pentaho/pentaho-kettle · error · KettleValueException

Function first_day only works on a date

Error message

Function first_day only works on a date

What it means

Guard in the legacy Value first_day() function: the value's type is not VALUE_TYPE_DATE, so the Calendar that resets the day-of-month to 1 cannot be initialized. The input at fault is the current Value with a non-date type.

Solutions

1. Ensure the field passed to first_day is a Date
2. Convert the value to a Date before calling FIRST_DAY

When it happens

Trigger: Thrown at core/src/main/java/org/pentaho/di/compatibility/Value.java:3439 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/c17cbde3fc46fb69. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/pentaho/di/compatibility/Value.java:3439

      int last_day = cal.getActualMaximum( Calendar.DAY_OF_MONTH );
      cal.set( Calendar.DAY_OF_MONTH, last_day );

      setValue( cal.getTime() );
    } else {
      throw new KettleValueException( "Function last_day only works on a date" );
    }

    return this;
  }

  public Value first_day() throws KettleValueException {
    if ( getType() == VALUE_TYPE_DATE ) {
      Calendar cal = Calendar.getInstance();
      cal.setTime( getDate() );
      cal.set( Calendar.DAY_OF_MONTH, 1 );
      setValue( cal.getTime() );
    } else {
      throw new KettleValueException( "Function first_day only works on a date" );
    }

    return this;
  }

  // implement the TRUNC function, version without arguments
  public Value trunc() throws KettleValueException {
    if ( isNull() ) {
      return this; // don't do anything, leave it at NULL!
    }
    if ( isInteger() ) {
      // Nothing
      return this;
    }

    if ( isBigNumber() ) {
      getBigNumber().setScale( 0, BigDecimal.ROUND_FLOOR );
    } else if ( isNumber() ) {

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