- আমি কি ঠিক বলছি যে এটি কোনও শর্ত ছাড়াই কোনও আদেশ ছাড়াই এই ক্ষেত্রে আদেশের গ্যারান্টি দেবে?
না। একটি ফ্লো ডিস্টিন্ট যা অর্ডার সংরক্ষণ করে ( ORDER BYকোনও ধরণের ছাড়াই অনুমতি দেওয়া ) আজ এসকিউএল সার্ভারে প্রয়োগ করা হয়নি। নীতিগতভাবে এটি করা সম্ভব, তবে তারপরে যদি আমাদের এসকিউএল সার্ভার উত্স কোড পরিবর্তন করার অনুমতি দেওয়া হয় তবে অনেক কিছুই সম্ভব। আপনি যদি এই উন্নয়ন কাজের জন্য ভাল কেস করতে পারেন তবে আপনি এটি মাইক্রোসফ্টের কাছে প্রস্তাব দিতে পারেন ।
- যদি তা না হয় তবে সলিউশন এ এর চেয়ে তাত্পর্যপূর্ণ এমন কোনও পরিকল্পনা জোর করার জন্য কি আরও একটি পদ্ধতি আছে, অগ্রাধিকারত এমনটি যা এড়িয়ে চলে?
হ্যাঁ। (কেবলমাত্র 2014-পূর্ব কার্ডিনালিটি প্রাক্কলনকারী ব্যবহার করার সময় সারণী ও ক্যোয়ারী ইঙ্গিতগুলি প্রয়োজন):
-- Additional index
CREATE UNIQUE NONCLUSTERED INDEX i
ON #Orders (StoreID, CustID, Amount, OrderID);
-- Query
SELECT TOP (500)
O.CustID,
O.Amount
FROM #Orders AS O
WITH (FORCESEEK(IX (StoreID)))
WHERE O.StoreID = 1
AND NOT EXISTS
(
SELECT NULL
FROM #Orders AS O2
WITH (FORCESEEK(i (StoreID, CustID, Amount)))
WHERE
O2.StoreID = O.StoreID
AND O2.CustID = O.CustID
AND O2.Amount >= O.Amount
AND
(
O2.Amount > O.Amount
OR
(
O2.Amount = O.Amount
AND O2.OrderID > O.OrderID
)
)
)
ORDER BY
O.Amount DESC
OPTION (MAXDOP 1);
(500 row(s) affected)
SQL Server Execution Times:
CPU time = 0 ms, elapsed time = 4 ms.
এসকিউএল সিএলআর সমাধান
নিম্নলিখিত স্ক্রিপ্ট বর্ণিত প্রয়োজনীয়তা মেটাতে একটি এসকিউএল সিএলআর টেবিল-মূল্যযুক্ত ফাংশন ব্যবহার করে দেখায়। আমি সি # বিশেষজ্ঞ নই, সুতরাং কোডটির উন্নতি হতে পারে:
USE Sandpit;
GO
-- Ensure SQLCLR is enabled
EXECUTE sys.sp_configure
@configname = 'clr enabled',
@configvalue = 1;
RECONFIGURE;
GO
-- Lazy, but effective to allow EXTERNAL_ACCESS
ALTER DATABASE Sandpit
SET TRUSTWORTHY ON;
GO
-- The CLR assembly
CREATE ASSEMBLY FlowDistinctOrder
AUTHORIZATION dbo
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WITH PERMISSION_SET = EXTERNAL_ACCESS;
GO
-- The CLR TVF with order guarantee
CREATE FUNCTION dbo.FlowDistinctOrder
(
@ServerName nvarchar(128),
@DatabaseName nvarchar(128),
@MaxRows bigint
)
RETURNS TABLE
(
CustID integer NULL,
Amount float NULL
)
ORDER (Amount DESC)
AS EXTERNAL NAME FlowDistinctOrder.UserDefinedFunctions.FlowDistinctOrder;
প্রশ্ন থেকে টেস্ট টেবিল এবং নমুনা ডেটা:
-- Test table
CREATE TABLE dbo.Orders
(
OrderID integer NOT NULL IDENTITY(1,1),
CustID integer NOT NULL,
StoreID integer NOT NULL,
Amount float NOT NULL
);
GO
-- Sample data
WITH
Cte0 AS (SELECT 1 AS C UNION ALL SELECT 1), --2 rows
Cte1 AS (SELECT 1 AS C FROM Cte0 AS A, Cte0 AS B),--4 rows
Cte2 AS (SELECT 1 AS C FROM Cte1 AS A ,Cte1 AS B),--16 rows
Cte3 AS (SELECT 1 AS C FROM Cte2 AS A ,Cte2 AS B),--256 rows
Cte4 AS (SELECT 1 AS C FROM Cte3 AS A ,Cte3 AS B),--65536 rows
Cte5 AS (SELECT 1 AS C FROM Cte4 AS A ,Cte2 AS B),--1048576 rows
