The LA Fox Developer Newsletter

June 1994

The LA Fox Developer is the monthly newslet-

ter of the LA Fox User Group. The purpose is

information sharing among application develop-

ers and users working with FoxPm.

LA Fox Address:

LA Fox User Group

Chuck Williams

(310) 539-9439

977 Ashbndge Lane

Harbor City, CA 90710

LA Fox Board of Directors

Chuck Williams, President

David Van Valkenburg, Treasurer

Allen Garfein, Membership

George Dvorak

Warren Rekow

Bill Seldon

Barry Lee, Newsletter Editor

Gregg Dunn

Kns Dahlin

The newsletter contains regular columns and

articles from other user groups.

XPro User Group

Randy Unruh

(310) 399-9159

2210 Wilshire Blvd. - #161

Santa Monica, CA 90403

OC FoxPro Developers Group

John Miller

(714) 661-5264

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Fox Developer Newsletter, is $45.

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LA Fox President’s Column (Con't from Page 1)

situations.

And FoxPro is at the forefront of this advance, with its

Rushmore query optimization technology, which was the focus

for most of this meeting. Rushmore operates with commands

that include a For clause containing an optimizable expression,

with files operating under Set Filter conditions, and with SQL

Select queries containing optimizable expressions in the Where

clause. The amount of performance improvement depends

largely on the relative size of the result set to the whole file, and

the relation of the query expression to the expressions for the

available indexes.

Despite the fact that Rushmore is “fully integrated and auto-

matic”, it really does require careful design and careful program-

ming to get the full benefit, or at least to stay out of the way and

let FoxPro do its thing. There are no hard and fast rules that

work in every situation, but there are guidelines that will steer

you in the right direction in laying out your data structure, build-

ing indexes, and expressing queries. If performance is really

critical, there is no substitute for carefully designed testing to

evaluate alternatives in your particular data and network envi-

ronment. As usual in complex situations, there are tradeoffs -

you may have to program for best response for one type of

query at the expense of slower response for other queries -

picking the right strategy depends on knowing your data and

knowing your queries.

Perry led us through a range of topics including the Append

From command for speed when adding records to a file, the

importance of exactly matching the For clause expression to an

index expression, the benefits of even partial optimization, the

need to build an index tag on the Deleted() function, the need to

avoid setting an Order, the benefits of Selecting into a cursor,

and many more. Needless to say, this brief column can’t do

justice to the topic, but I can point you at some other sources if

you want more information.

Much of the material we covered, including some of the same

examples, is included in George Goley’s book, Creating FoxPro

Applications. George devotes 22 pages in Chapter 15 to a

discussion of Rushmore and performance issues. This is a long

time area of specialization for George - he has written many

articles in Data Based Advisor and he speaks on this topic at

every FoxPro devcon - you won’t find it more thoroughly or

clearly described. However, this is a complex topic, and no

single approach works for everyone, so you might want to look

at David Kalman’s book, FoxPro 2.5 Developers Handbook.

David devotes 60 pages in Chapter 6 to Rushmore and SQL,

and part of Chapter 3 to indexing strategies (combination of

(Con’t, Page 3)

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