The deprecated parameters will be removed:

    innodb_defragment
    innodb_defragment_n_pages
    innodb_defragment_stats_accuracy
    innodb_defragment_fill_factor_n_recs
    innodb_defragment_fill_factor
    innodb_defragment_frequency

The mysql.innodb_index_stats.stat_name values 'n_page_split' and
'n_pages_freed' will lose their special meaning.

The related changes to OPTIMIZE TABLE in InnoDB will be removed as well.
The parameter innodb_optimize_fulltext_only will retain its special
meaning in OPTIMIZE TABLE.

Tested by: Matthias Leich

Before commit 6112853cdab2770e92f9cfefdfef9c0a14b71cb7 in MySQL 4.1.1
introduced the parameter innodb_file_per_table, all InnoDB data was
written to the InnoDB system tablespace (often named ibdata1).
A serious design problem is that once the system tablespace has grown to
some size, it cannot shrink even if the data inside it has been deleted.

There are also other design problems, such as the server hang MDEV-29930
that should only be possible when using innodb_file_per_table=0 and
innodb_undo_tablespaces=0 (storing both tables and undo logs in the
InnoDB system tablespace).

The parameter innodb_change_buffering was deprecated
in commit b5852ffbeebc3000982988383daeefb0549e058a.
Starting with commit baf276e6d4a44fe7cdf3b435c0153da0a42af2b6
(MDEV-19229) the number of innodb_undo_tablespaces can be increased,
so that the undo logs can be moved out of the system tablespace
of an existing installation.

If all these things (tables, undo logs, and the change buffer) are
removed from the InnoDB system tablespace, the only variable-size
data structure inside it is the InnoDB data dictionary.

DDL operations on .ibd files was optimized in
commit 86dc7b4d4cfe15a2d37f8b5f60c4fce5dba9491d (MDEV-24626).
That should have removed any thinkable performance advantage of
using innodb_file_per_table=0.

Since there should be no benefit of setting innodb_file_per_table=0,
the parameter should be deprecated. Starting with MySQL 5.6 and
MariaDB Server 10.0, the default value is innodb_file_per_table=1.

ha_innobase::defragment_table(): Skip corrupted indexes and
FULLTEXT INDEX. In InnoDB, FULLTEXT INDEX is implemented with
auxiliary tables. We will not defragment them on OPTIMIZE TABLE.

    Merge https://github.com/kakao/mariadb-10.0 that contains Facebook's
    implementation for defragmentation

    facebook/mysql-5.6@a2d3a74
    facebook/mysql-5.6@def96c8
    facebook/mysql-5.6@9c67c5d
    facebook/mysql-5.6@921a81b
    facebook/mysql-5.6@aa519bd
    facebook/mysql-5.6@fea7d13
    facebook/mysql-5.6@09b29d3
    facebook/mysql-5.6@9284abb
    facebook/mysql-5.6@dbd623d
    facebook/mysql-5.6@aed55dc
    facebook/mysql-5.6@aad5c82

    This version does not add new SQL-syntax and new handler API function.
    Instead optimize table is mapped to defragment table if
    innodb_defragment=ON, by default the feature is off.

    Contains changes authored by Sunguck Lee (Kakao).