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Creating Virtual Columns

By Bruce Momjian
Databases store data in table columns, but sometimes it is useful to create non-storage columns for code clarity. For example, you might need to access a combination of columns frequently and don't want to repeatedly perform the combining operation in your application. In this case, a column can be...

Instagram scales with Postgres

By Gary Carter
This engineering blog by Instagram co-founder Mike Krieger is another great example of the robust feature set available today in PostgreSQL to handle some of the most modern of database scalability problems. Note that he highlights not just core features, but tools from the Postgres ecosystem like...

Pg_Upgrade Bug with Invalid Concurrently-Created Indexes

By Bruce Momjian
Postgres, since version 8.2, has supported the ability to create indexes without blocking writes (insert, update, or delete) on the table being indexed. This is done by adding the keyword concurrently to the create index command. (Reads are never blocked by create index.) Implementing this feature...

Monitoring Postgres from the Command Line

By Bruce Momjian
You might already be aware that Postgres updates the process title of all its running processes. For example, this is a Debian Linux ps display for an idle Postgres server: postgres 2544 2543 0 10:47 ? 00:00:00 /u/pgsql/bin/postmaster -i postgres 2546 2544 0 10:47 ? 00:00:00 postgres: checkpointer...

List user privileges in PostgreSQL/PPAS 9.1

By Vibhor Kumar
PostgreSQL has some useful functions which can be use to know about the privilege of a user on a particular Database object. Those functions is available in following link: Functions has_*_privilege in PostgreSQL/PPAS is good to know...

Monitor CPU and MEMORY percentage used by each process in PostgreSQL/PPAS 9.1

By Vibhor Kumar
PostgreSQL has pg_stat_activity view which can be use to get the session details. This view gives following information: 1. datid: database OID 2. datname: database name 3. procpid: process ID 4. usesysid: user OID 5. usename: user name 6. application_name: application name 7. client_addr: client's...

What Are Oids

By Bruce Momjian
Object Identifiers (oids) were added to Postgres as a way to uniquely identify database objects, e.g. rows, tables, functions, etc. It is part of Postgres's object-relational heritage. Because oids where assigned to every data row by default, and were only four-bytes in size, they were increasingly...

Session Timeouts with Vaadin's Refresher Add-on

By Bobby Bissett
The Refresher add-on for Vaadin refreshes the UI without user input, allowing it to display information that has changed asynchronously on the server. It adds an invisible component to the client web page which polls the server for changes. A matching server-side handler is called when the server is polled.

Cluster, Cluster, Schema, Schema

By Bruce Momjian
There are 500k to 1-million words in the English language, so you would think that Postgres would be able to find a unique word for every aspect of the database, but unfortunately, that is not true. There are two cases where Postgres uses a single word to mean two different things, sometimes...

The Effectiveness of effective_cache_size

By Bruce Momjian
Friday, May 4, 2012 Having reported the methods for finding the size of the kernel cache on Linux, I wish to highlight the importance of the postgresql.conf setting effective_cache_size . Unlike other memory settings that control how memory is allocated, effective_cache_size tells the optimizer how...

When to Use Multiple Clusters, Databases, or Schemas?

By Bruce Momjian
I previously explained that Postgres allows multiple databases per cluster. The outstanding question might be, when should I use multiple clusters, multiple databases, or multiple schemas? The following table outlines the advantages of the various container types: Feature Cluster Database Schema...

Tuning shared_buffers and wal_buffers

By Robert Haas
I spend a lot of time answering questions about PostgreSQL, and one of the questions I get asked frequently is: how should I set shared_buffers? And, a bit less often, how should I set wal_buffers? I've got canned answers that I can rattle off so fast it'll make your head spin. Exceptions to my...

Limiting Postgres Connections

By Bruce Momjian
Friday, February 24, 2012 During recent training , I realized there five ways to control who can access Postgres, and it isn't totally clear in the documentation how they fit together. There are basically a series of gates that users must pass through to connect to a Postgres database. I thought I...

Sample App Tour

By enterprisedb enterprisedb
In my last blog , I performed a very short DB migration from a local PostgreSQL installation to one running in the cloud. In this blog, I want to share the small "wine database" application that I used. All of the code is available in this zip file , including a pom.xml file for building through...

Sorting Performance Improvement for Postgres 9.2

By Bruce Momjian
As part of the work on Postgres 9.2, yesterday Robert Haas applied a much-discussed ( December , January , February ) patch by Peter Geoghegan to improve sort performance. Having recently blogged about how work_mem affects sort performance, I thought I would re-run my tests to see the improvement:...

Virtual Private Database (VPD) in PPAS 9.1

By Vibhor Kumar
Great News is Postgres Plus Advanced 9.1 is now available for users. So, I thought to write something about Virtual Private Database features, which is part of 9.1 Virtual Private Database (VPD) is a feature which enables Administrator to create security around actual data (i.e row/columns) so that...