Use buffersize to reduce database connection when iterate (#2724)

* use buffersize to reduce database connection when iterate

* fix typo

* add default value on app.ini comment

modules/setting/setting.go

@@ -480,15 +480,16 @@ var (
 	ShowFooterTemplateLoadTime bool
 
 	// Global setting objects
-	Cfg           *ini.File
-	CustomPath    string // Custom directory path
-	CustomConf    string
-	CustomPID     string
-	ProdMode      bool
-	RunUser       string
-	IsWindows     bool
-	HasRobotsTxt  bool
-	InternalToken string // internal access token
+	Cfg               *ini.File
+	CustomPath        string // Custom directory path
+	CustomConf        string
+	CustomPID         string
+	ProdMode          bool
+	RunUser           string
+	IsWindows         bool
+	HasRobotsTxt      bool
+	InternalToken     string // internal access token
+	IterateBufferSize int
 )
 
 // DateLang transforms standard language locale name to corresponding value in datetime plugin.
@@ -873,6 +874,7 @@ func NewContext() {
 			log.Fatal(4, "Error saving generated JWT Secret to custom config: %v", err)
 		}
 	}
+	IterateBufferSize = Cfg.Section("database").Key("ITERATE_BUFFER_SIZE").MustInt(50)
 
 	sec = Cfg.Section("attachment")
 	AttachmentPath = sec.Key("PATH").MustString(path.Join(AppDataPath, "attachments"))