How to extend MySQL: from UDFs to components and to pull requests

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How to Add Stuff to MySQL
Georgi “Joro” Kodinov
Team Lead, SrvGen Team
A Guided Tour

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Safe Harbor Statement
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information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
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Agenda
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• The basic way: user defined functions
• The old way: plugins
• The new way: components
• The advanced way: pull requests

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User Defined Functions
The Basic Way
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Architecture of UDFs
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SQL
UDF call
Result
Client Server UDF Library

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Pros and Cons
Pros Cons
Easy A single return value
Well documented No way to generate SQL errors
SQL callable Limited data type support
Dynamically loadable Need to be defined one by one
Can also make aggregate functions
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User Defined Functions

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A User Defined Function: sql/udf_example.com
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A loop over
the
arguments
Check for
NULL
values
Argument
type
Returning a
result
To return a
NULL result
set to 1

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Compiling and Running
[gkodinov@loki01]~/work/mysql-8.0/sql: gcc -I ../include/ -I ../libbinlogevents/export/ -I
../bld/include/ -shared -std=c++11 -fPIC -o udf_example.so udf_example.cc
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Plugins
The Old Way
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Architecture of Plugins
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SQL
Plugin API call
Result
Client Server Plugin Library
Plugin Service

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Pros and Cons
Pros Cons
Better known Two plugins cannot co-operate directly
Documented Plugins are linked with the server symbols
Can respond to events in server Plugin APIs not easily extensible
Multiple active plugins Complex loading/unloading sequence
Can call back into the server code No explicit dependencies
Dynamically loadable Hard to add new plugin APIs
Lots of examples
Good amount of useful plugin APIs
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Plugins

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Sample plugin: plugin/auth/auth_socket.cc

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Compiling the plugin
• Need a source distro
• Put in plugin/
• Add CMakeLists.txt
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Using the plugin
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Install the
plugin
Create a
user using
the plugin
Authenticate
Verify the
result

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Components
The New Way
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Architecture of Components
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SQL
Client
Server
Services

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Pros and Cons
Pros Cons
Explicit Dependencies Not all plugin APIs are migrated to components
All components are equal and can communicate Not available in versions older than MySQL 8.0
Can dynamically add new service implementations Relatively new: lacks some refinements
Can override existing service implementations Currently supports mostly C APIs
Can provide soft transition by keeping the old and the
new
Dynamically loadable
Can be adaptive to the services present
Does not require the server binary to be built
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Components

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Sample Service Definition And Implementation
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Sample Component
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What service
implementations
a component
provides
What service
implementations
a component
requires
Component
metadata
Component
Definition
Shared Library
Definition

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How to Find And Use a Service: The Low Level Way
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How to Find And Use a Service: The Easier Way
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Pull Requests
The Advanced Way
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Pull Requests

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The New And Improved Doxygen Manual
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Summary
• Always consider a component first
• Go to plugin If you:
– need to implement an existing, not-yet-migrated plugin API
– need to call into an existing, not-yet-migrated plugin service
• Go to UDFs if you need an SQL callable function
• Go to pull requests if none of the above fits
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