PL/PGSQL + inserts+updates+limit - Postgres 9.3

- original_table1_b = Original table, where the BLOBS are
- table1_n_b = Table where everything related to the BLOBS is stored (file_id, account_id, note_id, etc)
- table2_y_b = Table BACKUP - The blobs+data will be copied to here before being deleted
- table3_n_b = On the table1_n_b, each blob is related to a note_id. Each note_id has three different file_id. I want to delete just the greatest one. So on this table3_n_b table I'm storing the greates file_id (by size) 

SELECT * INTO table3_n_b FROM
(       SELECT account_id, note_id, st_ino, size FROM       (               SELECT DISTINCT ON                       (note_id) note_id,                       MAX(size),                       file_id,                       id               FROM                       table1_n_b               GROUP BY                       note_id, size, file_id, id               ORDER BY                       note_id, size desc       ) AS r1
) AS r2;

FOR crtRow IN execute

'UPDATE original_table1_b SET data = NULL WHERE file_id = crtRow.file_id ' || $1 ||' offset '||

CREATE or REPLACE FUNCTION function_1_name(rows integer)

RETURNS INTEGER AS $$

declare

  completed integer;

  crtRow record;

BEGIN

  offset_num = 0;

-- Copiyng the data into the table which will store the data+blobs

FOR crtRow IN execute

    'INSERT INTO table2_y_b (note_id, size, file_id, full_path)

    (

            SELECT

                    t1.note_id,

                    t1.size,

                    t1.file_id,

                    t1.full_path

            INTO

                    table2_y_b

            FROM

                    table1_n_b t1

            JOIN

                    table3_n_b t3 ON t3.file_id = t1.file_id

    ) ' || $1 ||' offset '||

-- Copying the BLOBS

FOR crtRow IN execute

    'INSERT INTO table2_y_b (data)

    (

            SELECT

                    o1.data

            FROM

                    original_table1_b o1

            JOIN

                    table3_n_b t3 ON t3.file_id = o1.file_id

            JOIN

                    table2_y_b t2 ON t2.file_id = o1.file_id

            WHERE

                    t2.migrated = 0

    ) ' || $1 ||' offset '||

-- Update the migrated column from 0 to 1, for those rows that have been modified/copied.

FOR crtRow IN execute

'UPDATE table2_y_b SET migrated = 1 WHERE file_id = crtRow.file_id AND migrated = 0 ' || $1 ||' offset '||

FOR crtRow IN execute

'UPDATE original_table1_b SET data = NULL WHERE file_id = crtRow.file_id ' || $1 ||' offset '||

RETURN file_id;

END

$$ language 'plpgsql';