我的EF查询大约花了3秒钟来获取10个玩家,因为它获取了另一个表的所有500k +行,而不是我需要的几个。
这是PlayerEntity:
namespace RocketLeagueStats.Database.Entities
{
[Table("players", Schema = "public")]
public class PlayerEntity
{
[Key]
[Column("id")]
public int Id { get; set; }
[Column("unique_id")]
public string UniqueId { get; set; }
[Column("display_name")]
public string DiplayName { get; set; }
[Column("platform_id")]
[JsonIgnore]
public int PlatformId { get; set; }
[ForeignKey("PlatformId")]
public PlatformEntity Platform { get; set; }
[Column("avatar")]
public string Avatar { get; set; }
public PlayerStatsEntity Stats { get; set; }
public List<PlayerRankedEntity> Ranks { get; set; }
[Column("last_requested")]
public DateTime LastRequested { get; set; }
[Column("created_at")]
public DateTime CreatedAt { get; set; }
[Column("updated_at")]
public DateTime UpdatedAt { get; set; }
}
}
这是PlayerRankedEntity:
namespace RocketLeagueStats.Database.Entities
{
[Table("player_ranked", Schema = "public")]
public class PlayerRankedEntity
{
[ForeignKey("Player")]
[Column("player_id")]
[JsonIgnore]
public int PlayerId { get; set; }
[Column("season_id")]
[JsonIgnore]
public int SeasonId { get; set; }
[Column("playlist_id")]
[JsonIgnore]
public int PlaylistId { get; set; }
[Column("matches_played")]
public int MatchesPlayed { get; set; }
[Column("rank_points")]
public int RankPoints { get; set; }
[Column("tier")]
public int Tier { get; set; }
[Column("division")]
public int Division { get; set; }
public PlayerEntity Player { get; set; }
}
}
这是PlayerStatsEntity:
namespace RocketLeagueStats.Database.Entities
{
[Table("player_stats", Schema = "public")]
public class PlayerStatsEntity
{
[Key, ForeignKey("Player")]
[Column("player_id")]
[JsonIgnore]
public int PlayerId { get; set; }
[Column("wins")]
public int Wins { get; set; }
[Column("goals")]
public int Goals { get; set; }
[Column("mvps")]
public int Mvps { get; set; }
[Column("saves")]
public int Saves { get; set; }
[Column("shots")]
public int Shots { get; set; }
[Column("assists")]
public int Assists { get; set; }
public PlayerEntity Player { get; set; }
}
}
这是我的DatabaseContext.OnModelCreating方法:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<PlayerRankedEntity>()
.HasKey(k => new { k.PlayerId, k.SeasonId, k.PlaylistId });
}
这是需要3秒才能完成的代码(如果我删除'.Include(x =&gt; x.Ranks)'只需几毫秒):
using (var database = new DatabaseContext())
{
var serviceProvider = database.GetInfrastructure();
var loggerFactory = serviceProvider.GetService<ILoggerFactory>();
loggerFactory.AddNLog();
var stopwatch = Stopwatch.StartNew();
var players = database.Players
.Include(x => x.Ranks)
.Take(10)
.ToArray();
Console.WriteLine($"Took {stopwatch.ElapsedMilliseconds}ms to fetch {players.Length} players");
}
这是输出,请注意它生成两个查询而不是一个:
2016-10-31 22:50:18.6416 INFO Executed DbCommand (8ms) [Parameters=[@__p_0='?'], CommandType='Text', CommandTimeout='30']
SELECT "x"."id", "x"."avatar", "x"."created_at", "x"."display_name", "x"."last_requested", "x"."platform_id", "x"."unique_id", "x"."updated_at"
FROM "public"."players" AS "x"
ORDER BY "x"."id"
LIMIT @__p_0
2016-10-31 22:50:18.7128 INFO Executed DbCommand (0ms) [Parameters=[@__p_0='?'], CommandType='Text', CommandTimeout='30']
SELECT "p"."player_id", "p"."season_id", "p"."playlist_id", "p"."division", "p"."matches_played", "p"."rank_points", "p"."tier"
FROM "public"."player_ranked" AS "p"
WHERE EXISTS (
SELECT 1
FROM "public"."players" AS "x"
WHERE "p"."player_id" = "x"."id"
LIMIT @__p_0)
ORDER BY "p"."player_id"
Took 3991ms to fetch 10 players
我认为我搞砸了某处的关系,导致它选择所有行。但我不知道我搞砸了什么。
我该如何解决这个问题?我的属性还有其他问题吗?
我正在使用Microsoft.EntityFrameworkCore v1.0.1。
修改:如果我在查询中使用.OrderBy(x => x.CreatedAt)
或.Where(x => x.DiplayName.Contains("mike"))
,则会更快。
生成的查询:
2016-11-01 00:14:15.9638 INFO Executed DbCommand (24ms) [Parameters=[@__p_0='?'], CommandType='Text', CommandTimeout='30']
SELECT "x"."id", "x"."avatar", "x"."created_at", "x"."display_name", "x"."last_requested", "x"."platform_id", "x"."unique_id", "x"."updated_at"
FROM "public"."players" AS "x"
ORDER BY "x"."created_at", "x"."id"
LIMIT @__p_0
2016-11-01 00:14:16.0972 INFO Executed DbCommand (44ms) [Parameters=[@__p_0='?'], CommandType='Text', CommandTimeout='30']
SELECT "p"."player_id", "p"."season_id", "p"."playlist_id", "p"."division", "p"."matches_played", "p"."rank_points", "p"."tier"
FROM "public"."player_ranked" AS "p"
INNER JOIN (
SELECT DISTINCT "x"."created_at", "x"."id"
FROM "public"."players" AS "x"
ORDER BY "x"."created_at", "x"."id"
LIMIT @__p_0
) AS "x0" ON "p"."player_id" = "x0"."id"
ORDER BY "x0"."created_at", "x0"."id"
Took 314ms to fetch 10 players
答案 0 :(得分:1)
EF Core目前是一场噩梦。
您可以尝试以下解决方法(但如果您问我,最好切换回EF6)。
而不是:
var players = database.Players
.Include(x => x.Ranks)
.Take(10)
.ToArray();
使用:
var players = database.Players
.Take(10)
.ToArray();
var playerIds = players.Select(p => p.Id);
database.PlayerRanks.Where(r => playerIds.Contains(r.PlayerId)).Load();
应该产生与Include
相同的效果。