我正在寻找插入实体框架的最快方法。
我之所以问这个问题,是因为您有一个活动的TransactionScope,并且插入量很大(4000+)。它可能会持续超过10分钟(事务的默认超时),这将导致事务不完整。
我正在寻找插入实体框架的最快方法。
我之所以问这个问题,是因为您有一个活动的TransactionScope,并且插入量很大(4000+)。它可能会持续超过10分钟(事务的默认超时),这将导致事务不完整。
当前回答
因为这里从未提到过,我想在这里重新推荐EFCore.BulkExtensions
context.BulkInsert(entitiesList); context.BulkInsertAsync(entitiesList);
context.BulkUpdate(entitiesList); context.BulkUpdateAsync(entitiesList);
context.BulkDelete(entitiesList); context.BulkDeleteAsync(entitiesList);
context.BulkInsertOrUpdate(entitiesList); context.BulkInsertOrUpdateAsync(entitiesList); // Upsert
context.BulkInsertOrUpdateOrDelete(entitiesList); context.BulkInsertOrUpdateOrDeleteAsync(entitiesList); // Sync
context.BulkRead(entitiesList); context.BulkReadAsync(entitiesList);
其他回答
SqlBulkCopy速度极快
这是我的实现:
// at some point in my calling code, I will call:
var myDataTable = CreateMyDataTable();
myDataTable.Rows.Add(Guid.NewGuid,tableHeaderId,theName,theValue); // e.g. - need this call for each row to insert
var efConnectionString = ConfigurationManager.ConnectionStrings["MyWebConfigEfConnection"].ConnectionString;
var efConnectionStringBuilder = new EntityConnectionStringBuilder(efConnectionString);
var connectionString = efConnectionStringBuilder.ProviderConnectionString;
BulkInsert(connectionString, myDataTable);
private DataTable CreateMyDataTable()
{
var myDataTable = new DataTable { TableName = "MyTable"};
// this table has an identity column - don't need to specify that
myDataTable.Columns.Add("MyTableRecordGuid", typeof(Guid));
myDataTable.Columns.Add("MyTableHeaderId", typeof(int));
myDataTable.Columns.Add("ColumnName", typeof(string));
myDataTable.Columns.Add("ColumnValue", typeof(string));
return myDataTable;
}
private void BulkInsert(string connectionString, DataTable dataTable)
{
using (var connection = new SqlConnection(connectionString))
{
connection.Open();
SqlTransaction transaction = null;
try
{
transaction = connection.BeginTransaction();
using (var sqlBulkCopy = new SqlBulkCopy(connection, SqlBulkCopyOptions.TableLock, transaction))
{
sqlBulkCopy.DestinationTableName = dataTable.TableName;
foreach (DataColumn column in dataTable.Columns) {
sqlBulkCopy.ColumnMappings.Add(column.ColumnName, column.ColumnName);
}
sqlBulkCopy.WriteToServer(dataTable);
}
transaction.Commit();
}
catch (Exception)
{
transaction?.Rollback();
throw;
}
}
}
TL;博士我知道这是一个老帖子,但我已经实施了一个解决方案,从其中一个提议开始,扩展它并解决其中的一些问题;此外,我还阅读了所提出的其他解决方案,与这些方案相比,我似乎提出了一种更适合原始问题中提出的要求的解决方案。
在这个解决方案中,我扩展了Slauma的方法,我认为它非常适合原始问题中提出的情况,即使用实体框架和事务范围对数据库进行昂贵的写入操作。
在Slauma的解决方案中,这只是一个草稿,只是用来了解EF的速度与实施批量插入的策略-存在以下问题:
交易超时(默认情况下,1分钟可通过代码延长至最多10分钟);复制宽度等于事务结束时使用的提交大小的第一个数据块(这个问题很奇怪,可以通过变通方法解决)。
我还报告了一个例子,其中包括几个从属实体的上下文插入,从而扩展了Slauma提出的案例研究。
我能够验证的性能是10K记录/分钟,在数据库中插入200K宽的记录块,每个记录块大约1KB。速度是恒定的,性能没有下降,测试需要大约20分钟才能成功运行。
详细的解决方案
主持在示例存储库类中插入的批量插入操作的方法:
abstract class SomeRepository {
protected MyDbContext myDbContextRef;
public void ImportData<TChild, TFather>(List<TChild> entities, TFather entityFather)
where TChild : class, IEntityChild
where TFather : class, IEntityFather
{
using (var scope = MyDbContext.CreateTransactionScope())
{
MyDbContext context = null;
try
{
context = new MyDbContext(myDbContextRef.ConnectionString);
context.Configuration.AutoDetectChangesEnabled = false;
entityFather.BulkInsertResult = false;
var fileEntity = context.Set<TFather>().Add(entityFather);
context.SaveChanges();
int count = 0;
//avoids an issue with recreating context: EF duplicates the first commit block of data at the end of transaction!!
