EF6的MySQL子查询性能问题

我遇到了一个问题，MySQL运行以下查询需要30秒以上的时间。扁平化子查询可以简化问题。不幸的是，实体框架（或MySql.Data.Entity实现）也产生了糟糕的投影

我是否需要删除所有EF投影，或者是否有其他选项可供我选择

版本：

• 实体框架v6.1.3
• MySQL v5.7.15
• MySql.Data.Entity v6.9.9

SQL:

作为参考，以下等效查询在一秒钟内进行：

select * from Journals 
where `GeneralLedgerAccountId` = 'abc123' 
and `Synchronized` = 1 limit 1

查询计划：

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "55155.11"
    },
    "ordering_operation": {
      "using_filesort": true,
      "table": {
        "table_name": "Journals",
        "access_type": "ref",
        "possible_keys": [
          "PRIMARY"
        ],
        "key": "PRIMARY",
        "used_key_parts": [
          "GeneralLedgerAccountId"
        ],
        "key_length": "98",
        "ref": [
          "const"
        ],
        "rows_examined_per_scan": 273272,
        "rows_produced_per_join": 27327,
        "filtered": "10.00",
        "cost_info": {
          "read_cost": "500.71",
          "eval_cost": "5465.44",
          "prefix_cost": "55155.11",
          "data_read_per_join": "9M"
        },
        "used_columns": [
          "GeneralLedgerAccountId",
          "Id",
          "Number",
          "Synchronized"
        ],
        "attached_condition": "((`mydb`.`journals`.`GeneralLedgerAccountId` <=> 'abc123') and (`mydb`.`journals`.`Synchronized` = 1))"
      }
    }
  }
}

{
“查询块”：{
“选择id”：1，
“成本信息”：{
“查询成本”：“55155.11”
},
“订购操作”：{
“使用_filesort”：true，
“表格”：{
“表格名称”：“日记账”，
“访问类型”：“ref”，
“可能的_键”：[
“主要”
],
“密钥”：“主要”，
“使用过的关键部件”：[
“GeneralEdgeracCountId”
],
“密钥长度”：“98”，
“参考”：[
“常数”
],
“每次扫描检查的行数”：273272，
“每联接产生的行数”：27327，
“过滤”：“10.00”，
“成本信息”：{
“阅读成本”：“500.71”，
“评估成本”：“5465.44”，
“前缀成本”：“55155.11”，
“每个联接的数据读取”：“9M”
},
“已用列”：[
“GeneralEdgeracCountId”，
“身份证”，
“数字”，
“已同步”
],
“附加条件”：“（`mydb`.`journals`.`GeneralLedgerAccountId`'abc123'）和（`mydb`.`journals`.`Synchronized`=1”）”
}
}
}
}

我也面临同样的问题，你找到解决方案了吗？你有什么索引？这两个查询是不等价的——省略

ORDER BY

会使

限制变得不可预测，并加快查询速度。
{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "55155.11"
    },
    "ordering_operation": {
      "using_filesort": true,
      "table": {
        "table_name": "Journals",
        "access_type": "ref",
        "possible_keys": [
          "PRIMARY"
        ],
        "key": "PRIMARY",
        "used_key_parts": [
          "GeneralLedgerAccountId"
        ],
        "key_length": "98",
        "ref": [
          "const"
        ],
        "rows_examined_per_scan": 273272,
        "rows_produced_per_join": 27327,
        "filtered": "10.00",
        "cost_info": {
          "read_cost": "500.71",
          "eval_cost": "5465.44",
          "prefix_cost": "55155.11",
          "data_read_per_join": "9M"
        },
        "used_columns": [
          "GeneralLedgerAccountId",
          "Id",
          "Number",
          "Synchronized"
        ],
        "attached_condition": "((`mydb`.`journals`.`GeneralLedgerAccountId` <=> 'abc123') and (`mydb`.`journals`.`Synchronized` = 1))"
      }
    }
  }
}