[Koha-devel] Update database changes proposal

[Ian Walls]

Since right now we check that the DB is up to date with every page load,
we'd need something fast.  A numeric comparison is simple enough; checking
through a whole directory of updates, or scanning a hashref or some other
mechanism, would likely take much more processing power.

Also, we've got to factor in update's depending on one another.  We've got
to have some kind of chain of dependence; doing it as a linear value is the
easiest.  The other option would be for each update to specify it's
dependencies explicitly; that would give us a directed acyclic graph, like
Git uses, but would be MUCH more complex to implement and maintain.


-Ian


On Sat, Nov 5, 2011 at 6:01 AM, Edgar Fuß <ef at math.uni-bonn.de> wrote:

> > During the hackfest in Mumbaï, 5 of us had a brainstorming about
> > database changes to try to improve it.
> Would it be feasible for the database not to track a linear version number
> of the update status, but a list of tickets, one for every DB update?
> Given these tickets are unique (centrally managed or random, i.e., a hash
> of the DB statements) you would have no troubles whatsoever applying
> patches in any order. You would even (with a corresponding un-apply DB
> statements file) be able to roll back individual patches.
> Of course, this means the update has to walk through the ticket numbers
> instead of checking a single version number. In case that's too expensive
> for the general case of a non-patched system, the update script could be
> taught a list of tickets of the updates that each released version
> contains. But I guess looking up a ticket number in a list maintained by
> the DB is exactly what a DB is good at.
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-- 
Ian Walls
Lead Development Specialist
ByWater Solutions
Phone # (888) 900-8944
http://bywatersolutions.com
ian.walls at bywatersolutions.com
Twitter: @sekjal
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