fix(migrations): support MySQL 8.4 checks (#140)

server/app/goauto/migrations/migrate.go

@@ -1,11 +1,26 @@
 package migrations
 
 import (
+	"strings"
+
 	"go-admin/app/goauto/models"
 
 	"gorm.io/gorm"
 )
 
+const mysqlCheckConstraintQuery = `
+SELECT cc.check_clause
+FROM information_schema.table_constraints AS tc
+JOIN information_schema.check_constraints AS cc
+  ON cc.constraint_catalog = tc.constraint_catalog
+ AND cc.constraint_schema = tc.constraint_schema
+ AND cc.constraint_name = tc.constraint_name
+WHERE tc.constraint_schema = DATABASE()
+  AND tc.table_name = ?
+  AND tc.constraint_type = 'CHECK'
+  AND tc.constraint_name = ?
+LIMIT 1`
+
 // Migrate creates the complete GoAuto MVP schema. AutoMigrate is intentionally
 // kept behind this package so the CLI migration and tests use the same model set.
 // MigratedModels is the single source of truth for which models make up the
@@ -68,21 +83,23 @@ func ensureMySQLDirectSelectConstraint(db *gorm.DB) error {
 		return nil
 	}
 	const name = "ck_purchase_task_spec_source"
-	var total, current int64
-	base := `SELECT COUNT(*) FROM information_schema.check_constraints WHERE constraint_schema = DATABASE() AND table_name = 'purchase_task' AND constraint_name = ?`
-	if err := db.Raw(base, name).Scan(&total).Error; err != nil {
+	var constraints []struct {
+		CheckClause string `gorm:"column:check_clause"`
+	}
+	if err := db.Raw(mysqlCheckConstraintQuery, "purchase_task", name).Scan(&constraints).Error; err != nil {
 		return err
 	}
-	if err := db.Raw(base+` AND check_clause LIKE '%direct_select%'`, name).Scan(&current).Error; err != nil {
-		return err
-	}
-	if current > 0 {
+	if len(constraints) > 0 && checkConstraintAllowsDirectSelect(constraints[0].CheckClause) {
 		return nil
 	}
-	if total > 0 {
+	if len(constraints) > 0 {
 		if err := db.Exec("ALTER TABLE purchase_task DROP CHECK " + name).Error; err != nil {
 			return err
 		}
 	}
 	return db.Exec("ALTER TABLE purchase_task ADD CONSTRAINT " + name + " CHECK (spec_source IN ('unresolved','manual_mapping','exact_match','ai_match','direct_select'))").Error
 }
+
+func checkConstraintAllowsDirectSelect(clause string) bool {
+	return strings.Contains(strings.ToLower(clause), "direct_select")
+}

server/app/goauto/migrations/mysql_constraint_test.go

@@ -0,0 +1,43 @@
+package migrations
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestMySQLCheckConstraintQueryUsesTableConstraintsForTableName(t *testing.T) {
+	query := strings.ToLower(mysqlCheckConstraintQuery)
+	for _, required := range []string{
+		"from information_schema.table_constraints as tc",
+		"join information_schema.check_constraints as cc",
+		"tc.table_name = ?",
+		"tc.constraint_type = 'check'",
+		"cc.constraint_schema = tc.constraint_schema",
+		"cc.constraint_name = tc.constraint_name",
+	} {
+		if !strings.Contains(query, required) {
+			t.Fatalf("metadata query missing %q: %s", required, mysqlCheckConstraintQuery)
+		}
+	}
+	if strings.Contains(query, "cc.table_name") {
+		t.Fatalf("MySQL 8.4 CHECK_CONSTRAINTS has no TABLE_NAME column: %s", mysqlCheckConstraintQuery)
+	}
+}
+
+func TestCheckConstraintAllowsDirectSelect(t *testing.T) {
+	for _, test := range []struct {
+		name   string
+		clause string
+		want   bool
+	}{
+		{name: "legacy constraint", clause: "spec_source in ('unresolved','manual_mapping','exact_match','ai_match')", want: false},
+		{name: "upgraded constraint", clause: "spec_source in ('unresolved','manual_mapping','exact_match','ai_match','direct_select')", want: true},
+		{name: "mysql charset prefix", clause: "(`spec_source` in (_utf8mb4'DIRECT_SELECT',_utf8mb4'unresolved'))", want: true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if got := checkConstraintAllowsDirectSelect(test.clause); got != test.want {
+				t.Fatalf("checkConstraintAllowsDirectSelect(%q) = %v, want %v", test.clause, got, test.want)
+			}
+		})
+	}
+}