Map Functions and Operators¶

Subscript Operator: []¶

The [] operator is used to retrieve the value corresponding to a given key from a map:

SELECT name_to_age_map['Bob'] AS bob_age;

Map Functions¶

all_keys_match(x(K,V), function(K, boolean)) -> boolean()¶

Returns whether all keys of a map match the given predicate. Returns true if all the keys match the predicate (a special case is when the map is empty); false if one or more keys don’t match; NULL if the predicate function returns NULL for one or more keys and true for all other keys.

SELECT all_keys_match(map(array['a', 'b', 'c'], array[1, 2, 3]), x -> length(x) = 1); -- true

any_keys_match(x(K,V), function(K, boolean)) -> boolean()¶

Returns whether any keys of a map match the given predicate. Returns true if one or more keys match the predicate; false if none of the keys match (a special case is when the map is empty); NULL if the predicate function returns NULL for one or more keys and false for all other keys.

SELECT any_keys_match(map(array['a', 'b', 'c'], array[1, 2, 3]), x -> x = 'a'); -- true

any_values_match(x(K,V), function(V, boolean)) -> boolean()¶

Returns whether any values of a map matches the given predicate. Returns true if one or more values match the predicate; false if none of the values match (a special case is when the map is empty); NULL if the predicate function returns NULL for one or more values and false for all other values.

SELECT ANY_VALUES_MATCH(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), x -> x = 1); -- true

cardinality(x) -> bigint()

Returns the cardinality (size) of the map x.

element_at(map(K,V), key) -> V()

Returns value for given key, or NULL if the key is not contained in the map.

map() -> map<unknown, unknown>()¶

Returns an empty map.

SELECT map(); -- {}

map(array(K), array(V)) -> map(K, V)¶

Returns a map created using the given key/value arrays.

SELECT map(ARRAY[1,3], ARRAY[2,4]); -- {1 -> 2, 3 -> 4}

See also map_agg() and multimap_agg() for creating a map as an aggregation.

map_from_entries(array(row(K, V))) -> map(K, V)¶

Returns a map created from the given array of entries.

SELECT map_from_entries(ARRAY[(1, 'x'), (2, 'y')]); -- {1 -> 'x', 2 -> 'y'}

multimap_from_entries(array(row(K, V))) -> map(K, array(V))¶

Returns a multimap created from the given array of entries. Each key can be associated with multiple values.

SELECT multimap_from_entries(ARRAY[(1, 'x'), (2, 'y'), (1, 'z')]); -- {1 -> ['x', 'z'], 2 -> ['y']}

map_entries(map(K, V)) -> array(row(K, V))¶

Returns an array of all entries in the given map.

SELECT map_entries(MAP(ARRAY[1, 2], ARRAY['x', 'y'])); -- [ROW(1, 'x'), ROW(2, 'y')]

map_concat(map1(K, V), map2(K, V), ..., mapN(K, V)) -> map(K, V)¶

Returns the union of all the given maps. If a key is found in multiple given maps, that key’s value in the resulting map comes from the last one of those maps.

map_filter(map(K, V), function(K, V, boolean)) -> map(K, V)¶

Constructs a map from those entries of map for which function returns true:

SELECT map_filter(MAP(ARRAY[], ARRAY[]), (k, v) -> true); -- {}
SELECT map_filter(MAP(ARRAY[10, 20, 30], ARRAY['a', NULL, 'c']), (k, v) -> v IS NOT NULL); -- {10 -> a, 30 -> c}
SELECT map_filter(MAP(ARRAY['k1', 'k2', 'k3'], ARRAY[20, 3, 15]), (k, v) -> v > 10); -- {k1 -> 20, k3 -> 15}

map_remove_null_values(x(K, V)) -> map(K, V)¶

Removes all the entries where the value is null from the map x.

map_subset(map(K, V), array(k)) -> map(K, V)¶

Constructs a map from those entries of map for which the key is in the array given:

