4) Information schema & performanc schema.pdf

MySQL INFORMATION SCHEMA

& PERFORMANCE SCHEMA

Agenda

MySQL Information_schema

Tables in Information_schema

MySQL Performance schema

About Us

Karthik.P.R, Senior MySQL DBA,

Bharath Kumar.P, MySQL DBA

Blog : remotemysqldba.blogspot.in

Remotemysqldba.blogspot.in

MySQL Information Schema

Information_schema is a virtual MySQL database that stores metadata

information of all the MySQL databases.

From MySQL 5, when we execute

the show databases command

information_schema will be

listed in the database list.

The important thing to remember

about the information_schema database

is that you can query it, but you cannot

change its structure or modify its data.

It can not be dumped using mysqldump.



Using the information_schema views, you can execute the standard select SQL command to get the metadata information.

Contains following types of information:

Table Information

Partioning

Privileges

Character Set Support

Constraint and Indexes

Server Settings and Status

Routines and Related Infromation

InnoDB


Tables In Information_Schema

CHARACTER_SETS

COLLATIONS

COLLATION_CHARACTER_SET_APPLICABILITY

COLUMNS

COLUMN_PRIVILEGES

ENGINES

EVENTS

FILES

GLOBAL_STATUS

GLOBAL_VARIABLES

KEY_COLUMN_USAGE

OPTIMIZER_TRACE

PARAMETERS

PARTITIONS

PLUGINS

PROCESSLIST

PROFILING

REFERENTIAL_CONSTRAINTS

ROUTINES

SCHEMATA

SCHEMA_PRIVILEGES

SESSION_STATUS

SESSION_VARIABLES

STATISTICS

TABLES

TABLESPACES

TABLE_CONSTRAINTS

TABLE_PRIVILEGES

TRIGGERS

USER_PRIVILEGES

VIEWS

INNODB_CMP_RESET

INNODB_TRX

INNODB_CMPMEM_RESET

INNODB_LOCK_WAITS

INNODB_CMPMEM

INNODB_CMP

INNODB_LOCKS



CHARACTER_SETS :

This table provides the information about the available character sets.

Each language functions need different character sets.

COLLATIONS:

The collation table provides the information about the collations for

each character set.

COLLATION_CHARACTER_SET_APPLICABILITY:

This table indicates what character set is applicable for what collation.

COLUMNS :

The columns table provides information about columns in tables.



COLUMN_PRIVILEGES :

This table provides information about column privileges. This

information comes from the mysql.columns_priv table.

ENGINES :

This table provides the output of show engines; statements.

EVENTS :

It shows all the information about the event scheduler.

GLOBAL_STATUS & GLOBAL_VARIABLES:

They give the info about the server variables and status. show global

variables and show global status commands.



KEY_COLUMN_USAGE :

It shows which key columns have constraints. The column that has

foreign key references. It also shows the relation between tables.

PARAMETERS :

It gives information about stored procedure and function parameters. It

gets data from mysql.proc table.



PARTITIONS :

It gives information about the partitioned tables and their sub partitions.

PLUGINS :

It show what are the plug-ins installed and their description. It is

equivalent to show plugins

PROCESSLIST:

It gives the list of all the threads running inside the mysql server . It is equivalent to show full processlist.

It helps to get the queries running beyond certain duration or queries running by a certain user.



PROFILING :

This table provides statement profiling information. If profiling is enabled . It is similar to show profile.

Profiling helps us to identify the bottle neck in a query.

REFERENTIAL_CONSTRAINTS :

This table provides information about foreign keys.

ROUTINES :

This table provides information about stored routines in a detailed

manner.



SCHEMATA :

It show what are the databases present in the server.

SCHEMA_PRIVILEGES :

This table provides information about schema (database) privileges. It

takes them from mysql.db tables.

STATISTICS :

This table provides information about table indexes.



TABLES :

This table provides information about all tables in databases. It has

more and more data about the tables.

1) data size

2) index size

3) number of rows

4) average row length ,etc



TABLESPACES:

This table provides information about active tablespaces.

TABLE_CONSTRAINTS :

This table describes which tables have constraints. The information is

about the same as what you get from the show index from

table_name.



TABLE_PRIVILEGES :

This table provides information about table privileges. This information

comes from the mysql.tables_priv table.

TRIGGERS :

This table provides information about triggers.

USER_PRIVILEGES :

The table provides information about global privileges. This

information comes from the mysql.user table.

VIEWS :

The table provides information about views in databases.


Information_Schema Examples

Query to display tables with more than 1000 rows.



Query to list top 5 largest tables in the database.


MySQL Performance Schema

MySQL Performance Schema is a feature for monitoring MySQL Server

execution at a low level.

The Performance Schema is available as of MySQL 5.5.3 .

It provides a way to inspect internal execution of the server at runtime.

It monitors server as events.

An event is anything the server does that takes time and has been

instrumented so that timing information can be collected

The Performance Schema storage engine collects event data using

instrumentation points in server source code.

Collected events are stored in tables in the performance_schema database.



It provide access to useful information about server execution while having

minimal impact on server performance.

Tables in the performance_schema database are views or temporary tables

that use no persistent on-disk storage.

Monitoring is available on all platforms supported by MySQL.

No separate threads associated with the Performance Schema, unlike other

features such as replication or the Event Scheduler.



Activating the Performance Schema causes no changes in server

behavior.

No memory allocation is done beyond that which occurs during server

startup

Server monitoring occurs continuously and unobtrusively with very

little overhead. Activating the Performance Schema does not make the

server unusable.

Execution of server code proceeds normally even if the Performance

Schema fails internally.



To check whether performance_schema is available or not.

# mysqld --verbose --help

...

--performance_schema

Enable the performance schema.

--performance_schema_events_waits_history_long_size=#

Number of rows in events_waits_history_long.

...

To enable it, start the server with the performance_schema variable enabled in the

my.cnf file.

mysql > show variables like performance_schema;


THANK YOU

Documents

4) Information schema & performanc schema.pdf