[ARROW-10337] [C++] More liberal parsing of ISO8601 timestamps with fractional seconds

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/18334
• Assignee: Frank Smith
• Reporter: Frank Smith
• Created: 18/Oct/20 21:30
• Updated: 11/Jan/23 08:12
• Resolved: 07/Dec/20 15:48

Description

The current ISO8601 timestamp parser assumes MILLI timestamps have 3 decimal places, MICRO have 6 and NANO have 9. From ParseTimestampISO8601 in cpp/src/arrow/util/value_parsing.h:

{{ // We allow the following formats for all units:}}
{{ // - "YYYY-MM-DD"}}
{{ // - "YYYY-MM-DD[ T]hh"}}
{{ // - "YYYY-MM-DD[ T]hhZ"}}
{{ // - "YYYY-MM-DD[ T]hh:mm"}}
{{ // - "YYYY-MM-DD[ T]hh:mmZ"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ssZ"}}
{{ //}}
{{ // We allow the following formats for unit==MILLI:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.mmm"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.mmmZ"}}
{{ //}}
{{ // We allow the following formats for unit==MICRO:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.uuuuuu"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.uuuuuuZ"}}
{{ //}}
{{ // We allow the following formats for unit==NANO:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.nnnnnnnnn"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.nnnnnnnnnZ"}}
{{ //}}

I propose that we change the parser to accept 1 to 3 digits for MILLI, 1 to 6 digits for MICRO, and 1 to 9 digits for NANO, as follows:

{{ // We allow the following formats for all units:}}
{{ // - "YYYY-MM-DD"}}
{{ // - "YYYY-MM-DD[ T]hhZ?"}}
{{ // - "YYYY-MM-DD[ T]hh:mmZ?"}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ssZ?"}}
{{ //}}
{{ // We allow the following formats for unit == MILLI, MICRO, or NANO:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.s{1,3}Z?"}}
{{ //}}
{{ // We allow the following formats for unit == MICRO, or NANO:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.s{4,6}Z?"}}
{{ //}}
{{ // We allow the following formats for unit == NANO:}}
{{ // - "YYYY-MM-DD[ T]hh:mm:ss.s{7,9}Z?"}}

This will allow for parsing of timestamps when e.g. a CSV file does not write timestamps with trailing zeroes.

I am almost complete implementing this functionality, so a PR will be following soon.

 

 
  

Issue Links

• links to: GitHub Pull Request #8692