tagged by: database
Evolutionary Database Design
by Pramod Sadalage and Martin Fowler
Over the last few years we've developed a number of techniques that allow a database design to evolve as an application develops. This is a very important capability for agile methodologies. The techniques rely on applying continuous integration and automated refactoring to database development, together with a close collaboration between DBAs and application developers. The techniques work in both pre-production and released systems.
January 2003
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AggregateOrientedDatabase
One of the first topics to spring to mind as we worked on NosqlDistilled was that NoSQL databases use different data models than the relational model. Most sources I've looked at mention at least four groups of data model: key-value, document, column-family, and graph. Looking at this list, there's a big similarity between the first three - all have a fundamental unit of storage which is a rich structure of closely related data: for key-value stores it's the value, for document stores it's the document, and for column-family stores it's the column family. In DDD terms, this group of data is an aggregate.
19 January 2012
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DataModels
One of my early favorite books was Tsichritzis and Lochovsky's book on Data Models. The book discussed different models for thinking about data, in particular the three models most discussed at the time: RelationalDataModel, HierarchicDataModel and NetworkDataModel.
12 February 2004
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DatabaseThaw
A few years ago I heard programming language people talk about the "Nuclear Winter" in languages caused by Java. The feeling was that everyone had so converged on Java's computational model (C# at that point seen as little more than a rip-off) that creativity in programming languages had disappeared. That feeling is now abating, but perhaps a more important thaw that might be beginning - the longer and deeper freeze in thinking about databases.
24 November 2008
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InMemoryTestDatabase
An in-memory database is a database that runs entirely in main memory, without touching a disk. Often they run as an embedded database: created when a process starts, running embedded within that process, and is destroyed when the process finishes.
22 November 2005
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IntegrationDatabase
An integration database is a database which acts as the data store for multiple applications, and thus integrates data across these applications (in contrast to an ApplicationDatabase).
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NetworkDataModel
The network data model structures data as record types, with pointer links to allow to navigate between one record and another. So to query a network data model you begin at one record and move around pointer references.
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NosqlDistilled
Over the last few months I've been helping my colleague Pramod Sadalage work on a book on NoSQL technologies to be titled NoSQL Distilled. (You may know of Pramod's work on refactoring databases and evolutionary database design.) In the last year we've been doing a few projects that have used NoSQL technology, and we think it's going to play an important role in the next few years of software development.
4 January 2012
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RelationalDataModel
The relational data model is best known to most people through relational data bases, and through the SQL language. Colloquially, we think of the database as a set of tables, each row of which contains data. We can manipulate these tables in various ways to do queries, each query results in another table. In contrast to NetworkDataModel, there are no explicit pointers between tables, links are made by join tables on common values (although the use of surrogate keys means you have pointers in practice.)
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ResourcePool
Many programs need to make use of resources that are expensive to create and maintain. Examples of these are database connections and threads. A resource pool provides a good way to manage these resources.
29 March 2011
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gotoAarhus2011
goto (formerly known as JAOO) has long been a favorite conference of mine. They've done a great job over the years of keeping a high standard of content combined with an efficient and friendly organization. So while my over-consumption of conferences has generally led to conference-phobia, I still feel a sense of pleasant anticipation when heading off for the somewhat complicated trip to Aarhus.
26 October 2011
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Domain Logic and SQL
Over the last couple of decades we've seen a growing gap between database-oriented software developers and in-memory application software developers. This leads to many disputes about how to use database features such as SQL and stored procedures. In this article I look at the question of whether to place business logic in SQL queries or in-memory code, considering primarily performance and maintainability based on an example of a simple, but rich SQL query.
February 2003
article
ApplicationDatabase
I use the term Application Database for a database that is controlled and accessed by a single application, (in contrast to an IntegrationDatabase). Since only a single application accesses the database, the database can be defined specifically to make that one application's needs easy to satisfy. This leads to a more concrete schema that is usually easier to understand and often less complex than that for an IntegrationDatabase.
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DatabaseStyles
When I talk about databases and how they relate to applications, I've found it useful to distinguish between two styles of database: ApplicationDatabase and IntegrationDatabase. The difference between the two lies in whether the database is controlled and encapsulated within a single ApplicationBoundary.
24 May 2004
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HierarchicDataModel
A hierarchic data model organizes in the form of a hierarchy or tree structure. Early databases and programming data structures commonly used hierarchic models, but these fell out of favor. In the database world the RelationalDataModel became dominant, while for most in-memory programming the NetworkDataModel dominates. This was due to the fact that a hierarchy, while a simple organizational tool, breaks down as you get more complex data.
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IncrementalMigration
Like any profession, software development has it's share of oft-forgotten activities that are usually ignored but have a habit of biting back at just the wrong moment. One of these is data migration.
7 July 2008
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MemoryImage
When people start an enterprise application, one of the earliest questions is "how do we talk to the database". These days they may ask a slightly different question "what kind of database should we use - relational or one of these NOSQL databases?". But there's another question to consider: "should we use a database at all?"
31 August 2011
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NosqlDefinition
As soon as we started work on NosqlDistilled we were faced with a tricky conundrum - what are we writing about? What exactly is a NoSQL database? There's no strong definition of the concept out there, no trademarks, no standard group, not even a manifesto.
9 January 2012
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PolyglotPersistence
In 2006, my colleague Neal Ford coined the term Polyglot Programming, to express the idea that applications should be written in a mix of languages to take advantage of the fact that different languages are suitable for tackling different problems. Complex applications combine different types of problems, so picking the right language for the job may be more productive than trying to fit all aspects into a single language.
Over the last few years there's been an explosion of interest in new languages, particularly functional languages, and I'm often tempted to spend some time delving into Clojure, Scala, Erlang, or the like. But my time is limited and I'm giving a higher priority to another, more significant shift, that of the DatabaseThaw. The first drips have been coming through from clients and other contacts and the prospects are enticing. I'm confident to say that if you starting a new strategic enterprise application you should no longer be assuming that your persistence should be relational. The relational option might be the right one - but you should seriously look at other alternatives.
16 November 2011
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ReportingDatabase
If I'm using a domain model, how do I support ad hoc SQL queries?
2 April 2004
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Transactionless
A couple of years ago I was talking to a couple of friends of mine who were doing some work at eBay. It's always interesting to hear about the techniques people use on high volume sites, but perhaps one of the most interesting tidbits was that eBay mostly hardly ever uses database transactions.
18 March 2007
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