It is good practice to leave your database in a consistent state. There are different ways to do this. Foreign key constraints, indexes, typing of columns, are all strategies to keep your database in a consistent state. Transactions are another way providing you a tool to keep the database consistent: if one of the inserts or updates fail, your database will rollback to the state before the first in the series of inserts and updates within that transaction.
Some languages make it really simple to create a transaction. In Ruby on Rails it is simply opening a block:
User.transaction do
## ... all db operations are now in a transaction
end
But be cautious; transactions don't come for free: they lock the table or row, which is bad for performance. It can, by design, stop other processes from updating the same rows. And all this gets worse when transactions take longer, when for example they contain request to remote resources.
Hence, my approach to transact…
There are a few hard problems in computing. Correctly handling time, naming, preventing off by one errors… sorting text may not be one of them but recently we ran into a discussion where I couldn't make up my mind anymore. Hence, this post's topic: sorting text.
How do you sort the following words:
If you'd ask ruby I'd get:
%w[cheese Ape Drums dent Beer].sort
Results in:
Which in my useless and ramshackle programmer's brain translates to, well why not, it is sorted right?
But then we moved the data into a database which was correctly set up with a proper locale for 'collation', a term that I've seen but never meant anything to me until this problem. Collation is:
> the assembly of written information into a standard order.
(thanks Wikipedia - Collation)
Databas…
Recently a colleague was showing me a concept he was working on. He drafted a change in a fight against so-called 1+n-queries (actually for some reason unknown to me they're called n+1 queries, but my head isn't able to process the problem with just one more query after n queries…); in software development using ORMs like active record it is quite easy to make a single database request objects that when a presented within a view trigger other queries for every object because it has a relationship. Round trips to databases are generally bad as they take time.
For his change, he introduced a new class that we could seemingly reuse, with a just another (a bad code-smell) declaration of relations between objects and whether these should be preloaded when retrieving the primary object. This was in response to indeed a quite bad part of our code that entailed returning objects with counts of selected associations, but instead of counting these in the database, the current code was a…
Dit artikel van murblog van Maarten Brouwers (murb) is in licentie gegeven volgens een Creative Commons Naamsvermelding 3.0 Nederland licentie .