Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 13453)
+++ wp-includes/wp-db.php	(working copy)
@@ -1149,6 +1149,51 @@
 	 * @return int|false The number of rows inserted, or false on error.
 	 */
 	function insert( $table, $data, $format = null ) {
+		return $this->_insert_replace_helper($table, $data, $format, 'INSERT');
+	}
+
+	/**
+	 * Replace a row into a table.
+	 *
+	 * <code>
+	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 'bar' ) )
+	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( '%s', '%d' ) )
+	 * </code>
+	 *
+	 * @since 3.0.0
+	 * @see wpdb::prepare()
+	 * @see wpdb::$field_types
+	 * @see wp_set_wpdb_vars()
+	 *
+	 * @param string $table table name
+	 * @param array $data Data to replace (in column => value pairs).  Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
+	 * 	A format is one of '%d', '%s' (decimal number, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 * @return int|false The number of rows inserted, or false on error.
+	 */
+	function replace( $table, $data, $format = null ) {
+		return $this->_insert_replace_helper($table, $data, $format, 'REPLACE');
+	}
+
+	/**
+	 * Private helper function for insert and replace.
+	 *
+	 * Runs an insert or replace query based on type
+	 *
+	 * @since 3.0.0
+	 * @see wpdb::prepare()
+	 * @access private
+	 *
+	 * @param string $table table name
+	 * @param array $data Data to insert (in column => value pairs).  Both $data columns and $data values should be "raw" (neither should be SQL escaped).
+	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
+	 * 	A format is one of '%d', '%s' (decimal number, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
+	 * @return int|false The number of rows inserted, or false on error.
+	 */
+	function _insert_replace_helper($table, $data, $format = null, $type = 'INSERT') {
+		if ( !in_array( strtoupper($type), array( 'INSERT', 'REPLACE' ) ) )
+			return false;
+
 		$formats = $format = (array) $format;
 		$fields = array_keys( $data );
 		$formatted_fields = array();
@@ -1161,11 +1206,10 @@
 				$form = '%s';
 			$formatted_fields[] = $form;
 		}
-		$sql = "INSERT INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES ('" . implode( "','", $formatted_fields ) . "')";
+		$sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES ('" . implode( "','", $formatted_fields ) . "')";
 		return $this->query( $this->prepare( $sql, $data ) );
 	}
 
-
 	/**
 	 * Update a row in the table
 	 *