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Is there an open source object oriented database for C++ available?
I had looked at Object oriented Relationship Mapping (ORM) libraries like those posted here:
https://stackoverflow.com/questions/74141/good-orm-for-c-solutions
and these were intereting as well:
Object-oriented-like structures in relational databases
http://en.wikipedia.org/wiki/List_of_object-relational_mapping_software#C.2B.2B
My experience so far has been painful. The solutions don't appear to be mature and I've had difficulty even compiling some of them, and the documentation and support can be sparse.
I suppose at some level I'm trying to avoid learning SQL (I'm not a database developer). On the other hand, my gut feeling is that ORMs are an architectural 'workaround' in that they are creating a layer above a database system that inherently doesn't support objects.
My ideal database library would allow the following:
Allow one to specify the object hierarchy tree based on class names, perhaps in XML or just in C++.
Allow one to specify which fields of those classes should be persistent.
Provide an API to create, update, delete, retreive the hierarchy of objects.
Ideally, provide an API for the in-memory tree itself, including concurrent access to tree nodes.
I had worked on embedded system that had such a custom database and api.
I'm almost at the point where I'm just going to create my own and open source it.
Just wondering if there is anything off the shelf I can use.
I saw this:
http://en.wikipedia.org/wiki/Comparison_of_object_database_management_systems
and am trying to figure out this might work:
http://www.fastdb.org/fastdb.html
Thanks in advance.
I'm not going to make any recommendations, because I don't know of a high-quality FOSS OO database. I would however make the following observations:
OO database are not a way of avoiding SQL - you need both. Frankly, If you don't know SQL pretty well, your life as a professional programmer iis likely to be unhappy.
OO databases are mature - they have been around for well over 20 years. I personally first used one on a large project in the finance industry 15 years ago.
OO database are best used where relational databases fail - I've used them in complex financial instrument modeling, oil-pipeline optimisation and telco work.
ORM databases take the bad parts of the OO and the relational models and make something even worse of them.
My favourite commercial OODB is ObjectStore, but I haven't done any work with it for quite while now.
Hope that is vaguely helpful.
Honestly, unless you're into "bleeding edge", I would stay away from OO databases. In almost all cases, they're not well supported, immature, and have various support issues client side.
The problem is, only the relational databases (and certain non-relational ones) get 99% of the attention, and thus end up far more mature. ORM may be a workaround, but if you want reliability, it's really what you need.
UPDATE:
To clarify, I'm sure there are some very reliable open source OODB's out there, but my requirements for "realiability" are more than just whether it doesn't crash and doesn't corrupt data. It includes reliability of the client connectors, reliability of the integration with the object models of popular languages, etc...
This is about open source OODB's, not commercial ones.
this is a good OO database , currently I am working with it
http://www.garret.ru/goods.html
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I find myself very frequently taking the decision between storing a object in the data store more appropriate to its nature (Events, Documents, Graph, etc) or just sticking to the relational database and moving on with my life, and i bet some of you do too.
I'd like to know what criteria you use to take this decision, for example, when is using NoSQL with little data is "premature optmization" and when it is "good enginneering"...
So, When to use the best data store and when to stick to relational?
I see a lot of questions with the nosql tag that include the following:
They want to mix RDBMS and NoSQL systems.
They think NoSQL for large data out performs RDBMS always.
They believe data modeling is always easier with NoSQL.
From personal experience I would consider the cost of discovery when picking a new database.
It is far from easy to move data between relational stores and NoSQL. It's definitely not always intuitive how to model data when working with a document store. Also some of these databases are so new that their query optimization is no where near a relational system.
The things I mentioned above might not seem like a problem when you're doing a proof of concept or working with small amounts of data.
My recommendation would be to not let the hype get to you when picking a solution.
(I've worked with production implementations of Mongo, Couchbase, CouchDB and Redis.)
I'm working with Oracle and Couchbase(nosql document-oriented DB). I think that the use of the NoSql in most cases it is easier and less expensive. Every NoSql DB is a mechanism for solving a rather small range of tasks, and if under your task suited one of them, using NoSql solution will be more optimal than using monstrous large Oracle or MSSql Server. Ofter we use not more than ten per cent of the capabilities of these powerful databases, but not because we know them not at a high level, but because we just don't need all of leeway that they provide
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I am developing with Delphi XE2.
