Map Functions

This section provides reference information for the map functions in Databend. Map functions allow you to create, manipulate, and extract information from map data structures (key-value pairs).

Map Creation and Combination

Function	Description	Example
MAP_CAT	Combines multiple maps into a single map	MAP_CAT({'a':1}, {'b':2}) → {'a':1,'b':2}

Map Access and Information

Function	Description	Example
MAP_KEYS	Returns all keys from a map as an array	MAP_KEYS({'a':1,'b':2}) → ['a','b']
MAP_VALUES	Returns all values from a map as an array	MAP_VALUES({'a':1,'b':2}) → [1,2]
MAP_SIZE	Returns the number of key-value pairs in a map	MAP_SIZE({'a':1,'b':2,'c':3}) → 3
MAP_CONTAINS_KEY	Checks if a map contains a specific key	MAP_CONTAINS_KEY({'a':1,'b':2}, 'a') → TRUE

Map Modification

Function	Description	Example
MAP_INSERT	Inserts a key-value pair into a map	MAP_INSERT({'a':1,'b':2}, 'c', 3) → {'a':1,'b':2,'c':3}
MAP_DELETE	Removes a key-value pair from a map	MAP_DELETE({'a':1,'b':2,'c':3}, 'b') → {'a':1,'c':3}

Map Transformation

Function	Description	Example
MAP_TRANSFORM_KEYS	Applies a function to each key in a map	MAP_TRANSFORM_KEYS({'a':1,'b':2}, x -> UPPER(x)) → {'A':1,'B':2}
MAP_TRANSFORM_VALUES	Applies a function to each value in a map	MAP_TRANSFORM_VALUES({'a':1,'b':2}, x -> x * 10) → {'a':10,'b':20}

Map Filtering and Selection

Function	Description	Example
MAP_FILTER	Filters key-value pairs based on a predicate	MAP_FILTER({'a':1,'b':2,'c':3}, (k,v) -> v > 1) → {'b':2,'c':3}
MAP_PICK	Creates a new map with only specified keys	MAP_PICK({'a':1,'b':2,'c':3}, ['a','c']) → {'a':1,'c':3}