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MySQL: Know more about open Source Database
 

MySQL: Know more about open Source Database

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    MySQL: Know more about open Source Database MySQL: Know more about open Source Database Presentation Transcript

    • know more about MySQL open source database
      MySQL: Open Source Database
      1
      Salaria Software Services
    • Storage engines
      Schema
      Normalization
      Data types
      Indexes
      Know more about your SQL queries - Using EXPLAIN
      Character set and Collation
      Resources
      2
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      Outline
    • Generics are inefficient
      • If you have chosen MySQL, take advantage of its strengths
      • Having an understanding of the database helps you develop better-performing applications
      • better to design a well-performing database-driven application from the start
      • than try to fix a slow one after the fact!
      3
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      Why is it significant for a developerto know MySQL?
    • Salaria Software Services
      4
      MySQL Pluggable Storage EngineArchitecture
      MySQL supports several storage engines that act as handlers for different table types
      • No other database vendor offers this capability
    • Dynamically add and remove storage engines.
      Change the storage engine on a table with
      “ALTER TABLE <table> ENGINE=InnoDB;”
      5
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      Storage Engines
    • Concurrency: some have more granular locks than others
      • right locking can improve performance.
      • Storage: how the data is stored on disk
      • page size for tables, indexes, format used
      • Indexes: b-trees, hash
      • Memory usage
      • caching strategy
      • Transactions:
      • not every application table needs transactions
      6
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      What makes engines different?
    • “As a developer, what do I need to know about storage engines, without being a MySQL expert?”
      • Keep in mind the following questions:
      • What type of data will you be storing?
      • Is the data constantly changing?
      • Is the data mostly logs (INSERTs)?
      • requirements for reports?
      • need for transaction control?
      7
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      So…
    • Default MySQL engine
      • high-speed Query and Insert capability
      • insert uses shared read lock
      • updates, deletes use table-level locking, slower
      • full-text indexing
      • Good for text search
      • Non-transactional, No foreign key support
      • good choice for :
      • read-only or read-mostly application tables that don't require transactions
      • Web, data warehousing, logging, auditing
      8
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      MyISAM Pluggable Storage engine
    • Transaction-safe and ACID (atomicity, consistency, isolation, durability)compliant
      • crash recovery, foreign key constraints
      • good query performance, depending on indexes
      • row-level locking, Multi Version Concurrency Control (MVCC)
      • allows fewer row locks by keeping data snapshots
      – Depending on the isolation level, no locking for SELECT
      – high concurrency possible
      • uses more disk space and memory than ISAM
      • Good for Online transaction processing (OLTP)
      • Lots of users: eBay, Google, Yahoo!, Facebook, etc.
      9
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      InnoDB Storage engine
    • Entirely in-memory engine
      • stores all data in RAM for extremely fast access
      • Updated Data is not persisted
      – table loaded on restart
      • Hash index used by default
      • Good for
      • Summary and transient data
      • "lookup" tables,
      • calculated table counts,
      • for caching, temporary tables
      10
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      Memory Engine
    • Incredible insert speeds
      • Great compression rates (zlib)?
      • Typically 6-8x smaller than MyISAM
      • No UPDATEs
      • Ideal for storing and retrieving large amounts of historical data
      • audit data, log files,Web traffic records
      • Data that can never be updated
      11
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      Archive engine
    • Salaria Software Services
      12
      Pluggable storage engines offerFlexibility
      You can use multiple storage engines in a single application
      • A storage engine for the same table on a slave can be different than that of the master
      • Choose storage engine that's best for your applications requirements
      • can greatly improve performance
    • Creating a table with a specified engine
      • CREATE TABLE t1 (...)
      ENGINE=InnoDB;
      • Changing existing tables
      • ALTER TABLE t1 ENGINE=MyISAM;
      • Finding all your available engines
      • SHOW STORAGE ENGINES;
      13
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      Using different engines
    • Basic foundation of performance
      • Normalization
      • Data Types
      • Smaller, smaller, smaller
      - Smaller tables use less disk, less memory, can give better performance
      • Indexing
      • Speeds up retrieval
      14
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      The schema
    • Eliminate redundant data:
      • Don't store the same data in more than one table
      • Only store related data in a table
      • reduces database size and errors
      15
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      Goal of Normalization
    • updates are usually faster.
      • there's less data to change.
      • tables are usually smaller, use less memory, which can give better performance.
      • better performance for distinct or group by queries
      16
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      Normalization
    • However Normalized database causes joins for queries
      • excessively normalized database:
      • queries take more time to complete, as data has to be retrieved from more tables.
      • Normalized better for writes OLTP
      • De-normalized better for reads , reporting
      • Real World Mixture:
      • normalized schema
      • Cache selected columns in memory table
      17
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      taking normalization way too far
    • Smaller => less disk => less memory => better performance
      Use the smallest data type possible
      • The smaller your data types, The more index (and data) can fit into a block of memory, the faster your queries will be.
