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JSON Item Methods
Item methods are postfix operators that operate on a JSON value and return a JSON item. When run against a sequence the method is applied to each item in the sequence.
Multiple item methods can be used. For example: $.agestring.double().floor()
Note:  All item methods except for type() and size() unwrap arrays in lax mode.
Type()
Returns a character string
Returns “null”, “Boolean”, “number”, “string”, “array”, or “object”
Does not unwrap arrays. Returns “array” even in lax mode.
Example: LAX $.* ? (@.TYPE() == "number")
Size()
Returns an integer value
For an object or scalar, returns 1
For an array, returns the number of elements of the array
Does not unwrap arrays even in lax mode
Example: strict $.[1] ? (@.type() == "array" && @.size() > 1)
Numeric methods
Ceiling(), floor(), abs() have the same functionality as the numeric functions in SQL.
Double() coerces a string or numeric into a numeric float.
Keyvalue()
Used to examine an object with unknown schema.
Returns a sequence of objects with three key-value pairs whose keys are name, value, and id. One object is returned for each key:value pair of the input object.
Name and value will be the keys and values of the object.
Id is an integer that is a unique identifier for the input SQL or JSON object.
Assume a query runs the keyvalue() method on X objects and each object has Y key:value pairs. X*Y total objects are returned, and every “Y” object will have a unique ID that corresponds to the original object. The id allows reconstructing the original objects from the output of keyvalue().
Note: The ids are only unique within the scope of the query that uses keyvalue(). The same objects can have different id numbers when run in separate queries.
In lax mode, the input is unwrapped, so keyvalue() on an array of X items returns a sequence of X items.
Id numbers are only unique for the query in which keyvalue() is called. They can be reused in other queries.
Example: Given the object {who: "Fred", what: 64}, keyvalue() returns:
{name: "who", value: "Fred", id: 9045},
{name: "what", value: 64, id: 9045}
To find the value of all “names”, select Keyvalue().name which returns the sequence("who", "what").
Example: Given the sequence:
[{"Building":"Empire", "Unit":"3F"}, {"row":"A", "Seat":6}]
keyvalue() returns four objects:
{ name: "Building", value: "Empire", id: 1000 },
{ name: "Unit", value: "3F", id: 1000 },
{ name: "row", value: "A", id: 1001 },
{ name: "Seat", value: 6, id: 1001 }
 
Last modified date: 11/09/2022