SELECT map_subset(MAP(ARRAY[1,2], ARRAY['a','b']), ARRAY[10]); -- {}
SELECT map_subset(MAP(ARRAY[1,2], ARRAY['a','b']), ARRAY[1]); -- {1->'a'}
SELECT map_subset(MAP(ARRAY[1,2], ARRAY['a','b']), ARRAY[1,3]); -- {1->'a'}
SELECT map_subset(MAP(ARRAY[1,2], ARRAY['a','b']), ARRAY[]); -- {}
SELECT map_subset(MAP(ARRAY[], ARRAY[]), ARRAY[1,2]); -- {}

map_key_exists(x(K, V), k) -> boolean()¶

Returns whether the given key exists in the map. Returns true if key is present in the input map, returns false if not present.:

SELECT map_key_exists(MAP(ARRAY['x','y'], ARRAY[100,200]), 'x'); -- TRUE

map_keys(x(K, V)) -> array(K)¶

Returns all the keys in the map x.

map_top_n_keys(x(K, V), n) -> array(K)¶

Returns top n keys in the map x by sorting its keys in descending order. n must be a non-negative integer.

For bottom n keys, use the function with lambda operator to perform custom sorting

SELECT map_top_n_keys(map(ARRAY['a', 'b', 'c'], ARRAY[3, 2, 1]), 2) --- ['c', 'b']

map_top_n_keys(x(K, V), n, function(K, K, int)) -> array(K)¶

Returns top n keys in the map x by sorting its keys using the given comparator function. The comparator takes two non-nullable arguments representing two keys of the map. It returns -1, 0, or 1 as the first key is less than, equal to, or greater than the second key. If the comparator function returns other values (including NULL), the query will fail and raise an error

SELECT map_top_n_keys(map(ARRAY['a', 'b', 'c'], ARRAY[3, 2, 1]), 2, (x, y) -> IF(x < y, -1, IF(x = y, 0, 1))) --- ['c', 'b']

map_keys_by_top_n_values(x(K, V), n) -> array(K)¶

Returns top n keys in the map x by sorting its values in descending order. If two or more keys have equal values, the higher key takes precedence. n must be a non-negative integer.:

SELECT map_top_n_keys_by_value(map(ARRAY['a', 'b', 'c'], ARRAY[2, 1, 3]), 2) --- ['c', 'a']

map_top_n(x(K, V), n) -> map(K, V)¶

Truncates map items. Keeps only the top n elements by value. Keys are used to break ties with the max key being chosen. Both keys and values should be orderable. n must be a non-negative integer.

SELECT map_top_n(map(ARRAY['a', 'b', 'c'], ARRAY[2, 3, 1]), 2) --- {'b' -> 3, 'a' -> 2}

map_normalize(x(varchar, double)) -> map(varchar, double)¶

Returns the map with the same keys but all non-null values are scaled proportionally so that the sum of values becomes 1. Map entries with null values remain unchanged.

map_values(x(K, V)) -> array(V)¶

Returns all the values in the map x.

map_top_n_values(x(K, V), n) -> array(K)¶

Returns top n values in the map x. n must be a positive integer For bottom n values, use the function with lambda operator to perform custom sorting.:

SELECT map_top_n_values(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), 2) --- [3, 2]

map_top_n_values(x(K, V), n, function(V, V, int)) -> array(V)¶

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

SELECT map_top_n_values(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), 2, (x, y) -> IF(x < y, -1, IF(x = y, 0, 1))) --- [3, 2]

map_zip_with(map(K, V1), map(K, V2), function(K, V1, V2, V3)) -> map(K, V3)¶

Merges the two given maps into a single map by applying function to the pair of values with the same key. For keys only presented in one map, NULL will be passed as the value for the missing key.

