TweetFollow Us on Twitter

dtF
Volume Number:10
Issue Number:9
Column Tag:Tools of the Trade

dtF

A royalty-free relational database management system

By Jeff Fisher, SalesKit Software Corp.

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

About the Author

Jeff Fisher - Jeff works at SalesKit Software Corp. While looking around for a good database to use with their application software, they ran across dtF. Skeptical at first, he checked it out. Now he’s uses it and loves it. Apparently he’s not alone in how he feels about it. His former partner liked it so much he became the US distributor for it (dtF Americas).

Finally there’s a royalty-free relational database management system for Macintosh C/C++ application developers. The performance may surprise you, yet the library is small and requires only a few hundred K of RAM at runtime. It features SQL, full transaction control, error recovery, client server architecture and is optimized for the Macintosh. The new product is call dtF and was developed in Germany. Like German automobiles, dtF is well built and efficient in every aspect. Unlike German automobiles, dtF does not cost an arm and a leg.

Performance

Many SQL database management systems are just an SQL interface plopped on top of an ISAM record access system. Such a system can’t deliver the performance of a system designed from the ground up. dtF is a true set-oriented SQL engine designed specifically for optimum performance on personal computer architectures.

The performance of dtF is unequaled in our tests. We have clients who want to access large databases (>22,000 records) from a standalone version of our software. With our old database engine, queries that took more than five minutes now take less than thirteen seconds with dtF! I always hate performance comparisons because they never compare aspects relevant to my projects. There is really no substitute for doing your own tests. We compared dtF’s data access speed with 4D, Oracle, Inside Out, and FoxPro 2.5. We found dtF to be over eight times faster on multi-table ordered queries (an aspect relevant to our project) than the nearest competitor.

Client/Server

dtF implements a client/server architecture. It does not use file sharing to support multi-user table access over the network. The dtF server processes queries and sends only results to the client. This ensures high performance, efficient use of the network bandwidth, and data security. File sharing approaches place high demands on a network and the onus of doing lock management, deadlock detection, and error recovery on the application developer.

One interesting aspect of dtF is how it divides labor between client and server. Many client server systems assume a “dumb” client. This traditional approach creates a bottleneck at the server - not only does the server perform client requests but each time a user scrolls a list window the client must ask the server to send down more data. This can create a lot of unwanted network traffic as well as bog the server down with intermittent requests for data. The dtF server passes results to the client so no network traffic is generated when accessing results. This approach is ideal for modern network environments and puts your existing equipment to good use. The precious power of the server is reserved for processing transactions and the client can get right to the job of displaying results.

Both single-user standalone and client-server versions of dtF use the same client-server model and interface.

Stand alone applications with dtF can be converted to multi user client/server applications by simply adding three library calls to your code. This helps dtF offer a practical standalone interface, perhaps the only one for a Macintosh SQL DBMS.

Transaction Control

dtF supports true transaction processing. This is the only way to ensure data integrity. Consider an order processing application that requires one transaction to add the order and five more transactions to add line items to another table. If there is a network failure on the third line item, it is essential to abort the entire transaction. In such a case dtF would simply rollback the transactions and return the database to a state which looks like they never took place.

The current Macintosh version of dtF server can handle 63 parallel concurrent transactions with automatic lock management, automatic deadlock detection, and error recovery. With an ISAM record access system, you have to explicitly lock records and indexes when performing updates and deletes. Lock management and deadlock avoidance can become very complex when you have multiple related tables. For example:


/* 1 */
// must lock both tables to avoid deadlock

act_locked = bogus_lock(accounts);
cnt_locked = bogus_lock(contacts);

if (!act_locked || !cnt_locked )
 return errorDeadLocked;

bogus_use(accounts); // use the accounts table
if (bogus_seek (theAccountID))//  find the desired record
{
 bogus_delete(); // delete the account record
 bogus_use(contacts);// use the contacts table
 bogus_settag(“act_id”);
 if (bogus_seek (theAccountID))  //  find the desired record
 {
 bogus_delete(); // delete the account record
 }
}
bogus_unlock(accounts);
bogus_unlock(contacts);

On the other hand, all lock management and deadlock detection is done by dtF. Client/server applications require no special multiuser considerations. You don’t have to write anything similar to the above code.

Security

All data within a dtF database is encrypted and compressed. Tables requiring 22MB in another database management system took less than 4MB in dtF. Data encryption ensures that data cannot be pilfered, even with disk editors. Access rights are granted at the table level. Read, update, insert, and delete privileges can be set at the table level. Administration rights (create and delete tables and indexes) are also granted at the table level.

Utilities

dtF comes with a database administration tool and browser (written with MacApp) call dtFQuery.

You can use dtFQuery to:

• Import data

• Export data

• Issue SQL statements.

• Create databases with your own creators and file types

• Repair corrupted database files.

