Before commit 6112853cda 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 b5852ffbee.
Starting with commit baf276e6d4
(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 86dc7b4d4c (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.
The test innodb.innodb_wl6326 that had been disabled in 10.4 due to
MDEV-21535 is failing on 10.5 due to a different reason: the removal
of the MLOG_COMP_END_COPY_CREATED operations in MDEV-12353
commit 276f996af9 caused PAGE_LAST_INSERT
to be set to something nonzero by the function page_copy_rec_list_end().
This in turn would cause btr_page_get_split_rec_to_right() to behave
differently: we would not attempt to split the page at all, but simply
insert the new record into the new, empty, right leaf page.
Even though the change reduced the sizes of some tables, it is better
to aim for balanced trees.
page_copy_rec_list_end(), PageBulk::finishPage():
Preserve PAGE_LAST_INSERT, PAGE_N_DIRECTION, PAGE_DIRECTION.
PageBulk::finish(): Move some common code from PageBulk::finishPage().
Instead of writing the high-level redo log records
MLOG_LIST_END_COPY_CREATED, MLOG_COMP_LIST_END_COPY_CREATED
write log for each individual insert of a record.
page_copy_rec_list_end_to_created_page(): Remove.
This will improve the fill factor of some pages.
Adjust some tests accordingly.
PageBulk::init(), PageBulk::finish(): Avoid setting bogus limits
to PAGE_HEAP_TOP and PAGE_N_DIR_SLOTS. Avoid accessor functions
that would enforce these limits before the correct ones are set
at the end of PageBulk::finish().
