You're reading from PostgreSQL High Performance Cookbook Mastering query optimization, database monitoring, and performance-tuning for PostgreSQL

Product type Paperback

Published in Mar 2017

Publisher Packt

ISBN-13 9781785284335

Length 360 pages

Edition 1st Edition

Languages

SQL

Tools

PostgreSQL

Concepts

High Performance Programming

Authors (2):

Chauhan

Dinesh Kumar

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Table of Contents (13) Chapters

Preface

1. Database Benchmarking FREE CHAPTER

2. Server Configuration and Control

3. Device Optimization

4. Monitoring Server Performance

5. Connection Pooling and Database Partitioning

6. High Availability and Replication

7. Working with Third-Party Replication Management Utilities

8. Database Monitoring and Performance

9. Vacuum Internals

10. Data Migration from Other Databases to PostgreSQL and Upgrading the PostgreSQL Cluster

11. Query Optimization

12. Database Indexing

Aggregate and hash aggregate

In this recipe, we will be discussing aggregate and hash aggregate mechanisms in PostgreSQL.

Getting ready

Aggregate is a node type that only evaluates the aggregate operators. Some of the aggregate operators are SUM, MIN, MAX, and so on.

Hash aggregate is a node type that requires an aggregate operator, and a group key column. In general, we see this node type being utilized during the GROUP BY, DISTINCT, or set operations.

How to do it…

Aggregate

To demonstrate the aggregates behavior, let's query the benchmarsql as follows:

benchmarksql=# EXPLAIN SELECT max(i_price) FROM bmsql_item;
                               QUERY PLAN                               
------------------------------------------------------------------------

Aggregate
  (cost=2549.00..2549.01 rows=1 width=6)
   ->  Seq Scan on bmsql_item  (cost=0.00..2299.00 rows=100000
          width=6)
(2 rows)

From the preceding plan, as expected we got the aggregate node type, which is followed...

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Authors (2)

Chauhan

Chitij Chauhan currently works as a senior database administrator at an IT-based MNC in Chandigarh. He has over 10 years of work experience in the field of database and system administration, with specialization in MySQL clustering, PostgreSQL, Greenplum, Informix DB2, SQL Server 2008, Sybase, and Oracle. He is a leading expert in the area of database security, with expertise in database security products such as IBM InfoSphere Guardium, Oracle Database Vault, and Imperva.

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Dinesh Kumar

Dinesh Kumar is an enthusiastic open source developer and has written several open source tools for PostgreSQL. He recently announced pgBucket, a brand new job scheduler for PostgreSQL. He is also a frequent blogger at manojadinesh.blogpsot.com, where he talks more about PostgreSQL. He is currently working as a senior database engineer in OpenSCG and building the PostgreSQL cloud operations. He has more than 6 years of experience as an Oracle and PostgreSQL database administrator and developer, and is currently focusing on PostgreSQL.

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