Atualizando tabelas do SQL Server com menos interrupção usando a alternância de partição

Exemplo simplificado de uma tabela de preparo:analogia de mercado de um agricultor

• Quando você traz uma carga de legumes novos, levará 20 minutos para limpar a mesa e substituir o estoque restante pelo produto mais novo.
• Você não quer que os clientes fiquem sentados e esperem 20 minutos para que a troca aconteça, já que a maioria vai buscar seus vegetais em outro lugar.

Atualizando tabelas no SQL Server

• Trick Shots:Schema Switch-a-Roo
• Schema Switch-a-Roo, Parte 2

Exemplo de alternância de partição do SQL Server

CREATE DATABASE NewWay;
CREATE DATABASE OldWay;
GO

USE NewWay;
GO
 
CREATE TABLE dbo.Vegetables_NewWay
(
  VegetableID int,
  Name        sysname,
  WhenPicked  datetime,
  BackStory   nvarchar(max)
);
GO
 
-- we need to create two extra copies of the table.
 
CREATE TABLE dbo.Vegetables_NewWay_prev
(
  VegetableID int,
  Name        sysname,
  WhenPicked  datetime,
  BackStory   nvarchar(max)
);
GO
 
CREATE TABLE dbo.Vegetables_NewWay_hold
(
  VegetableID int,
  Name        sysname,
  WhenPicked  datetime,
  BackStory   nvarchar(max)
);
GO

CREATE PROCEDURE dbo.DoTheVeggieSwap_NewWay
AS
BEGIN
  SET NOCOUNT ON;
 
  TRUNCATE TABLE dbo.Vegetables_NewWay_prev;
 
  INSERT dbo.Vegetables_NewWay_prev
    SELECT TOP (1000000) s.session_id, o.name, s.last_successful_logon, 
      LEFT(m.definition, 500)
    FROM sys.dm_exec_sessions AS s
    CROSS JOIN model.sys.all_objects AS o
    INNER JOIN model.sys.all_sql_modules AS m
    ON o.[object_id] = m.[object_id];
 
  -- need to take Sch-M locks here:
 
  BEGIN TRANSACTION;
    ALTER TABLE dbo.Vegetables_NewWay 
      SWITCH TO dbo.Vegetables_NewWay_hold
      WITH (WAIT_AT_LOW_PRIORITY 
            (MAX_DURATION = 1 MINUTES,
             ABORT_AFTER_WAIT = BLOCKERS));
 
    ALTER TABLE dbo.Vegetables_NewWay_prev
      SWITCH TO dbo.Vegetables_NewWay;
  COMMIT TRANSACTION;
 
  -- and now users will query the new data in dbo
  -- can switch the old copy back and truncate it 
  -- without interfering with other queries
 
  ALTER TABLE dbo.Vegetables_NewWay_hold
	SWITCH TO dbo.Vegetables_NewWay_prev;
 
  TRUNCATE TABLE dbo.Vegetables_NewWay_prev;
END
GO

Em comparação com a antiga maneira de alternar entre esquemas

USE OldWay;
GO
 
-- create two schemas and two copies of the table
 
CREATE SCHEMA prev AUTHORIZATION dbo;
GO
 
CREATE SCHEMA hold AUTHORIZATION dbo;
GO
 
CREATE TABLE dbo.Vegetables_OldWay
(
  VegetableID int,
  Name sysname,
  WhenPicked datetime,
  BackStory nvarchar(max)
);
GO
 
CREATE TABLE prev.Vegetables_OldWay
(
  VegetableID int,
  Name sysname,
  WhenPicked datetime,
  BackStory nvarchar(max)
);
GO
 
CREATE PROCEDURE dbo.DoTheVeggieSwap_OldWay
AS
BEGIN
  SET NOCOUNT ON;
 
  TRUNCATE TABLE prev.Vegetables_OldWay;
 
  INSERT prev.Vegetables_OldWay
    SELECT TOP (1000000) s.session_id, o.name, s.last_successful_logon, 
      LEFT(m.definition, 500)
    FROM sys.dm_exec_sessions AS s
    CROSS JOIN model.sys.all_objects AS o
    INNER JOIN model.sys.all_sql_modules AS m
    ON o.[object_id] = m.[object_id];
 
  -- need to take Sch-M locks here:
  BEGIN TRANSACTION;
    ALTER SCHEMA hold TRANSFER dbo.Vegetables_OldWay;
    ALTER SCHEMA dbo  TRANSFER prev.Vegetables_OldWay;
  COMMIT TRANSACTION;
 
  -- and now users will query the new data in dbo
  -- can transfer the old copy back and truncate it without 
  -- interfering with other queries:
 
  ALTER SCHEMA prev TRANSFER hold.Vegetables_OldWay;
  TRUNCATE TABLE prev.Vegetables_OldWay;
END
GO

BEGIN TRANSACTION;
 
UPDATE TOP (1) dbo.<table> SET name += 'x';
SELECT TOP (10) name FROM dbo.<table> ORDER BY NEWID();
WAITFOR DELAY '00:00:02';
 
COMMIT TRANSACTION;

Mudança de partição versus transferência de renomear/esquema para atualizar tabelas do SQL Server