[英]What is the fastest way to compare two tables?
例如,有兩個表具有相同的架構,但是內容不同:
表格1
| field1 | field2 | field3 |
----------------------------------------
| 1 | aaaaa | 100 |
| 2 | bbbbb | 200 |
| 3 | ccccc | 300 |
| 4 | ddddd | 400 |
表2
| field1 | field2 | field3 |
----------------------------------------
| 2 | xxxxx | 200 |
| 3 | ccccc | 999 |
| 4 | ddddd | 400 |
| 5 | eeeee | 500 |
預期的比較結果將是:
在B中刪除:
| 1 | aaaaa | 100 |
不匹配:
Table1:| 2 | bbbbb | 200 |
Table2:| 2 | xxxxx | 200 |
Table1:| 3 | ccccc | 300 |
Table2:| 3 | ccccc | 999 |
在B中新增
| 5 | eeeee | 500 |
使用C#,比較兩個表的最快方法是什么?
當前我的實現是:檢查table1中的每一行在table2中是否完全匹配; 檢查表2中的每一行在表1中是否完全匹配。
效率為n*n
因此對於100k行,在服務器上運行需要20分鍾。
非常感謝
您可以嘗試這樣的操作,應該很快:
class objType
{
public int Field1 { get; set; }
public string Field2 { get; set; }
public int Field3 { get; set; }
public bool AreEqual(object other)
{
var otherType = other as objType;
if (otherType == null)
return false;
return Field1 == otherType.Field1 && Field2 == otherType.Field2 && Field3 == otherType.Field3;
}
}
var tableOne = new objType[] {
new objType { Field1 = 1, Field2 = "aaaa", Field3 = 100 },
new objType { Field1 = 2, Field2 = "bbbb", Field3 = 200 },
new objType { Field1 = 3, Field2 = "cccc", Field3 = 300 },
new objType { Field1 = 4, Field2 = "dddd", Field3 = 400 }
};
var tableTwo = new objType[] {
new objType { Field1 = 2, Field2 = "xxxx", Field3 = 200 },
new objType { Field1 = 3, Field2 = "cccc", Field3 = 999 },
new objType { Field1 = 4, Field2 = "dddd", Field3 = 400 },
new objType { Field1 = 5, Field2 = "eeee", Field3 = 500 }
};
var originalIds = tableOne.ToDictionary(o => o.Field1, o => o);
var newIds = tableTwo.ToDictionary(o => o.Field1, o => o);
var deleted = new List<objType>();
var modified = new List<objType>();
foreach (var row in tableOne)
{
if(!newIds.ContainsKey(row.Field1))
deleted.Add(row);
else
{
var otherRow = newIds[row.Field1];
if (!otherRow.AreEqual(row))
{
modified.Add(row);
modified.Add(otherRow);
}
}
}
var added = tableTwo.Where(t => !originalIds.ContainsKey(t.Field1)).ToList();
可能值得重寫Equals
而不是AreEqual
(或使AreEqual
成為類定義之外的幫助方法),但這取決於您的項目的設置方式。
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