postgresql

In some effort to avoid time-zone drama, or perhaps due to fantasies of efficiency, some developer put a date-time field in a PostgreSQL database as an integer; specifically as a UNIX Time value. ¯\_(ツ)_/¯

How to present this as a normal date in a query result?

Dates in databases are a tedious thing. Sometimes a time value is recorded as a timestamp, at other times - probably in most cases - it is recorded as a date. Yet it can be useful to perform date-time queries using a representation of time distinct from what is recorded in the table. For example a database which records timestamps, but I want to look-up records by date.

To this end PostgreSQL supports indexing a table by a cast of a field.

Upgrading a database is always a tedious process - a responsible administrator will have to read through the Changelog for every subsequent version from the version ze is upgrading from to the one ze is upgrading to.

Then I found this! This is a Changelog viewer which allows you to select a from and a to version and shows you all the changelogs in between; on one page. You still have to read it, of course, but this is a great time saver.

Distribution: CentOS 6.x / RHEL 6.x

If you already have a current version of PostgreSQL server installed on your server from the PGDG repository you should skip these first two steps.

A powerful feature of PostgreSQL is the ability to create table spaces and to move database objects between them. Each table space represents a physical storage location; so using table spaces you can tier data onto different grades of storage [SSD vs. fast disk vs. slow disk] as well as move data from storage being retired [like an iSCSI SAN] to a new storage [a Fiber-Channel SAN!].

One of the key steps for performing tuning a database is to test indexing strategies and their effect on performance. It is a series of:

1. Drop the indexes
2. Create new indexes
3. Update statistics
4. EXPLAIN the important queries.

Rinse and repeat.

In recent versions of PostgreSQL there is a magical view called pg_stat_user_tables which provides per table information on usage; there is one row per table and eight counters per row.

Fields