# Functions for maps

## map​

Creates a value of type Map(key, value) from key-value pairs.

Syntax

map(key1, value1[, key2, value2, ...])

Arguments

• key_n — The keys of the map entries. Any type supported as key type of Map.
• value_n — The values of the map entries. Any type supported as value type of Map.

Returned value

Examples

Query:

SELECT map('key1', number, 'key2', number * 2) FROM numbers(3);

Result:

┌─map('key1', number, 'key2', multiply(number, 2))─┐│ {'key1':0,'key2':0}                              ││ {'key1':1,'key2':2}                              ││ {'key1':2,'key2':4}                              │└──────────────────────────────────────────────────┘

## mapFromArrays​

Creates a map from an array or map of keys and an array or map of values.

The function is a convenient alternative to syntax CAST([...], 'Map(key_type, value_type)'). For example, instead of writing

• CAST((['aa', 'bb'], [4, 5]), 'Map(String, UInt32)'), or
• CAST([('aa',4), ('bb',5)], 'Map(String, UInt32)')

you can write mapFromArrays(['aa', 'bb'], [4, 5]).

Syntax

mapFromArrays(keys, values)

Alias: MAP_FROM_ARRAYS(keys, values)

Arguments

• keys — Array or map of keys to create the map from Array or Map. If keys is an array, we accept Array(Nullable(T)) or Array(LowCardinality(Nullable(T))) as its type as long as it doesn't contain NULL value.
• values - Array or map of values to create the map from Array or Map.

Returned value

• A map with keys and values constructed from the key array and value array/map.

Example

Query:

select mapFromArrays(['a', 'b', 'c'], [1, 2, 3])

Result:

┌─mapFromArrays(['a', 'b', 'c'], [1, 2, 3])─┐│ {'a':1,'b':2,'c':3}                       │└───────────────────────────────────────────┘

mapFromArrays also accepts arguments of type Map. These are casted to array of tuples during execution.

SELECT mapFromArrays([1, 2, 3], map('a', 1, 'b', 2, 'c', 3))

Result:

┌─mapFromArrays([1, 2, 3], map('a', 1, 'b', 2, 'c', 3))─┐│ {1:('a',1),2:('b',2),3:('c',3)}                       │└───────────────────────────────────────────────────────┘
SELECT mapFromArrays(map('a', 1, 'b', 2, 'c', 3), [1, 2, 3])

Result:

┌─mapFromArrays(map('a', 1, 'b', 2, 'c', 3), [1, 2, 3])─┐│ {('a',1):1,('b',2):2,('c',3):3}                       │└───────────────────────────────────────────────────────┘

## extractKeyValuePairs​

Converts a string of key-value pairs to a Map(String, String). Parsing is tolerant towards noise (e.g. log files). Key-value pairs in the input string consist of a key, followed by a key-value delimiter, and a value. Key value pairs are separated by a pair delimiter. Keys and values can be quoted.

Syntax

extractKeyValuePairs(data[, key_value_delimiter[, pair_delimiter[, quoting_character]]])

Alias:

• str_to_map
• mapFromString

Arguments

• data - String to extract key-value pairs from. String or FixedString.
• key_value_delimiter - Single character delimiting keys and values. Defaults to :. String or FixedString.
• pair_delimiters - Set of character delimiting pairs. Defaults to  , , and ;. String or FixedString.
• quoting_character - Single character used as quoting character. Defaults to ". String or FixedString.

