Question:structural vs non-structural index?

Question:structural vs non-structural index?

Post by Bill Wils » Mon, 27 Nov 1995 04:00:00



I understand what a stand alone index is (*.idx) but I am a little
confused on what a structural and non-structural index is. They are
stored in *.cdx and need to be referenced using TAG but from there I am
not sure of what they are. an someone offer further explanantion?
Thanks.
 
 
 

Question:structural vs non-structural index?

Post by Joe Ha » Tue, 28 Nov 1995 04:00:00


Bill - basically a .cdx is always updated, as it is automatically
opened with the dbf.  An .idx is udated only if you open it.

For example, with idx, you must say
  use dbfile index indexfile1, indexfile2, etc.
(if you have multiple indices, you must open each one)
with .cdx, they are opened along with the dbf, and updated.
And with .cdx, you set order to 1  or  to tagname

I hope this helps.  I have used .cdx exclusively with no problems.
Joe


>I understand what a stand alone index is (*.idx) but I am a little
>confused on what a structural and non-structural index is. They are
>stored in *.cdx and need to be referenced using TAG but from there I am
>not sure of what they are. an someone offer further explanantion?
>Thanks.


 
 
 

Question:structural vs non-structural index?

Post by Ronals Abt » Tue, 28 Nov 1995 04:00:00


Quote:>Bill - basically a .cdx is always updated, as it is automatically
>opened with the dbf.  An .idx is udated only if you open it.

I usually use a cdx with another name than the DBF.
So it is not automatically opened but gives me more flexability if the
index is damaged on lets say a network.
I open the DBF with the appriopriate cdx once at the start of the program
and keep it open for that session.
You can use indexes by the same name, in that case it is opened
automatically.
 
 
 

Question:structural vs non-structural index?

Post by Toby K H » Wed, 29 Nov 1995 04:00:00


: I understand what a stand alone index is (*.idx) but I am a little
: confused on what a structural and non-structural index is. They are
: stored in *.cdx and need to be referenced using TAG but from there I am
: not sure of what they are. an someone offer further explanantion?

The most important difference to me is that if a structural index with the
same name as the database is available, it is opened automatically when the
database is opened and updated whenever the database is changed (records
added, data edited, etc.).  So the index always reflects the current
state of the database - which is not the case with my IDX indexes which I
always forget to open.

 
 
 

Question:structural vs non-structural index?

Post by Toby K H » Wed, 29 Nov 1995 04:00:00


: Bill - basically a .cdx is always updated, as it is automatically
: opened with the dbf.  An .idx is udated only if you open it.
. . . snip . . .

I think this is true only of a structural compound index file
(structural CDX) - i.e. the CDX with the same name as the DBF that is
created when you specify indexing in the create database window, or index
to a TAG without providing OF <cdxName> (he writes, shamelessly copying
from the Language Refernce entry for INDEX).  It is possible to create
non-structural CDXs (the name is different from the name of the DBF) and
they will not be opened when the DBF is opened unless you specifically
ask.  
 Just to cover one more base, FoxPro knows that a CDX exists when it
opens a DBF because its existence is recorded in the DBF header.  So I
can't make a non-structural CDX into a structural one by renaming it to
the same name as the DBF - FoxPro will open the DBF, check the header, and
say "Nope, no structural CDX.", and ignore the CDX I so carefully renamed.

 
 
 

Question:structural vs non-structural index?

Post by Bill Urms » Wed, 29 Nov 1995 04:00:00


Can anybody tell me what the differences are between VFP and VB?

I've heard that VB has very good ability with different data
structures.  Any comments would be appreciated, Thanks.

-Bill

 
 
 

Question:structural vs non-structural index?

Post by Cy Wel » Thu, 30 Nov 1995 04:00:00



>I understand what a stand alone index is (*.idx) but I am a little
>confused on what a structural and non-structural index is. They are
>stored in *.cdx and need to be referenced using TAG but from there I am
>not sure of what they are. an someone offer further explanantion?

Its pretty easy actually.  A structural .CDX is one where the base
part of the name of the CDX is the same as the table.  If its got a
different base name, its a non-structural CDX.

--
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* Cy Welch                              All views are my own *

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**************************************************************

 
 
 

Question:structural vs non-structural index?

Post by Bill Wils » Fri, 01 Dec 1995 04:00:00



Quote:

>>Bill - basically a .cdx is always updated, as it is automatically
>>opened with the dbf.  An .idx is udated only if you open it.

>I usually use a cdx with another name than the DBF.
>So it is not automatically opened but gives me more flexability if the
>index is damaged on lets say a network.
>I open the DBF with the appriopriate cdx once at the start of the
program
>and keep it open for that session.
>You can use indexes by the same name, in that case it is opened
>automatically.

So a structural index is a cdx with the same name as the dbf and it
opens automatically when the table is opened? And a non-structural index
a cdx file with a name other than the dbf and has to be opened
explicitly?
 
 
 

1. Further inquiry: Question:structural vs non-structural index

     No, a non-CDX index must be explicitly opened ragardless of its name.

Sincerely,

Gene Wirchenko

--
Three views of the proverbial partial glass of water:
     Optimist:          half full
     Pessimist:         half empty
     C Programmer:      implementation defined

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