MySQL 8.0: not only good, it’s GREAT! - PHP UK 2019

MySQL 8.0: not only good,
it’s GREAT!
Gabriela D'Ávila Ferrara
@gabidavila
Developer Advocate @ Google Cloud
gabi.fyi/me

@gabidavila
Brief History ● Created to handle from up
to 10 to 100M rows or
around 100MB/table
● Now supports terabyte-
sized databases
● Supports SQL standards as
new as SQL 2016
● But... some stuff from SQL
2003 just became available
(Window Functions, CTEs)
● What is awesome now?
23 OF MAY
1995
GPL V2

@gabidavila
Non-deterministic defaults for
table creation

@gabidavila
FUNCTIONS or EXPRESSIONS
inside CREATE TABLE

@gabidavila
UUID() Support
CREATE TABLE users
(
uid binary(16) NOT NULL DEFAULT (UUID_TO_BIN(UUID())),
username varchar(255) NOT NULL,
PRIMARY KEY (uid)
);

@gabidavila
User Management
● Reusable Permissions/Roles
● Password policy
● New Password
● Reuse of Password
● Expiration
● Rotation
gabi.fyi/roles-mysql

@gabidavila
User Management
● GRANT doesn’t create users anymore, it just… grants!!!
● No more FLUSH PRIVILEGES
● No more googling all the time how to create users with the right
permissions!

@gabidavila
Creating a READONLY role
CREATE ROLE 'readonly';
GRANT SELECT ON app.* TO 'readonly';
● Create the Role
● Define the Privileges

@gabidavila
Creating a user with READONLY role
● Create the User
● Grant the Role
CREATE USER 'gabriela'@'%' IDENTIFIED BY 'my_pwd';
GRANT 'readonly' TO 'gabriela'@'%';

@gabidavila
New Defaults & Variables

@gabidavila
New default Charset
● Default:
● 5.7: latin1
● 8.0: utf8mb4
● Improvements:
● ➕ Mathematical Equations 𝑒=𝑚·𝑐²
● 😁 🙄 $
● & more SMP (Supplementary Multilingual Plane) Characters

@gabidavila
New default Collation
● utf8mb4_0900_ai_ci
● UTF-8 version 9.0 support
● Accent Insensitive
● Case Insensitive
● No more 🍣 = 🍺 bug
● Caused by utf8mb4_general_ci or utf8mb4_unicode_ci
More information on how collations behave here.

@gabidavila
Other defaults & variables
● Binary log (log_bin) is enabled by default
● SHA-2 for authentication
● Mandatory default value for TIMESTAMP
● New variable to dedicated servers (default OFF),
innodb_dedicated_server=ON , controls dynamically:
● innodb_buffer_pool_size
● innodb_log_file_size
● innodb_flush_method

@gabidavila
Descending Indexes

@gabidavila
Descending Indexes
Up to 5.7
● Syntax allowed ASC or DESC when defining an index
However...
An index_col_name specification can end with ASC or DESC. These keywords are
permitted for future extensions for specifying ascending or descending index value
storage. Currently, they are parsed but ignored; index values are always stored in
ascending order.

@gabidavila
Descending Indexes
● No longer ignored and forcibly created as ASC
● Actually works!!!
ALTER TABLE users
ADD INDEX ix_username (username DESC);

@gabidavila
Descending Indexes
Can be scanned as intended or backwards
SELECT *
FROM users
WHERE username LIKE 'g%'
ORDER BY username DESC;
-- OR WITH THE SAME COST
SELECT *
FROM users
WHERE username LIKE 'g%'
ORDER BY username;

@gabidavila
Invisible (?) indexes

@gabidavila
DESCRIBE ùsers`;
Type Null Key Default Extra
ìd`
bigint(20)
unsigned
NO PRI auto_increment
ùsername` varchar(255) NO
`created_at` timestamp NO CURRENT_TIMESTAMP DEFAULT_GENERATED
ùpdated_at` timestamp NO CURRENT_TIMESTAMP
DEFAULT_GENERATED on
update CURRENT_TIMESTAMP

