Do large longtext necessarily slow down a database I have a MySQL database that is over a million rows, and has a longtext type data column. Most of these are fairly short, but a few dozen of these rows have more than a MB in the longtext column. No WHERE or LIKE statements are made on the longtext column. Only select statements a few rows at most at a time. It would be nice to keep this data in the database, but the database is slow. I have two tables with a million records, one is 100MB, but this one is 4GB, mostly in the longtext column. I'm not sure if that's a performance concern or not.

We're wondering if removing these rows would result in a performance increase for SELECT, CREATE, UPDATE commands, or if it should not have an effect.
On MyISAM tables, fragmentation can easily occur where rows have variable length and deletions are frequent. This can affect index reads and full table scan performance by increasing the number of pages that need to be read to find the data, and preventing the use of sequential read-ahead technology.

See this Serverfault question for good info on fragmentation, how to detect it and react to it: https://serverfault.com/questions/202000/how-find-and-fix-fragmented-mysql-tables

This is less applicable on InnoDB, where large objects are stored separately to the rest of the rows, and tables are index-oriented.