From: "Campbell, Lance" <lance@illinois.edu>
To: "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
Subject: Sequence Cycle question
Thread-Topic: Sequence Cycle question
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Date: Thu, 23 Jan 2025 17:13:05 +0000
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PostgreSQL 16

Question on how Cycle works with example:

I have table X with a primary key ID which is an integer that uses a sequen=
ce.

Sequence Settings:
start_value=3D1
min_value=3D1
max_value=3D1,000,000
cycle=3Dtrue

Use Case:
Table X has records that have been removed over time randomly.  There are I=
Ds that cover a wide range of values between 1 and 1,000,000.

When the primary key ID, which is a sequence, reaches 1,000,000 then the ne=
xt sequence value will start back at 1.

What would happen if I had a primary key for ID of 5 still in use?  When I =
reach 5 will the sequence skip that number and go to 6 instead?

Could you please add some text in the documentation to explain this Use Cas=
e? It seems very important.

Thanks,

Lance

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<p class=3D"MsoNormal"><b>PostgreSQL 16<o:p></o:p></b></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Question on how Cycle works with example:<br>
<br>
<o:p></o:p></p>
<p class=3D"MsoNormal">I have table X with a primary key ID which is an int=
eger that uses a sequence. &nbsp;<br>
<br>
<b><o:p></o:p></b></p>
<p class=3D"MsoNormal"><b>Sequence Settings:</b><br>
start_value=3D1<o:p></o:p></p>
<p class=3D"MsoNormal">min_value=3D1<o:p></o:p></p>
<p class=3D"MsoNormal">max_value=3D1,000,000<o:p></o:p></p>
<p class=3D"MsoNormal">cycle=3Dtrue<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal"><b>Use Case:</b><br>
Table X has records that have been removed over time randomly.&nbsp; There =
are IDs that cover a wide range of values between 1 and 1,000,000.<o:p></o:=
p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">When the primary key ID, which is a sequence, reache=
s 1,000,000 then the next sequence value will start back at 1.&nbsp;
<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">What would happen if I had a primary key for ID of 5=
 still in use?&nbsp; When I reach 5 will the sequence skip that number and =
go to 6 instead?<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Could you please add some text in the documentation =
to explain this Use Case? It seems very important.<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Thanks,<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Lance<o:p></o:p></p>
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