data0data.ic, data0data.h, row0sel.c:

  Fix bug #2483 with InnoDB, UNIQUE secondary index, and NULL values in that unique index; with the IS NULL predicate, InnoDB returned only the first matching row, though there can be many

innobase/include/data0data.h

@@ -262,6 +262,14 @@ dtuple_set_types_binary(
 /*====================*/
 	dtuple_t*	tuple,	/* in: data tuple */
 	ulint		n);	/* in: number of fields to set */
+/**************************************************************************
+Checks if a dtuple contains an SQL null value. */
+UNIV_INLINE
+ibool
+dtuple_contains_null(
+/*=================*/
+				/* out: TRUE if some field is SQL null */
+	dtuple_t*	tuple);	/* in: dtuple */
 /**************************************************************
 Checks that a data field is typed. Asserts an error if not. */
 

innobase/include/data0data.ic

@@ -406,3 +406,28 @@ data_write_sql_null(
 		data[j] = '\0';
 	}
 }
+
+/**************************************************************************
+Checks if a dtuple contains an SQL null value. */
+UNIV_INLINE
+ibool
+dtuple_contains_null(
+/*=================*/
+				/* out: TRUE if some field is SQL null */
+	dtuple_t*	tuple)	/* in: dtuple */
+{
+	ulint	n;
+	ulint	i;
+
+	n = dtuple_get_n_fields(tuple);
+
+	for (i = 0; i < n; i++) {
+		if (dfield_get_len(dtuple_get_nth_field(tuple, i))
+		    == UNIV_SQL_NULL) {
+
+			return(TRUE);
+		}
+	}
+
+	return(FALSE);
+}
\ No newline at end of file

innobase/row/row0sel.c

@@ -2818,7 +2818,16 @@ row_search_for_mysql(
 	if (match_mode == ROW_SEL_EXACT
 	    && index->type & DICT_UNIQUE
 	    && dtuple_get_n_fields(search_tuple)
-				== dict_index_get_n_unique(index)) {
+					== dict_index_get_n_unique(index)
+	    && (index->type & DICT_CLUSTERED
+		 || !dtuple_contains_null(search_tuple))) {
+
+		/* Note above that a UNIQUE secondary index can contain many
+		rows with the same key value if one of the columns is the SQL
+		null. A clustered index under MySQL can never contain null
+		columns because we demand that all the columns in primary key
+		are non-null. */
+
 		unique_search = TRUE;
 
 		/* Even if the condition is unique, MySQL seems to try to