130 lines
4.7 KiB
HTML
130 lines
4.7 KiB
HTML
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<title>Database Snapshot</title>
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<!-- keywords: snapshot sqlite3_snapshot -->
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
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<h2>Database Snapshot</h2>
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</div>
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<blockquote><pre>
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typedef struct sqlite3_snapshot {
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unsigned char hidden[48];
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} sqlite3_snapshot;
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</pre></blockquote>
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<p>
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An instance of the snapshot object records the state of a <a href="../wal.html">WAL mode</a>
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database for some specific point in history.</p>
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<p>In <a href="../wal.html">WAL mode</a>, multiple <a href="../c3ref/sqlite3.html">database connections</a> that are open on the
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same database file can each be reading a different historical version
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of the database file. When a <a href="../c3ref/sqlite3.html">database connection</a> begins a read
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transaction, that connection sees an unchanging copy of the database
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as it existed for the point in time when the transaction first started.
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Subsequent changes to the database from other connections are not seen
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by the reader until a new read transaction is started.</p>
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<p>The sqlite3_snapshot object records state information about an historical
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version of the database file so that it is possible to later open a new read
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transaction that sees that historical version of the database rather than
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the most recent version.
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</p><p>Constructor: <a href="../c3ref/snapshot_get.html">sqlite3_snapshot_get()</a></p>
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<p>Destructor: <a href="../c3ref/snapshot_free.html">sqlite3_snapshot_free()</a></p>
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<p>Methods:
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<a href="../c3ref/snapshot_cmp.html">sqlite3_snapshot_cmp()</a>,
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<a href="../c3ref/snapshot_open.html">sqlite3_snapshot_open()</a>,
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<a href="../c3ref/snapshot_recover.html">sqlite3_snapshot_recover()</a></p>
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<p>See also lists of
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<a href="objlist.html">Objects</a>,
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<a href="constlist.html">Constants</a>, and
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<a href="funclist.html">Functions</a>.</p>
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