select @test_compress_string:='string for test compress function aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa '; @test_compress_string:='string for test compress function aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ' string for test compress function aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa Warnings: Warning 1287 Setting user variables within expressions is deprecated and will be removed in a future release. Consider alternatives: 'SET variable=expression, ...', or 'SELECT expression(s) INTO variables(s)'. select length(@test_compress_string); length(@test_compress_string) 117 select uncompress(compress(@test_compress_string)); uncompress(compress(@test_compress_string)) string for test compress function aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa explain select uncompress(compress(@test_compress_string)); id select_type table partitions type possible_keys key key_len ref rows filtered Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used Warnings: Note 1003 /* select#1 */ select uncompress(compress((@`test_compress_string`))) AS `uncompress(compress(@test_compress_string))` select uncompressed_length(compress(@test_compress_string))=length(@test_compress_string); uncompressed_length(compress(@test_compress_string))=length(@test_compress_string) 1 explain select uncompressed_length(compress(@test_compress_string))=length(@test_compress_string); id select_type table partitions type possible_keys key key_len ref rows filtered Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used Warnings: Note 1003 /* select#1 */ select (uncompressed_length(compress((@`test_compress_string`))) = length((@`test_compress_string`))) AS `uncompressed_length(compress(@test_compress_string))=length(@test_compress_string)` select uncompressed_length(compress(@test_compress_string)); uncompressed_length(compress(@test_compress_string)) 117 select length(compress(@test_compress_string))