evalengine: Implement FROM_DAYS

[beingnoble03]

Description

This PR adds implementation of FROM_DAYS func in evalengine.

Related Issue(s)

Fixes part of #9647

Checklist

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[vitess-bot]

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[dbussink]

@beingnoble03 We also already have https://github.com/vitessio/vitess/blob/main/go/mysql/datetime/mydate.go#L49-L83 which is used in a number of cases, so maybe that's what we need to use here too?

[beingnoble03]

@beingnoble03 We also already have https://github.com/vitessio/vitess/blob/main/go/mysql/datetime/mydate.go#L49-L83 which is used in a number of cases, so maybe that's what we need to use here too?

@dbussink true. So, should we write a func DateFromDayNumber in mysql/datetime package which uses this func to return datetime.Date?

[dbussink]

I think we can rename it to export it so we can use it from the evalengine.

[dbussink]

This conversion seems unneeded? I think you can just straight set the properties from what MysqlDateFromDayNumber returns?

var dt datetime.Date
dt.Year, dt.Month, dt.Day = mysqldt.MysqlDateFromDayNumber(int(arg.i))

Then you also only have to check dt.Year > 9999, the zero case also automatically falls out?

Same for the compiler, no need for the conversion there either through Go's Time library.

[beingnoble03]

The struct fields of datetime.Date are not exported. So, I think we can't follow this.

Also, don't know why I imported mysql/datetime twice. Fixing it.

[dbussink]

Instead of exporting the existing function, we can also add a new one that returns the date already so you don’t have that issue.

I think we really should avoid going through the go type if not strictly needed here.

[beingnoble03]

got it. done.

[beingnoble03]

Fixing the failing tests.

[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (f751c83) 47.49% compared to head (e44193a) 47.51%.

Files	Patch %	Lines
go/vt/vtgate/evalengine/cached_size.go	0.00%	10 Missing ⚠️
go/mysql/datetime/mydate.go	0.00%	4 Missing ⚠️
go/vt/vtgate/evalengine/fn_time.go	89.28%	2 Missing and 1 partial ⚠️
go/vt/vtgate/evalengine/translate_builtin.go	40.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15058      +/-   ##
==========================================
+ Coverage   47.49%   47.51%   +0.01%     
==========================================
  Files        1149     1149              
  Lines      239475   239532      +57     
==========================================
+ Hits       113730   113804      +74     
+ Misses     117138   117122      -16     
+ Partials     8607     8606       -1     

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[dbussink]

Nice work! Is TO_DAYS next to keep it symmetric 😉?

[beingnoble03]

@dbussink sure!

[vmg]

Looks great! Thanks for contributing to Vitess!