Compatibility

dtF supports a large subset of ISO standard SQL, and it is optimized for performance and ease of use on the Macintosh. dtF libraries are included for the latest MPW C/C++ and Symantec environments. I use dtF with MacApp 3.0.1 and TCL and have included a sample MacApp application [available on this month’s source disk and the online services - Ed stb].

API

Both the multi user and stand alone versions of dtF have the same C interface. This allows you to develop applications with client server architecture that will perform great in single user, single platform situations. Converting a single user applications using dtF into a multi user application is easy. Add three function calls to select a dtF server and relink with the multiuser object library.

There are two interface levels called simply Level 1 and Level 2. This provides the developer with two possible levels of abstraction and encapsulation. The Level 2 interface is a high-level, easy-to-use interface. The Level 1 interface gives you raw access to dtF. We use the high-level interface for all of our testing and development and have found no need to access the low level interface so far.

In our MacApp 3.0.1 application, we call 15 different dtF functions. A fully functional application could use as few as three: select database (or server), logon, and execute. While this seems almost too simple, remember that all operations are encapsulated in the SQL you submit to the server.

All memory used by dtF is allocated at startup, so you won’t have to struggle with intermittent low-memory conditions caused by the DBMS. And because it has its own virtual memory and caching system, you will never have to preflight queries. The virtual memory and caching systems can be optimized by adjusting values in a resource.

dtF is ideal for use with MacApp because it will not interfere with MacApp memory allocation and segment management schemes. Other database management systems require you to jump through a few hoops to fit in with MacApp. dtF requires no explicit call to initialize or shutdown, and you don’t have to provide idle handlers to dtF.

Why SQL?

An SQL database management system like dtF offers the developer a single interface for data definition, data manipulation and data administration. ISAM (Indexed Sequential Access Method) architectures aren’t as convenient for getting at your data (selecting indexes, filtering unwanted records, etc ). With an SQL database management system, you describe the results you want with the SQL statement and the database engine does the rest.

As an example, suppose that you are developing a contact management system and you want a list of the contacts with last name equal to “Smith” grouped by account name. The code required to retrieve the desired result from dtF is shown below.


/* 2 */
char theSQL[255];

strcpy(theSQL, "select * from accounts,contacts where
 accounts.act_id = contact.act_id and 
 contacts.l_name = 'Smith' group by
 account.act_name order by contacts.zipcode");

dtF2exec(theSQL);

   // now access the results which are already sorted

All you have to do is submit a simple SQL statement and dtF does all the processing.

The same query with a typical ISAM record access system would look something like the following.


/* 3 */
bogus_use(accounts); // use the accounts table
bogus_settag(“act_name”);
actRecNum = bogus_recordcount();

for (act_index = 1; act_index <= actRecNum; ++act_index)
{
 bogus_fieldstring(“act_name”,accountName);
 bogus_fieldstring(“act_id”,accountID);

 bogus_use(contacts);
 bogus_settag(“l_name”);
 cntRecNum = bogus_recordcount();

 bogus_seek (“Smith”)
 do     // look for hits
 {
 bogus_fieldstring(“act_id”,cntAccountID);
 if (strcmp(cntAccountID,accountID) == 0) // if account ids match
 {
 // we finally found one
 }
 }while (bogus_skip(1));

 bogus_use(accounts);
 bogus_settag(“act_name”);
 bogus_skip(1);
}

Or even worse.


/* 4 */
bogus_act_ref = bogus_open(accounts);// use the accounts table
bogus_cnt_ref = bogus_open(contacts);// use the contacts table

bogus_setbuffer(bogus_act_ref ,&bogus_act_struct); 
 // <<hardcoded structs
bogus_setbuffer(bogus_cnt_ref ,&bogus_cnt_struct); 
 // <<hardcoded structs

bogus_setkey(bogus_act_ref ,”act_name”);
bogus_setkey(bogus_act_ref ,”l_name”);

while (bogus_posvalid(bogus_ref,&bogus_struct))
{
 bogus_cnt_hardcodestruct.act_id = bogus_act_struct.act_id;
 
 // use up a bunch of memory building a result set

 bogus_do_find(bogus_cnt_ref,&bogus_cnt_struct)
 tempSet = bogus_build_set(bogus_cnt_ref ,bogus_cnt_struct);
 bogus_set_read(bogus_cnt_ref ,tempSet );
 bogus_sort_set(tempSet );

 // intersect result set with previous result sets
 bogus_intersection(resultSet,tempSet);
 bogus_skip(bogus_cnt_ref ,1);
}
   // finally use the result set to access selected records

This seems like an extreme example, but I’ve used a database engine that even required me to check to see if the current record was marked as deleted before using the result.