Returned values

Examples

Query

SELECT extractKeyValuePairs('name:neymar, age:31 team:psg,nationality:brazil') as kv

Result:

┌─kv──────────────────────────────────────────────────────────────────────┐│ {'name':'neymar','age':'31','team':'psg','nationality':'brazil'}        │└─────────────────────────────────────────────────────────────────────────┘

With a single quote ' as quoting character:

SELECT extractKeyValuePairs('name:\'neymar\';\'age\':31;team:psg;nationality:brazil,last_key:last_value', ':', ';,', '\'') as kv

Result:

┌─kv───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ {'name':'neymar','age':'31','team':'psg','nationality':'brazil','last_key':'last_value'}                                 │└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

Escape sequences without escape sequences support:

SELECT extractKeyValuePairs('age:a\\x0A\\n\\0') AS kv

Result:

┌─kv─────────────────────┐│ {'age':'a\\x0A\\n\\0'} │└────────────────────────┘

To restore a map string key-value pairs serialized with toString:

SELECT    map('John', '33', 'Paula', '31') AS m,    toString(m) as map_serialized,    extractKeyValuePairs(map_serialized, ':', ',', '\'') AS map_restoredFORMAT Vertical;

Result:

Row 1:──────m:              {'John':'33','Paula':'31'}map_serialized: {'John':'33','Paula':'31'}map_restored:   {'John':'33','Paula':'31'}

## extractKeyValuePairsWithEscaping​

Same as extractKeyValuePairs but supports escaping.

Supported escape sequences: \x, \N, \a, \b, \e, \f, \n, \r, \t, \v and \0. Non standard escape sequences are returned as it is (including the backslash) unless they are one of the following: \\, ', ", backtick, /, = or ASCII control characters (c <= 31).

This function will satisfy the use case where pre-escaping and post-escaping are not suitable. For instance, consider the following input string: a: "aaaa\"bbb". The expected output is: a: aaaa\"bbbb.

• Pre-escaping: Pre-escaping it will output: a: "aaaa"bbb" and extractKeyValuePairs will then output: a: aaaa
• Post-escaping: extractKeyValuePairs will output a: aaaa\ and post-escaping will keep it as it is.

Leading escape sequences will be skipped in keys and will be considered invalid for values.

Examples

Escape sequences with escape sequence support turned on:

SELECT extractKeyValuePairsWithEscaping('age:a\\x0A\\n\\0') AS kv

Result:

┌─kv────────────────┐│ {'age':'a\n\n\0'} │└───────────────────┘

Collect all the keys and sum corresponding values.

Syntax

mapAdd(arg1, arg2 [, ...])

Arguments

Arguments are maps or tuples of two arrays, where items in the first array represent keys, and the second array contains values for the each key. All key arrays should have same type, and all value arrays should contain items which are promoted to the one type (Int64, UInt64 or Float64). The common promoted type is used as a type for the result array.

Returned value

• Depending on the arguments returns one map or tuple, where the first array contains the sorted keys and the second array contains values.

Example

Query with Map type:

SELECT mapAdd(map(1,1), map(1,1));

Result:

┌─mapAdd(map(1, 1), map(1, 1))─┐│ {1:2}                        │└──────────────────────────────┘

Query with a tuple:

SELECT mapAdd(([toUInt8(1), 2], [1, 1]), ([toUInt8(1), 2], [1, 1])) as res, toTypeName(res) as type;

Result:

┌─res───────────┬─type───────────────────────────────┐│ ([1,2],[2,2]) │ Tuple(Array(UInt8), Array(UInt64)) │└───────────────┴────────────────────────────────────┘

## mapSubtract​

Collect all the keys and subtract corresponding values.

Syntax

mapSubtract(Tuple(Array, Array), Tuple(Array, Array) [, ...])

Arguments

Arguments are maps or tuples of two arrays, where items in the first array represent keys, and the second array contains values for the each key. All key arrays should have same type, and all value arrays should contain items which are promote to the one type (Int64, UInt64 or Float64). The common promoted type is used as a type for the result array.

Returned value

• Depending on the arguments returns one map or tuple, where the first array contains the sorted keys and the second array contains values.

