149 lines
5.5 KiB
HTML
149 lines
5.5 KiB
HTML
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<!-- keywords: sqlite3_snapshot_get -->
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
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<h2>Record A Database Snapshot</h2>
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</div>
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<blockquote><pre>
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int sqlite3_snapshot_get(
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sqlite3 *db,
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const char *zSchema,
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sqlite3_snapshot **ppSnapshot
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);
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</pre></blockquote>
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<p>
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The <a href="../c3ref/snapshot_get.html">sqlite3_snapshot_get(D,S,P)</a> interface attempts to make a
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new <a href="../c3ref/snapshot.html">sqlite3_snapshot</a> object that records the current state of
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schema S in database connection D. On success, the
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<a href="../c3ref/snapshot_get.html">sqlite3_snapshot_get(D,S,P)</a> interface writes a pointer to the newly
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created <a href="../c3ref/snapshot.html">sqlite3_snapshot</a> object into *P and returns SQLITE_OK.
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If there is not already a read-transaction open on schema S when
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this function is called, one is opened automatically.</p>
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<p>The following must be true for this function to succeed. If any of
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the following statements are false when sqlite3_snapshot_get() is
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called, SQLITE_ERROR is returned. The final value of *P is undefined
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in this case.</p>
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<p><ul>
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<li> The database handle must not be in <a href="../c3ref/get_autocommit.html">autocommit mode</a>.</p>
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<p><li> Schema S of <a href="../c3ref/sqlite3.html">database connection</a> D must be a <a href="../wal.html">WAL mode</a> database.</p>
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<p><li> There must not be a write transaction open on schema S of database
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connection D.</p>
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<p><li> One or more transactions must have been written to the current wal
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file since it was created on disk (by any connection). This means
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that a snapshot cannot be taken on a wal mode database with no wal
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file immediately after it is first opened. At least one transaction
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must be written to it first.
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</ul></p>
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<p>This function may also return SQLITE_NOMEM. If it is called with the
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database handle in autocommit mode but fails for some other reason,
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whether or not a read transaction is opened on schema S is undefined.</p>
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<p>The <a href="../c3ref/snapshot.html">sqlite3_snapshot</a> object returned from a successful call to
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<a href="../c3ref/snapshot_get.html">sqlite3_snapshot_get()</a> must be freed using <a href="../c3ref/snapshot_free.html">sqlite3_snapshot_free()</a>
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to avoid a memory leak.</p>
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<p>The <a href="../c3ref/snapshot_get.html">sqlite3_snapshot_get()</a> interface is only available when the
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<a href="../compile.html#enable_snapshot">SQLITE_ENABLE_SNAPSHOT</a> compile-time option is used.
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</p><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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