Cursors

When you are going to deal with queries which will generate very large results, sometimes it’s better to let the server keep track of the results, and then use a set of “cursor” calls to navigate through the results without needing to bring them all into the client’s memory all at once. A cursor is a reference into the results, and it can be used to index through the results. Developers familiar with DAL, ODBC, Oracle call interface, Sybase DBLib or any other SQL C programming interface are probably already familiar with this concept.

For an example, consider the large database that MacTech Magazine uses to keep track of its subscribers. The subscription guy needs to notify individuals who’s subscriptions will run out soon to help prevent them from missing a single excellent MacTech issue. He needs a subset of the total subscribers and he may also want them ordered by zip code (so he can save some money on postage). A cursor is an efficient way of producing the ordered subset without building a table in the client’s memory.

In a graphical operating system like the Macintosh, you may want several cursors, one for each list view or one for each window. For example, in a contact management application, you have a list of all available contacts ordered by last name. In another window, you might have a list of contacts with whom you have an appointment, ordered by appointment date. There could be thousands of contacts (my boss has over 6000 in his contact manager) and the query results might just be too big to hold in memory. If every window has its own cursor, each window can display different result sets from the appointments table at the same time. This is supported by a dtF concept called workspaces. Each cursor is referenced by a unique workspace identifier.

dtF allows forward and backward cursor movement. Some client server systems will only move forward or require you to build a result buffer in memory to move backward. Bi-directional cursor movement can really simplify your application.

Support

After using several different DBMS systems, we have amassed many support horror stories and were very concerned about using a database developed in Germany. We decided go to Germany and get the story first hand. dtF was developed by the Theta Group and I was very pleased to find out that they are true Macintosh fanatics. We have been developing with dtF for almost six months and have been thrilled with the support we have received. While all support is currently provided by the Theta Group, plans are well underway to provide support in the United States through dtF Americas, the new US distributor of dtF.

Future of dtF

Currently in the works are a multi user version using TCP/IP rather than AppleTalk, further performance optimization, and cross-platform support. An AppleScript extension using dtF is already available from Graphical Business Interfaces and many other third parties tools and applications will be available in the US by the printing of this article.

Conclusion

dtF is a relational database management system created by Macintosh developers for Macintosh developers. Efficient. Fast. SQL. Compact. Safe. We have examined all of the options and have chosen dtF and now you know why.

Pricing information: dtF Evaluation $129, dtF Macintosh SDK $695, dtf LAN Macintosh SDK $1595, dtf Server $1295.

For more information, contact dtF Americas, Inc. at 14720 Plumas Drive, Chesterfield, MO 63017. (800) DTF-1790 voice, (314) 530-1697 fax, AppleLink DTF.AMERICA.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Arq 5.8.5 - Online backup to Google Driv...
Arq is super-easy online backup for Mac and Windows computers. Back up to your own cloud account (Amazon Cloud Drive, Google Drive, Dropbox, OneDrive, Google Cloud Storage, any S3-compatible server... Read more
Backblaze 4.3.0.44 - Online backup servi...
Backblaze is an online backup service designed from the ground-up for the Mac. With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
Instaradio 7.1 - Listen to your favorite...
Instaradio is fast, and it could be the radio player you have been waiting for. Try the app thousands of people rely on for listening to radio. Features Listen to radio from all around the world... Read more
EtreCheck 3.3.3 - For troubleshooting yo...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
Hopper Disassembler 4.2.1- - Binary disa...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32-bit and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about... Read more
Slack 2.6.2 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.6.2: Fixed Inexplicably, context menus and spell-check... Read more
Apple Final Cut Pro X 10.3.4 - Professio...
Apple Final Cut Pro X is a professional video editing solution.Completely redesigned from the ground up, Final Cut Pro adds extraordinary speed, quality, and flexibility to every part of the post-... Read more
Numi 3.15 - Menu-bar calculator supports...
Numi is a calculator that magically combines calculations with text, and allows you to freely share your computations. Numi combines text editor and calculator Support plain English. For example, '5... Read more
TunnelBear 3.0.14 - Subscription-based p...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
Apple iMovie 10.1.6 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more

