Skip to main content

What VFP 9's Removal of Array Limits Really Means

Interesting post by John K. about how the limits in VFP 9 have been substantially removed and yet may still rear their ugly head because of machine constraints.

But it explains very well how and why you may want to rethink how your applications may be built.

A great example is the removal of the limitations of an array.

Let's say you have 1,000,000 records in a table named X.

I created this table by listing all of the files in a folder showing two columns: one for the file name and another for the size.
CFIELD1 C(30)
NSIZE N(10)

=ADIR(la,"C:\windows\system32\*.*")
CREATE TABLE x (cField1 C(30), nsize N(10))
lnRow = 1
FOR lni = 1 TO 1000000
IF lnRow+lni>ALEN(la,1)
lnRow = 1
ELSE
lnRow = lnRow+lni
ENDIF
INSERT INTO X VALUES (la(lnRow,1),la(lnRow,2))
ENDFOR

This ensured I had at least some variety of data in my results.

In VFP 7, you couldn't do

SELECT * FROM x INTO ARRAY la

You would run out of memory.

However you CAN do it in VFP 9 which means that even though VFP is super fast with tables, it's even faster with memory.

Examples
Sorting Data
ASORT(la,2) took .698 seconds on a P IV with 512MB RAM.
INDEX ON nSize TAG t took 4.355 seconds in VFP 9

(note: ASORT(la,1) - which is the field name took approximately 2.5 seconds, the Index took 7 seconds)

Interestingly, not doing the index to a tag but to its own IDX took 1.6 seconds

Looking for Data
ASCAN(la,"WRITE.EXE") took .329 seconds
LOCATE FOR cField1="WRITE.EXE" took close to 1 second

(Note: If you do a SELECT * FROM X INTO CURSOR y and try the same things, the locate statement only takes about .600 seconds)

See where this is leading? If you have to process data in memory, it makes far more sense to put it into a cursor or better yet into an array.

And you can even put these arrays into objects for quick retrieval:

loCustomers = CREATEOBJECT("Custom")
loCustomers.AddProperty("myData(1,2)")
SELECT * FROM X INTO ARRAY loCustomers.myData

All the same performance benefits apply.

As database developers, we often think of things as tables for storing temporary data, but now with VFP 9, we can store them as memory variables and wow! the performance gets instantly better.

If performance is your thing, then VFP 9 is definitely king.


The Limits of Architecture vs. The Architecture of Limits (by John Koziol)

Comments

Popular posts from this blog

Well, that explains CodePlex...

In a move that will be sure to anger open source (or rather anti-paid software, anti-Microsoft open source)  zealots, Microsoft is planning to buy GitHub . A year ago, I mused about why Microsoft would shut down CodePlex and how the world needs competing source code repositories to be strong. I'm not the only one per this Slashdot article  : "...   people have warned about GitHub becoming as large as it did as problematic because it concentrates too much of the power to make or break the open source world in a single entity, moreso because there were valid questions about GitHubs financial viability...." - Jacques Mattheij I will be interested in seeing this play out - whether developers jump ship or not. Have all the efforts Microsoft has made in pushing towards open source be seen as genuine or will all the zealots jump ship or maybe even attack? Microsoft's comment about why they shut down CodePlex referred to how spammers were using CodePlex. Well, GitHub

Attending Southwest Fox 2019 could change your life - Find out how

Southwest Fox is coming up in October and as I do every year, I spoke with the organizers Rick , Doug and Tamar on the FoxShow. Deadlines for Southwest Fox: Super-saver price (before July 1): $695 Early-bird price (before August 1): $770 Regular price (August 1 and later): $820 This year, I took a different approach with separate shows for each organizer but the main message is still the same : July 1st is their Go/No-Go date. Conferences don't talk about this very often. I don't think developers really question if Apple will hold their WWDC in June or Microsoft will hold their Build conference - but that's because those conferences are vendor-led. Southwest Fox is a community-driven conference - it's not driven by a company with an agenda. Listen to the interviews and you can hear how important each of the organizers feel the live connection between speakers and among attendees.

eero icons - What the heck?

How to change icons used by eero.... Formerly titled: Eero router - Nicknames and icons UPDATE: Finally!!!! The most recent update to the eero now allows you to specify icons from their library. And it's a GOOD library - thank you. Finally! If you've extended your wireless network using eero , you have downloaded the app. I upgraded my network when I noticed a bunch of dead spots in what should have been a fairly reasonable coverage space (1700 sqft home). With two eero devices, our home is pretty well covered. Click on Connected devices and every device connected to your network is displayed. The eero app identifies the manufacturer and, with some devices, even the name of a given device. The eero app may also show an icon that represents its use. Some of the more obvious icons are those for phones, laptops and TVs. Unfortunately, the majority of devices get a fairly generic "wifi" icon. But you can change this. Give devices a nickname using ce