Configuration storage setup [file vs. database]

Question

I see programmers putting a lot of information into databases that could otherwise be put in a file that holds arrays. Instead of arrays, they'll use many tables of SQL which, I believe, is slower.

CitrusDB has a table in the database called "holiday". This table consists of just one date column called "holiday_date" that holds dates that are holidays. The idea is to let the user add holidays to the table. Citrus and the programmers I work with at my workplace will prefer to put all this information in tables because it is "standard".

I don't see why this would be true unless you are allowing the user, through a user interface, to add holidays. I have a feeling there's something I'm missing.

Answer 1

Sometimes you want to design in a bit of flexibility to a product. What if your product is released in a different country with different holidays? Just tweak the table and everything will work fine. If it's hard coded into the application, or worse, hard coded in many different places through the application, you could be in a world of pain trying to get it to work in the new locale.

By using tables, there is also a single way of accessing this information, which probably makes the program more consistent, and easier to maintain.

Sometimes efficiency/speed is not the only motivation for a design. Maintainability, flexibility, etc are very important factors.

Answer 2

The actual dates of some holidays change every year. The flexibility to update the holidays with a query or with a script makes putting it in the database the easiest way. One could easily implement a script that updates the holidays each year for their country or region when it is stored in the database.

Answer 3

The main advantage I have found of storing 'configuration' in a database, rather than in a property file, or a file full of arrays, is that the database is usually centrally stored, whereas a server may often be split across a farm of several, or even hundreds of servers.

I have implemented, in a corporate environment, such a solution, and the power of being able to change configuration at a single point of access, knowing that it will immediately be propagated to all servers, without the concern of a deployment process is actually very powerful, and one that we have come to rely on quite heavily.

Answer 4

Theoretically, databases are designed and tuned to provide faster access to data than doing a disk read from a file. In practice, for small to mid-sized applications this difference is minuscule. Best practices, however, are typically oriented at larger scale. By implementing best practices on your small application, you create one that is capable of scaling up.

There is also the consideration of the accessibility of the data in terms of other aspects of the project. Where is most of the data in a web-based application? In the database. Thus, we try to keep ALL the data in the database, or as much as is feasible. That way, in the future, if you decide that now you need to join the holiday dates again a list of events (for example), all the data is in a single place. This segmenting of disparate layers creates tiers within your application. When each tier can be devoted to exclusive handling of the roles within its domain (database handles data, HTML handles presentation, etc), it is again easier to change or scale your application.

Last, when designing an application, one must consider the "hit by a bus principle". So you, Developer 'A', put the holidays in a PHP file. You know they are there, and when you work on the code it doesn't create a problem. Then.... you get hit by a bus. You're out of commission. Developer 'B' comes along, and now your boss wants the holiday dates changed - we don't get President's Day off any more. Um. Johnny Next Guy has no idea about your PHP file, so he has to dig. In this example, it sounds a little trivial, maybe a little silly, but again, we always design with scalability in mind. Even if you KNOW it isn't going to scale up. These standards make it easier for other developers to pick up where you left off, should you ever leave off.

Answer 5

The answer lays in many realms. I used to code my own software to read and write to my own flat-file database format. For small systems, with few fields, it may seem worth it. Once you learn SQL, you'll probably use it for even the smallest things.

1. File parsing is slow. String readers, comparing characters, looking for character sequences, all take time. SQL Databases do have files, but they are read and then cached, both more efficiently.

2. Updating & saving arrays require you to read all, rebuild all, write all, save all, then close the file.

3. Options: SQL has many built-in features to do many powerful things, from putting things in order to only returning x through y results.

4. Security

5. Synchronization - say you have the same page accessed twice at the same time. PHP will read from your flatfile, process, and write at the same time. They will overwrite each other, resulting in dataloss.

The amount of features SQL provides, the ease of access, the lack of things you need to code, and plenty other things contribute to why hard-coded arrays aren't as good.

Answer 6

The answer is it depends on what kind of lists you are dealing with. It seems that here, your list consists of a small, fixed set of values.

For many valid reasons, database administrators like having value tables for enumerated values. It helps with data integrity and for dealing wtih ETL, as two examples for why you want it.

At least in Java, for these kinds of short, fixed lists, I usually use Enums. In PHP, you can use what seems to be a good way of doing enums in PHP.

The benefit of doing this is the value is an in-memory lookup, but you can still get data integrity that DBAs care about.

Answer 7

If you need to find a single piece of information out of 10, reading a file vs. querying a database may not give a serious advantage either way. Reading a single piece of data from hundreds or thousands, etc, has a serious advantage when you read from a database. Rather than load a file of some size and read all the contents, taking time and memory, querying from the database is quick and returns exactly what you query for. It's similar to writing data to a database vs text files - the insert into the database includes only what you are adding. Writing a file means reading the entire contents and writing them all back out again.

If you know you're dealing with very small numbers of values, and you know that requirement will never change, put data into files and read them. If you're not 100% sure about it, don't shoot yourself in the foot. Work with a database and you're probably going to be future proof.

Answer 8

This is a big question. The short answer would be, never store 'data' in a file.

First you have to deal with read/write file permission issues, which introduces security risk.

Second, you should always plan on an application growing. When the 'holiday' array becomes very large, or needs to be expanded to include holiday types, your going to wish it was in the DB.

I can see other answers rolling in, so I'll leave it at that.

Answer 9

Generally, application data should be stored in some kind of storage (not flat files). Configuration/settings can be stored in a KVP storage (such as Redis) then access it via REST API.