Fluentd configuration for ORACLE clob datatype

I'm using fluentd configuration to read data from a text file and it is pushed to the Oracle database, I have clob & nclob type of datatype when fluentd pushed data, the column is always null and I don't see any errors. I'm not sure how to resolve this issue in fluentd, below is the configuration that I have done.

I 'm using oracle enhanced adapter & sql plugin

https://github.com/rsim/oracle-enhanced

https://github.com/fluent/fluent-plugin-sql/issues

#
# Fluentd configuration file
#

# Config input 
<source>
  @type forward
  port 24224
</source>

# Config output
<match cpu_*>
  @type stdout
</match>

<match foo_*>
  @type stdout
</match>

<match memory_*>
  @type sql
  host {DATABASE_HOSTNAME}
  port 1521
  database {DATABASE_NAME}
  adapter oracle_enhanced
  username {DATABASE_USERNAME}
  password {DATABASE_PASSWORD}

  <table>
    table fluentd_log
    column_mapping 'timestamp:created_at,Mem.text:mem_text,Mem.used:mem_used'
    # This is the default table because it has no "pattern" argument in <table>
    # The logic is such that if all non-default <table> blocks
    # do not match, the default one is chosen.
    # The default table is required.
  </table>
</match>

CREATE TABLE FLUENTD_LOG ( ID NUMBER(8), CREATED_AT VARCHAR2(50 BYTE), MEM_TEXT CLOB, MEM_USED VARCHAR2(50 BYTE) )

 ID    CREATED_AT    MEM_TEXT   MEMUSED
    1     29-08-99      null       test