SLOW/CRASHES SEMAPHORE
Problem:
There are 2 lakh tables - fk_000001, fk_000002 ... fk_200000. All of them
are related to the same parent_table through a foreign key constraint.
When the parent_table is loaded into the dictionary cache, all the child table
will also be loaded. This is taking lot of time. Since this operation happens
when the dictionary latch is taken, the scenario leads to "long semaphore wait"
situation and the server gets killed.
Analysis:
A simple performance analysis showed that the slowness is because of the
dict_foreign_find() function. It does a linear search on two linked list
table->foreign_list and table->referenced_list, looking for a particular
foreign key object based on foreign->id as the key. This is called two
times for each foreign key object.
Solution:
Introduce a rb tree in table->foreign_rbt and table->referenced_rbt, which
are some sort of index on table->foreign_list and table->referenced_list
respectively, using foreign->id as the key. These rbt structures will be
solely used by dict_foreign_find().
rb#5599 approved by Vasil
This patch allows up to 64K pages for tables with DYNAMIC, COMPACT
and REDUNDANT row types. Tables with COMPRESSED row type allows
still only <= 16K page size. Note that single row size must be
still <= 16K and max key length is not affected.
special builds UNIV_PAGECOMPRESS_DEBUG and UNIV_MTFLUSH_DEBUG).
Added a new status variable compress_pages_page_compression_error to count possible
compression errors.
Analysis: This was merge error on file fil0fil.cc. fil_system mutex was taken twice because of this.
Fix: Remove unnecessary mutex_enter and fixed the issue with slow posix_fallocate usage.
unnecessary. There is a lot more index pages than there is normal pages.
Earlier all pages were compressed and this provided best performance and
compression ratio. Added status variable to show how many non index pages
are written.
innodb_force_primary_key default off. If option is true, create table without
primary key or unique key where all keyparts are NOT NULL is not
accepted. Instead an error message is printed. Variable value can
be changed with set global innodb_force_primary_key = <value>.
This is not yet a fix. This is change to print additional information at the point
when this assertion is going to happen. Print as much information about the pages
and index to find out why next page is not a compact format.
Added option to disable multi-threaded flush with innodb_use_mtflush = 0
option, by default multi-threaded flush is used.
Updated innochecksum tool, still it does not support new checksums.
execution and global memory heap on shutdown.
Added a funcition to get work items from queue without waiting and
additional info when there is no work to do for a extended periods.
Fixed issue on multi-threaded flush at shutdown.
Removed unnecessary startup option innodb_compress_pages.
Added a new startup option innodb_mtflush_threads, default 8.
Update InnoDB to 5.6.14
Apply MySQL-5.6 hack for MySQL Bug#16434374
Move Aria-only HA_RTREE_INDEX from my_base.h to maria_def.h (breaks an assert in InnoDB)
Fix InnoDB memory leak
SYNTAX: ATOMIC_WRITES=['DEFAULT','ON','OFF']
Idea here is to be able to define innodb_doublewrite = 1 but with following rules:
ATOMIC_WRITES='DEFAULT' - if innodb_use_atomic_writes = 1, we do not write to doublewrite buffer the changes
if innodb_use_atomic_writes = 0, we write to doublewrite buffer
ATOMIC_WRITES='ON' - do not write to doublewrite buffer
ATOMIC_WRITES='OFF' - write to doublewrite buffer
Note that doublewrite buffer can't be used if innodb_doublewrite = 0.
