Basically, swapping values of columns involved in a unique index causes
the problem.
Example:
I wrote a synchronization script that syncs data between multiple
databases. It retrieves primary key information from the system tables,
joins remote tables and updates corresponding values.
Suppose I have a table:
Employee (FirstName, LastName, id)
PrimaryKey: id
UniqueIndex: FirstName, LastName
Suppose on each database instance this table contains two records:
Jane Doe 1
Jane Smith 2
Now, suppose we swap the last names between the two emplyees on one
instance, so we end up with:
Jane Smith 1
Jane Doe 2
Now, I want to propagate this data to another database instance and run
this query:
UPDATE Employee1
SET LastName=e2.LastName
FROM Employee2 e2
WHERE Employee1.id = e2.id;
In the above query Employee1 is the Employee table from the first DB
instance and Employee2 - from the second DB instance.
The query will throw an error saying that it UniqueIndex is violated
when assigning last name Doe to employee with id 1.
Thanks.
Oleg
-----Original Message-----
From: Joshua D. Drake [mailto:jd@commandprompt.com]
Sent: Friday, January 09, 2004 10:37 AM
To: Oleg Lebedev
Cc: Bruce Momjian; pgsql-general@postgresql.org
Subject: Re: [GENERAL] deferring/disabling unique index
>So, does it mean that the only way to disable the index is to drop and
>recreate it? What about setting indisunique to false temporarily?
>
>
>
I am just curious... why would you want to defer a unique constraint?
Sincerely,
Joshua Drake
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