Package dev.frostlake.functions.scalar.semistructured

Class MapCat

java.lang.Object
dev.frostlake.functions.BuiltInFunction
dev.frostlake.functions.scalar.semistructured.MapCat
public class MapCat extends BuiltInFunction
MAP_CAT(map1, map2) — the concatenation (merge) of two MAPs. Frostlake models a MAP as an OBJECT, so the result is the object holding every key of both inputs; on a key present in both, map2's value wins.

A NULL on EITHER side makes the whole result NULL — it is not treated as an empty map. Frostlake used to merge the other side through and answer it, which is the plausible reading and the wrong one: live, MAP_CAT(<{'a':1}>, NULL::MAP(VARCHAR,INT)) is NULL, and so is the same call over two MAP COLUMNS where one row's second map is NULL — measured both ways round, and on columns as well as literals, because a single spelling could not tell a NULL-propagating function from a NULL-tolerant one.

  • Constructor Details

    • MapCat

      public MapCat()

  • 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