Percona Server has extended secure-file-priv server option. When used with no argument, the LOAD_FILE() function will always return NULL. The LOAD DATA INFILE and SELECT INTO OUTFILE statements will fail with the following error: "The MySQL server is running with the --secure-file-priv option so it cannot execute this statement". LOAD DATA LOCAL INFILE is not affected by the --secure-file-priv option and will still work when it’s used without an argument.
In Percona Server 5.6.34-79.1 empty secure-file-priv became an alias for NULL value: both disable LOAD_FILE(), LOAD DATA INFILE, and SELECT INTO OUTFILE. With this change it is no longer possible to disable security checks by omitting the option as that would take the default value (/var/lib/mysql-files/ for .deb and .rpm and NULL for .tar.gz packages. Instead, --secure-file-priv='' (or =/) should be used.
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