Add user settings key/value DB table (#16834)

models/user/setting.go

@@ -0,0 +1,116 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package user
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/models/db"
+
+	"xorm.io/builder"
+)
+
+// Setting is a key value store of user settings
+type Setting struct {
+	ID           int64  `xorm:"pk autoincr"`
+	UserID       int64  `xorm:"index unique(key_userid)"`              // to load all of someone's settings
+	SettingKey   string `xorm:"varchar(255) index unique(key_userid)"` // ensure key is always lowercase
+	SettingValue string `xorm:"text"`
+}
+
+// TableName sets the table name for the settings struct
+func (s *Setting) TableName() string {
+	return "user_setting"
+}
+
+func init() {
+	db.RegisterModel(new(Setting))
+}
+
+// GetSettings returns specific settings from user
+func GetSettings(uid int64, keys []string) (map[string]*Setting, error) {
+	settings := make([]*Setting, 0, len(keys))
+	if err := db.GetEngine(db.DefaultContext).
+		Where("user_id=?", uid).
+		And(builder.In("setting_key", keys)).
+		Find(&settings); err != nil {
+		return nil, err
+	}
+	settingsMap := make(map[string]*Setting)
+	for _, s := range settings {
+		settingsMap[s.SettingKey] = s
+	}
+	return settingsMap, nil
+}
+
+// GetUserAllSettings returns all settings from user
+func GetUserAllSettings(uid int64) (map[string]*Setting, error) {
+	settings := make([]*Setting, 0, 5)
+	if err := db.GetEngine(db.DefaultContext).
+		Where("user_id=?", uid).
+		Find(&settings); err != nil {
+		return nil, err
+	}
+	settingsMap := make(map[string]*Setting)
+	for _, s := range settings {
+		settingsMap[s.SettingKey] = s
+	}
+	return settingsMap, nil
+}
+
+// DeleteSetting deletes a specific setting for a user
+func DeleteSetting(setting *Setting) error {
+	_, err := db.GetEngine(db.DefaultContext).Delete(setting)
+	return err
+}
+
+// SetSetting updates a users' setting for a specific key
+func SetSetting(setting *Setting) error {
+	if strings.ToLower(setting.SettingKey) != setting.SettingKey {
+		return fmt.Errorf("setting key should be lowercase")
+	}
+	return upsertSettingValue(setting.UserID, setting.SettingKey, setting.SettingValue)
+}
+
+func upsertSettingValue(userID int64, key string, value string) error {
+	return db.WithTx(func(ctx context.Context) error {
+		e := db.GetEngine(ctx)
+
+		// here we use a general method to do a safe upsert for different databases (and most transaction levels)
+		// 1. try to UPDATE the record and acquire the transaction write lock
+		//    if UPDATE returns non-zero rows are changed, OK, the setting is saved correctly
+		//    if UPDATE returns "0 rows changed", two possibilities: (a) record doesn't exist  (b) value is not changed
+		// 2. do a SELECT to check if the row exists or not (we already have the transaction lock)
+		// 3. if the row doesn't exist, do an INSERT (we are still protected by the transaction lock, so it's safe)
+		//
+		// to optimize the SELECT in step 2, we can use an extra column like `revision=revision+1`
+		//    to make sure the UPDATE always returns a non-zero value for existing (unchanged) records.
+
+		res, err := e.Exec("UPDATE user_setting SET setting_value=? WHERE setting_key=? AND user_id=?", value, key, userID)
+		if err != nil {
+			return err
+		}
+		rows, _ := res.RowsAffected()
+		if rows > 0 {
+			// the existing row is updated, so we can return
+			return nil
+		}
+
+		// in case the value isn't changed, update would return 0 rows changed, so we need this check
+		has, err := e.Exist(&Setting{UserID: userID, SettingKey: key})
+		if err != nil {
+			return err
+		}
+		if has {
+			return nil
+		}
+
+		// if no existing row, insert a new row
+		_, err = e.Insert(&Setting{UserID: userID, SettingKey: key, SettingValue: value})
+		return err
+	})
+}