Package dev.frostlake.functions.scalar.semistructured

Class MapConstruct

java.lang.Object
dev.frostlake.functions.BuiltInFunction
dev.frostlake.functions.scalar.semistructured.MapConstruct
public class MapConstruct extends BuiltInFunction
MAP_CONSTRUCT(key, value [, key, value …]) — a MAP built from alternating key/value arguments. The one member of the family that MAKES a map rather than reading one, so it takes no MAP argument and is not subject to the MAP-requiring strictness rule.

Its arguments must PAIR UP: live, an odd count is "not enough arguments for function [MAP_CONSTRUCT], expected 4, got 3" — the count named is the next EVEN one, not the maximum — and fewer than two is the same sentence with the call quoted back.

NULL handling was measured over a two-row table so that no all-NULL column could be folded to a NULL literal by the optimiser: a NULL KEY drops the whole pair (MAP_CONSTRUCT(k, v) is {} on the row where k is NULL) while a NULL VALUE is KEPT as a JSON null member ({"a":null}, which MAP_SIZE counts as one entry). A duplicate key is a run-time error, "Duplicate field key 'a'", exactly as in MAP_INSERT.

  • Constructor Details

    • MapConstruct

      public MapConstruct()

  • Method Details

    • evaluate

      public Object evaluate(List<Object> args)
      Description copied from class: BuiltInFunction
      Computes the function's result over its already-evaluated argument values. A SQL NULL argument arrives as Java null, and returning null makes the SQL result NULL.
      Specified by:
      evaluate in class BuiltInFunction
      Parameters:
      args - the argument values, in call order
      Returns:
      the function's value for these arguments, or null for SQL NULL

    • getMinArgCount

      public int getMinArgCount()
      Description copied from class: BuiltInFunction
      The fewest arguments a call to this function may pass; fewer is an argument-count error.
      Specified by:
      getMinArgCount in class BuiltInFunction
      Returns:
      the minimum accepted argument count

    • getMaxArgCount

      public int getMaxArgCount()
      Description copied from class: BuiltInFunction
      The most arguments a call to this function may pass; Integer.MAX_VALUE marks a variadic function (see BuiltInFunction.isVariadic()).
      Specified by:
      getMaxArgCount in class BuiltInFunction
      Returns:
      the maximum accepted argument count