Example

Query with Map type:

SELECT mapSubtract(map(1,1), map(1,1));

Result:

┌─mapSubtract(map(1, 1), map(1, 1))─┐│ {1:0}                             │└───────────────────────────────────┘

Query with a tuple map:

SELECT mapSubtract(([toUInt8(1), 2], [toInt32(1), 1]), ([toUInt8(1), 2], [toInt32(2), 1])) as res, toTypeName(res) as type;

Result:

┌─res────────────┬─type──────────────────────────────┐│ ([1,2],[-1,0]) │ Tuple(Array(UInt8), Array(Int64)) │└────────────────┴───────────────────────────────────┘

## mapPopulateSeries​

Fills missing key-value pairs in a map with integer keys. To support extending the keys beyond the largest value, a maximum key can be specified. More specifically, the function returns a map in which the the keys form a series from the smallest to the largest key (or max argument if it specified) with step size of 1, and corresponding values. If no value is specified for a key, a default value is used as value. In case keys repeat, only the first value (in order of appearance) is associated with the key.

Syntax

mapPopulateSeries(map[, max])mapPopulateSeries(keys, values[, max])

For array arguments the number of elements in keys and values must be the same for each row.

Arguments

Arguments are Maps or two Arrays, where the first and second array contains keys and values for the each key.

Mapped arrays:

• map — Map with integer keys. Map.

or

Returned value

• Depending on the arguments a Map or a Tuple of two Arrays: keys in sorted order, and values the corresponding keys.

Example

Query with Map type:

SELECT mapPopulateSeries(map(1, 10, 5, 20), 6);

Result:

┌─mapPopulateSeries(map(1, 10, 5, 20), 6)─┐│ {1:10,2:0,3:0,4:0,5:20,6:0}             │└─────────────────────────────────────────┘

Query with mapped arrays:

SELECT mapPopulateSeries([1,2,4], [11,22,44], 5) AS res, toTypeName(res) AS type;

Result:

┌─res──────────────────────────┬─type──────────────────────────────┐│ ([1,2,3,4,5],[11,22,0,44,0]) │ Tuple(Array(UInt8), Array(UInt8)) │└──────────────────────────────┴───────────────────────────────────┘

## mapContains​

Returns if a given key is contained in a given map.

Syntax

mapContains(map, key)

Arguments

• map — Map. Map.
• key — Key. Type must match the key type of map.

Returned value

• 1 if map contains key, 0 if not. UInt8.

Example

Query:

CREATE TABLE tab (a Map(String, String)) ENGINE = Memory;INSERT INTO tab VALUES ({'name':'eleven','age':'11'}), ({'number':'twelve','position':'6.0'});SELECT mapContains(a, 'name') FROM tab;

Result:

┌─mapContains(a, 'name')─┐│                      1 ││                      0 │└────────────────────────┘

## mapKeys​

Returns the keys of a given map.

This function can be optimized by enabling setting optimize_functions_to_subcolumns. With enabled setting, the function only reads the keys subcolumn instead the whole map. The query SELECT mapKeys(m) FROM table is transformed to SELECT m.keys FROM table.

Syntax

mapKeys(map)

Arguments

• map — Map. Map.

Returned value

• Array containing all keys from the map. Array.

Example

Query:

CREATE TABLE tab (a Map(String, String)) ENGINE = Memory;INSERT INTO tab VALUES ({'name':'eleven','age':'11'}), ({'number':'twelve','position':'6.0'});SELECT mapKeys(a) FROM tab;

Result:

┌─mapKeys(a)────────────┐│ ['name','age']        ││ ['number','position'] │└───────────────────────┘

## mapValues​

Returns the values of a given map.

This function can be optimized by enabling setting optimize_functions_to_subcolumns. With enabled setting, the function only reads the values subcolumn instead the whole map. The query SELECT mapValues(m) FROM table is transformed to SELECT m.values FROM table.

Syntax

mapValues(map)

Arguments

• map — Map. Map.

Returned value

• Array containing all the values from map. Array.

Example

Query:

CREATE TABLE tab (a Map(String, String)) ENGINE = Memory;INSERT INTO tab VALUES ({'name':'eleven','age':'11'}), ({'number':'twelve','position':'6.0'});SELECT mapValues(a) FROM tab;

Result:

┌─mapValues(a)─────┐│ ['eleven','11']  ││ ['twelve','6.0'] │└──────────────────┘

## mapContainsKeyLike​

Syntax

mapContainsKeyLike(map, pattern)

Arguments

• map — Map. Map.
• pattern - String pattern to match.

