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_cum_sum(array(T)) -> array(T)¶

Returns the array whose elements are the cumulative sum of the input array, i.e. result[i] = input[1]+input[2]+…+input[i]. If there there is null elements in the array, the cumulative sum at and after the element is null.

SELECT array_cum_sum(ARRAY [1, 2, null, 3]) -- array[1, 3, null, null]

array_distinct(x) -> array()¶

Remove duplicate values from the array x. This function uses IS DISTINCT FROM to determine the distinct elements.

SELECT array_distinct(ARRAY [1, 2, null, null, 2]) -- ARRAY[1, 2, null]
SELECT array_distinct(ARRAY [ROW(1, null), ROW (1, null)] -- ARRAY[ROW(1, null)

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

Returns a set of elements that occur more than once in array. Throws an exception if any of the elements are rows or arrays that contain nulls.

SELECT array_duplicates(ARRAY[1, 2, null, 1, null, 3]) -- ARRAY[1, null]
SELECT array_duplicates(ARRAY[ROW(1, null), ROW(1, null)]) -- "map key cannot be null or contain nulls"

array_except(x, y) -> array()¶

Returns an array of elements in x but not in y, without duplicates. This function uses IS NOT DISTINCT FROM to determine which elements are the same.

SELECT array_except(ARRAY[1, 3, 3, 2, null], ARRAY[1,2, 2, 4]) -- ARRAY[3, null]

array_frequency(array(E)) -> map(E, 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. Throws an exception if any of the elements are rows or arrays that contain nulls.

SELECT array_has_duplicates(ARRAY[1, 2, null, 1, null, 3]) -- true
SELECT array_has_duplicates(ARRAY[ROW(1, null), ROW(1, null)]) -- "map key cannot be null or contain nulls"

array_intersect(x, y) -> array()¶

Returns an array of the elements in the intersection of x and y, without duplicates. This function uses IS NOT DISTINCT FROM to determine which elements are the same.

SELECT array_intersect(ARRAY[1, 2, 3, 2, null], ARRAY[1,2, 2, 4, null]) -- ARRAY[1, 2, null]

array_intersect(array(array(E))) -> array(E)¶

Returns an array of the elements in the intersection of all arrays in the given array, without duplicates. This function uses IS NOT DISTINCT FROM to determine which elements are the same.

SELECT array_intersect(ARRAY[ARRAY[1, 2, 3, 2, null], ARRAY[1,2,2, 4, null], ARRAY [1, 2, 3, 4 null]])  -- ARRAY[1, 2, null]

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_least_frequent(array(T)) -> array(T)¶

Returns the least frequent non-null element of an array. If there are multiple elements with the same frequency, the function returns the smallest element. If the array has more than one element and any elements are ROWS with null fields or ARRAYS with null elements, an exception is returned.

SELECT array_least_frequent(ARRAY[1, 0 , 5])  -- ARRAY[0]
select array_least_frequent(ARRAY[1, null, 1]) -- ARRAY[1]
select array_least_frequent(ARRAY[ROW(1,null), ROW(1, null)]) -- "map key cannot be null or contain nulls"

array_least_frequent(array(T), n) -> array(T)¶

Returns n least frequent non-null elements of an array. The elements are ordered in increasing order of their frequencies. If two elements have the same frequency, smaller elements will appear first. If the array has more than one element and any elements are ROWS with null fields or ARRAYS with null elements, an exception is returned.

SELECT array_least_frequent(ARRAY[3, 2, 2, 6, 6, 1, 1], 3) -- ARRAY[3, 1, 2]
select array_least_frequent(ARRAY[1, null, 1], 2) -- ARRAY[1]
select array_least_frequent(ARRAY[ROW(1,null), ROW(1, null)], 2) -- "map key cannot be null or contain nulls"

array_max(x) -> x()¶

Returns the maximum value of input array.

array_min(x) -> x()¶

Returns the minimum value of input array.

array_max_by(array(T), function(T, U)) -> T()¶

Applies the provided function to each element, and returns the element that gives the maximum value. U can be any orderable type.

SELECT array_max_by(ARRAY ['a', 'bbb', 'cc'], x -> LENGTH(x)) -- 'bbb'

array_min_by(array(T), function(T, U)) -> T()¶

Applies the provided function to each element, and returns the element that gives the minimum value. U can be any orderable type.

SELECT array_min_by(ARRAY ['a', 'bbb', 'cc'], x -> LENGTH(x)) -- 'a'

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 are 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_sort_desc(x) -> array()¶

Returns the array sorted in the descending order. Elements of the array must be orderable. Null elements are placed at the end of the returned array.

