[Info-vax] Indexed file read question

[abrsvc]

On Wednesday, 18 November 2020 at 23:50:37 UTC-5, Hein RMS van den Heuvel wrote:
> >On Wednesday, November 18, 2020 at 10:02:58 PM UTC-5, abrsvc wrote: 
> > 
> > That makes sense. So as I thought I stated: If a read is done using a primary key first then a read using a secondary key, the "starting >point" is the position within the file based upon the first read such that read #2 will return the first record with the matching >secondary key that appears AFTER the first record read rather than the first record in the file that matches the secondary key.
> Again, as I wrote before ---- Noop. Incorrect. A keyed record lookup establishes a fresh context. 
> 
> What part of that do you not understand?
> > example. Wouldn't the returned record for the keyed read using the 
> > secondary key return the aap A record since it is the first in the file 
> > with the secondary key of A
> NOOP. From the example:
> $ conver/merge tt: tmp.idx 
> noot A 
> vuur B 
> aap A
> Therefor the first record inserted ( BY TIME! ) with key A was 'noot', not ' aap' 
> The first record - by primary key - is ' aap' but that was not the first alternate key 'A' to be inserted. 
> 
> Hoff wrote>> Hein is assuming a key search on the secondary key to start the sequential access on the secondary key, 
> 
> I assume nothing. I simply know how it is. That's a Dutch thing. Much like: https://images.app.goo.gl/QhdvQ7CvxordwGEj6 
> Key search is NOT sequential search. Sequential access and context is established by either 
> 1) a $REWIND or $CONNECT with KRF=xxx , pointing to the first row by that key, and with duplicates the first (by time) inserted with that first key. 
> 2) a $GET with KRF=xxx, pointing to the first row with alternate key satisfying the key ( KBF,KSZ,RAC)... independent on any other action/context on that stream ($CONNECT) 
> 
> Hoff>> then switching to and doing sequential $get operations on the secondary 
> 
> That functionality does NOT exist in RMS 
> 
> Hoff>> what record might you sequentially $get on the secondary key is indeterminate. 
> 
> Noop. You'll get the next record by primary key as you cannot switch key context on sequential access as per above. 
> 
> Cheers, 
> Hein

Got it.  Thanks for the clarification.