5. I’ll just tune MySQL Parameters…
Will get you out of SOME trouble
But not a good “default” solution, specially if the
base is flawed
Please do tune MySQLs defaults
Not the theme for today
6.
7. Start with your Schema
Your schema is probably the root cause of your
“My DB doesn’t scale” problems
The solution is not “have a loose/no schema”
How to fake a DB Design (Curtis Ovid Poe)
https://www.youtube.com/watch?v=y1tcbhWLiUM
8. Data types: how (not) to bloat your DB
Selecting data types with a bit of care is very
productive
It makes more data fit in less space
Optimizes use of InnoDB Buffer Pool, MyISAM Key
Buffer, Join Buffer, Sort Buffer, Smaller indexes
9. Your new best friend
http://dev.mysql.com/doc/refman/5.6/en/storage-requirements.html
http://dev.mysql.com/doc/refman/5.5/en/storage-requirements.html
…
10. DataTypes: NULL vs NOT NULL
I don’t care about the NULL debate
Saves Space
Gives the DB hints
Use NULLs wisely
14. INTS and surrogate keys
It’s good to have a surrogate key
Just unique index the unique column
Why?
InnoDB stores the PK on the leafs of all indexes
Indexes bloat if they’re “big keys”
15. Id columns for your tables
INT by default for “things that can get big”
Smaller INTs for smaller sets
Do you really need a BIGINT?
The magnitude comparison trick:
Epochs in Unix have 4 bytes
The epoch has been counting since 1970. Will run out in 2038
An INT can identify ONE THING HAPPENING EVERY SECOND for 68 YEARS!
Do you STILL need a BIGINT?
23. DataTypes: Texts
BINARY(10) == 10 bytes
CHAR(10) ==? 10 bytes
CHAR(10) latin1: 10 bytes
CHAR(10) utf-8: 30 bytes
VARBINARY(10) == 1 to 11 bytes
VARCHAR(10) ==? 1 to 11 bytes
VARCHAR(10) latin 1: 1 to 11 bytes
VARCHAR(10) utf-8: 1 to 31 bytes
24. So I’ll just go for VARCHAR(255) on all
text columns
“After all… I’ll just consume the number of bytes + 1”
25. So I’ll just go for VARCHAR(255) on all
text columns
“After all… I’ll just consume the number of bytes + 1”
When we need a temporary table
https://dev.mysql.com/doc/refman/5.6/en/memory-storage-engine.html
“MEMORY tables use a fixed-length row-storage format. Variable-length types such
as VARCHAR are stored using a fixed length”
26.
27. So I’ll just go for VARCHAR(255) on all
text columns
Congrats! All your VARCHAR(255) are now
CHAR(255) in memory
That’s 255 bytes latin-1. Or 765 bytes utf-8
O_o
Note: do the maths on VARCHAR(65535)
28. DataTypes: BLOBS
TEXT == BLOB == problems
TEXT = BLOB + charset + collation
TEXT fields are not unlimited!
TINYTEXT and TINYBLOB (up to 256 bytes == x chars)
TEXT / BLOB (up to 65KB == x chars)
MEDIUMBLOB / MEDIUMTEXT (up to 16MB == x chars)
LONGTEXT / LONGBLOB (up to 2GB == x chars)
29. SELECT * IS YOUR FRIEND?
IF a SELECT contains a BLOB/TEXT column
Temporary tables go DIRECTLY to DISK
30.
31. SELECT * IS YOUR FRIEND?
IF a SELECT contains a BLOB/TEXT column
Temporary tables go DIRECTLY to DISK
Note: “Big” columns belong on a filesystem or an object store
32. DataTypes: Small Sets
ENUM
One value out of the possibilities (‘big’, ‘small’)
SET
A set of possible values (‘pool’,’terrace’,’fence’)
SETS are NOT good for finding stuff
FIND_IN_SET is a function. No indexes
Default to a separate table + relation
33. DataTypes: Dates
YEAR = 1 byte (range from 1901 to 2155)
DATE = 3 bytes
TIME = 3 bytes
DATETIME = 8 bytes
TIMESTAMP = 4 bytes
Timestamp is an epoch. Ideal for “things that
happen now” (sold time, renewal date, etc)
45. Index the two sides of relations
Index this guy too!
46. Index the two sides of relations
Index this guy too!
And this guy!
47.
48.
49. PK is (contract_id, customer_id)
(Implied uniqueness)
Index “both ways”:
(customer_id, contract_id)
InnoDB optimization: Don’t index the full (customer_id, contract_id). The
index ALREADY HAS customer_id in it’s leafs. So just index (customer_id)
N-M relation: Junction tables
50.
51. Don’t operate on fields
Because they can’t use indexes
WHERE column = ‘x’
WHERE column > 2000
WHERE column LIKE ‘prefix%’
WHERE column + 2000 > 2013
WHERE FIND_IN_SET(column)
WHERE CONCAT(f1,f2) = “xxxx.com”
WHERE YEAR(date) = 2015
WHERE column LIKE ‘%.com’
52. Polish your maths: Algebra
Doesn’t use index
WHERE column + 2000 > 2013
WHERE FIND_IN_SET(‘pool’,column)
WHERE CONCAT(f1,’.’,f2) =
“xxxx.com”
WHERE YEAR(date) = 2015
WHERE column LIKE ‘%.com’
Uses index
WHERE column > 13
?
WHERE f1 = ‘xxxx’ AND f2 = ‘com’
WHERE date BETWEEN ’01-01-2015’
and ’31-12-2015’
?
53. The old switcheroo…
Doesn’t use index
WHERE column + 2000 > 2013
WHERE FIND_IN_SET(‘pool’,column)
WHERE CONCAT(f1,’.’,f2) =
“xxxx.com”
WHERE YEAR(date) = 2015
WHERE column LIKE ‘%.com’
Uses index
WHERE has_pool = 1
WHERE column_rev LIKE ‘moc.%’
54. The old switcheroo…
Doesn’t use index
WHERE column + 2000 > 2013
WHERE FIND_IN_SET(‘pool’,column)
WHERE CONCAT(f1,’.’,f2) =
“xxxx.com”
WHERE YEAR(date) = 2015
WHERE column LIKE ‘%.com’
Uses index
WHERE has_pool = 1
UPDATE t SET has_pool =
FIND_IN_SET(‘pool’,column);
WHERE column_rev LIKE ‘moc.%’
UPDATE t SET
column_rev=REVERSE(column)