Returned value

• 1 if map contains key like specified pattern, 0 if not.

Example

Query:

CREATE TABLE tab (a Map(String, String)) ENGINE = Memory;INSERT INTO tab VALUES ({'abc':'abc','def':'def'}), ({'hij':'hij','klm':'klm'});SELECT mapContainsKeyLike(a, 'a%') FROM tab;

Result:

┌─mapContainsKeyLike(a, 'a%')─┐│                           1 ││                           0 │└─────────────────────────────┘

## mapExtractKeyLike​

Give a map with string keys and a LIKE pattern, this function returns a map with elements where the key matches the pattern.

Syntax

mapExtractKeyLike(map, pattern)

Arguments

• map — Map. Map.
• pattern - String pattern to match.

Returned value

• A map containing elements the key matching the specified pattern. If no elements match the pattern, an empty map is returned.

Example

Query:

CREATE TABLE tab (a Map(String, String)) ENGINE = Memory;INSERT INTO tab VALUES ({'abc':'abc','def':'def'}), ({'hij':'hij','klm':'klm'});SELECT mapExtractKeyLike(a, 'a%') FROM tab;

Result:

┌─mapExtractKeyLike(a, 'a%')─┐│ {'abc':'abc'}              ││ {}                         │└────────────────────────────┘

## mapApply​

Applies a function to each element of a map.

Syntax

mapApply(func, map)

Arguments

Returned value

• Returns a map obtained from the original map by application of func(map1[i], ..., mapN[i]) for each element.

Example

Query:

SELECT mapApply((k, v) -> (k, v * 10), _map) AS rFROM(    SELECT map('key1', number, 'key2', number * 2) AS _map    FROM numbers(3))

Result:

┌─r─────────────────────┐│ {'key1':0,'key2':0}   ││ {'key1':10,'key2':20} ││ {'key1':20,'key2':40} │└───────────────────────┘

## mapFilter​

Filters a map by applying a function to each map element.

Syntax

mapFilter(func, map)

Arguments

Returned value

• Returns a map containing only the elements in map for which func(map1[i], ..., mapN[i]) returns something other than 0.

Example

Query:

SELECT mapFilter((k, v) -> ((v % 2) = 0), _map) AS rFROM(    SELECT map('key1', number, 'key2', number * 2) AS _map    FROM numbers(3))

Result:

┌─r───────────────────┐│ {'key1':0,'key2':0} ││ {'key2':2}          ││ {'key1':2,'key2':4} │└─────────────────────┘

## mapUpdate​

Syntax

mapUpdate(map1, map2)

Arguments

• map1 Map.
• map2 Map.

Returned value

• Returns a map1 with values updated of values for the corresponding keys in map2.

Example

Query:

SELECT mapUpdate(map('key1', 0, 'key3', 0), map('key1', 10, 'key2', 10)) AS map;

Result:

┌─map────────────────────────────┐│ {'key3':0,'key1':10,'key2':10} │└────────────────────────────────┘

## mapConcat​

Concatenates multiple maps based on the equality of their keys. If elements with the same key exist in more than one input map, all elements are added to the result map, but only the first one is accessible via operator []

Syntax

mapConcat(maps)

Arguments

• maps – Arbitrarily many Maps.

Returned value

• Returns a map with concatenated maps passed as arguments.

Examples

Query:

SELECT mapConcat(map('key1', 1, 'key3', 3), map('key2', 2)) AS map;

Result:

┌─map──────────────────────────┐│ {'key1':1,'key3':3,'key2':2} │└──────────────────────────────┘

Query:

SELECT mapConcat(map('key1', 1, 'key2', 2), map('key1', 3)) AS map, map['key1'];

Result:

┌─map──────────────────────────┬─elem─┐│ {'key1':1,'key2':2,'key1':3} │    1 │└──────────────────────────────┴──────┘

## mapExists([func,], map)​

Returns 1 if at least one key-value pair in map exists for which func(key, value) returns something other than 0. Otherwise, it returns 0.

note

mapExists is a higher-order function. You can pass a lambda function to it as the first argument.

