Demand Indexes and deleting records.

[Reggie Freedman]

Demand indexes are simply a 'snapshot or photograph' taken of the database at the moment in time the demand index is created. If (if) the database 'photograph' is changed by the deletion or addition of a record the possibility of a record number being occupied by new data or replaced data will be observed. 

The demand index is only a temporary database picture, updated manually and is frozen in time pointing to the position in the database of a record number. Therefore the demand index is no longer valid and is now void. It should not be used again (unless rebuilt). filePro demand indexes has always, since version one, worked that way.

Reggie



----- Original Message -----
From: Nancy Palmquist via Filepro-list <filepro-list at lists.celestial.com>
Reply-To: Nancy Palmquist <Nancy.Palmquist at vss3.com>
To: filePro Mailing List <filepro-list at lists.celestial.com>
Sent: 12/14/2020 12:11:16 PM
Subject: Demand Indexes and deleting records.
________________________________________________________________________________

filePro People,

I just noticed a very strange thing but it makes sense in a way.

Once a week I build a demand index with the oldest stuff in a very large 
database.  I then run through that index and delete items until I run 
out of time.

So I have an index with some items deleted and some not.

What I just noticed is that when new records are added into the slots 
where records were deleted, they seem to be included in the index. It 
makes sense in that the index has record pointers.  The data is not in 
sorted order but it is picking up the data on the record as if it should 
be in the index.

I offer this as a caution that if you are depending on a demand index to 
remain the same, you may be surprised if you are deleting records to 
find new records in their place in the index.

I am not entirely happy with this behavior but I can understand the 
cause. In all the years I have been using filePro I never noticed this 
behavior before and thought it worth mentioning.  I can't decide if I 
would qualify it as a bug or what.

Nancy

-- 
Nancy Palmquist
Owner
Virtual Software Systems - www.vss3.com
(412) 835-9417

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