125 lines
4.4 KiB
HTML
125 lines
4.4 KiB
HTML
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
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<h2>Virtual Table Instance Object</h2>
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</div>
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<blockquote><pre>
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struct sqlite3_vtab {
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const sqlite3_module *pModule; /* The module for this virtual table */
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int nRef; /* Number of open cursors */
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char *zErrMsg; /* Error message from sqlite3_mprintf() */
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/* Virtual table implementations will typically add additional fields */
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};
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</pre></blockquote>
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<p>
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Every <a href="../c3ref/module.html">virtual table module</a> implementation uses a subclass
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of this object to describe a particular instance
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of the <a href="../vtab.html">virtual table</a>. Each subclass will
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be tailored to the specific needs of the module implementation.
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The purpose of this superclass is to define certain fields that are
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common to all module implementations.</p>
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<p>Virtual tables methods can set an error message by assigning a
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string obtained from <a href="../c3ref/mprintf.html">sqlite3_mprintf()</a> to zErrMsg. The method should
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take care that any prior string is freed by a call to <a href="../c3ref/free.html">sqlite3_free()</a>
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prior to assigning a new string to zErrMsg. After the error message
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is delivered up to the client application, the string will be automatically
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freed by sqlite3_free() and the zErrMsg field will be zeroed.
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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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