读Effective Mysql:optimizing SQL Statements 笔记之max_heap_table_size

  The total size of a MEMORY storage engine table can be determined by the SHOW TABLE STATUS command and the INFORMATION_SCHEMA.TABLES table.
  For additional reference, a MEMORY storage engine table used a fixed width value for any character columns. In the receding example,the VARCHAR(1000) column is effectively a CHAR(1000) column when defined in a MEMORY table.Given this constraint, a MEMORY table cannot contain any TEXT or BLOB fields. This is also important  for the tmp_table_size variable.


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