Versioning the contents of a table as a set


#1

I am looking at using acts_as_versioned to manage revisions of data in
several tables in my application. However, the default behavior of
acts_as_versioned appears to apply to individual rows within a table.
The
tables I want to version are complicated lookup tables and what I really
want is to version the entire contents of each table as a single set.
Adding a row, deleting a row, or updating one or more rows should update
the
version of all rows. Is there a way to use acts_as_versioned to
accomplish
this? Is there a different approach that anyone can recommend?

The second part of this question stems from a bit of self-doubt as to
whether I took a sensible approach with these tables. Essentially what
I
have is the following table (c1…c3 represent criteria, r represents
result)
for each set of criteria:

r c1 c2 c3

1 1 1 1
1 1 1 0
0 1 0 1
1 1 0 0
0 0 1 1
0 0 1 0
0 0 0 1
0 0 0 0

This allows me to select a result as follows myresult =
mylookup.find(:conditions
=> [“c1 = ?”, “c2 = ?”, “c3 = ?”, a, b, c]).r

In this example, r is true when c1 is true and c3 is false or when c1 is
true and c2 and c3 are true.

This example is extremely simplified in the hopes of conveying the
concept.
The actual criteria tables include 5 or 6 conditions, some boolean, some
integer.

The reason that I would like to version the contents of this table as a
set
(all move to the next revision when one changes) is that I plan to store
the
revision of the criteria used along with the thing being evaluated.
This
should allow me to determine why an evaluated item failed or passed the
criteria even in the future when the criteria have changed (possibly
changing the evaluation result) by simply requesting the criteria for
the
revision that was originally used to evaluate the item in question.

I chose to put the criteria into tables instead of directly into models
because I want to allow the system administrators to update the criteria
in
the future through the application.

Any ideas on other approaches?


#2

Reposting to see if anyone in the PST time zone has any suggestions.

Thanks,

Eden


#3

Hello? Bumping this one more time just in case someone has some free
time
to think this through on a Friday.

Just to summarize, I am looking for a way to version all rows in a table
as
a set. Any changes to any row would up rev all rows. Accessing a row
should happen in the context of the set version, not the row version.

My current inclination is to keep the schema below (since I can’t think
of
another one) and modify acts_as_versioned so that it is really
acts_as_versioned_set.

Any other suggestions?

Thank you,

Eden


#4

Let me see if I understand correctly. Every time any field in any row
is changed, you need to store a copy of the whole table so that you can
reference it later?


#5

On May 5, 2006, at 1:52 PM, Eden B. wrote:

really acts_as_versioned_set.
(Assuming you need locking on the set, not full versioning.)

You’re working with rulesets which aggregate rules, so lock the
ruleset itself. Don’t CRUD rules directly; operate on them via their
ruleset.

Doesn’t have a version column (and likely no separate pk if AR

didn’t need it.)
class Rule < AR::Base; end

Has a version column.

class Ruleset < AR::Base
has_many :rules

 # Saving the ruleset bumps its version, so so save its rules in

the same transaction.
after_save :save_changed_rules
end

ruleset.rules << Rule.new(foo, bar)
ruleset.save!

Check out Eric Evan’s Domain Driven Design for an excellent
discussion of locking on domain boundaries.

Best,
jeremy


#6

Charlie,

Thank you for responding. Yes, I want at least a diff of the whole
table
each time anything changes. The table is essentially a complicated
lookup
table (lots of variables in, one answer out), so the number of total
rows is
limited (about 10 right now). The table is functioning as a set of
criteria. I pass in a bunch of true/false values (plus one or two ints)
and
get a pass or fail type result out of the table. Each combination of
inputs
will only match one row in the table.

Does that help? I can post the actual contents of one of these criteria
tables (there are several) if you think it will clarify things.

Thanks,

Eden


#7

I think you hit the nail on the head Jeremy! I think all I would need
to do
is store the ruleset id in the item that is evaluated. Then I can
always
refer back to the ruleset that was used for the evaluation even if the
rules
are modified (each modification is actually a new ruleset).

I will check out the reference.

Thanks again,

Eden