0. They work really well if you have a read heavy system, since they do not have row level locking; What we did was create a new memory table with the Memory Table type. MySQL supports several storage engines that store data in different ways. The image shows tmp tables how increasing is: My.cnf: 0. mysql memory temp table creation SLOW. It seems like the temporary table or cursor has some memory between calls or something. There are many temp tables is increasing slowly after mysql restart and then the innodb_buffer_pool_size is finishing. Creation of memory-optimized tables takes longer than creation of traditional tables, due … When MySQL restarts, all data is completely erased. In MySQL, by default, the temp tables created with the memory engine can quickly grow beyond the 16mb limit of max-heap-table-size and tmp-table-size because more memory is allocated per row than is usually required. So if MySQL gets restarted the table goes away. Replacing a global temporary table with a memory-optimized SCHEMA_ONLY table is fairly straightforward. When MySQL creates a temp table, it has to materialize every single row, and that includes the functions as well. MySQL also creates temporary tables automatically for certain types of queries, as needed. Use another disk for “optimize table” temporary file. MySQL always writes simple temporary/memory tables to disk (both tmp_table_size and max_heap_table_size are set to 8GB) 2. MySQL also allocates memory for temporary tables unless it becomes too large (determined by tmp_table_size and max_heap_table_size). In contrast, Temporary Table in MySQL can be created on disk or as a MEMORY table type, dependent on the syntax in the CREATE TABLE statement. 1. An internal temporary table can be held in memory and processed by the MEMORY storage engine, or stored on disk by the InnoDB or MyISAM storage engine. A table declared with Engine=Memory will persist across user sessions / connections but will only exist in the lifetime of the MySQL instance. Table data is stored completely in memory. I wish i had more to give than just an upvote. Temporary tables with indexes can be joined to circumvent the limitation of a joining a temp table to itself, and it seems in my case the index was essential. The stored procedure does not manipulate any data outside of this temporary table. A temporary table will only exist for the duration of your session. An internal temporary table can be held in memory and processed by the MEMORY storage engine, or stored on disk and processed by the MyISAM storage engine. There are a few important points to note about Memory Tables. If an internal temporary table is created as an in-memory table but becomes too large, MySQL automatically converts it to an on-disk table. In the example you provided, the VARCHAR(400) will allocate memory based upon the maximum string size, not the actual size of your data. No 'Copying to tmp table' state in profiling a mysql query. A heap table refers to a table created with the MEMORY storage engine. It often makes sense to use the MEMORY storage engine for temporary tables. Don't confuse yourself with MySQL memory table type which is also temporary in nature because it stores data in computers memory only. When temp tables are involved, MySQL will use a different logic and do the evaluation before/during the group by when it creates the temp tables. Another oddity: If I create a new session, run CALL B followed by CALL A followed by CALL B, the third invocation of CALL B works as expected (it does not fetch any rows). The biggest change is to create the table at deployment time, not at runtime. – Plasmarob May 23 '18 at 16:27 At risk of sounding like a useless "thanks" comment, i want you to know you saved my booty. 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