From 0b09873891d31222ac309fe73b291066c28b36a6 Mon Sep 17 00:00:00 2001
From: Icemap <qizhi.wang@pingcap.com>
Date: Sun, 29 Jan 2023 14:03:04 +0800
Subject: [PATCH 1/3] feat: support auto_random through default tag

---
 mysql.go | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/mysql.go b/mysql.go
index 8617eb6..0a68b95 100644
--- a/mysql.go
+++ b/mysql.go
@@ -21,6 +21,10 @@ import (
 	"gorm.io/gorm/utils"
 )
 
+const (
+	AutoRandomTag = "auto_random()" // Treated as an auto_random field for tidb
+)
+
 type Config struct {
 	DriverName                    string
 	ServerVersion                 string
@@ -417,7 +421,32 @@ func (dialector Dialector) getSchemaBytesType(field *schema.Field) string {
 	return "longblob"
 }
 
+// autoRandomType
+// field.DataType MUST be `schema.Int` or `schema.Uint`
+// Judgement logic:
+// 1. Is PrimaryKey;
+// 2. Has default value;
+// 3. Default value is "auto_random()";
+// 4. IGNORE the field.Size, it MUST be bigint;
+// 5. CLEAR the default tag, and return true;
+// 6. Otherwise, return false.
+func autoRandomType(field *schema.Field) (bool, string) {
+	if field.PrimaryKey && field.HasDefaultValue &&
+		strings.ToLower(strings.TrimSpace(field.DefaultValue)) == AutoRandomTag {
+		field.HasDefaultValue = false
+		field.DefaultValue = ""
+
+		return true, "bigint auto_random"
+	}
+
+	return false, ""
+}
+
 func (dialector Dialector) getSchemaIntAndUnitType(field *schema.Field) string {
+	if autoRandom, typeString := autoRandomType(field); autoRandom {
+		return typeString
+	}
+
 	constraint := func(sqlType string) string {
 		if field.DataType == schema.Uint {
 			sqlType += " unsigned"

From 120c47ff4031e3589c266b82f78324bc60cd6b69 Mon Sep 17 00:00:00 2001
From: Icemap <qizhi.wang@pingcap.com>
Date: Mon, 30 Jan 2023 14:43:50 +0800
Subject: [PATCH 2/3] fix: unsigned type support

---
 mysql.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mysql.go b/mysql.go
index 0a68b95..0ddefdd 100644
--- a/mysql.go
+++ b/mysql.go
@@ -436,7 +436,12 @@ func autoRandomType(field *schema.Field) (bool, string) {
 		field.HasDefaultValue = false
 		field.DefaultValue = ""
 
-		return true, "bigint auto_random"
+		sqlType := "bigint"
+		if field.DataType == schema.Uint {
+			sqlType += " unsigned"
+		}
+		sqlType += " auto_random"
+		return true, sqlType
 	}
 
 	return false, ""

From b3a1a34c829a1208cb2d3575316c1e7a8dee6590 Mon Sep 17 00:00:00 2001
From: Icemap <qizhi.wang@pingcap.com>
Date: Mon, 30 Jan 2023 21:30:39 +0800
Subject: [PATCH 3/3] fix: keeping the HasDefaultValue value is true for
 auto_random

---
 mysql.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mysql.go b/mysql.go
index 0ddefdd..9865b55 100644
--- a/mysql.go
+++ b/mysql.go
@@ -433,7 +433,6 @@ func (dialector Dialector) getSchemaBytesType(field *schema.Field) string {
 func autoRandomType(field *schema.Field) (bool, string) {
 	if field.PrimaryKey && field.HasDefaultValue &&
 		strings.ToLower(strings.TrimSpace(field.DefaultValue)) == AutoRandomTag {
-		field.HasDefaultValue = false
 		field.DefaultValue = ""
 
 		sqlType := "bigint"