Example

Query:

SELECT mapExists((k, v) -> (v = 1), map('k1', 1, 'k2', 2)) AS res

Result:

┌─res─┐│   1 │└─────┘

## mapAll([func,] map)​

Returns 1 if func(key, value) returns something other than 0 for all key-value pairs in map. Otherwise, it returns 0.

note

Note that the mapAll is a higher-order function. You can pass a lambda function to it as the first argument.

Example

Query:

SELECT mapAll((k, v) -> (v = 1), map('k1', 1, 'k2', 2)) AS res

Result:

┌─res─┐│   0 │└─────┘

## mapSort([func,], map)​

Sorts the elements of a map in ascending order. If the func function is specified, the sorting order is determined by the result of the func function applied to the keys and values of the map.

Examples

SELECT mapSort(map('key2', 2, 'key3', 1, 'key1', 3)) AS map;
┌─map──────────────────────────┐│ {'key1':3,'key2':2,'key3':1} │└──────────────────────────────┘
SELECT mapSort((k, v) -> v, map('key2', 2, 'key3', 1, 'key1', 3)) AS map;
┌─map──────────────────────────┐│ {'key3':1,'key2':2,'key1':3} │└──────────────────────────────┘

For more details see the reference for arraySort function.

## mapPartialSort​

Sorts the elements of a map in ascending order with additional limit argument allowing partial sorting. If the func function is specified, the sorting order is determined by the result of the func function applied to the keys and values of the map.

Syntax

mapPartialSort([func,] limit, map)

Arguments

• func – Optional function to apply to the keys and values of the map. Lambda function.
• limit – Elements in range [1..limit] are sorted. (U)Int.
• map – Map to sort. Map.

Returned value

• Partially sorted map. Map.

Example

SELECT mapPartialSort((k, v) -> v, 2, map('k1', 3, 'k2', 1, 'k3', 2));
┌─mapPartialSort(lambda(tuple(k, v), v), 2, map('k1', 3, 'k2', 1, 'k3', 2))─┐│ {'k2':1,'k3':2,'k1':3}                                                    │└───────────────────────────────────────────────────────────────────────────┘

## mapReverseSort([func,], map)​

Sorts the elements of a map in descending order. If the func function is specified, the sorting order is determined by the result of the func function applied to the keys and values of the map.

Examples

SELECT mapReverseSort(map('key2', 2, 'key3', 1, 'key1', 3)) AS map;
┌─map──────────────────────────┐│ {'key3':1,'key2':2,'key1':3} │└──────────────────────────────┘
SELECT mapReverseSort((k, v) -> v, map('key2', 2, 'key3', 1, 'key1', 3)) AS map;
┌─map──────────────────────────┐│ {'key1':3,'key2':2,'key3':1} │└──────────────────────────────┘

For more details see function arrayReverseSort.

## mapPartialReverseSort​

Sorts the elements of a map in descending order with additional limit argument allowing partial sorting. If the func function is specified, the sorting order is determined by the result of the func function applied to the keys and values of the map.

Syntax

mapPartialReverseSort([func,] limit, map)

Arguments

• func – Optional function to apply to the keys and values of the map. Lambda function.
• limit – Elements in range [1..limit] are sorted. (U)Int.
• map – Map to sort. Map.

Returned value

• Partially sorted map. Map.

Example

SELECT mapPartialReverseSort((k, v) -> v, 2, map('k1', 3, 'k2', 1, 'k3', 2));
┌─mapPartialReverseSort(lambda(tuple(k, v), v), 2, map('k1', 3, 'k2', 1, 'k3', 2))─┐│ {'k1':3,'k3':2,'k2':1}                                                           │└──────────────────────────────────────────────────────────────────────────────────┘