Package dev.frostlake.functions.window

Class BooleanArgumentWindowFunctions

java.lang.Object
dev.frostlake.functions.window.BooleanArgumentWindowFunctions
public final class BooleanArgumentWindowFunctions extends Object
The two conditional-event window functions, and what their plan echo shows about their argument. Live prints the conversions its plan carries, and these two do NOT carry the same ones — measured side by side across nine argument shapes each: 
                                  CONDITIONAL_TRUE_EVENT      CONDITIONAL_CHANGE_EVENT
   b            BOOLEAN column    CE.B                        CE.B
   NOT b / b AND b / TRUE         as written                  as written
   i > 1        a comparison      CAST(CE.I > 1 AS BOOLEAN)   CAST(CE.I > 1 AS BOOLEAN)
   b IS NULL                      CAST(… AS BOOLEAN)          CAST(… AS BOOLEAN)
   STARTSWITH(t,'1')              CAST(… AS BOOLEAN)          CAST(… AS BOOLEAN)
   t            VARCHAR column    CAST(CE.T AS BOOLEAN)       CE.T
   UPPER(t)     a VARCHAR call    CAST(… AS BOOLEAN)          UPPER(CE.T)
   i + 1        arithmetic        —                           CE.I + 1

★ TWO SEPARATE RULES PRODUCE THAT TABLE, and they have to be kept apart:

1. A BOOLEAN-VALUED EXPRESSION THAT IS NOT ONE OF THE LOGICAL NODES is materialised as a cast, by BOTH functions. A comparison, an IS NULL and a boolean-returning call are all booleans already, and all three are cast anyway; a BOOLEAN column, a boolean literal and NOT / AND / OR are not. So the cast is not "the type had to change" — it is the plan spelling out a predicate it did not build from its own logical vocabulary.

2. THE PARAMETER'S OWN TYPE. CONDITIONAL_TRUE_EVENT counts how often a PREDICATE holds, so a non-boolean argument is converted and the conversion is printed. CONDITIONAL_CHANGE_EVENT counts how often a VALUE changes and takes any type, so it converts nothing — which is why the last three rows of the table differ.

  • Method Details

    • spellsOutABooleanArgument

      public static boolean spellsOutABooleanArgument(String name)
      Whether this function's echo spells out a boolean argument it did not build itself — rule 1. Measured for these two; every other window function's echo is left as it was.
      Parameters:
      name - the upper-cased function name
      Returns:
      true for the two conditional-event functions

    • coercesArgumentToBoolean

      public static boolean coercesArgumentToBoolean(String name)
      Whether this function CONVERTS its argument to a boolean — rule 2, which is CONDITIONAL_TRUE_EVENT alone.
      Parameters:
      name - the upper-cased function name
      Returns:
      true when the parameter is a predicate rather than a value