The field the user wants to filter by.
Indicates the filter type, can be 'equal,', 'notEqual', 'greaterThan', 'greaterThanAndEqual', 'lessThan', 'lessThanAndEqual', 'memberOf' or 'notMemberOf'.
Value to compare. when using 'memberOf' or 'notMemberOf', the value can be an array (discrete set) or string (continuous set). For example, [1,2,3,4] means only left values equals to 1 or 2 or 3 or 4; '(1, 4]' means only left values larger than 1 and less than or equal to 4.
Defines type of filter descriptor.