SELECT map_zip_with(MAP(ARRAY[1, 2, 3], ARRAY['a', 'b', 'c']), -- {1 -> ad, 2 -> be, 3 -> cf}
                    MAP(ARRAY[1, 2, 3], ARRAY['d', 'e', 'f']),
                    (k, v1, v2) -> concat(v1, v2));
SELECT map_zip_with(MAP(ARRAY['k1', 'k2'], ARRAY[1, 2]), -- {k1 -> ROW(1, null), k2 -> ROW(2, 4), k3 -> ROW(null, 9)}
                    MAP(ARRAY['k2', 'k3'], ARRAY[4, 9]),
                    (k, v1, v2) -> (v1, v2));
SELECT map_zip_with(MAP(ARRAY['a', 'b', 'c'], ARRAY[1, 8, 27]), -- {a -> a1, b -> b4, c -> c9}
                    MAP(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]),
                    (k, v1, v2) -> k || CAST(v1/v2 AS VARCHAR));

no_keys_match(x(K,V), function(K, boolean)) -> boolean()¶

Returns whether no keys of a map match the given predicate. Returns true if none of the keys match the predicate (a special case is when the map is empty); false if one or more keys match; NULL if the predicate function returns NULL for one or more keys and false for all other keys.

SELECT no_keys_match(map(array['a', 'b', 'c'], array[1, 2, 3]), x -> x = 'd'); -- true

no_values_match(x(K,V), function(V, boolean)) -> boolean()¶

Returns whether no values of a map match the given predicate. Returns true if none of the values match the predicate (a special case is when the map is empty); false if one or more values match; NULL if the predicate function returns NULL for one or more values and false for all other values.

SELECT no_values_match(map(array['a', 'b', 'c'], array[1, 2, 3]), x -> x = 'd'); -- true

transform_keys(map(K1, V), function(K1, V, K2)) -> map(K2, V)¶

Returns a map that applies function to each entry of map and transforms the keys:

SELECT transform_keys(MAP(ARRAY[], ARRAY[]), (k, v) -> k + 1); -- {}
SELECT transform_keys(MAP(ARRAY [1, 2, 3], ARRAY ['a', 'b', 'c']), (k, v) -> k + 1); -- {2 -> a, 3 -> b, 4 -> c}
SELECT transform_keys(MAP(ARRAY ['a', 'b', 'c'], ARRAY [1, 2, 3]), (k, v) -> v * v); -- {1 -> 1, 4 -> 2, 9 -> 3}
SELECT transform_keys(MAP(ARRAY ['a', 'b'], ARRAY [1, 2]), (k, v) -> k || CAST(v as VARCHAR)); -- {a1 -> 1, b2 -> 2}
SELECT transform_keys(MAP(ARRAY [1, 2], ARRAY [1.0, 1.4]), -- {one -> 1.0, two -> 1.4}
                      (k, v) -> MAP(ARRAY[1, 2], ARRAY['one', 'two'])[k]);

transform_values(map(K, V1), function(K, V1, V2)) -> map(K, V2)¶

Returns a map that applies function to each entry of map and transforms the values:

SELECT transform_values(MAP(ARRAY[], ARRAY[]), (k, v) -> v + 1); -- {}
SELECT transform_values(MAP(ARRAY [1, 2, 3], ARRAY [10, 20, 30]), (k, v) -> v + k); -- {1 -> 11, 2 -> 22, 3 -> 33}
SELECT transform_values(MAP(ARRAY [1, 2, 3], ARRAY ['a', 'b', 'c']), (k, v) -> k * k); -- {1 -> 1, 2 -> 4, 3 -> 9}
SELECT transform_values(MAP(ARRAY ['a', 'b'], ARRAY [1, 2]), (k, v) -> k || CAST(v as VARCHAR)); -- {a -> a1, b -> b2}
SELECT transform_values(MAP(ARRAY [1, 2], ARRAY [1.0, 1.4]), -- {1 -> one_1.0, 2 -> two_1.4}
                        (k, v) -> MAP(ARRAY[1, 2], ARRAY['one', 'two'])[k] || '_' || CAST(v AS VARCHAR));