src/main/java/com/conveyal/gtfs/graphql/fetchers/JDBCFetcher.java
static String filterEquals(String filterField, String string, List<String> parameters) {
        // Add string to list of parameters (to be later used to set parameters for prepared statement).
        parameters.add(string);
        return String.format("%s = ?", filterField);
    }
static String filterEquals(String filterField, String string, List<String> parameters) {
        // Add string to list of parameters (to be later used to set parameters for prepared statement).
        parameters.add(string);
        return String.format("%s = ?", filterField);
    }
Construct filter clause with '=' (single string) and add values to list of parameters.