[Info-vax] Indexed file read question

[Hein RMS van den Heuvel]

>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