From 88f947dfe514851d656121fd17d035607eb7b214 Mon Sep 17 00:00:00 2001
From: wangzhiqiang <wzq@123456>
Date: Mon, 28 Dec 2020 23:58:23 +0800
Subject: [PATCH] [fix] describe sometimes not work

---
 .../table/gateway/operation/DescribeTableOperation.java   | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/main/java/com/ververica/flink/table/gateway/operation/DescribeTableOperation.java b/src/main/java/com/ververica/flink/table/gateway/operation/DescribeTableOperation.java
index 39c6763..b155b2b 100644
--- a/src/main/java/com/ververica/flink/table/gateway/operation/DescribeTableOperation.java
+++ b/src/main/java/com/ververica/flink/table/gateway/operation/DescribeTableOperation.java
@@ -85,10 +85,10 @@ public ResultSet execute() {
 			boolean isNullable = logicalType.isNullable();
 			String key = fieldToPrimaryKey.getOrDefault(column.getName(), null);
 
-			/**
-			 * todo
-			 */
-			String computedColumn = ((TableColumn.ComputedColumn)column).getExpression();
+			String computedColumn = null;
+			if (column instanceof TableColumn.ComputedColumn) {
+				computedColumn = ((TableColumn.ComputedColumn) column).getExpression();
+			}
 			String watermark = fieldToWatermark.getOrDefault(column.getName(), null);
 
 			data.add(Row.of(name, type, isNullable, key, computedColumn, watermark));