Обсуждение: Character fields and length

Brandon Aiken wrote:

I know that in PostgreSQL, there is no performance difference between character and character varying.  

 

Is there any penalty in either performance or disk space for not specifying a length on char and varchar fields?  Is it really just there only as a basic check constraint for the logical model?

If you omit the length on a char field it will be char(1) .

Varchar without a length is basically a text type - it will accept strings of up to 1gb in size. 

varchar, text, and char fields have no performance differences (aside from the space padding stored in a char field - which takes up extra space).

Keep in mind that by limiting the size you can also prevent things like TOAST from being used (alternately, you could set the storage type on the column to prevent TOAST).

Chander Ganesan
Open Technology Group, Inc. - Expert PostgreSQL Training
One Copley Parkway, Suite 210
Morrisville, NC  27560
Phone: 877-258-8987/919-463-0999
http://www.otg-nc.com

 

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Brandon Aiken

CS/IT Systems Engineer

 

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