code: private String tryConvertAvroColNameToJdbcColName(String avroColName) {
      if (!avroToJdbcColPairs.isPresent()) {
        String converted = avroColName.replaceAll(AVRO_NESTED_COLUMN_DELIMITER_REGEX_COMPATIBLE, JDBC_FLATTENED_COLUMN_DELIMITER);
        jdbcToAvroColPairs.put(converted, avroColName);
        return converted;
      }
  
      String converted = avroToJdbcColPairs.get().get(avroColName);
      converted = converted != null ? converted : avroColName;
      jdbcToAvroColPairs.put(converted, avroColName);
      return converted;
    }
docs: Convert Avro column name to JDBC column name. If name mapping is defined, follow it. Otherwise, just return avro column name,
  while replacing nested column delimiter, dot, to underscore.
  This method also updates, mapping from JDBC column name to Avro column name for reverse look up.
  @param avroColName
  @return