      • Period.
      • Especially for indexed fields
      18
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      Data Types: Smaller, smaller, smaller
    • MySQL has 9 numeric data types
      • Compared to Oracle's 1
      • Integer:
      • TINYINT , SMALLINT, MEDIUMINT, INT, BIGINT
      • Require 8, 16, 24, 32, and 64 bits of space.
      • Use UNSIGNED when you don't need negative numbers – one more level of data integrity
      • BIGINT is not needed for AUTO_INCREMENT
      • INT UNSIGNED stores 4.3 billion values!
      • Summation of values... yes, use BIGINT
      Floating Point: FLOAT, DOUBLE
      • Approximate calculations
      • Fixed Point: DECIMAL
      • Always use DECIMAL for monetary/currency fields, never use FLOAT or DOUBLE!
      • Other: BIT
      • Store 0,1 values
      19
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      Choose your Numeric Data Type
    • VARCHAR(n) variable length
      • uses only space it needs
      – Can save disk space = better performance
      • Use :
      – Max column length > avg
      – when updates rare (updates fragment)
      • CHAR(n) fixed length
      • Use:
      – short strings, Mostly same length, or changed frequently
      20
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      Character Data Types
    • Always define columns as NOT NULL
      – unless there is a good reason not to
      • Can save a byte per column
      • nullablecolumns make indexes, index statistics, and value comparisons more complicated.
      • Use the same data types for columns that will be compared in JOINs
      • Otherwise converted for comparison
      • Use BLOBs very sparingly
      • Use the filesystem for what it was intended
      21
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      Appropriate Data Types
    • “The more records you can fit into a single page of memory/disk, the faster your seeks and scans will be.”
      • Use appropriate data types
      • Keep primary keys small
      • Use TEXT sparingly
      • Consider separate tables
      • Use BLOBs very sparingly
      • Use the filesystem for what it was intended
      22
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      smaller, smaller, smaller
    • Indexes Speed up Queries,
      • SELECT...WHERE name = 'carol'
      • only if there is good selectivity:
      – % of distinct values in a column
      • But... each index will slow down INSERT, UPDATE, and DELETE operations
      23
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      Indexes
    • Always have an index on join conditions
      • Look to add indexes on columns used in WHERE and GROUP BY expressions
      • PRIMARY KEY, UNIQUE , and Foreign key Constraint columns are automatically indexed.
      • other columns can be indexed (CREATE INDEX..)
      24
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      Missing Indexes
    • use the MySQL slow query log and use Explain
      • Append EXPLAIN to your SELECT statement
      • shows how the MySQL optimizer has chosen to execute the query
      • You Want to make your queries access less data:
      • are queries accessing too many rows or columns?
      – select only the columns that you need
      • Use to see where you should add indexes
      • Consider adding an index for slow queries or cause a lot of load.
      – ensures that missing indexes are picked up early in the development process
      25
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      Know how your Queries are executed by MySQL
    • Find and fix problem SQL:
      • how long a query took
      • how the optimizer handled it
      • Drill downs, results of EXPLAIN statements
      • Historical and real-time analysis
      • query execution counts, run time
      “Its not just slow running queries that are a problem, Sometimes its SQL that executes a lot that kills your system”
      26
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      MySQLQuery Analyzer
    • Salaria Software Services
      27
      Understanding EXPLAIN
      Just append EXPLAIN to your SELECT statement
      • Provides the execution plan chosen by the MySQL optimizer for a specific SELECT statement
      • Shows how the MySQL optimizer executes the query
      • Use to see where you should add indexes
      • ensures that missing indexes are picked up early in the development process
    • A character set is a set of symbols and encodings.
      A collation is a set of rules for comparing characters in a character set.
      MySQL can do these things for you:
      • Store strings using a variety of character sets
      • Compare strings using a variety of collations
      • Mix strings with different character sets or collations in the same server, the same database, or even the same table
      • Allow specification of character set and collation at any level
      - Mysql > SET NAMES 'utf8';
      - Mysql > SHOW CHARACTER SET
      28
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      Character set and Collation
    • Two different character sets cannot have the same collation.
      Each character set has one collation that is the default collation. For example, the default collation for latin1 is latin1_swedish_ci. The output for “SHOW CHARACTER SET” indicates which collation is the default for each displayed character set.
      There is a convention for collation names: They start with the name of the character set with which they are associated, they usually include a language name, and they end with _ci (case insensitive), _cs (case sensitive), or _bin (binary).
      29
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      Collations have these general characteristics
    • <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
      <?phpmysql_query('SET NAMES utf8'); ?>
      CREATE DATABASE mydatabase DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
      CREATE TABLE mytable (  mydata VARCHAR(128) NOT NULL) ENGINE=MyISAM DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
      30
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      How to handle Unicode (UTF-8)
    • MySQL Forge and the Forge Wiki
      http://forge.mysql.com/
      Planet MySQL
      http://planetmysql.org/
      MySQLDevZone
      http://dev.mysql.com/
      High Performance MySQL book
      31
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      Resources
    • ?
      Open Questions
      32
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    • Salaria Software Services
      33
      Thanks and Regards
      Mahesh Salaria
      mahesh@salaria.net
      Salaria Software Services
      http://salariasoft.com