Fix issue #2218

Author: mzitnik

clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseColumn.java

@@ -249,8 +249,9 @@ private static ClickHouseColumn update(ClickHouseColumn column) {
             case FixedString:
                 if (size > 0) {
                     column.precision = Integer.parseInt(column.parameters.get(0));
-                    if (!column.nullable) {
-                        column.estimatedByteLength += column.precision;
+                    column.estimatedByteLength += column.precision;
+                    if (column.nullable) {
+                        column.estimatedByteLength -= 1;
                     }
                 }
                 column.template = ClickHouseStringValue.ofNull();

jdbc-v2/src/test/java/com/clickhouse/jdbc/StatementTest.java

@@ -573,4 +573,36 @@ public void testSwitchDatabase() throws Exception {
             }
         }
     }
+
+    @Test(groups = { "integration" })
+    public void testNullableFixedStringType() throws Exception {
+        try (Connection conn = getJdbcConnection()) {
+            String sqlCreate = "CREATE TABLE `data_types` (`f1` FixedString(4),`f2` LowCardinality(FixedString(4)), `f3` Nullable(FixedString(4)), `f4` LowCardinality(Nullable(FixedString(4))) ) ENGINE Memory;";
+            try (Statement stmt = conn.createStatement()) {
+                int r = stmt.executeUpdate(sqlCreate);
+                assertEquals(r, 0);
+            }
+            try(Statement stmt = conn.createStatement()) {
+                String sqlInsert = "INSERT INTO `data_types` VALUES ('val1', 'val2', 'val3', 'val4')";
+                int r = stmt.executeUpdate(sqlInsert);
+                assertEquals(r, 1);
+            }
+            try(Statement stmt = conn.createStatement()) {
+                String sqlSelect = "SELECT * FROM `data_types`";
+                ResultSet rs = stmt.executeQuery(sqlSelect);
+                assertTrue(rs.next());
+                assertEquals(rs.getString(1), "val1");
+                assertEquals(rs.getString(2), "val2");
+                assertEquals(rs.getString(3), "val3");
+                assertEquals(rs.getString(4), "val4");
+                assertFalse(rs.next());
+            }
+            try(Statement stmt = conn.createStatement()) {
+                String sqlSelect = "SELECT f4 FROM `data_types`";
+                ResultSet rs = stmt.executeQuery(sqlSelect);
+                assertTrue(rs.next());
+                assertEquals(rs.getString(1), "val4");
+            }
+        }
+    }
 }