Additional Resources Storage:  Rows are compressed as they are inserted. The  ARCHIVE  engine uses  zlib  lossless data compression (see http://www.zlib.net/). You can use  OPTIMIZE TABLE  to analyze the table and pack it into a smaller format (for a reason to use  OPTIMIZE TABLE , see later in this section). The engine also supports  CHECK TABLE . There are several types of insertions that are used: •An  INSERT  statement just pushes rows into a compression buffer, and that buffer flushes as necessary. The insertion into the buffer is protected by a lock. A  SELECT  forces a flush to occur. •A bulk insert is visible only after it completes, unless other inserts occur at the same time, in which case it can be seen partially. A  SELECT  never causes a flush of a bulk insert unless a normal insert occurs while it is loading. Additional Resources Retrieval : On retrieval, rows are uncompressed on demand; there is no row cache. A  SELECT  operation performs a complete table scan: When a  SELECT  occurs, it finds out how many rows are currently available and reads that number of rows.  SELECT  is performed as a consistent read. Note that lots of SELECT  statements during insertion can deteriorate the compression, unless only bulk inserts are used. To achieve better compression, you can use  OPTIMIZE TABLE  or  REPAIR TABLE . The number of rows in ARCHIVE  tables reported by  SHOW TABLE STATUS  is always accurate. See Section 13.7.3.4, “OPTIMIZE TABLE Statement” , Section 13.7.3.5, “REPAIR TABLE Statement” , and Section 13.7.7.38, “SHOW TABLE STATUS Statement” . The  BLACKHOLE  storage engine acts as a “black hole”  that accepts data but throws it away and does not store it. Retrievals always return an empty result: •A forum dedicated to the  ARCHIVE  storage engine is available at https://forums.mysql.com/list.php?112. mysql>  SELECT * FROM test; Empty set (0.00 sec) 16.6 The BLACKHOLE Storage Engine mysql>  INSERT INTO test VALUES(1,’record one’),(2,’record two’); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql>  CREATE TABLE test(i INT, c CHAR(10)) ENGINE = BLACKHOLE; Query OK, 0 rows affected (0.03 sec) To enable the  BLACKHOLE  storage engine if you build MySQL from source, invoke  CMake  with the  - DWITH_BLACKHOLE_STORAGE_ENGINE  option. To examine the source for the  BLACKHOLE  engine, look in the  sql  directory of a MySQL source distribution. When you create a  BLACKHOLE  table, the server creates the table definition in the global data dictionary. There are no files associated with the table. The  BLACKHOLE  storage engine supports all kinds of indexes. That is, you can include index declarations in the table definition. The maximum key length is 3072 bytes as of MySQL 8.0.27. Prior to 8.0.27, the maximum key length is 1000 bytes. The  BLACKHOLE  storage engine does not support partitioning. You can check whether the  BLACKHOLE  storage engine is available with the  SHOW ENGINES  statement. 3418