I am planning a software for primary and secondary school. This school have 1,500 students. The database model is relational and we plan to keep the whole history of each student as the years move on. (well at some point it will be archived, but mostly all the relationships will be maintained for a good time)
I used to write Delphi apps using DBISAM V4 from Elevate Software. I hold a licence of it, so it is still a possibility for use it.
However I had contact with many companies using Firebird recently, some using Postgres and many websites with MySQL.
I don`t see a need to go paid databases, since this type of customer is sensitive in investment. So any database that is free for such use, plus the option of keep using DBISAM. I like it but it is getting old.
I prefer to put the business logic on the software, not in the database, so no need to intricate logic or procedures on the database side.
My questions is: What I need to consider to choose the correct database?
This Wiki post can help you. Besides that, you have to decide for using OLE-DB, ODBC or DBX as middleware technology. Depending on which one you will find or not support for Delphi.
Another criteria include know-how on the database options and rectrictions/requirements on security and scalability.
However, no matter what DBMS you choose, my best advice for you is to isolate the access to it in a dedicated service layer so most of your application won't be directly dependent of it.
In your place I would model the application in terms of domain classes and would invest in a persistence layer. If you have to go for another DBMS in the future, most of you code will be preserved.
DBISAM will work here, and you can even write a webservice in Delphi, to provide access to tablets and such. You need to start thinking about the things that really matter here, such as what platform the users are on, how many users total, how many users will be using the database simultaneously (average and peak), how many rows are kept per student, how many add/delete/updated rows daily, etc.. DBISAM has limited SQL. It does a lot, but not everything that you can do in other databases. Their newer product, ElevateDB, addresses most shortfalls, including Unicode.
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What's the diference between using relational database and relational database-object(hybrid).
Im making an application of adverts. Using common relational database, i think I could make tables of each type of adverts: cars,technology,estates,employment, services, this is the way a I do it.But reading about relational database-object I found that you can create a type field in the database(Oracle) that allows you to encapsulate another fields and methods, so what if I make only a table of adverts, knowing that all adverts have fields in common like title, description,the date it publish, images, but I can add a field that encapsulate another objects that will be cars,technology, employment, and inside of each one encapsulate attributes to them like
cars(model,brand,price),
technology(state,price,accesories,dimensions)
emloyment(job,payment)
Well this is the idea, actually for every advert you can actually enlarged the functionality, making a database for each one.
My question is: what are the potencial problems using relational database-object?
What is the best option?
Most if not all, of the worst database designs of the last ten years have at their root tables built to an object model rather than fitted to a relational model.
OOP is a programming thang; its concept of combining behaviour and data together works well when building APIs, etc. But it sucks when it comes to persistence, leading to horribly large tables, lots of duplicated data and monstrously slow queries. I'm not saying that's inevitable but it is the way to bet.
So why does Oracle support Types in the database? Because there are advantages to defining complex data types with behaviour: XMLType is one such, and Oracle Spatial makes extensive use of objects. But these usages are limited to individual columns of regular relational tables. The intention is not, and never has been, that we use object tables to store all the data in the database.
By all means use Types in your Pl/SQL programming. I have done this extensively, and for the right use case they can be extremely effective. Just don't store your data in them.
The most significant difference is that Oracle's object-relational technology is rarely used.
Very few programmers or DBAs have significant experience with object-relational technology. Database tools do not support objects well, or at all. Oracle does not support the technology well - it's buggy and does not get updated frequently.
Of course, just because a feature is rare does not mean you should ignore it. There are cases where Oracle's object-relational features work very well. But if you're planing to build a significant part of your database using objects, you need to consider the loss of skills, technology, and support.
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I have several SQL Server 2005 databases ranging from 20 – 600 tables in an application and no documentation. I am looking for a database diagramming tool that is smart enough to pick tables that seem to be related to one entity (e.g., tables related to Patient, tables related to Orders) or one functionality (e.g., Patient Management, Order Management) and show them separately instead of drawing the entire database.
In the past, I have seen tables related to one piece of functionality represented in one color in the ER diagrams. In a well designed database, perhaps there will be multiple schemas that group tables related to one functionality together. But as all these tables are in one schema, and I want a tool that is smart enough to perhaps suggest which tables should go together under one schema. It won’t be perfect but perhaps it is intelligent enough to examine which tables should go together (for example based on relationships between them or based on which tables seem to be accessed together in the stored procs).