Latest Forum Discussions

See All

Goat Simulator PAYDAY (Games)
Goat Simulator PAYDAY 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ** IMPORTANT - SUPPORTED DEVICES **iPhone 4S, iPad 2, iPod Touch 5 or better Goat Simulator: Payday is the most... | Read more »
Zombie Gunship Survival Beginner's...
The much anticipated Zombie Gunship Survival is here. In this latest entry in the Zombie Gunship franchise, you're tasked with supporting ground troops and protecting your base from the zombie horde. There's a lot of rich base building fun, and... | Read more »
Mordheim: Warband Skirmish (Games)
Mordheim: Warband Skirmish 1.2.2 Device: iOS Universal Category: Games Price: $3.99, Version: 1.2.2 (iTunes) Description: Explore the ruins of the City of Mordheim, clash with other scavenging warbands and collect Wyrdstone -... | Read more »
Mordheim: Warband Skirmish brings tablet...
Legendary Games has just launched Mordheim: Warband Skirmish, a new turn-based action game for iOS and Android. | Read more »
Magikarp Jump splashes onto Android worl...
If you're tired ofPokémon GObut still want something to satisfy your mobilePokémon fix,Magikarp Jumpmay just do the trick. It's out now on Android devices the world over. While it looks like a simple arcade jumper, there's quite a bit more to it... | Read more »
Purrfectly charming open-world RPG Cat Q...
Cat Quest, an expansive open-world RPG from former Koei-Tecmo developers, got a new gameplay trailer today. The video showcases the combat and exploration features of this feline-themed RPG. Cat puns abound as you travel across a large map in a... | Read more »
Jaipur: A Card Game of Duels (Games)
Jaipur: A Card Game of Duels 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: ** WARNING: iPad 2, iPad Mini 1 & iPhone 4S are NOT compatible. ** *** Special Launch Price for a limited... | Read more »
Subdivision Infinity (Games)
Subdivision Infinity 1.03 Device: iOS Universal Category: Games Price: $2.99, Version: 1.03 (iTunes) Description: Launch sale! 40% Off! Subdivision Infinity is an immersive and pulse pounding sci-fi 3D space shooter. https://www.... | Read more »
Clash of Clans' gets a huge new upd...
Clash of Clans just got a massive new update, and that's not hyperbole. The update easily tacks on a whole new game's worth of content to the hit base building game. In the update, that mysterious boat on the edge of the map has been repaired and... | Read more »
Thimbleweed Park officially headed to iO...
Welp, it's official. Thimbleweed Park will be getting a mobile version. After lots of wondering and speculation, the developers confirmed it today. Thimbleweed Park will be available on both iOS and Android sometime in the near future. There's no... | Read more »

Price Scanner via MacPrices.net

Free Tread Wisely Mobile App Endorsed By Fath...
Just in time for the summer driving season, Cooper Tire & Rubber Company has announced the launch of a new Tread Wisely mobile app. Designed to promote tire and vehicle safety among teens and... Read more
Commercial Notebooks And Detachable Tablets W...
Worldwide shipments of personal computing devices (PCDs), comprised of traditional PCs (a combination of desktop, notebook, and workstations) and tablets (slates and detachables), are forecast to... Read more
Best value this Memorial Day weekend: Touch B...
Apple has Certified Refurbished 2016 15″ and 13″ MacBook Pros available for $230 to $420 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2.6GHz... Read more
13-inch MacBook Airs on sale for up to $130 o...
Overstock.com has 13″ MacBook Airs on sale for up to $130 off MSRP including free shipping: - 13″ 1.6GHz/128GB MacBook Air (sku MMGF2LL/A): $869.99 $130 off MSRP - 13″ 1.6GHz/256GB MacBook Air (sku... Read more
2.8GHz Mac mini available for $973 with free...
Adorama has the 2.8GHz Mac mini available for $973, $16 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
15-inch 2.2GHz Retina MacBook Pro on sale for...
Amazon has 15″ 2.2GHz Retina MacBook Pros (MJLQ2LL/A) available for $1749.99 including free shipping. Apple charges $1999 for this model, so Amazon’s price is represents a $250 savings. Note that... Read more
Huawei Unveils New ‘Business-Styled’ MateBook...
Huawei has introduced a trio of new MateBook laptops, expanding its mobile portfolio and building on its success in delivering attractive and powerful high-end devices. The company claims the HUAWEI... Read more
Deal! Gold 12-inch 1.2GHz Retina MacBook for...
Amazon has the 2016 Gold 12″ 1.2GHz Retina MacBook (MLHF2LL/A) on sale for $350 off MSRP for a limited time. Shipping is free: - 12″ 1.2GHz Gold Retina MacBook: $1249.99 $350 off MSRP We expect this... Read more
13-inch 2.0GHz MacBook Pros on sale for $100...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $100 off MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 13″ 2.0GHz MacBook Pro Space... Read more
15-inch 2.2GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP, and it’s the lowest price available for a 15″ MacBook Pro. An Apple one-year warranty is... Read more

Jobs Board

*Apple* Mac and Mobility Engineer - Infogrou...
Title: Apple Mac and Mobility Engineer Location: Portland, OR Area Type: 12 month contract Job: 17412 Here's a chance to take your skills to the limit, learn new Read more
*Apple* Retail - Multiple Positions, White P...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Best Buy *Apple* Computing Master - Best Bu...
**509110BR** **Job Title:** Best Buy Apple Computing Master **Location Number:** 000048-Topeka-Store **Job Description:** **What does a Best Buy Apple Computing Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.