FinalCte AS (SELECT ROW_NUMBER() OVER (ORDER BY C) AS Number FROM Cte5)
INSERT dbo.Orders
(CustID, StoreID, Amount)
SELECT
CustID = Number / 10,
StoreID = Number % 4,
Amount = 1000 * RAND(Number)
FROM FinalCte
WHERE
Number <= 1000000;
GO
-- Index
CREATE CLUSTERED INDEX IX
ON dbo.Orders
(StoreID ASC, Amount DESC, CustID ASC);
ফাংশন পরীক্ষা:
-- Test the function
-- Run several times to ensure connection is cached
-- and CLR code fully compiled
DECLARE @Start datetime2 = SYSUTCDATETIME();
SELECT TOP (500)
FDO.CustID
FROM dbo.FlowDistinctOrder
(
@@SERVERNAME, -- For external connection
DB_NAME(), -- For external connection
500 -- Number of rows to return
) AS FDO
ORDER BY
FDO.Amount DESC;
SELECT DATEDIFF(MILLISECOND, @Start, SYSUTCDATETIME());
সম্পাদন পরিকল্পনা ( ORDERগ্যারান্টিটির বৈধতা নোট করুন ):
আমার ল্যাপটপে, এটি সাধারণত 80-100 মিমি কার্যকর করে। এটি উপরের টি-এসকিউএল পুনরায় লেখার মতো দ্রুততর কাছাকাছি আর কোথাও নেই, তবে এটি বিভিন্ন ডেটা বিতরণের ক্ষেত্রে ভাল পারফরম্যান্সের স্থায়িত্ব প্রদর্শন করা উচিত।
সোর্স কোড:
using Microsoft.SqlServer.Server;
using System.Collections;
using System.Collections.Generic;
using System.Data.SqlClient;
public partial class UserDefinedFunctions
{
private sealed class ReverseComparer<T> : IComparer<T>
{
private readonly IComparer<T> original;
public ReverseComparer(IComparer<T> original)
{
this.original = original;
}
public int Compare(T left, T right)
{
return original.Compare(right, left);
}
}
[SqlFunction
(
DataAccess = DataAccessKind.Read,
SystemDataAccess = SystemDataAccessKind.None,
FillRowMethodName = "FillRow",
TableDefinition = "CustID integer NULL, Amount float NULL"
)
]
public static IEnumerable FlowDistinctOrder
(
[SqlFacet (MaxSize=128)]string ServerName,
[SqlFacet (MaxSize=128)]string DatabaseName,
long MaxRows
)
{
var list = new SortedDictionary<double, int>
(new ReverseComparer<double>(Comparer<double>.Default));
var csb = new SqlConnectionStringBuilder();
csb.ConnectTimeout = 10;
csb.DataSource = ServerName;
csb.Enlist = false;
csb.InitialCatalog = DatabaseName;
csb.IntegratedSecurity = true;
using (var conn = new SqlConnection(csb.ConnectionString))
{
conn.Open();
using (var cmd = conn.CreateCommand())
{
cmd.CommandText =
@"
SELECT
O.CustID,
O.Amount
FROM dbo.Orders AS O
WHERE
O.StoreID = 1
ORDER BY
O.Amount DESC";
int custid;
double amount;
using (var rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
custid = rdr.GetInt32(0);
amount = rdr.GetDouble(1);
if (!list.ContainsKey(amount))
{
list.Add(amount, custid);
if (list.Count == MaxRows)
{
break;
}
}
}
}
}
}
return list;
}
public static void FillRow(object obj, out int CustID, out double Amount)
{
var v = (KeyValuePair<double, int>)obj;
CustID = v.Value;
Amount = v.Key;
}
}
ORDER BY।