The bottom line is that I want to understand the data-model as quickly as possible. A tool called Schema Spy ( http://schemaspy.sourceforge.net/ ) seem to be headed in the right direction, but I was wondering if anyone knew better/more comprehensive tools.
Thanks.
Have you tried Visio at all? While it does not satisfy everything you asked for it can reverse engineer a database and make very appealing diagrams with a little work.
I have never used it to understand an existing database, but I have used it to explain databases I have created.
You could have a look at wsSqlSrvDoc. It's a nice little tool that works with Sql Server extended properties and creates a MS Word document.
The print-out of all column properties (with foreign key relations) works out of the box. For further descriptions on each field you have to set up extended properties of those columns in Sql Server Management Studio.
The downside however is that it's not free (but quite afordable). And if you just need to create a documentation for a "not work in progress" DB that's more or less finished than it would be enough to use the free trial i'll guess.
This question is related to an older question, Link:A good database modeling tool?
From the answer to this question, e.g. fabFORCE.net dbDesigner might be what you are looking for.
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I'm looking at implementing an RDBMS. Are there any good resources out there about how a database works internally, and the kinds of things I'd need to know when starting out to build my own? (Please no comments about whether it's a practical idea or not - just imagine it's for a hobby project or something).
Again - interested in the RDBMS design, not the Database design. And efficiency is very important (it seems like it's reasonably easy to design some kind of relational database like structure if I don't care about speed).
There are a few textbooks about this sort of stuff out there, when I was in college, we did this for a class project. This book should really help you on your way Database Systems: The Complete Book
I forgot to mention it, but my code is on googlecode here: cs4420-dbase
Please forgive the fact it is written in java, but I was outvoted by my teammates on that decision. but the basic ideas are all still there. It handles file creation and handling as well as a simple SQL parser and optimizer. It handles basic indexing (b-tree) and "memory" management. Please forgive some of the lack of commenting and strange commenting, many late nights were spent on that project.
I'd suggest starting with Introduction to Database Systems and Transactional Information Systems. They should both have bibliographies to take you further.
Building a RDMS is not trival, you need to combine classic CS knowledge from several fields together with deep knowledge about harddrives, OS specifics, filesystems, memory, cpu, caches to make it efficient.
A good article about architecture we are required to read is:
http://www.nowpublishers.com/product.aspx?product=DBS&doi=1900000002
For theoretical knowledge about databases I would recommend to buy a book on this topic, I can only talk about the book I use for this, which is Database Systems an Application-Oriented Approach by Kifer, Bernstein and Lewis.
You might want to look at some opensource databases for ideas.
I recently came to the same question, and like others, struggled a bit finding a book that helped in building an actual RDBMS from scratch (minimal, of course). Contrary to what occurs in other CS areas (OS, Compilers, etc); the Databases area seems to have fewer resources in this regard. Probably because RDBMS are among the hardest to grasp and implement ;-|
Nevertheless, I finally found what appears to be a satisfying answer. Sciore's book "Database Design and Implementation":
http://www.wiley.com/WileyCDA/WileyTitle/productCd-EHEP000711.html
The first two parts are dedicated to learning to use RDBMS, which you probably know already. But the last two parts cover implementation details; and the interesting thing is that a minimal RDBMS (SimpleDB) is used to illustrate the concepts, and also can serve as the platform to perform programming exercises. The Wiley site has a quote that says it better:
"Comes with SimpleDB, a free-to-download, fully functional simplified database system that is (unlike commercial DB systems) small, easily readable and easily modified. SimpleDB can be used as the platform on which students complete homework projects and implement the concepts covered in the book."
Do not bother by the fact the sample RDBMS is written in Java; that has the advantage (IMHO) of hiding the low-level details of implementing in C/Unix. If you come like me from the applications world, you may be unfamiliar with system-programming stuff; but learning the RDBMS implementation concepts in a high level language like Java, can serve as a good bridge for the transition.
The Wiley site allows to buy an electronic version of the book, but the source code is available regardless you buy it. I can not post more than two links, but just google this term (including double quotes), and you will easily find the SimpleDB home page (where you can download it):
"The SimpleDB Database System"
If you are unsure about buying the book (which like other core-CS books, are not cheap for the student); probably you can start reading the code and this introductory article:
http://www.cs.bc.edu/~sciore/papers/SIGCSE07.pdf
If you find it appealing, buying the book may be a good investment.
Hope that helps,
Cheers.