@gabidavila
Invisible Indexes
● Not used by the optimizer
● Visible by default, to create an invisible index:
ALTER TABLE users
ADD INDEX ix_username (username) INVISIBLE;
ALTER TABLE users ALTER INDEX ix_username INVISIBLE;
ALTER TABLE users ALTER INDEX ix_username VISIBLE;
● Toggle visibility:

@gabidavila
Invisible Indexes
SELECT *
FROM users
WHERE username = 'fancy';
Visible
Cost: 0.98 
Rows: 1
Invisible
Cost: 518,331.25 
Rows: 5.04M

@gabidavila
Instant
● Add columns without doing a INPLACE/COPY operation
● Must be appending a column to a table
● Must not have a DEFAULT on the new column
● Rename Table
● Modify Columns
● Virtual Columns
● SET/DROP DEFAULT value of a column

@gabidavila
Example
mysql> ALTER TABLE orders ADD COLUMN total DECIMAL(10,2) NOT NULL,
ALGORITHM=INSTANT;
Query OK, 0 rows affected (0.26 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SELECT count(*) FROM orders;
+----------+
| COUNT(*) |
+----------+
| 50996708 |
+----------+
1 row in set (7.80 sec)

@gabidavila
What they do?
● Allows to analyze the rows of a given result set
● Can behave like a GROUP BY without changing the result set
● Allows you to use a frame to "peek" OVER a PARTITION of a window

@gabidavila
Window Functions
● Examples:
● Enumerate rows - ROW_NUMBER()
● Show Aggregated sums - SUM()
● Rank results - RANK()
● Look at neighboring rows - LEAD(), LAG()

@gabidavila
DESCRIBE òrders`;
CREATE TABLE òrders`
(
ìd` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
ùser_id` bigint(20) UNSIGNED NOT NULL,
`status` varchar(20) NOT NULL DEFAULT 'new',
`created_at` datetime NOT NULL,
ùpdated_at` datetime NOT NULL
)

@gabidavila
SELECT … FROM `orders` WHERE … ORDER BY created_at LIMIT 10;
+---------+---------+-----------+---------------------+
| id | user_id | status | created_at |
+---------+---------+-----------+---------------------+
| 6534954 | 654321 | canceled | 2011-08-21 19:06:59 |
| 6534949 | 654321 | canceled | 2013-11-16 09:02:19 |
| 6534953 | 654321 | completed | 2015-10-28 02:21:30 |
| 6534951 | 654321 | new | 2018-01-05 17:12:23 |
| 6534952 | 654321 | new | 2018-07-19 04:23:41 |
| 6534955 | 654321 | new | 2018-11-12 05:37:48 |
| 6534950 | 654321 | pending | 2018-12-20 06:11:23 |
+---------+---------+-----------+---------------------+

@gabidavila
Previous and Next orders | LAG and LEAD
SELECT id,
user_id,
status,
LAG(created_at) OVER(ORDER BY created_at) AS previous_order,
created_at,
LEAD(created_at) OVER(ORDER BY created_at) AS next_order
FROM orders
WHERE user_id = 654321
ORDER BY created_at
LIMIT 10;

@gabidavila
SELECT … FROM `orders` WHERE … ORDER BY created_at LIMIT 10;
+---------+---------+-----------+---------------------+---------------------+---------------------+
| id | user_id | status | previous_order | created_at | next_order |
+---------+---------+-----------+---------------------+---------------------+---------------------+
| 6534954 | 654321 | canceled | NULL | 2011-08-21 19:06:59 | 2013-11-16 09:02:19 |
| 6534949 | 654321 | canceled | 2011-08-21 19:06:59 | 2013-11-16 09:02:19 | 2015-10-28 02:21:30 |
| 6534953 | 654321 | completed | 2013-11-16 09:02:19 | 2015-10-28 02:21:30 | 2018-01-05 17:12:23 |
| 6534951 | 654321 | new | 2015-10-28 02:21:30 | 2018-01-05 17:12:23 | 2018-07-19 04:23:41 |
| 6534952 | 654321 | new | 2018-01-05 17:12:23 | 2018-07-19 04:23:41 | 2018-11-12 05:37:48 |
| 6534955 | 654321 | new | 2018-07-19 04:23:41 | 2018-11-12 05:37:48 | 2018-12-20 06:11:23 |
| 6534950 | 654321 | pending | 2018-11-12 05:37:48 | 2018-12-20 06:11:23 | NULL |
+---------+---------+-----------+---------------------+---------------------+---------------------+

