From 46cb6dc679959227135ad3def0762a8a6ac9cf28 Mon Sep 17 00:00:00 2001
From: Hangjie Mo <mohangjie1995@gmail.com>
Date: Thu, 4 Aug 2022 15:30:06 +0800
Subject: [PATCH] executor: fix column_default with timestamp and bit type
 (#36851)

close pingcap/tidb#36027
---
 executor/infoschema_reader.go      | 17 +++++++++++++----
 executor/infoschema_reader_test.go | 12 ++++++++++++
 executor/show.go                   | 12 +++++++-----
 executor/showtest/show_test.go     |  7 +++++++
 4 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/executor/infoschema_reader.go b/executor/infoschema_reader.go
index eef554e77b..c026ed1f1e 100644
--- a/executor/infoschema_reader.go
+++ b/executor/infoschema_reader.go
@@ -939,10 +939,19 @@ ForColumnsTag:
 		var columnDefault interface{}
 		if columnDesc.DefaultValue != nil {
 			columnDefault = fmt.Sprintf("%v", columnDesc.DefaultValue)
-			if ft.GetType() == mysql.TypeBit {
-				defaultStr := fmt.Sprintf("%v", columnDesc.DefaultValue)
-				defaultValBinaryLiteral := types.BinaryLiteral(defaultStr)
-				columnDefault = defaultValBinaryLiteral.ToBitLiteralString(true)
+			switch col.GetDefaultValue() {
+			case "CURRENT_TIMESTAMP":
+			default:
+				if ft.GetType() == mysql.TypeTimestamp && columnDefault != types.ZeroDatetimeStr {
+					timeValue, err := table.GetColDefaultValue(sctx, col)
+					if err == nil {
+						columnDefault = timeValue.GetMysqlTime().String()
+					}
+				}
+				if ft.GetType() == mysql.TypeBit && !col.DefaultIsExpr {
+					defaultValBinaryLiteral := types.BinaryLiteral(columnDefault.(string))
+					columnDefault = defaultValBinaryLiteral.ToBitLiteralString(true)
+				}
 			}
 		}
 		record := types.MakeDatums(
diff --git a/executor/infoschema_reader_test.go b/executor/infoschema_reader_test.go
index e2eb23122c..b19e8cefbc 100644
--- a/executor/infoschema_reader_test.go
+++ b/executor/infoschema_reader_test.go
@@ -153,6 +153,18 @@ func TestColumnsTables(t *testing.T) {
 	tk.MustQuery("SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 't'").Check(testkit.Rows(
 		"def test t bit 1 b'100' YES bit <nil> <nil> 10 0 <nil> <nil> <nil> bit(10) unsigned   select,insert,update,references  "))
 	tk.MustExec("drop table if exists t")
+
+	tk.MustExec("set time_zone='+08:00'")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (b timestamp(3) NOT NULL DEFAULT '1970-01-01 08:00:01.000')")
+	tk.MustQuery("select column_default from information_schema.columns where TABLE_NAME='t' and TABLE_SCHEMA='test';").Check(testkit.Rows("1970-01-01 08:00:01.000"))
+	tk.MustExec("set time_zone='+04:00'")
+	tk.MustQuery("select column_default from information_schema.columns where TABLE_NAME='t' and TABLE_SCHEMA='test';").Check(testkit.Rows("1970-01-01 04:00:01.000"))
+	tk.MustExec("set time_zone=default")
+
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (a bit DEFAULT (rand()))")
+	tk.MustQuery("select column_default from information_schema.columns where TABLE_NAME='t' and TABLE_SCHEMA='test';").Check(testkit.Rows("rand()"))
 }
 
 func TestEngines(t *testing.T) {
diff --git a/executor/show.go b/executor/show.go
index 938d4f9d62..8f10e78127 100644
--- a/executor/show.go
+++ b/executor/show.go
@@ -1013,13 +1013,15 @@ func ConstructResultOfShowCreateTable(ctx sessionctx.Context, tableInfo *model.T
 						defaultValStr = timeValue.GetMysqlTime().String()
 					}
 
-					if col.GetType() == mysql.TypeBit {
-						defaultValBinaryLiteral := types.BinaryLiteral(defaultValStr)
-						fmt.Fprintf(buf, " DEFAULT %s", defaultValBinaryLiteral.ToBitLiteralString(true))
-					} else if col.DefaultIsExpr {
+					if col.DefaultIsExpr {
 						fmt.Fprintf(buf, " DEFAULT %s", format.OutputFormat(defaultValStr))
 					} else {
-						fmt.Fprintf(buf, " DEFAULT '%s'", format.OutputFormat(defaultValStr))
+						if col.GetType() == mysql.TypeBit {
+							defaultValBinaryLiteral := types.BinaryLiteral(defaultValStr)
+							fmt.Fprintf(buf, " DEFAULT %s", defaultValBinaryLiteral.ToBitLiteralString(true))
+						} else {
+							fmt.Fprintf(buf, " DEFAULT '%s'", format.OutputFormat(defaultValStr))
+						}
 					}
 				}
 			}
diff --git a/executor/showtest/show_test.go b/executor/showtest/show_test.go
index 22fa539175..b3bcf6a1c9 100644
--- a/executor/showtest/show_test.go
+++ b/executor/showtest/show_test.go
@@ -465,6 +465,13 @@ func TestShowCreateTable(t *testing.T) {
 			"  `a` set('a','b') CHARACTER SET binary COLLATE binary DEFAULT NULL,\n"+
 			"  `b` enum('a','b') CHARACTER SET ascii COLLATE ascii_bin DEFAULT NULL\n"+
 			") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin"))
+
+	tk.MustExec(`drop table if exists t`)
+	tk.MustExec(`create table t(a bit default (rand()))`)
+	tk.MustQuery(`show create table t`).Check(testkit.RowsWithSep("|", ""+
+		"t CREATE TABLE `t` (\n"+
+		"  `a` bit(1) DEFAULT rand()\n"+
+		") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin"))
 }
 
 func TestShowCreateTablePlacement(t *testing.T) {