(S, R)) → R#

Returns a single value reduced from array. inputFunction will be invoked for each element in array in order. In addition to taking the element, inputFunction takes the current state, initially initialState, and returns the new state. outputFunction will be invoked to turn the final state into the result value. It may be the identity function (i -> i).

SELECT reduce(ARRAY [], 0, (s, x) -> s + x, s -> s); -- 0
SELECT reduce(ARRAY [5, 20, 50], 0, (s, x) -> s + x, s -> s); -- 75
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> s + x, s -> s); -- NULL
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> s + COALESCE(x, 0), s -> s); -- 75
SELECT reduce(ARRAY [5, 20, NULL, 50], 0, (s, x) -> IF(x IS NULL, s, s + x), s -> s); -- 75
SELECT reduce(ARRAY [2147483647, 1], CAST (0 AS BIGINT), (s, x) -> s + x, s -> s); -- 2147483648
SELECT reduce(ARRAY [5, 6, 10, 20], -- calculates arithmetic average: 10.25
              CAST(ROW(0.0, 0) AS ROW(sum DOUBLE, count INTEGER)),
              (s, x) -> CAST(ROW(x + s.sum, s.count + 1) AS ROW(sum DOUBLE, count INTEGER)),
              s -> IF(s.count = 0, NULL, s.sum / s.count));

repeat(element, count) → array#: Repeat element for count times.

reverse(x) → array: Returns an array which has the reversed order of array x.

sequence(start, stop)#: Generate a sequence of integers from start to stop, incrementing by 1 if start is less than or equal to stop, otherwise -1.

sequence(start, stop, step)#: Generate a sequence of integers from start to stop, incrementing by step.

sequence(start, stop)#: Generate a sequence of dates from start date to stop date, incrementing by 1 day if start date is less than or equal to stop date, otherwise -1 day.

sequence(start, stop, step)#: Generate a sequence of dates from start to stop, incrementing by step. The type of step can be either INTERVAL DAY TO SECOND or INTERVAL YEAR TO MONTH.

sequence(start, stop, step)#: Generate a sequence of timestamps from start to stop, incrementing by step. The type of step can be either INTERVAL DAY TO SECOND or INTERVAL YEAR TO MONTH.

shuffle(x) → array#: Generate a random permutation of the given array x.

slice(x, start, length) → array#: Subsets array x starting from index start (or starting from the end if start is negative) with a length of length.

transform(array(T), function(T, U)) -> array(U)#

Returns an array that is the result of applying function to each element of array:

SELECT transform(ARRAY [], x -> x + 1); -- []
SELECT transform(ARRAY [5, 6], x -> x + 1); -- [6, 7]
SELECT transform(ARRAY [5, NULL, 6], x -> COALESCE(x, 0) + 1); -- [6, 1, 7]
SELECT transform(ARRAY ['x', 'abc', 'z'], x -> x || '0'); -- ['x0', 'abc0', 'z0']
SELECT transform(ARRAY [ARRAY [1, NULL, 2], ARRAY[3, NULL]], a -> filter(a, x -> x IS NOT NULL)); -- [[1, 2], [3]]

zip(array1, array2[, ...]) -> array(row)#

Merges the given arrays, element-wise, into a single array of rows. The M-th element of the N-th argument will be the N-th field of the M-th output element. If the arguments have an uneven length, missing values are filled with NULL.

SELECT zip(ARRAY[1, 2], ARRAY['1b', null, '3b']); -- [ROW(1, '1b'), ROW(2, null), ROW(null, '3b')]

zip_with(array(T), array(U), function(T, U, R)) -> array(R)#

Merges the two given arrays, element-wise, into a single array using function. If one array is shorter, nulls are appended at the end to match the length of the longer array, before applying function:

SELECT zip_with(ARRAY[1, 3, 5], ARRAY['a', 'b', 'c'], (x, y) -> (y, x)); -- [ROW('a', 1), ROW('b', 3), ROW('c', 5)]
SELECT zip_with(ARRAY[1, 2], ARRAY[3, 4], (x, y) -> x + y); -- [4, 6]
SELECT zip_with(ARRAY['a', 'b', 'c'], ARRAY['d', 'e', 'f'], (x, y) -> concat(x, y)); -- ['ad', 'be', 'cf']
SELECT zip_with(ARRAY['a'], ARRAY['d', null, 'f'], (x, y) -> coalesce(x, y)); -- ['a', null, 'f']