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Re: How to migrate column type from uuid to serial - Mailing list pgsql-general

From Hemil Ruparel
Subject Re: How to migrate column type from uuid to serial
Date
Msg-id CANW1aT8N1KeyjK2dR_01hZookOTxP9=AP4rZR0AaEK7QRXeKRA@mail.gmail.com
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In response to Re: How to migrate column type from uuid to serial  (Hemil Ruparel <hemilruparel2002@gmail.com>)
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Is it because they are hex characters and hence only need 4 bit to store per character but we display each of those 4 bits as a character as a hex value (0 to 9 and a-f) all of which in ASCII and UTF-8 require a byte to represent? Hence the length of 32 (or 36 with dashes)? 

On Wed, Oct 7, 2020 at 8:10 PM Hemil Ruparel <hemilruparel2002@gmail.com> wrote:
Sorry if this is silly but if it is a 128 bit number, why do we need 32 characters to represent it? Isn't 8 bits one byte?

On Wed, Oct 7, 2020 at 8:08 PM Thomas Kellerer <shammat@gmx.net> wrote:
Hemil Ruparel schrieb am 07.10.2020 um 16:21:
> it is declared as uuid. But how does it occupy only 16 bytes?

Because a UUID is internally simply a 128bit number - the dashes you see are just formatting.

But if you can only send the text represnation, then yes 32 characters aren't enough.


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