private static List<Integer> getInputChannels(Iterable<RowExpression> expressions) {
TreeSet<Integer> channels = new TreeSet<>();
for (RowExpression expression : Expressions.subExpressions(expressions)) {
if (expression instanceof InputReferenceExpression) {
channels.add(((InputReferenceExpression) expression).getField());
}
}
return ImmutableList.copyOf(channels);
}
private static boolean isConstantExpression(RowExpression expression) {
List<RowExpression> rowExpressions = Expressions.subExpressions(ImmutableList.of(expression));
return rowExpressions.size() == 1
&& Iterables.getOnlyElement(rowExpressions) instanceof ConstantExpression
&& ((ConstantExpression) Iterables.getOnlyElement(rowExpressions)).getValue() != null;
}
private static boolean isIdentityExpression(RowExpression expression) {
List<RowExpression> rowExpressions = Expressions.subExpressions(ImmutableList.of(expression));
return rowExpressions.size() == 1
&& Iterables.getOnlyElement(rowExpressions) instanceof InputReferenceExpression;
}