From c6511a0dc6c882ba5e8868d07dbd98968da5d582 Mon Sep 17 00:00:00 2001
From: "Laisky.Cai" <public@laisky.com>
Date: Fri, 3 Sep 2021 05:46:22 +0000
Subject: [PATCH] feat: support unique

---
 clause/on_conflict.go |  2 +-
 model.go              |  7 ++++
 schema/index.go       | 20 +++++++++++
 soft_delete_unique.go | 80 +++++++++++++++++++++++++++++++++++++++++++
 tests/query_test.go   |  2 +-
 5 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 soft_delete_unique.go

diff --git a/clause/on_conflict.go b/clause/on_conflict.go
index 64ee7f53..309c5fcd 100644
--- a/clause/on_conflict.go
+++ b/clause/on_conflict.go
@@ -26,7 +26,7 @@ func (onConflict OnConflict) Build(builder Builder) {
 		}
 		builder.WriteString(`) `)
 	}
-	
+
 	if len(onConflict.TargetWhere.Exprs) > 0 {
 		builder.WriteString(" WHERE ")
 		onConflict.TargetWhere.Build(builder)
diff --git a/model.go b/model.go
index 3334d17c..201ced5e 100644
--- a/model.go
+++ b/model.go
@@ -13,3 +13,10 @@ type Model struct {
 	UpdatedAt time.Time
 	DeletedAt DeletedAt `gorm:"index"`
 }
+
+type ModelSupportUnique struct {
+	ID          uint `gorm:"primarykey"`
+	CreatedAt   time.Time
+	UpdatedAt   time.Time
+	DeletedFlag DeletedFlag `gorm:"type:BIGINT UNSIGNED NOT NULL DEFAULT 0" json:"deleted_flag"`
+}
diff --git a/schema/index.go b/schema/index.go
index b54e08ad..ce501cc0 100644
--- a/schema/index.go
+++ b/schema/index.go
@@ -51,6 +51,26 @@ func (schema *Schema) ParseIndexes() map[string]Index {
 				}
 
 				idx.Fields = append(idx.Fields, index.Fields...)
+
+				// create combined index for unique
+				if index.Class == "UNIQUE" {
+					if df := schema.LookUpField("deleted_flag"); df != nil {
+						var exists bool
+						for _, f := range idx.Fields {
+							if f.Field.Name == df.Name {
+								exists = true
+								break
+							}
+						}
+
+						if !exists {
+							idx.Fields = append(idx.Fields, IndexOption{
+								Field: df,
+							})
+						}
+					}
+				}
+
 				sort.Slice(idx.Fields, func(i, j int) bool {
 					return idx.Fields[i].priority < idx.Fields[j].priority
 				})
diff --git a/soft_delete_unique.go b/soft_delete_unique.go
new file mode 100644
index 00000000..bb58fd25
--- /dev/null
+++ b/soft_delete_unique.go
@@ -0,0 +1,80 @@
+package gorm
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"gorm.io/gorm/clause"
+	"gorm.io/gorm/schema"
+)
+
+type DeletedFlag uint
+
+// // Scan implements the Scanner interface.
+// func (n *DeletedFlag) Scan(value interface{}) error {
+// 	return (*sql.NullTime)(n).Scan(value)
+// }
+
+// // Value implements the driver Valuer interface.
+// func (n DeletedFlag) Value() (driver.Value, error) {
+// 	if !n.Valid {
+// 		return nil, nil
+// 	}
+// 	return n.Time, nil
+// }
+
+// func (n DeletedFlag) MarshalJSON() ([]byte, error) {
+// 	if n.Valid {
+// 		return json.Marshal(n.Time)
+// 	}
+// 	return json.Marshal(nil)
+// }
+
+// func (n *DeletedFlag) UnmarshalJSON(b []byte) error {
+// 	if string(b) == "null" {
+// 		n.Valid = false
+// 		return nil
+// 	}
+// 	err := json.Unmarshal(b, &n.Time)
+// 	if err == nil {
+// 		n.Valid = true
+// 	}
+// 	return err
+// }
+
+func (DeletedFlag) QueryClauses(f *schema.Field) []clause.Interface {
+	return []clause.Interface{SoftDeleteQueryClause{Field: f}}
+}
+
+func (DeletedFlag) DeleteClauses(f *schema.Field) []clause.Interface {
+	return []clause.Interface{SoftDeleteUniqueDeleteClause{Field: f}}
+}
+
+type SoftDeleteUniqueDeleteClause struct {
+	Field *schema.Field
+}
+
+func (sd SoftDeleteUniqueDeleteClause) Name() string {
+	return ""
+}
+
+func (sd SoftDeleteUniqueDeleteClause) Build(clause.Builder) {
+}
+
+func (sd SoftDeleteUniqueDeleteClause) MergeClause(*clause.Clause) {
+}
+
+func (sd SoftDeleteUniqueDeleteClause) ModifyStatement(stmt *Statement) {
+	re := regexp.MustCompile(`UPDATE (.*) WHERE `)
+	if sql := stmt.SQL.String(); sql != "" {
+		setClause := re.FindStringSubmatch(sql)[1]
+		if setClause == "" {
+			return
+		}
+
+		newSetClause := fmt.Sprintf("%s, %s = `%s`.`id`", setClause, sd.Field.DBName, stmt.Table)
+		stmt.SQL.Reset()
+		stmt.SQL.WriteString(strings.Replace(sql, setClause, newSetClause, 1))
+	}
+}
diff --git a/tests/query_test.go b/tests/query_test.go
index 8a476598..e3321ed7 100644
--- a/tests/query_test.go
+++ b/tests/query_test.go
@@ -440,7 +440,7 @@ func TestNot(t *testing.T) {
 	if !regexp.MustCompile("SELECT \\* FROM .*users.* WHERE .*name.* IS NOT NULL").MatchString(result.Statement.SQL.String()) {
 		t.Fatalf("Build NOT condition, but got %v", result.Statement.SQL.String())
 	}
-	
+
 	result = dryDB.Not(map[string]interface{}{"name": []string{"jinzhu", "jinzhu 2"}}).Find(&User{})
 	if !regexp.MustCompile("SELECT \\* FROM .*users.* WHERE .*name.* NOT IN \\(.+,.+\\)").MatchString(result.Statement.SQL.String()) {
 		t.Fatalf("Build NOT condition, but got %v", result.Statement.SQL.String())