EF/EFCore擴展支持with(nolock)查詢

sqlserver執行sql的時候是帶有lock的，這樣可能會造成死鎖現象

 

在使用ef/efcore時，生成的sql都是帶有lock的，所以當使用ef組件時，需要單獨設置一下with nolock

1. net fx集成

我的項目基於net fx4.6.1，ef版本是6.1.3版本

 

首先在項目中增加WithNoLockInterceptor

/// <summary>
    /// ef實現withnolock，給表名后面添加with(nolock)，不適用.net core
    /// </summary>
    public class WithNoLockInterceptor : DbCommandInterceptor
    {
        private static readonly Regex TableAliasRegex = new Regex(@"(?<tableAlias>\[dbo\].\[\w+\] AS \[Extent\d+\](?! WITH\(NOLOCK\)))", RegexOptions.Multiline | RegexOptions.IgnoreCase);

        /// <summary>
        /// https://www.bbsmax.com/A/8Bz8V6V65x/
        /// 建議不要為標記為 ThreadStaticAttribute 的字段指定初始值，因為這樣的初始化只會發生一次，因此在類構造函數執行時只會影響一個線程。
        /// 在不指定初始值的情況下，如果它是值類型，可依賴初始化為其默認值的字段，如果它是引用類型，則可依賴初始化為空引用的字段。
        /// </summary>
        [ThreadStatic]
        public static bool Uselocking;

        [ThreadStatic]
        public static string CommandText;

        public override void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
        {
            if (!Uselocking)
            {
                command.CommandText = TableAliasRegex.Replace(command.CommandText, "${tableAlias} WITH(NOLOCK) ");
                CommandText = command.CommandText;
            }
        }

        public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            if (!Uselocking)
            {
                command.CommandText = TableAliasRegex.Replace(command.CommandText, "${tableAlias} WITH(NOLOCK) ");
                CommandText = command.CommandText;
            }
        }
    }

　　然后在Global.asax.cs里面添加引用

DbInterception.Add(new WithNoLockInterceptor());

 

 

這樣全局設置，可能有些sql想帶lock，所以新建一個擴展類：

WithNoLockUtility

public static class WithNoLockUtility
    {
        /// <summary>
        /// 部分查詢需要使用鎖查詢的，可以調用此擴展（默認全局查詢使用with(nolock)）
        /// 參考：https://github.com/aspnetboilerplate/aspnetboilerplate/issues/1637/
        /// 示例：
        /// 1、query.OrderByCustom(filters.orderFields).Select({...}).UseLocking(querable => querable.PagingAsync(filters.page, filters.rows));
        /// 2、repository.EntitiesAsNoTracking.Select(...).UseLocking(item=>item.FirstOrDefaultAsync());
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="query"></param>
        /// <param name="queryAction"></param>
        /// <returns></returns>
        public static TResult UseLocking<T, TResult>(this IQueryable<T> query, Func<IQueryable<T>, TResult> queryAction)
        {
            WithNoLockInterceptor.Uselocking = true;

            TResult queryableResult = default(TResult);
            try
            {
                queryableResult = queryAction(query);
            }
            finally
            {
                WithNoLockInterceptor.Uselocking = false;
            }

            return queryableResult;
        }
    }

　　使用方式參考示例，不過這個方法我沒有測試使用

2. netcore集成

這個直接參考這一篇文章：https://www.cnblogs.com/weihanli/p/12623934.html

使用攔截器：

public class QueryWithNoLockDbCommandInterceptor : DbCommandInterceptor
{
    private static readonly Regex TableAliasRegex =
        new Regex(@"(?<tableAlias>AS \[[a-zA-Z]\w*\](?! WITH \(NOLOCK\)))",
            RegexOptions.Multiline | RegexOptions.Compiled | RegexOptions.IgnoreCase);

    public override InterceptionResult<object> ScalarExecuting(DbCommand command, CommandEventData eventData, InterceptionResult<object> result)
    {
        command.CommandText = TableAliasRegex.Replace(
            command.CommandText,
            "${tableAlias} WITH (NOLOCK)"
            );
        return base.ScalarExecuting(command, eventData, result);
    }

    public override Task<InterceptionResult<object>> ScalarExecutingAsync(DbCommand command, CommandEventData eventData, InterceptionResult<object> result,
        CancellationToken cancellationToken = new CancellationToken())
    {
        command.CommandText = TableAliasRegex.Replace(
            command.CommandText,
            "${tableAlias} WITH (NOLOCK)"
            );
        return base.ScalarExecutingAsync(command, eventData, result, cancellationToken);
    }

    public override InterceptionResult<DbDataReader> ReaderExecuting(DbCommand command, CommandEventData eventData, InterceptionResult<DbDataReader> result)
    {
        command.CommandText = TableAliasRegex.Replace(
            command.CommandText,
            "${tableAlias} WITH (NOLOCK)"
            );
        return result;
    }

    public override Task<InterceptionResult<DbDataReader>> ReaderExecutingAsync(DbCommand command, CommandEventData eventData, InterceptionResult<DbDataReader> result,
        CancellationToken cancellationToken = new CancellationToken())
    {
        command.CommandText = TableAliasRegex.Replace(
            command.CommandText,
            "${tableAlias} WITH (NOLOCK)"
            );
        return base.ReaderExecutingAsync(command, eventData, result, cancellationToken);
    }
}

　　然后在configservice里面添加

var services = new ServiceCollection();
services.AddDbContext<TestDbContext>(options =>
{
    options
        .UseLoggerFactory(loggerFactory)
        .UseSqlServer(DbConnectionString)
        .AddInterceptors(new QueryWithNoLockDbCommandInterceptor())
        ;
});

　　這樣就可以全局開啟with nolock了

 

以上均是參考網上資料寫的，mark一下防止丟失

參考：

1.https://www.cnblogs.com/weihanli/p/12623934.html

2.https://www.cnblogs.com/slyzly/articles/11452341.html