[Info-vax] Indexed file read question

[abrsvc]

On Wednesday, 18 November 2020 at 12:24:10 UTC-5, Stephen Hoffman wrote:
> On 2020-11-18 16:35:41 +0000, abrsvc said: 
> 
> > On Wednesday, 18 November 2020 at 11:20:54 UTC-5, Stephen Hoffman wrote: 
> >> On 2020-11-18 15:23:13 +0000, abrsvc said: 
> >> 
> >>> Situation: Indexed file with 2 keys, the first key no duplicates, 
> >>> second key no duplicates. For clarity, the first key is a record 
> >>> number and the second key is one of 4 values: A,B,L or blank. 
> >> With only four records possible, why is this even a file? Which 
> >> implies there *are* duplicates on the secondary? 
> >
> > I have over simplified the situation just to provide a context for the 
> > question. This is just one of many questionable practices wihtin this 
> > code system. 
> > More time is spent opening and closing files with singular records than 
> > anything else. I am not in a position to change this, I am just trying 
> > to assist with understanding how the current system works. 
> > 
> > Update: There are duplicates for the second key.
> I've long assumed the order of record retrieval is indeterminate when 
> switching to a secondary key with duplicates; that's what is documented. 
> 
> That secondary key would usually be created as a segmented key here, if 
> the primary is to (also) be involved in the ordering of secondary 
> record retrieval.
> -- 
> Pure Personal Opinion | HoffmanLabs LLC
OK  Thanks.  That is what I thought.  These are not segmented keys.  I will look further, but posts here have supplied what I needed.

RE: The overall application design:  There are numerous instances of files being used as message communication mechanisms with 1-10 records each.  Not very efficient, but that is how this system was created.  Many cases of the  following sequence:  Open file, update 1 field in a record, close file.  Very crude synchronization technique as each open is in a loop such that if file is locked, go back and try again (forever...) until you get it open.

Many other such items throughout the code.  I am not involved with "fixing' the problem, only to explain how it currently "works".