# Preventing duplicate inserts?

**URL:** <https://www.ruby-forum.com/t/preventing-duplicate-inserts/82153>\
**Category:** Rails\
**Created:** [January 17, 2007, 8:53pm UTC](https://www.ruby-forum.com/t/preventing-duplicate-inserts/82153 "2007-01-17T20:53:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![bataras](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/3ab097/32.png) [@bataras](https://www.ruby-forum.com/u/bataras)\
**Post date:** [January 17, 2007, 8:53pm UTC](https://www.ruby-forum.com/t/preventing-duplicate-inserts/82153/1 "2007-01-17T20:53:14Z")

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Apologies if this looks like a dupe. I posted something similar a  
couple days ago but I can’t seem to find the thread. In my profile it  
claims I posted the thread, but then won’t give me a link to it.  
anyway…

I have 2 ruby processes that are chugging along adding or updating  
email addresses from different sources. Occasionally, they both see the  
same email address at the same time. They’re inserting into a table  
that has a unique index on the email address.

So I have code along the lines of:

def address\_seen(newaddr)  
transaction  
addrinfo = AddrInfo.find(:addr =\> newaddr)  
if addrinfo == nil  
addrinfo = AddrInfo.create!(:addr =\> newaddr, …)  
end  
end  
end

The problem is this doesn’t prevent a duplicate insert error (resulting  
in Mysql::Error: #23000Duplicate entry).

How, using rails, can I make 2 or more ruby processes coordinate  
through the DB so that they don’t try to insert the same row more than  
once?

---

<div class="post-metadata">

**Author:** ![bataras](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/3ab097/32.png) [@bataras](https://www.ruby-forum.com/u/bataras)\
**Post date:** [January 17, 2007, 10:47pm UTC](https://www.ruby-forum.com/t/preventing-duplicate-inserts/82153/2 "2007-01-17T22:47:46Z")

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> So I have code along the lines of:  
> The problem is this doesn’t prevent a duplicate insert error (resulting  
> in Mysql::Error: #23000Duplicate entry).
> 
> How, using rails, can I make 2 or more ruby processes coordinate  
> through the DB so that they don’t try to insert the same row more than  
> once?

Wrap your ‘create’ line in a begin/rescue/end block and catch the error  
coming from mysql…

Although the error you give above suggests that mysql is _NOT_ allowing  
duplicate entries. If you simply wanted to shut it up just do:

begin  
addrinfo = AddrInfo.create!(:addr =\> newaddr, …)  
rescue  
nil  
end

and get rid of the transaction all together…