Optimizing Queries with Materialized Views: Definition and Management

What is a Materialized View

A materialized view is a technique used in a DBMS that can cache data in memory, reduce access to the original table, and thus improve query performance.

Why Use Materialized Views

Using materialized views can optimize the following scenarios:

  • High-frequency read operations
  • Aggregation calculations on large volumes of data
  • Queries that do not require all data

How to Define a Materialized View

Definition Syntax

CREATE MATERIALIZED VIEW [view_name] 
AS 
SELECT [columns] 
FROM [original_table];

Option Parameters

  • The MATERIALIZED VIEW keyword indicates this is a materialized view.
  • [view_name] is the name of the materialized view, which can be any valid SQL table name.
  • [columns] are the columns to be selected.
  • [original_table] is the name of the original table.

Optimization Options

WITH CHECKSUM

CREATE MATERIALIZED VIEW [view_name] 
AS 
SELECT [columns] 
FROM [original_table]
WITH CHECKSUM;
  • The CHECKSUM option can reduce the amount of computation, but increases storage space and refresh time.

Deleting a Materialized View

DROP MATERIALIZED VIEW [view_name];

Management of Materialized Views

Refreshing a Materialized View

REFRESH MATERIALIZED VIEW [view_name];
  • The highest priority refresh method is using REFRESH WITH FORCE, which will rewrite the original table if there are conflicts.

Updating a Materialized View

  • Use the following command to manually update a materialized view:
ALTER MATERIALIZED VIEW [view_name]
REBUILD;

Or

UPDATE MATERIALIZED VIEW [view_name]
SET OPTIONS ('option1', 'value1');

Compressing a Materialized View

  • Use the following command to compress a materialized view:
VACUUM MATERIALIZED VIEW [view_name];
  • VACUUM releases physical space and makes it as compact as possible.

Summary

Using materialized views is an effective optimization technique that can significantly improve data processing performance. Understanding how to define, manage, and maintain materialized views is very important for more advanced SQL development and DBAs.