[Info-vax] CRTL and RMS vs SSIO

[Arne Vajhøj]

On 10/13/2021 10:54 PM, Dave Froble wrote:
> On 10/13/2021 8:31 PM, Arne Vajhøj wrote:
>> On 10/13/2021 4:53 PM, Dave Froble wrote:
>>> On 10/13/2021 1:59 PM, Arne Vajhøj wrote:
>>>> Here is an example of some (Python) code using SQL to
>>>> join, select, aggregate, sort and limit some data.

>>>> I believe that it would take a lot more code to
>>>> retrieve data from index-sequential files and
>>>> do the work on the data.
>>>
>>> Not a lot, however the sorting by customer name would entail some
>>> additional code.
>>>
>>> However, reading the order file, doing the selection, look-up customer
>>> record, and release to record sort, then read back sorted records is
>>> not "a lot more" code.
>>
>> I tried writing it in Pascal using index-sequential files.

> Gee, I'm sure glad I never tried Pascal.

I like Pascal. I know Pascal reasonable well. And Pascal
got good support for index-sequential files (not like C
where one would need to use direct RMS calls).

I don't think there is that big potential
improvements.

Record definitions are a must.

Opening and closing index-sequential files is a must.

Iteration over customers and nested iteration over orders is not
a must. But I think iterating over orders and updating an
in-memory customer list will be more code.

If statements for conditions are a must,

2 loops + 1 if + 3 assignments for sorting can not be done
easier unless there is a builtin sort function.

I chose to map the 3 tables to 2 index-sequential files
because I cnsider it realistic to have order and all orderlines
in a 32K record but unrealistic to have a customer and all orders
in a 32K record.

Arne