@gabidavila
Break down
windowfunction
column
# rows preceding
LAG(created_at, 1) OVER (ORDER BY created_at)

@gabidavila
Repetition?
SELECT id,
user_id,
status,
LAG(created_at) OVER(ORDER BY created_at) AS previous_order,
created_at,
LEAD(created_at) OVER(ORDER BY created_at) AS next_order
FROM orders
ORDER BY created_at
LIMIT 10;

@gabidavila
SELECT id,
user_id,
status,
LAG(created_at) OVER(dates) AS previous_order,
created_at,
LEAD(created_at) OVER(dates) AS next_order
FROM orders
WINDOW dates AS (ORDER BY created_at)
ORDER BY created_at
LIMIT 10;
Named Windows!

@gabidavila
CTE 
Common Table Expressions
CTE

@gabidavila
Common Table Expressions
● Similar to CREATE [TEMPORARY] TABLE
● Doesn’t need CREATE privilege
● Can reference other CTEs (if those are already defined)
● Can be recursive
● Easier to read

@gabidavila
Recursive CTE
● Useful with hierarchical data
● The Recipe is:
● Base query comes first
● Second query comes after an UNION statement
● And the stop condition should be on the recursive call

@gabidavila
SELECT * FROM `blog`.`categories`;
+------+-------------------------------+--------------------+
| id | name | parent_category_id |
+------+-------------------------------+--------------------+
| 1 | Animal | 0 |
| 2 | Plant | 0 |
| 3 | Dog | 1 |
| 4 | Cat | 1 |
| 5 | Tulip | 10 |
| 6 | West Highlander White Terrier | 12 |
| 7 | Lettuce | 11 |
| 8 | Sunflower | 10 |
| 10 | Flowers | 2 |
| 11 | Veggies | 2 |
| 12 | Terrier | 3 |
+------+-------------------------------+--------------------+
11 rows in set (0.00 sec)

@gabidavila
Recursive CTE
WITH RECURSIVE tree (depth_level, node, path, node_id) AS (
SELECT 1,
CAST('root' AS CHAR(255)),
0
)
SELECT * FROM tree;

@gabidavila
Recursive CTE
WITH RECURSIVE tree (depth_level, node, path, node_id) AS (
SELECT 1,
0
UNION ALL
SELECT tree.depth_level + 1,
categories.name,
CONCAT_WS('/', tree.path, categories.name),
categories.id
FROM tree
INNER JOIN categories
ON tree.node_id = categories.parent_category_id
WHERE tree.depth_level < 5
)
SELECT * FROM tree ORDER BY path;

@gabidavila
Who never did this? | The most expensive order for each user
SELECT users.id,
users.username,
(SELECT id FROM orders
WHERE users.id = user_id
ORDER BY total LIMIT 1) AS order_id,
(SELECT total FROM orders
WHERE users.id = user_id
ORDER BY total LIMIT 1) AS order_total
FROM users
ORDER BY users.id
LIMIT 10;

@gabidavila
LATERAL
SELECT users.id,
users.username,
total_orders.id AS order_id,
total_orders.total AS order_total
FROM users,
LATERAL(
SELECT id, total FROM orders
WHERE users.id = user_id ORDER BY total LIMIT 1
) AS total_orders
ORDER BY users.id
LIMIT 10;

@gabidavila
Thank you!
● About me: gabi.fyi/me
● Twitter: @gabidavila (DMs are open!)
● Host at: gcppodcast.com

MySQL 8.0: not only good, it’s GREAT! - PHP UK 2019

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