当需要存储相关的数据集和收集统计信息，例如answer -> queustion给答案或问题投票时，Redis集合就非常好使。假设我们有很多的问题（queustion）和答案（answer ），需要将它们存储在缓存中。使用Redis，我们可以这么做：
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/// <summary>
/// Gets or sets the Redis Manager. The built-in IoC used with ServiceStack autowires this property.
/// </summary>
IRedisClientsManager RedisManager { get; set; }
/// <summary>
/// Delete question by performing compensating actions to
/// StoreQuestion() to keep the datastore in a consistent state
/// </summary>
/// <param name="questionId">
public void DeleteQuestion(long questionId)
{
using (var redis = RedisManager.GetClient())
{
var redisQuestions = redis.As<question>();
var question = redisQuestions.GetById(questionId);
if (question == null) return;
//decrement score in tags list
question.Tags.ForEach(tag => redis.IncrementItemInSortedSet("urn:tags", tag, -1));
//remove all related answers
redisQuestions.DeleteRelatedEntities<answer>(questionId);
//remove this question from user index
redis.RemoveItemFromSet("urn:user>q:" + question.UserId, questionId.ToString());
//remove tag => questions index for each tag
question.Tags.ForEach("urn:tags>q:" + tag.ToLower(), questionId.ToString()));
redisQuestions.DeleteById(questionId);
}
}
public void StoreQuestion(Question question)
{
using (var redis = RedisManager.GetClient())
{
var redisQuestions = redis.As<question>();
if (question.Tags == null) question.Tags = new List<string>();
if (question.Id == default(long))
{
question.Id = redisQuestions.GetNextSequence();
question.CreatedDate = DateTime.UtcNow;
//Increment the popularity for each new question tag
question.Tags.ForEach(tag => redis.IncrementItemInSortedSet("urn:tags", tag, 1));
}
redisQuestions.Store(question);
redisQuestions.AddToRecentsList(question);
redis.AddItemToSet("urn:user>q:" + question.UserId, question.Id.ToString());
//Usage of tags - Populate tag => questions index for each tag
question.Tags.ForEach(tag => redis.AddItemToSet
("urn:tags>q:" + tag.ToLower(), question.Id.ToString()));
}
}
/// <summary>
/// Delete Answer by performing compensating actions to
/// StoreAnswer() to keep the datastore in a consistent state
/// </summary>
/// <param name="questionId">
/// <param name="answerId">
public void DeleteAnswer(long questionId, long answerId)
{
using (var redis = RedisManager.GetClient())
{
var answer = redis.As<question>().GetRelatedEntities<answer>
(questionId).FirstOrDefault(x => x.Id == answerId);
if (answer == null) return;
redis.As<question>().DeleteRelatedEntity<answer>(questionId, answerId);
//remove user => answer index
redis.RemoveItemFromSet("urn:user>a:" + answer.UserId, answerId.ToString());
}
}
public void StoreAnswer(Answer answer)
{
using (var redis = RedisManager.GetClient())
{
if (answer.Id == default(long))
{
answer.Id = redis.As<answer>().GetNextSequence();
answer.CreatedDate = DateTime.UtcNow;
}
//Store as a 'Related Answer' to the parent Question
redis.As<question>().StoreRelatedEntities(answer.QuestionId, answer);
//Populate user => answer index
redis.AddItemToSet("urn:user>a:" + answer.UserId, answer.Id.ToString());
}
}
public List<answer> GetAnswersForQuestion(long questionId)
{
using (var redis = RedisManager.GetClient())
{
return redis.As<question>().GetRelatedEntities<answer>(questionId);
}
}
public void VoteQuestionUp(long userId, long questionId)
{
//Populate Question => User and User => Question set indexes in a single transaction
RedisManager.ExecTrans(trans =>
{
//Register upvote against question and remove any downvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:q>user+:" + questionId, userId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:q>user-:" + questionId, userId.ToString()));
//Register upvote against user and remove any downvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:user>q+:" + userId, questionId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:user>q-:" + userId, questionId.ToString()));
});
}
public void VoteQuestionDown(long userId, long questionId)
{
//Populate Question => User and User => Question set indexes in a single transaction
RedisManager.ExecTrans(trans =>
{
//Register downvote against question and remove any upvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:q>user-:" + questionId, userId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:q>user+:" + questionId, userId.ToString()));
//Register downvote against user and remove any upvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet"urn:user>q-:" + userId, questionId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:user>q+:" + userId, questionId.ToString()));
});
}
public void VoteAnswerUp(long userId, long answerId)
{
//Populate Question => User and User => Question set indexes in a single transaction
RedisManager.ExecTrans(trans =>
{
//Register upvote against answer and remove any downvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:a>user+:" + answerId, userId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:a>user-:" + answerId, userId.ToString()));
//Register upvote against user and remove any downvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:user>a+:" + userId, answerId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:user>a-:" + userId, answerId.ToString()));
});
}
public void VoteAnswerDown(long userId, long answerId)
{
//Populate Question => User and User => Question set indexes in a single transaction
RedisManager.ExecTrans(trans =>
{
//Register downvote against answer and remove any upvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:a>user-:" + answerId, userId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:a>user+:" + answerId, userId.ToString()));
//Register downvote against user and remove any upvotes if any
trans.QueueCommand(redis =>
redis.AddItemToSet("urn:user>a-:" + userId, answerId.ToString()));
trans.QueueCommand(redis =>
redis.RemoveItemFromSet("urn:user>a+:" + userId, answerId.ToString()));
});
}
public QuestionResult GetQuestion(long questionId)
{
var question = RedisManager.ExecAs<question>
(redisQuestions => redisQuestions.GetById(questionId));
if (question == null) return null;
var result = ToQuestionResults(new[] { question })[0];
var answers = GetAnswersForQuestion(questionId);
var uniqueUserIds = answers.ConvertAll(x => x.UserId).ToHashSet();
var usersMap = GetUsersByIds(uniqueUserIds).ToDictionary(x => x.Id);
result.Answers = answers.ConvertAll(answer =>
new AnswerResult { Answer = answer, User = usersMap[answer.UserId] });
return result;
}
public List<user> GetUsersByIds(IEnumerable<long> userIds)
{
return RedisManager.ExecAs<user>(redisUsers => redisUsers.GetByIds(userIds)).ToList();
}
public QuestionStat GetQuestionStats(long questionId)
{
using (var redis = RedisManager.GetReadOnlyClient())
{
var result = new QuestionStat
{
VotesUpCount = redis.GetSetCount("urn:q>user+:" +questionId),
VotesDownCount = redis.GetSetCount("urn:q>user-:" + questionId)
};
result.VotesTotal = result.VotesUpCount - result.VotesDownCount;
return result;
}
}
public List<tag> GetTagsByPopularity(int skip, int take)
{
using (var redis = RedisManager.GetReadOnlyClient())
{
var tagEntries = redis.GetRangeWithScoresFromSortedSetDesc("urn:tags", skip, take);
var tags = tagEntries.ConvertAll(kvp => new Tag { Name = kvp.Key, Score = (int)kvp.Value });
return tags;
}
}
public SiteStats GetSiteStats()
{
using (var redis = RedisManager.GetClient())
{
return new SiteStats
{
QuestionsCount = redis.As<question>().TypeIdsSet.Count,
AnswersCount = redis.As<answer>().TypeIdsSet.Count,
TopTags = GetTagsByPopularity(0, 10)
};
}
}
