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Storing Images in MySQL

Boston MySQL Meetup GroupMonday June 12th, 2006

Sheeri Kritzerawfief@gmail.com

http://www.sheeri.com

mailto:awfief@gmail.commailto:awfief@gmail.com

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A BLOB By Any Other Name

Text is data

BLOB is data

Images are BLOBs

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Similarities

Syncing images across multiple servers

Web server image caching

Performance

Adding another server

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Similarities

A filesystem is a DB

Isolation locking

Durability transactions committed not lost

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Why Not?

Filesystems store files

Hard to backup/restore/repair

Partial restore tedious

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Why Not?(continued)

Binary logging doubles space

More db connections, queries

Bottleneck

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Why Not?(continued)

Database fragmentation

Portability

Single storage engine for all data ???

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Why?

Snapshots easier, less expensive

Scalability

Indexing and sorting

Access Control

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Why?(continued)

Atomicity

Consistency

Database features

Remote storage easier

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Why?(continued)

Replication easy

Single storage engine for all data

Dual-level caching

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Why?(continued)

Oracle recommends it

http://www.oracle.com/technology/products/intermedia

/htdocs/why_images_in_database.html

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Caveats

SELECT *

Full table scan

max_allowed_packet

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Compromise

Do both

Originals in db

Written to disk

Transformations also written to disk

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What We Chose

700,000 users, 6 pictures each

20,000 online at peak time

Online user image retrieval

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What We Chose

Add 17-19,000 users a week

Possible 102-114,000 pictures a week

Need referential integrity

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BLOB Sizes

TINYBLOB 2^8 bytes

BLOB 2^16 bytes MEDIUMBLOB

LONGBLOB

variable-length

256 bytes

64 Kb16 Mb

4 Gb

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What Storage Engine?

1 datafile per table?

Table-level or row-level locking?

Compressed, read-only storage?

Fulltext indexing?

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What Storage Engine?(continued)

InnoDB for row-level locking

Can specify 1 datafile per table if desired

No captions or text

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Architecture

2 tables 1 fixed-length

Single write master to many read slaves

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Creating the Table

CREATE TABLE ImageMd (imageNum int unsigned not null primary key,

ownerUid int unsigned not null,

modified timestamp,

uploaded datetime) ENGINE=InnoDB

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Creating the Table

CREATE TABLE Images (

imageNum int unsigned not null primary keyauto_increment,

modified timestamp,

image mediumblob) ENGINE=InnoDB

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Populating the Tables

LOAD_FILE('path/to/file.jpg')(max_allowed_packet)

Application code

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Retrieving the Images

Browser needs to know the data is an image

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Questions?

Who's done this?

Other stories....