context = MyDbContext.AddToContext<TChild>(context, null, 0, 1, true);
foreach (var entityToInsert in entities)
{
++count;
entityToInsert.EntityFatherRefId = fileEntity.Id;
context = MyDbContext.AddToContext<TChild>(context, entityToInsert, count, 100, true);
}
entityFather.BulkInsertResult = true;
context.Set<TFather>().Add(fileEntity);
context.Entry<TFather>(fileEntity).State = EntityState.Modified;
context.SaveChanges();
}
finally
{
if (context != null)
context.Dispose();
}
scope.Complete();
}
}
}
仅用于示例目的的接口:
public interface IEntityChild {
//some properties ...
int EntityFatherRefId { get; set; }
}
public interface IEntityFather {
int Id { get; set; }
bool BulkInsertResult { get; set; }
}
db上下文中,我将解决方案的各个元素实现为静态方法:
public class MyDbContext : DbContext
{
public string ConnectionString { get; set; }
public MyDbContext(string nameOrConnectionString)
: base(nameOrConnectionString)
{
Database.SetInitializer<MyDbContext>(null);
ConnectionString = Database.Connection.ConnectionString;
}
/// <summary>
/// Creates a TransactionScope raising timeout transaction to 30 minutes
/// </summary>
/// <param name="_isolationLevel"></param>
/// <param name="timeout"></param>
/// <remarks>
/// It is possible to set isolation-level and timeout to different values. Pay close attention managing these 2 transactions working parameters.
/// <para>Default TransactionScope values for isolation-level and timeout are the following:</para>
/// <para>Default isolation-level is "Serializable"</para>
/// <para>Default timeout ranges between 1 minute (default value if not specified a timeout) to max 10 minute (if not changed by code or updating max-timeout machine.config value)</para>
/// </remarks>
public static TransactionScope CreateTransactionScope(IsolationLevel _isolationLevel = IsolationLevel.Serializable, TimeSpan? timeout = null)
{
SetTransactionManagerField("_cachedMaxTimeout", true);
SetTransactionManagerField("_maximumTimeout", timeout ?? TimeSpan.FromMinutes(30));
var transactionOptions = new TransactionOptions();
transactionOptions.IsolationLevel = _isolationLevel;
transactionOptions.Timeout = TransactionManager.MaximumTimeout;
return new TransactionScope(TransactionScopeOption.Required, transactionOptions);
}
private static void SetTransactionManagerField(string fieldName, object value)
{
typeof(TransactionManager).GetField(fieldName, BindingFlags.NonPublic | BindingFlags.Static).SetValue(null, value);
}
/// <summary>
/// Adds a generic entity to a given context allowing commit on large block of data and improving performance to support db bulk-insert operations based on Entity Framework
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="context"></param>
/// <param name="entity"></param>
/// <param name="count"></param>
/// <param name="commitCount">defines the block of data size</param>
/// <param name="recreateContext"></param>
/// <returns></returns>
public static MyDbContext AddToContext<T>(MyDbContext context, T entity, int count, int commitCount, bool recreateContext) where T : class
{
if (entity != null)
context.Set<T>().Add(entity);
if (count % commitCount == 0)
{
context.SaveChanges();
if (recreateContext)
{
var contextConnectionString = context.ConnectionString;
context.Dispose();
context = new MyDbContext(contextConnectionString);
context.Configuration.AutoDetectChangesEnabled = false;
}
}
return context;
}
}
使用此技术可以提高实体框架中插入记录的速度。这里我使用一个简单的存储过程来插入记录。为了执行这个存储过程,我使用实体框架的.FromSql()方法来执行Raw SQL。
存储过程代码:
CREATE PROCEDURE TestProc
@FirstParam VARCHAR(50),
@SecondParam VARCHAR(50)
AS
Insert into SomeTable(Name, Address) values(@FirstParam, @SecondParam)
GO
接下来,循环遍历所有4000条记录,并添加执行存储的
该过程每100次循环一次。
为此,我创建了一个字符串查询来执行这个过程,并继续将每一组记录附加到它。
然后检查循环是否以100的倍数运行,在这种情况下,使用.FromSql()执行它。
所以对于4000条记录,我只需要执行以下步骤4000/100=40次。
检查以下代码:
string execQuery = "";
var context = new MyContext();
for (int i = 0; i < 4000; i++)
{
execQuery += "EXEC TestProc @FirstParam = 'First'" + i + "'', @SecondParam = 'Second'" + i + "''";
if (i % 100 == 0)
{
context.Student.FromSql(execQuery);
execQuery = "";
}
}
Configuration.LazyLoadingEnabled=false;Configuration.ProxyCreationEnabled=false;
如果没有AutoDetectChangesEnabled=false,这些速度太快;我建议使用不同于dbo的表头。通常我使用nop、sop、tbl等。。
〔2019更新〕EF Core 3.1
如上所述,在EF Core中禁用AutoDetectChangesEnabled非常有效:插入时间除以100(从几分钟到几秒,10k条记录具有交叉表关系)
更新的代码为:
context.ChangeTracker.AutoDetectChangesEnabled = false;
foreach (IRecord record in records) {
//Add records to your database
}
context.ChangeTracker.DetectChanges();
context.SaveChanges();
context.ChangeTracker.AutoDetectChangesEnabled = true; //do not forget to re-enable