COPY allows DELIMITER and NULL to be specified which don't allow the data to be copied back in properly. Using any delimiter that could be part of a backslash escape sequence (\n \0 \t) will break if any of the data has a character matching the delimiter because it will be escaped and then be read as a special character.
It also allows DELIMITER and NULL to overlap. No character in the NULL specification should be the DELIMITER. Kris Jurka
DROP TABLE copytest; CREATE TABLE copytest (a text, b text); INSERT INTO copytest VALUES ('t,n,g','a'); INSERT INTO copytest VALUES (NULL,NULL); COPY copytest TO STDOUT WITH DELIMITER 'n' NULL 'n';
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