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Date: Sat, 5 Jul 2008 04:19:52 -0700 (PDT)
From: Jessica Richard <rjessil@yahoo.com>
Subject: performance cost for varchar(20), varchar(255), and text
To: pgsql-admin@postgresql.org
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I am tuning a database created by someone else.

I noticed that some column lengths were defined longer than needed.

For example, an Id column is holding a stand length of 20 characters but was defined as varchar(255).

On some other columns, for example, a Description column is supposed to hold less than 100 characters but defined as text.

I am trying to understand the performance impact if a column is over defined in the following cases:

1. char(20) vs varchar(20)

2. varchar(20) vs varchar(255)

3. varchar(255) vs text


thanks,
Jessica



      
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<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><div>I am tuning a database created by someone else.<br><br>I noticed that some column lengths were defined longer than needed.<br><br>For example, an Id column is holding a stand length of 20 characters but was defined as varchar(255).<br><br>On some other columns, for example, a Description column is supposed to hold less than 100 characters but defined as text.<br><br>I am trying to understand the performance impact if a column is over defined in the following cases:<br><br>1. char(20) vs varchar(20)<br><br>2. varchar(20) vs varchar(255)<br><br>3. varchar(255) vs text<br><br><br>thanks,<br>Jessica<br></div></div><br>

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