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might be helpful in improving performance, because it can reduce the need for the server to perform memory allocation during query execution operations. 

• rand_seed1 

<img src='content_image/868797.jpg'>

The rand_seed1  and rand_seed2  variables exist as session variables only, and can be set but not read. The variables—but not their values—are shown in the output of SHOW VARIABLES . 

The purpose of these variables is to support replication of the RAND()  function. For statements that invoke RAND() , the source passes two values to the replica, where they are used to seed the random number generator. The replica uses these values to set the session variables rand_seed1  and rand_seed2  so that RAND()  on the replica generates the same value as on the source. 

• rand_seed2 

See the description for rand_seed1 . 

• range_alloc_block_size 

<img src='content_image/868796.jpg'>

The size in bytes of blocks that are allocated when doing range optimization. 

• range_optimizer_max_mem_size 

<img src='content_image/868795.jpg'>

