191 lines
7.2 KiB
HTML
191 lines
7.2 KiB
HTML
<!DOCTYPE html>
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<link href="sqlite.css" rel="stylesheet">
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<title>Benefits of SQLite As A File Format</title>
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Small. Fast. Reliable.<br>Choose any three.
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<h1 align="center">
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SQLite As An Application File Format
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</h1>
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<p><i>(Note: The current page is a brief summary of why SQLite makes
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a good application file format. The topic is considered at greater
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detail in a <a href="appfileformat.html">separate technical note</a>.)</i></p>
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<p>
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SQLite has been used with great success as the on-disk file format
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for desktop applications such as version control systems,
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financial analysis tools, media cataloging and editing suites, CAD
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packages, record keeping programs, and so forth. The traditional
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File/Open operation calls sqlite3_open() to attach to the database
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file. Updates happen automatically as application content is revised
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so the File/Save menu option becomes superfluous. The File/Save_As
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menu option can be implemented using the <a href="backup.html">backup API</a>.
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</p>
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<p>
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There are many advantages to using SQLite as an application file format,
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including:
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</p>
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<ol type="1">
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<li><b>Better performance</b>
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<ul>
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<li> Reading and writing from an SQLite database
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is often faster than reading and writing individual files from disk.
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See <a href="fasterthanfs.html">35% Faster Than The Filesystem</a>
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and <a href="intern-v-extern-blob.html">Internal Versus External BLOBs</a>.
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<li> The application only has to load the data it needs, rather
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than reading the entire file and holding a complete parse
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in memory.
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<li> Small edits only overwrite the parts of the file that change,
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reducing write time and wear on SSD drives.
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</ul>
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<li><b>Reduced application cost and complexity</b>
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<ul>
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<li> No application file I/O code to write and debug.
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<li> Content can be accessed and updated using concise SQL queries instead
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of lengthy and error-prone procedural routines.
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<li> The file format can be extended in future releases simply
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by adding new tables and/or column, preserving backwards compatibility.
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<li> Applications can leverage the
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<a href="fts3.html">full-text search</a> and <a href="rtree.html">RTREE</a> indexes and use triggers to implement
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an <a href="undoredo.html">automated undo/redo stack</a>.
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<li> Performance problems can often be resolved, even late in the
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development cycle, using <a href="lang_createindex.html">CREATE INDEX</a>, avoiding costly
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redesign, rewrite, and retest efforts.
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</ul>
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<li><b>Portability</b>
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<ul>
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<li> The application file is portable across all operating systems,
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32-bit and 64-bit and big- and little-endian architectures.
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<li> A federation of programs, perhaps all written in different programming
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languages, can access the same application file with no
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compatibility concerns.
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<li> Multiple processes can attach to the same application
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file and can read and write without interfering with each another.
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<li> Diverse content which might otherwise be stored as a "pile-of-files"
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is encapsulated into a single disk file for simpler transport
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via scp/ftp, USB stick, and/or email attachment.
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</ul>
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<li><b>Reliability</b>
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<ul>
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<li> Content can be updated continuously and atomically so
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that little or no work is lost in a power failure or crash.
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<li> Bugs are far less likely in SQLite than in custom-written file I/O code.
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<li> SQL queries are many times smaller than the equivalent procedural
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code, and since the number of bugs per line of code is roughly
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constant, this means fewer bugs overall.
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</ul>
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<li><b>Accessibility</b>
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<ul>
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<li> SQLite database content can be viewed using a wide variety
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third-party tools.
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<li> Content stored in an SQLite database is more likely to be
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recoverable decades in the future, long after all traces of
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the original application have been lost. Data lives longer than code.
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<li> SQLite database files are <a href="locrsf.html">recommended by the US Library of Congress</a>
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as a storage format for long-term preservation of digital content.
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</ul>
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</ol>
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<p>
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SQLite allows database files to have any desired filename extension, so
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an application can choose a custom filename extension for its own use, if
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desired. The <a href="pragma.html#pragma_application_id">application_id pragma</a> can be used to set an "Application ID"
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integer in the database file so that tools like
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<a href="http://www.darwinsys.com/file/">file(1)</a> can determine that the file
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is associated with your application and is not just a generic
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SQL database.</p>
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