DESIGN.md

Regarding Calendars and other Temporal features.

MySQL

While creating queries to answer the question: "How much inventory will I have on FutureDate?" I needed to join On Hand inventory (tabBin) against future dates. However, you cannot write a Table Valued Function in MySQL. That feature doesn't exist. So I couldn't write a function to return the next N days.

Luckily, this is not necessary. Future calendar dates are fixed datapoints; they aren't going to change. I can just permanently store them. So I created a new DocType tabTemporal Dates

Testing

Testing Redis

I highly recommend downloading Another Redis Desktop Manager

Otherwise, you can always examine a Redis database using the redis-cli CLI application:

$  redis-cli -p 13003

If you already know your Redis command, you can cat and pipes too:

$  echo 'SMEMBERS v12testdb|temporal/calyears' | redis-cli -p 13003

Testing Temporal

We can use Frappe's Unit Test framework to run some tests, and verify our mathematics are okay.

To run these tests:

1. bench --site <sitename> set-config allow_tests true
2. bench run-tests --module "temporal.temporal.test_temporal"

MySQL Keywords and Reserved Words

https://dev.mysql.com/doc/refman/8.0/en/keywords.html#keywords-8-0-detailed-D

1. Calendar Years

These are straightforward. They are stored in Redis for performance reasons.

calyears

• Key: v12testdb|temporal/calyears
• Value: [ 2020, 2021, 2022 ]
• Redis CLI GET: SMEMBERS v12testdb|temporal/calyears
• Pyhon GET: temporal.cget_calendar_years()

calyear

• Key: v12testdb|temporal/calyear/2020

• Value: { year: 2020, startdate: "1/1/2020", enddate: "12/31/2020", length_in_days: 365}

• Redis CLI GET: SMEMBERS v12testdb|temporal/calyear/2020

• Python: get_calendar_year(year_number)

Traditional Calendar Weeks

The following rules are observed when calculating a "Week Number" using Google Docs:

1. January 1st is always the beginning of Week #1.
   • This week probably has fewer than seven(7) days.
2. The first Sunday after January 1st is the beginning of Week #2.
3. Weeks 2 thru Week L-1 are seven(7) days in length.
4. Week L (final week) ends on December 31st.
   • This week probably has fewer than seven(7) days.

Temporal Weeks

1. Every week contains 7 days, without exception. There is no such thing as a partial week.
2. Weeks begin on Sunday, so Wednesday is the middle day of a week.
3. Week #1 will always contain January 1st.

For example. Each hypothetical week below would be considered "Week #1"

--------------------------------
S    M    T    W    T    F    S
--------------------------------
26   27   28   29   30   31   1
27   28   29   30   31   1    2
28   29   30   31   1    2    3
29   30   31   1    2    3    4
30   31   1    2    3    4    5
31   1    2    3    4    5    6
1    2    3    4    5    6    7

3. Week #L (final week) contains December 25th.

--------------------------------
S    M    T    W    T    F    S
--------------------------------
19   20   21   22   23   24   25
20   21   22   23   24   25   26
21   22   23   24   25   26   27
22   23   24   25   26   27   28
23   24   25   26   27   28   29
24   25   26   27   28   29   30
25   26   27   28   29   30   31

Snippets

• datetime.strptime(date_string, format)

• Parsing a date from a string:

from dateutil.parser import parse
now = parse("Sat Oct 11 17:13:46 UTC 2003")

Redis Articles

• https://redis.io/topics/data-types
• https://pythontic.com/database/redis/hash%20-%20add%20and%20remove%20elements
• https://www.shellhacks.com/redis-get-all-keys-redis-cli/

Datetime Articles

• datetime.date.isocalendar
• https://pypi.org/project/isoweek/
• https://docs.python.org/3/library/calendar.html