** Setup ** SET @start_value = @@global.query_prealloc_size; CREATE TABLE t1 (id INT AUTO_INCREMENT PRIMARY KEY, val TEXT(200)); INSERT INTO t1 VALUES(NULL,'a'); INSERT INTO t1 VALUES(NULL,'b'); INSERT INTO t1 VALUES(NULL,'c'); INSERT INTO t1 VALUES(NULL,'d'); SELECT * FROM t1 ORDER BY val; id val 1 a 2 b 3 c 4 d SET SESSION query_prealloc_size = 8192; '#----------------------------FN_DYNVARS_137_05-----------------#' SET GLOBAL query_prealloc_size = 8192; connect con_int1,localhost,root,,; connection con_int1; SELECT @@SESSION.query_prealloc_size; @@SESSION.query_prealloc_size 8192 Expected Value : 8192; SET SESSION query_prealloc_size = 16384; connect con_int2,localhost,root,,; connection con_int2; SELECT @@SESSION.query_prealloc_size; @@SESSION.query_prealloc_size 8192 Expected Value : 8192; SET SESSION query_prealloc_size = 8192; connection con_int1; SELECT @@SESSION.query_prealloc_size; @@SESSION.query_prealloc_size 16384 Expected Value : 16384; connection con_int2; SELECT @@SESSION.query_prealloc_size; @@SESSION.query_prealloc_size 8192 Expected Value : 8192; SELECT @@GLOBAL.query_prealloc_size; @@GLOBAL.query_prealloc_size 8192 Expected Value : 8192; connection default; disconnect con_int1; disconnect con_int2; DROP TABLE t1; SET @@global.query_prealloc_size = @start_value;