MySQL8 Status Variables: Internal Temporary Tables and Files

These status variables show you how many times MySQL has created internal temporary tables and files. These are expensive operations and can help you diagnose poorly performing queries. They include:

• Create_tmp_disk_tables:
  • If an internal temporary table becomes too large in memory, MySQL automatically writes it to disk.
    • The on-disk version of the table is considerably slower than the one in memory.
  • If Create_tmp_disk_tables is large, you might want to increase the temptable_max_ram value or, better still, optimize your query.
• Created_tmp_tables:
  • It shows the number of in-memory internal temporary tables created by the server while executing statements.
  • Note that each invocation of SHOW GLOBAL|SESSION STATUS uses an in-memory internal temporary table.
• Create_tmp_files:
  • It shows the nu