Not updating the updated_at field

This is for Rails 3.1.1

I have a field called last_seen in a model. This field will be updated
when the something about the record is seen in the real world (don’t
worry about this part)

So I go x.update_attribute(:last_seen, Time.now) and the following
happens is

UPDATE “blah” SET “last_seen” = ‘2012-10-23 08:57:46.179288’,
“updated_at” = ‘2012-10-23 08:57:54.872808’ WHERE “blah”.“id” = 2673

Now, just for this one attribute, I would like the updated_at field to
be unmolested. Is there some way of updating the last_seen field
without ActiveRecord updating the updated_at field?

On 23 October 2012 10:09, Peter H. [email protected]
wrote:

Now, just for this one attribute, I would like the updated_at field to
be unmolested. Is there some way of updating the last_seen field
without ActiveRecord updating the updated_at field?

So you want to update a record without setting update_at? I suggest
that this is not a good idea as it subverts the purpose of updated_at.
If you want a field that only records the date when the record is
updated under certain circumstances then it would probably be better
to add a new field that you maintain yourself.

If you feel you really want to do it then you use raw sql to update the
record.

Colin

The problem is that the updated_at field is useful for other functions
but the last_seen field being updated is causing the updated_at field
to update and records are being processed if they have been updated
since the system was last checked (I hope I explained that correctly).
Basically the records are being polled for changes based on the
updated_at time. The last_seen field is causing the records to appear
to be updated when they are not, at least not in any way that we are
interested in.

Creating a ‘real_updated_at’ field would be confusing by itself and
require code changes to make sure that it always gets updated when
anything but the last_seen field is updated (not a big problem I know
but less than obvious to anyone reading the code).

Another alternative that I can see is a new table for last_seen that
has a strict one to one relationship with the master record. Which
normalisation would say should be part of the master record, just to
get round the updated_at field.

I suspect that raw SQL will be the way round this. I was just hoping
to make this transparent (you just know someone will see the raw SQL
and not read the comments and ‘improve’ the code).

On Wed, Oct 24, 2012 at 6:02 PM, Peter H. <
[email protected]> wrote:

require code changes to make sure that it always gets updated when
and not read the comments and ‘improve’ the code).

this may help
http://stackoverflow.com/questions/1386490/manually-set-updated-at-in-rails
or you can skip using raw sql and use AR’s update_column method

http://api.rubyonrails.org/classes/ActiveRecord/Persistence.html

On Oct 24, 2012, at 6:02 AM, Peter H. wrote:

The problem is that the updated_at field is useful for other functions
but the last_seen field being updated is causing the updated_at field
to update and records are being processed if they have been updated
since the system was last checked (I hope I explained that correctly).
Basically the records are being polled for changes based on the
updated_at time. The last_seen field is causing the records to appear
to be updated when they are not, at least not in any way that we are
interested in.

This feels like you are mixing metaphors. The act of seeing the record
is external to the record, or its current state of having been edited at
a particular time. If you had a separate object that encapsulated the
act of viewing one of these objects, then the max created_at of that
external “I saw it” object would be your last-viewed time. This would
also let you record views for other types of objects, should you need
that.

Walter

On Tuesday, October 23, 2012 10:09:50 AM UTC+1, Peter H. wrote:

UPDATE “blah” SET “last_seen” = ‘2012-10-23 08:57:46.179288’,
“updated_at” = ‘2012-10-23 08:57:54.872808’ WHERE “blah”.“id” = 2673

Now, just for this one attribute, I would like the updated_at field to
be unmolested. Is there some way of updating the last_seen field
without ActiveRecord updating the updated_at field?

try

x.record_timestamps = false
x.update_attribute :last_seen, Time.now

You may wish to reset record_timestamps to its original value if you’re
going to keep using that particular instance for other purposes, where
you
will want to record updated at. If you do this a lot you could write
something like

def without_timestamps
begin
old = record_timestamps
self.record_timestamps = false
yield
ensure
self.record_timestamps = old
end
end

and then x.without_timestamps {x.update_attribute :last_seen, Time.now}

Fred

On 24 October 2012 11:02, Peter H. [email protected]
wrote:

require code changes to make sure that it always gets updated when
anything but the last_seen field is updated (not a big problem I know
but less than obvious to anyone reading the code).

I think you have the name wrong. The normal updated_at is the ‘real’
updated at time. You are asking for a non-standard updated_at field.
The code would go in a before_save filter probably. I think it could
be more confusing for anyone reading the code to have an updated_at
field which did not reflect the actual time the record was updated
rather than a new one which is only updated under certain
circumstances.

Another alternative that I can see is a new table for last_seen that
has a strict one to one relationship with the master record. Which
normalisation would say should be part of the master record, just to
get round the updated_at field.

I suspect that raw SQL will be the way round this. I was just hoping
to make this transparent (you just know someone will see the raw SQL
and not read the comments and ‘improve’ the code).

An additional field would solve all the problems.

Colin

On Tuesday, 23 October 2012 05:09:50 UTC-4, Peter H. wrote:

UPDATE “blah” SET “last_seen” = ‘2012-10-23 08:57:46.179288’,
“updated_at” = ‘2012-10-23 08:57:54.872808’ WHERE “blah”.“id” = 2673

Now, just for this one attribute, I would like the updated_at field to
be unmolested. Is there some way of updating the last_seen field
without ActiveRecord updating the updated_at field?

update_column will do exactly what you’re looking for, and has the
advantage of not being on the short list to go away in Rails 4.1 like
update_attribute. :slight_smile:

–Matt J.

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