Partizionamento a livello di applicazione
Si applica a: 
SQL Server, Database SQL di Azure e Istanza gestita di SQL di Azure
Questa applicazione elabora gli ordini. Gli ordini recenti vengono sottoposti a numerose elaborazioni. Gli ordini meno recenti non vengono sottoposti a numerose elaborazioni. Gli ordini recenti sono in una tabella ottimizzata per la memoria. Gli ordini meno recenti sono in una tabella basata su disco. Tutti gli ordini dopo hotDate sono nella tabella ottimizzata per la memoria. Tutti gli ordini prima di hotDate sono nella tabella basata su disco. Si supponga un pesante carico di lavoro OLTP con molte transazioni simultanee. Questa regola di business (ordini recenti in una tabella ottimizzata per la memoria) deve essere applicata anche se diverse transazioni simultanee stanno tentando di modificare hotDate.
In questo esempio non viene utilizzata una tabella partizionata della tabella basata su disco ma si tiene traccia di un punto di divisione esplicito tra le due tabelle, utilizzando una terza tabella. Il punto di divisione può essere usato per garantire che i dati appena aggiunti vengano inseriti sempre nella tabella appropriata in base alla data. Inoltre, può essere usato per determinare la posizione in cui cercare i dati. I dati che arrivano in ritardo vengono ancora inseriti nella tabella appropriata.
Per un esempio correlato, vedere Modello di applicazione per il partizionamento di tabelle con ottimizzazione per la memoria.
Listato di codice
USE MASTER
GO
IF NOT EXISTS(SELECT name FROM sys.databases WHERE name = 'hkTest')
CREATE DATABASE hkTest
-- enable for In-Memory OLTP - change file path as needed
ALTER DATABASE hkTest ADD FILEGROUP hkTest_mod CONTAINS MEMORY_OPTIMIZED_DATA
ALTER DATABASE hkTest ADD FILE( NAME = 'hkTest_mod' , FILENAME = 'c:\data\hkTest_mod') TO FILEGROUP hkTest_mod;
GO
use hkTest
go
-- create memory-optimized table
if OBJECT_ID(N'hot',N'U') IS NOT NULL
drop table [hot]
create table hot
(id int not null primary key nonclustered,
orderDate datetime not null,
custName nvarchar(10) not null
) with (memory_optimized=on)
go
-- create disk-based table for older order data
if OBJECT_ID(N'cold',N'U') IS NOT NULL
drop table [cold]
create table cold (
id int not null primary key,
orderDate datetime not null,
custName nvarchar(10) not null
)
go
-- the hotDate is maintained in this memory-optimized table. The current hotDate is always the single date in this table
if OBJECT_ID(N'hotDataSplit') IS NOT NULL
drop table [hotDataSplit]
create table hotDataSplit (
hotDate datetime not null primary key nonclustered hash with (bucket_count = 1)
) with (memory_optimized=on)
go
-- Stored Procedures
-- set the hotDate
-- snapshot: if any other transaction tries to update the hotDate, it will fail immediately due to a
-- write/write conflict
if OBJECT_ID(N'usp_hkSetHotDate') IS NOT NULL
drop procedure usp_hkSetHotDate
go
create procedure usp_hkSetHotDate @newDate datetime
with native_compilation, schemabinding, execute as owner
as begin atomic with
(
transaction isolation level = snapshot,
language = N'english'
)
delete from dbo.hotDataSplit
insert dbo.hotDataSplit values (@newDate)
end
go
-- extract data up to a certain date [presumably the new hotDate]
-- must be serializable, because you don't want to delete rows that are not returned
if OBJECT_ID(N'usp_hkExtractHotData') IS NOT NULL
drop procedure usp_hkExtractHotData
go
create procedure usp_hkExtractHotData @hotDate datetime
with native_compilation, schemabinding, execute as owner
as begin atomic with
(
transaction isolation level = serializable,
language = N'english'
)
select id, orderDate, custName from dbo.hot where orderDate < @hotDate
delete from dbo.hot where orderDate < @hotDate
end
go
-- insert order
-- inserts an order either in recent or older table, depending on the current hotDate
-- it is important that the SP for retrieving the hotDate is repeatableread, in order to ensure that
-- the hotDate is not changed before the decision is made where to insert the order
-- note that insert operations [in both disk-based and memory-optimized tables] are always fully isolated, so the transaction
-- isolation level has no impact on the insert operations; this whole transaction is effectively repeatableread
if OBJECT_ID(N'usp_InsertOrder') IS NOT NULL
drop procedure usp_InsertOrder
go
create procedure usp_InsertOrder(@id int, @orderDate date, @custName nvarchar(10))
as begin
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
begin tran
-- get hot date under repeatableread isolation; this is to guarantee it does not change before the insert is executed
declare @hotDate datetime
set @hotDate = (select hotDate from hotDataSplit with (repeatableread))
if (@orderDate >= @hotDate) begin
insert into hot values (@id, @orderDate, @custName)
end
else begin
insert into cold values (@id, @orderDate, @custName)
end
commit tran
end
go
-- change hot date
-- changes the hotDate and moves the rows between the recent and older order tables as appropriate
-- the hotDate is updated in this transaction; this means that if the hotDate is changed by another transaction
-- the update will fail due to a write/write conflict and the transaction is rolled back
-- therefore, the initial (snapshot) access of the hotDate is effectively repeatable read
if OBJECT_ID(N'usp_ChangeHotDate') IS NOT NULL
drop procedure usp_ChangeHotDate
go
create procedure usp_ChangeHotDate(@newHotDate datetime)
as
begin
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
begin tran
declare @oldHotDate datetime
set @oldHotDate = (select hotDate from hotDataSplit with (snapshot))
-- get hot date under repeatableread isolation; this is to guarantee it does not change before the insert is executed
if (@oldHotDate < @newHotDate) begin
insert into cold exec usp_hkExtractHotData @newHotDate
end
else begin
insert into hot select * from cold with (serializable) where orderDate >= @newHotDate
delete from cold with (serializable) where orderDate >= @newHotDate
end
exec usp_hkSetHotDate @newHotDate
commit tran
end
go
-- Deploy and populate tables
-- cleanup
delete from cold
go
-- init hotDataSplit
exec usp_hkSetHotDate '2012-1-1'
go
-- verify hotDate
select * from hotDataSplit
go
EXEC usp_InsertOrder 1, '2011-11-14', 'cust1'
EXEC usp_InsertOrder 2, '2012-3-4', 'cust1'
EXEC usp_InsertOrder 3, '2011-1-23', 'cust1'
EXEC usp_InsertOrder 4, '2011-8-6', 'cust1'
EXEC usp_InsertOrder 5, '2010-11-1', 'cust1'
EXEC usp_InsertOrder 6, '2012-1-9', 'cust1'
EXEC usp_InsertOrder 7, '2012-2-14', 'cust1'
EXEC usp_InsertOrder 8, '2010-1-17', 'cust1'
EXEC usp_InsertOrder 9, '2012-3-8', 'cust1'
EXEC usp_InsertOrder 10, '2011-9-24', 'cust1'
go
-- Demo Portion
-- verify contents of the tables
-- hotDate is 2012-1-1
-- all orders from 2012 are in the recent table
-- all orders before 2012 are in the older order table
-- query hot data
select * from hot order by orderDate desc
-- query cold date
select * from cold order by orderDate desc
-- move hot date to Mar 2012
EXEC usp_ChangeHotDate '2012-03-01'
-- Verify that all orders before Mar 2012 were moved to older order table
-- query hot data
select * from hot order by orderDate desc
-- query old data
select * from cold order by orderDate desc