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The result of calling this interface +from outside of an xBestIndex method are undefined and probably harmful.</p> + +<p>When the sqlite3_vtab_rhs_value(P,J,V) interface is invoked from within +the <a href="../vtab.html#xbestindex">xBestIndex</a> method of a <a href="../vtab.html">virtual table</a> implementation, with P being +a copy of the <a href="../c3ref/index_info.html">sqlite3_index_info</a> object pointer passed into xBestIndex and +J being a 0-based index into P->aConstraint[], then this routine +attempts to set *V to the value of the right-hand operand of +that constraint if the right-hand operand is known. If the +right-hand operand is not known, then *V is set to a NULL pointer. +The sqlite3_vtab_rhs_value(P,J,V) interface returns SQLITE_OK if +and only if *V is set to a value. The sqlite3_vtab_rhs_value(P,J,V) +inteface returns SQLITE_NOTFOUND if the right-hand side of the J-th +constraint is not available. The sqlite3_vtab_rhs_value() interface +can return an result code other than SQLITE_OK or SQLITE_NOTFOUND if +something goes wrong.</p> + +<p>The sqlite3_vtab_rhs_value() interface is usually only successful if +the right-hand operand of a constraint is a literal value in the original +SQL statement. If the right-hand operand is an expression or a reference +to some other column or a <a href="../c3ref/bind_blob.html">host parameter</a>, then sqlite3_vtab_rhs_value() +will probably return <a href="../rescode.html#notfound">SQLITE_NOTFOUND</a>.</p> + +<p>Some constraints, such as <a href="../c3ref/c_index_constraint_eq.html">SQLITE_INDEX_CONSTRAINT_ISNULL</a> and +<a href="../c3ref/c_index_constraint_eq.html">SQLITE_INDEX_CONSTRAINT_ISNOTNULL</a>, have no right-hand operand. For such +constraints, sqlite3_vtab_rhs_value() always returns SQLITE_NOTFOUND.</p> + +<p>The <a href="../c3ref/value.html">sqlite3_value</a> object returned in *V is a protected sqlite3_value +and remains valid for the duration of the xBestIndex method call. +When xBestIndex returns, the sqlite3_value object returned by +sqlite3_vtab_rhs_value() is automatically deallocated.</p> + +<p>The "_rhs_" in the name of this routine is an abbreviation for +"Right-Hand Side". +</p><p>See also lists of + <a href="../c3ref/objlist.html">Objects</a>, + <a href="../c3ref/constlist.html">Constants</a>, and + <a href="../c3ref/funclist.html">Functions</a>.</p> + |