presto-main/src/main/java/io/prestosql/sql/planner/EffectivePredicateExtractor.java/Visitor/pullNullableConjunctsThroughOuterJoin
class Visitor:        private Iterable<Expression> pullNullableConjunctsThroughOuterJoin(List<Expression> conjuncts, Collection<Symbol> outputSymbols, Predicate<Symbol>... nullSymbolScopes)
        {
            // Conjuncts without any symbol dependencies cannot be applied to the effective predicate (e.g. FALSE literal)
            return conjuncts.stream()
                    .map(expression -> pullExpressionThroughSymbols(expression, outputSymbols))
                    .map(expression -> SymbolsExtractor.extractAll(expression).isEmpty() ? TRUE_LITERAL : expression)
                    .map(expressionOrNullSymbols(nullSymbolScopes))
                    .collect(toImmutableList());
        }