[Lazarus] Web development and XML database (Mattias)

Mattias Gaertner nc-gaertnma at netcologne.de
Thu Nov 17 11:28:50 CET 2011

On Thu, 17 Nov 2011 11:38:25 +0200
Juha Manninen <juha.manninen62 at gmail.com> wrote:

> Thanks for the explanation.
> In essence it is a database optimized for reading but not writing.


> For updating the XML file contents there is no concurrency checks or atomic
> transactions.

At the moment the projects only edit the files by svn and other
external tools.
In the later project phase editing will be added. Concurrency checks
are already there.

> That is fine with many use cases but for example e-commerce sites could not
> use it. They need safe transactions for user profile and sales action
> management.
> This is partly why the SQL databases are slow, they take care
> of concurrency also when data is updated.

That explains why writing is slow, not why reading and searching is

> Your solution could be used to provide fast access to a slow SQL DB data by
> generating data dumps eg. once a day.

Ehm, SQL is for relational databases. A XML database is hierarchical.
You can easily map data between those two, but their optimizations are
different. A simple search in a XML database often require complex
joins in SQL.

> eXist DB is made with Java. It would be interesting to compare how much
> their performance differs. Java has become very fast but it still hogs
> memory.


> Good luck with the project!



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