You may find what I am about to suggest a little surprising
Add the following indexes
ALTER TABLE mytable ADD INDEX id_value_ndx (id,value);
ALTER TABLE mytable ADD INDEX value_id_ndx (value,id);
This will actually cache id and value together in the MyISAM Key Cache. That way, all queries are in memory only. Queries will not go to the table at all.
I would also propose you make a dedicated 1GB MyISAM Key Cache just for your table
STEP 01: Create a script to load the table into the dedicated key cache
cd /var/lib/mysql
echo "SET GLOBAL mykeycache.key_buffer_size = 1024 * 1024 * 1024;" > init-file.sql
echo "CACHE INDEX mytable IN mykeycache; >> init-file.sql
echo "LOAD INDEX INTO CACHE mykeycache; >> init-file.sql
STEP 02 : Add this to /etc/my.cnf
[mysqld]
init-file=/var/lib/mysql/init-file/sql
STEP 03 : service mysql restart
From here on, every restart of mysql will setup this private key cache for your table
Give it a Try !!!
YOUR QUERY
SELECT post.postid, post.attach FROM newbb_innopost AS post WHERE post.threadid = 51506;
At first glance, that query should only touches 1.1597% (62510 out of 5390146) of the table. It should be fast given the key distribution of threadid 51506.
REALITY CHECK
No matter which version of MySQL (Oracle, Percona, MariaDB) you use, none of them can fight to one enemy they all have in common : The InnoDB Architecture.
CLUSTERED INDEX
Please keep in mind that the each threadid entry has a primary key attached. This means that when you read from the index, it must do a primary key lookup within the ClusteredIndex (internally named gen_clust_index). In the ClusteredIndex, each InnoDB page contains both data and PRIMARY KEY index info. See my post Best of MyISAM and InnoDB for more info.
REDUNDANT INDEXES
You have a lot of clutter in the table because some indexes have the same leading columns. MySQL and InnoDB has to navigate through the index clutter to get to needed BTREE nodes. You should reduced that clutter by running the following:
ALTER TABLE newbb_innopost
DROP INDEX threadid,
DROP INDEX threadid_2,
DROP INDEX threadid_visible_dateline,
ADD INDEX threadid_visible_dateline_index (`threadid`,`visible`,`dateline`,`userid`)
;
Why strip down these indexes ?
- The first three indexes start with threadid
threadid_2
and threadid_visible_dateline
start with the same three columns
threadid_visible_dateline
does not need postid since it's the PRIMARY KEY and it's embedded
BUFFER CACHING
The InnoDB Buffer Pool caches data and index pages. MyISAM only caches index pages.
Just in this area alone, MyISAM does not waste time caching data. That's because it's not designed to cache data. InnoDB caches every data page and index page (and its grandmother) it touches. If your InnoDB Buffer Pool is too small, you could be caching pages, invalidating pages, and removing pages all in one query.
TABLE LAYOUT
You could shave of some space from the row by considering importthreadid
and importpostid
. You have them as BIGINTs. They take up 16 bytes in the ClusteredIndex per row.
You should run this
SELECT importthreadid,importpostid FROM newbb_innopost PROCEDURE ANALYSE();
This will recommend what data types these columns should be for the given dataset.
CONCLUSION
MyISAM has a lot less to contend with than InnoDB, especially in the area of caching.
While you revealed the amount of RAM (32GB
) and the version of MySQL (Server version: 10.0.12-MariaDB-1~trusty-wsrep-log mariadb.org binary distribution, wsrep_25.10.r4002
), there are still other pieces to this puzzle you have not revealed
- The InnoDB settings
- The Number of Cores
- Other settings from
my.cnf
If you can add these things to the question, I can further elaborate.
UPDATE 2014-08-28 11:27 EDT
You should increase threading
innodb_read_io_threads = 64
innodb_write_io_threads = 16
innodb_log_buffer_size = 256M
I would consider disabling the query cache (See my recent post Why query_cache_type is disabled by default start from MySQL 5.6?)
query_cache_size = 0
I would preserve the Buffer Pool
innodb_buffer_pool_dump_at_shutdown=1
innodb_buffer_pool_load_at_startup=1
Increase purge threads (if you do DML on multiple tables)
innodb_purge_threads = 4
GIVE IT A TRY !!!
Best Answer
The MyISAM vs InnoDB Myth
That's an old wives' tale. Erase it from your mind.
Bottom line: Use InnoDB for all tables. There are very few exceptions to this simple rule. In no particular order:
COUNT(*)
withoutWHERE
is 'instantaneous' in MyISAM.AUTO_INCREMENT
-- standard in MyISAM; clumsy to simulate in InnoDB. (Rarely asked for.)FULLTEXT
constitute an issue.On the flip side, Oracle has taken the stand that MyISAM will be removed from MySQL.
The CHAR vs VARCHAR Myth
Another _old_wives' tale. Even in MyISAM, that quote is often taken out of context.
CHAR
overVARCHAR
.CHAR
andVARCHAR
are mostly implemented identically.Bottom line: Use
CHAR
only for strings that are truly fixed length.The need-to-optimize-the-little-things Myth
I'll start with the 'answer' first.
Even before looking at the data, there are other tasks.
In the grand scheme of things, locating a record is far more costly than anything that is done with the record. (This is a generalization, not an absolute.)
NULL
checks, length checks (eg, forVARchar
, etc, we are talking nanoseconds per column.Now, what was your question? Oh, yeah, you were concerned about some tiny part of the last step.
General
UPDATE
orDELETE
+INSERT
.CHAR
is effectively variable length when using utf8.(And stop reading any MySQL reference that is over a decade old.)