How to insert NULL values into a PostgreSQL table

I have data in CSV file I am trying to insert into a postgresSQL table using pgloader. The input file is from MS SQL server export, and NULL values are already explicitly cast as NULL.

My pgloader scripts seems to fail for the keywords NULL, noticeably for integer and timestamp fields.

I really don't know what I am missing. Your help will be much appreciated.

I can successfully insert into the table from psql console:

insert into raw.a2
(NUM , F_FILENO , F_FOLIONO , F_DOC_TYPE , F_DOCDATE , F_BATCH , F_BOX , F_BLUCPY , F_ROUTOPOST , F_ROUTOUSR , F_WFCREATE , LINKEDFILE , DATECREATE , USERCREATE , DATEUPDATE , USERUPDATE , MEDIA , PGCOUNT , GROUPNUM , SUBJECT , PRI , F_FILECAT)
values
(
16,'18',3,'Nomination Details',NULL,NULL,NULL,1,NULL,NULL,1,'00000016.TIF','2011-02-08 13:02:11.000','isaac','2012-01-12 08:52:31.000','henrey','Multi',4,1.0,0,'-',NULL
);

INSERT 0 1

file-sample

1,'6',1,'Details',2011-02-22 00:00:00.000,NULL,NULL,1,NULL,NULL,2,'00000001.TIF',2011-02-08 09:42:24.000,'kevin',2011-10-27 09:08:42.000,'james','Multi',1,1.0,0,'-',NULL
2,'6',2,'Bio data',NULL,NULL,NULL,1,NULL,NULL,2,'00000002.TIF',2011-02-08 10:25:11.000,'kevin',2012-11-19 16:20:49.000,'pattie','Multi',4,1.0,0,'-',NULL
4,'10',1,'Details',2011-02-22 00:00:00.000,NULL,NULL,1,NULL,NULL,2,'00000004.TIF',2011-02-08 10:43:38.000,'kevin',2014-07-18 10:46:06.000,'brian','Multi',1,1.0,0,'-',NULL

pgloader commands

pgloader --type csv --with truncate --with "fields optionally enclosed by '''" --with "fields terminated by ','" --set "search_path to 'raw'" - "postgresql://postgres:postgres@localhost/doc_db?a2" < null_test

Table

                               Table "raw.a2"
   Column    |            Type             | Collation | Nullable | Default 
-------------+-----------------------------+-----------+----------+---------
 num         | integer                     |           | not null | 
 f_fileno    | character varying(15)       |           |          | 
 f_foliono   | integer                     |           |          | 
 f_doc_type  | character varying(50)       |           |          | 
 f_docdate   | timestamp without time zone |           |          | 
 f_batch     | integer                     |           |          | 
 f_box       | integer                     |           |          | 
 f_blucpy    | integer                     |           |          | 
 f_routopost | integer                     |           |          | 
 f_routousr  | character varying(49)       |           |          | 
 f_wfcreate  | integer                     |           |          | 
 linkedfile  | character varying(255)      |           |          | 
 datecreate  | timestamp without time zone |           |          | 
 usercreate  | character varying(50)       |           |          | 
 dateupdate  | timestamp without time zone |           |          | 
 userupdate  | character varying(50)       |           |          | 
 media       | character varying(5)        |           |          | 
 pgcount     | smallint                    |           |          | 
 groupnum    | double precision            |           |          | 
 subject     | smallint                    |           |          | 
 pri         | character varying(1)        |           |          | 
 f_filecat   | character varying(50)       |           |          | 

Indexes:

"a2_pkey" PRIMARY KEY, btree (num)

Output/Error

2019-07-24T05:55:24.231000Z WARNING Target table "\"raw\".\"a2\"" has 1 indexes defined against it.
2019-07-24T05:55:24.237000Z WARNING That could impact loading performance badly.
2019-07-24T05:55:24.237000Z WARNING Consider the option 'drop indexes'.
2019-07-24T05:55:24.460000Z ERROR PostgreSQL ["\"raw\".\"a2\""] Database error 22P02: invalid input syntax for integer: "NULL"
CONTEXT: COPY a2, line 1, column f_batch: "NULL"
2019-07-24T05:55:24.461000Z ERROR PostgreSQL ["\"raw\".\"a2\""] Database error 22007: invalid input syntax for type timestamp: "NULL"
CONTEXT: COPY a2, line 1, column f_docdate: "NULL"