SELECT array_sort_desc(ARRAY [100, 1, 10, 50]); -- [100, 50, 10, 1]
SELECT array_sort_desc(ARRAY [null, 100, null, 1, 10, 50]); -- [100, 50, 10, 1, null, null]
SELECT array_sort_desc(ARRAY [ARRAY ["a", null], null, ARRAY ["a"]); -- [["a", null], ["a"], null]

array_split_into_chunks(array(T), int) -> array(array(T))¶

Returns an array of arrays splitting the input array into chunks of given length. The last chunk will be shorter than the chunk length if the array’s length is not an integer multiple of the chunk length. Ignores null inputs, but not elements.

SELECT array_split_into_chunks(ARRAY [1, 2, 3, 4], 3); – [[1, 2, 3], [4]] SELECT array_split_into_chunks(null, null); – null SELECT array_split_into_chunks(array[1, 2, 3, cast(null as int)], 2]); – [[1, 2], [3, null]]

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.

array_top_n(array(T), int) -> array(T)¶

Returns an array of the top n elements from a given array, sorted according to its natural descending order. If n is larger than the size of the given array, the returned list will be the same size as the input instead of n.

SELECT array_top_n(ARRAY [1, 100, 2, 5, 3], 3); -- [100, 5, 3]
SELECT array_top_n(ARRAY [1, 100], 5); -- [100, 1]
SELECT array_top_n(ARRAY ['a', 'zzz', 'zz', 'b', 'g', 'f'], 3); -- ['zzz', 'zz', 'g']

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. Throws a NOT_SUPPORTED exception on elements of ROW or ARRAY type that contain null values.

SELECT arrays_overlap(ARRAY [1, 2, null], ARRAY [2, 3, null]) -- true
SELECT arrays_overlap(ARRAY [1, 2], ARRAY [3, 4]) -- false
SELECT arrays_overlap(ARRAY [1, null], ARRAY[2]) -- null
SELECT arrays_overlap(ARRAY[ROW(1, null)], ARRAY[1, 2]) -- "ROW comparison not supported for fields with null elements"

array_union(x, y) -> array()¶

Returns an array of the elements in the union of x and y, without duplicates. This function uses IS NOT DISTINCT FROM to determine which elements are the same.

SELECT array_union(ARRAY[1, 2, 3, 2, null], ARRAY[1,2, 2, 4, null]) -- ARRAY[1, 2, 3, 4 null]

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.

find_first(array(E), function(T,boolean)) -> E()¶

Returns the first element of array which returns true for function(T,boolean), throws exception if the returned element is NULL. Returns NULL if no such element exists.

find_first(array(E), index, function(T,boolean)) -> E()¶

Returns the first element of array which returns true for function(T,boolean), throws exception if the returned element is NULL. Returns NULL if no such element exists. If index > 0, the search for element starts at position index until the end of array. If index < 0, the search for element starts at position abs(index) counting from last, until the start of array.

SELECT find_first(ARRAY[3, 4, 5, 6], 2, x -> x > 0); -- 4
SELECT find_first(ARRAY[3, 4, 5, 6], -2, x -> x > 0); -- 5
SELECT find_first(ARRAY[3, 4, 5, 6], 2, x -> x < 4); -- NULL
SELECT find_first(ARRAY[3, 4, 5, 6], -2, x -> x > 5); -- NULL

find_first_index(array(E), function(T,boolean)) -> BIGINT()¶

Returns the index of the first element of array which returns true for function(T,boolean). Returns NULL if no such element exists.

find_first_index(array(E), index, function(T,boolean)) -> BIGINT()¶

Returns the index of the first element of array which returns true for function(T,boolean). Returns NULL if no such element exists. If index > 0, the search for element starts at position index until the end of array. If index < 0, the search for element starts at position abs(index) counting from last, until the start of array.

SELECT find_first(ARRAY[3, 4, 5, 6], 2, x -> x > 0); -- 2
SELECT find_first(ARRAY[3, 4, 5, 6], -2, x -> x > 0); -- 3
SELECT find_first(ARRAY[3, 4, 5, 6], 2, x -> x < 4); -- NULL
SELECT find_first(ARRAY[3, 4, 5, 6], -2, x -> x > 5); -- NULL

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));

remove_nulls(array(T)) -> array()¶

Remove all null elements in the array.

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) -> array(bigint)¶

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) -> array(bigint)¶

Generate a sequence of integers from start to stop, incrementing by step.

sequence(start, stop) -> array(date)¶

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) -> array(date)¶

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) -> array(timestamp)¶

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.

trim_array(x, n) -> array()¶

Remove n elements from the end of array:

SELECT trim_array(ARRAY[1, 2, 3, 4], 1);
-- [1, 2, 3]

SELECT trim_array(ARRAY[1, 2, 3, 4], 2);
-- [1, 2]

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']