src/main/java/com/conveyal/gtfs/loader/Table.java
public static String commaSeparatedNames(List<Field> fieldsToJoin, String prefix, boolean csvOutput) {
        return fieldsToJoin.stream()
                // NOTE: This previously only prefixed fields that were foreign refs or key fields. However, this
                // caused an issue where shared fields were ambiguously referenced in a select query (specifically,
                // wheelchair_accessible in routes and trips). So this filter has been removed.
                .map(f -> f.getColumnExpression(prefix, csvOutput))
                .collect(Collectors.joining(", "));
    }
public static String commaSeparatedNames(List<Field> fieldsToJoin, String prefix, boolean csvOutput) {
        return fieldsToJoin.stream()
                // NOTE: This previously only prefixed fields that were foreign refs or key fields. However, this
                // caused an issue where shared fields were ambiguously referenced in a select query (specifically,
                // wheelchair_accessible in routes and trips). So this filter has been removed.
                .map(f -> f.getColumnExpression(prefix, csvOutput))
                .collect(Collectors.joining(", "));
    }
Prepend a prefix string to each field and join them with a comma + space separator.
Also, if an export to GTFS is being performed, certain fields need a translation from the database format to the
GTFS format.  Otherwise, the fields are assumed to be asked in order to do a database-to-database export and so
the verbatim values of the fields are needed.