[DOCS-15857] [SERVER] Investigate changes in SERVER-50336: $dateFromString support for additional format specifiers (such as "%j" for day of year) Created: 27/Jan/23  Updated: 13/Nov/23  Resolved: 13/Jul/23

Status: Closed
Project: Documentation
Component/s: manual, Server
Affects Version/s: None
Fix Version/s: 6.3.0-rc0, Server_Docs_20231030, Server_Docs_20231106, Server_Docs_20231105, Server_Docs_20231113

Type: Task Priority: Major - P3
Reporter: Backlog - Core Eng Program Management Team Assignee: Kanchana Sekhar
Resolution: Fixed Votes: 0
Labels: server-docs-bug-bash
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Backports
Documented
documents SERVER-50336 $dateFromString support for additiona... Closed
Participants:
Days since reply: 1 year, 1 week, 5 days ago

 Description   
Original Downstream Change Summary

$dateFromString now supports the %j format specifier, "Day of Year", which allows a user to parse a date from a string containing only the year and a number to indicate which day it is of that year.

Example here: https://github.com/10gen/mongo/blob/33190227bdd2c21328afe7f41ace33bf5d64eeab/jstests/aggregation/expressions/date_from_string.js#L556

Note that %j counts the days from 0-355, not 1-356.

Description of Linked Ticket

The $dateFromString Format Specifiers don't include the strftime %j modifier which is used to decode the day of the year as a decimal number (range 001 to 366).

It appears that this modifier is understood as part of kDateToStringFormatMap from timelib's TIMELIB_FORMAT_DAY_OF_YEAR when converting from a date to a string, but not from a string to a date.

For example:

db.foo.drop()
db.foo.insert({ _id: 1, d: "2020-194-14:24:45.463" });
db.foo.aggregate( [ {
   $project: {
      date: {
         $dateFromString: {
            dateString: "%d",
            format: "%Y-%j-%H:%M:%S.%L"
         }
      }
   }
} ] )
// "errmsg" : "Failed to optimize pipeline :: caused by :: Invalid format character '%j' in format string",

Note that for the above we were able to work around this limitation as follows:

db.foo.drop()
db.foo.insert({ _id: 1, d: "2020-194-14:24:45.463" });
db.foo.aggregate([
{ $project: {
    date: {
        $let: {
            vars: {
                parts: { $split: [ "$d", "-" ] }
            },
            in: { 
                $add: [ 
                    { $toDate: { $concat: [ 
                        { $arrayElemAt: [ "$$parts", 0 ] }, 
                        "-01-01T", 
                        { $arrayElemAt: [ "$$parts", 2 ] } ] 
                    } }, 
                    { $multiply: [ 
                        { $subtract: [ 
                            { $toInt: { $arrayElemAt: [ "$$parts", 1 ] } }, 
                            1 ] }, 86400000 ] }
                ] 
            } 
        }
    }
}}
]);
// { "_id" : 1, "date" : ISODate("2020-07-12T14:24:45.463Z") }



 Comments   
Comment by Jennifer Peshansky (Inactive) [ 27/Jan/23 ]

Update the dateFromString docs to include the %j format specifier, Day Of Year. Example of its use here.

Also, I noticed that %b and %B are not included on this page, despite being supported in the code as well. These are Textual Month 3 Letter and Textual Month Full, respectively. Examples here.

Comment by Education Bot [ 27/Jan/23 ]

Fix Version updated for upstream SERVER-50336:
6.3.0-rc0

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