MySql IDB files not named after tables In my Linux filesystem, there are many ibd files (InnoDB file per table is ON) which are not named after tables. What are these files and what data do they contain? The question has arisen due to space limitations on the server.
4.2G    ./var/lib/mysql/wift/#sql-ib179-1438865579.ibd
4.2G    ./var/lib/mysql/wift/#sql-ib179-1413146901.ibd
4.2G    ./var/lib/mysql/wift/#sql-ib179-1376672335.ibd
4.2G    ./var/lib/mysql/wift/#sql-ib179-1355103119.ibd
4.2G    ./var/lib/mysql/wift/#sql-ib179-1163730678.ibd
128M    ./var/lib/mysql/wift/customers.ibd
That are orphaned temporary files, when mysql crashes during an alter table

Orphan temporary table names begin with an #sql- prefix (e.g., #sql-540_3). The accompanying .frm file has the same base name as the orphan temporary table.

see manual
There you will find also how to deal with them
in mysql 8 they don't appear any more