169 lines
5.6 KiB
HTML
169 lines
5.6 KiB
HTML
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The dbhash.exe Utility Program
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<h1 id="overview"><span>1. </span>Overview</h1>
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<p>The <b>dbhash</b> (or <b>dbhash.exe</b> on Windows) utility is a
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command-line program that computes the SHA1 hash of the schema and content
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for an SQLite database.
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</p><p>Dbhash ignores extraneous formatting details and hashes only the database
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schema and content. Hence the hash is constant even if the database file
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is modified by:
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</p><ul>
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<li> <a href="lang_vacuum.html">VACUUM</a>
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</li><li> <a href="pragma.html#pragma_page_size">PRAGMA page_size</a>
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</li><li> <a href="pragma.html#pragma_journal_mode">PRAGMA journal_mode</a>
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</li><li> <a href="lang_reindex.html">REINDEX</a>
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</li><li> <a href="lang_analyze.html">ANALYZE</a>
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</li><li> copied via the <a href="backup.html">backup API</a>
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</li><li> ... and so forth
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</li></ul>
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<p>The operations above can potentially cause vast changes the raw database file,
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and hence cause very different SHA1 hashes at the file level.
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But since the content represented in the database file is unchanged by these
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operations, the hash computed by dbhash is also unchanged.
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</p><p>Dbhash can be used to compare two databases to confirm that they
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are equivalent, even though their representation on disk is quite different.
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Dbhash might also be used to verify the content of a remote database without having
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to transmit the entire content of the remote database over a slow link.
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</p><h1 id="usage"><span>2. </span>Usage</h1>
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<p>Dbhash is a command-line utility.
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To run it, type "dbhash" on a command-line prompt followed by the names of
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one or more SQLite database files that are to be hashed.
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The database hashes will be displayed on standard output.
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For example:
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</p><div class="codeblock"><pre>drh@bella:~/sqlite/bld$ dbhash ~/Fossils/sqlite.fossil
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8d3da9ff87196312aaa33076627ccb7943ef79e3 /home/drh/Fossils/sqlite.fossil
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</pre></div>
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<p>Dbhash supports command-line options that can restrict the tables of the
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database file that are hashed, or restrict the hash to only content or only
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the schema. Run "dbhash --help" for further information.
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</p><h1 id="building"><span>3. </span>Building</h1>
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<p>To build a copy of the dbhash utility program on unix, get a copy of the
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canonical SQLite source code and enter:
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</p><div class="codeblock"><pre>./configure
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make dbhash
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</pre></div>
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<p>On Windows, enter:
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</p><div class="codeblock"><pre>nmake /f makefile.msc dbhash.exe
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</pre></div>
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<p>The dbhash program is implemented by a single file of C-code
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called <a href="https://www.sqlite.org/src/artifact?ci=trunk&filename=tool/dbhash.c">dbhash.c</a>.
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To build the dbhash program manually, simply compile the dbhash.c source file
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and link it against the SQLite library.
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</p>
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