Hi Jacek, I'm not sure I fully understand the proposal, could you elaborate with more examples/details? For instance DAY_TIME isn't just a UINT64, it actually contains 2 seperate fields (days and milliseconds).
In terms of closed vs half-open, in my limited understanding, that is more a concern of functions using interval types rather than the type itself. For instance a quick search of postgres [1] docs only talks about half-open in relation to the "Overlaps" operator Thanks, -Micah [1] https://www.postgresql.org/docs/9.1/functions-datetime.html On Sun, May 2, 2021 at 12:25 AM Jacek Pliszka <jacek.plis...@gmail.com> wrote: > Hi! > > I wonder if it were possible to have generic interval with integers of > specified size just to have common base for interval arithmetic. > > Then user can convert their period to ordinals and use the arithmetic > (joining, deoverlapping, common parts, explosion etc.). > > So YEAR_MONTH and DAY_TIME would be just special cases of > INTERVAL_UINT32 and INTERVAL_UINT64 > > Also I believe it is worth to state whether there are only closed > intervals or open/semi-open ones are allowed as well. > > I believe I am just one of many reinventing the wheel here and writing > own versions of the above. > > BR, > > Jacek > > > pt., 2 kwi 2021 o 21:53 Micah Kornfield <emkornfi...@gmail.com> > napisał(a): > > > > Andrew is the use-case you have simply postgres compatibility or is it > more > > extensive? > > > > One potential problem with combining Month and Day fields, is that the > type > > no longer has a defined sort order (the existing Day-Millisecond type > > without assumptions, in particular because I don't think today there is > an > > explicit constraint on the bounds for the millisecond component). > > > > -Micah > > > > > > > > On Wed, Mar 31, 2021 at 9:03 AM Antoine Pitrou <anto...@python.org> > wrote: > > > > > > > > Le 31/03/2021 à 17:55, Micah Kornfield a écrit : > > > > Thanks for the feedback. A couple of points here and some responses > > > below. > > > > > > > > * One other question is whether the Nanoseconds should actually be > > > > configurable (i.e. use milliseconds or microseconds). I would lean > > > towards > > > > no. > > > > > > Same for me. > > > > > > > * I'm also still not 100% convinced we need this as a first class > type in > > > > arrow or if we should be looking more closely at the Struct (in the > Arrow > > > > sense) based implementation. In the future where alternative > encodings > > > are > > > > supported, this could allow for much smaller footprints for this > type. > > > > > > Having a "packed" first class type allows for better locality when > > > accessing data. It doesn't sound very likely that you'd access only > one > > > component of the interval. > > > > > > But I have no idea how important this is, and temporal datetypes are > > > generally cumbersome to add support for (conversions, arithmetic, > etc.), > > > so it would be nice to avoid adding too many of them :-) > > > > > > Regards > > > > > > Antoine. > > > > > > > > > > > > > > > > > The 3 > > > >> field implementation doesn't seem to have any way to represent > integral > > > >> days, so I am also not sure about that one. > > > > > > > > > > > > Sorry this was an email gaffe. I intended Month (32 bit int), Day > (32 > > > bit > > > > int), Nanosecond (64 bit int). > > > > > > > > OTOH I don't really understand the point of supporting "the most > > > >> reasonable ranges for Year, Month and Nanoseconds independently". > What > > > >> does it bring to encode more than one month in the nanoseconds > field? > > > > > > > > > > > > I'm happy with simplicity. In the past there has been some > reference to > > > > people wanting to store very large timestamps (fall out of > Nanoseconds > > > max > > > > representable value) but we've concluded that this wasn't something > that > > > we > > > > wanted to really support. > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Mar 31, 2021 at 4:49 AM Antoine Pitrou <anto...@python.org> > > > wrote: > > > > > > > >> > > > >> I would favour the following characteristics : > > > >> - support for nanoseconds (especially as other Arrow temporal types > > > >> support it) > > > >> - easy to handle (which excludes the ZetaSQL representtaion IMHO) > > > >> > > > >> OTOH I don't really understand the point of supporting "the most > > > >> reasonable ranges for Year, Month and Nanoseconds independently". > What > > > >> does it bring to encode more than one month in the nanoseconds > field? > > > >> You can already use the Duration type for that. > > > >> > > > >> Regards > > > >> > > > >> Antoine. > > > >> > > > >> > > > >> Le 31/03/2021 à 05:48, Micah Kornfield a écrit : > > > >>> To follow-up on this conversation I did some analysis on interval > > > types: > > > >>> > > > >>> > > > >> > > > > https://docs.google.com/document/d/1i1E_fdQ_xODZcAhsV11Pfq27O50k679OYHXFJpm9NS0/edit > > > >> Please feel free to add more details/systems I missed. > > > >>> > > > >>> Given the disparate requirements of different systems I think the > > > >> following might make sense for official types (if there isn't > > > consensus, I > > > >> might try to contributation extension Array implementations for > them to > > > >> Java and C++/Python separately). > > > >>> > > > >>> 1. 3 fields: Year (32 bit), Month (32 bit), Nanoseconds (64 bit) > all > > > >> signed. > > > >>> 2. Postgres representation (Downside is it doesn't support > > > Nanoseconds, > > > >> only microseconds). > > > >>> 3. ZetaSQL implementation (Requires some bit manipulation) but > > > supports > > > >> the most reasonable ranges for Year, Month and Nanoseconds > > > independently. > > > >>> > > > >>> Thoughts? > > > >>> > > > >>> Micah > > > >>> > > > >>> On 2021/02/18 04:30:55 Micah Kornfield wrote: > > > >>>>> > > > >>>>> I didn’t find any page/documentation on how to do RFC in Arrow > > > >> protocol, > > > >>>>> so can anyone point me to it or PR with email will be enough? > > > >>>> > > > >>>> That is enough to start discussion. Before formal acceptance and > > > >> merging > > > >>>> of the PR there needs to be a Java and C++ implementations for the > > > type > > > >>>> that pass integration tests. At the time this guideline was > > > instituted > > > >>>> Java and C++ were considered the "reference" implementations (I > think > > > >> they > > > >>>> still have the most complete integration test coverage). > > > >>>> > > > >>>> My understanding is that the current modelling of intervals > mimics SQL > > > >>>> standards (e.g. SQL Server [1]). So it would also be good to step > > > back > > > >> and > > > >>>> understand what problem DF is trying to solve and how it differs > from > > > >> other > > > >>>> SQL implementations. I'd be hesitant to accept COMPLEX as a new > type > > > >>>> without a much deeper analysis into calendar representations > within > > > >> Arrow > > > >>>> and how they relate to other existing systems (e.g. Hive and some > > > >>>> assortment of existing SQL databases). For instance the current > > > >> modelling > > > >>>> of timestamps does not lend itself to constructing a COMPLEX > interval > > > >> type > > > >>>> particularly well. (Duration was introduced for this reason). > > > >>>> > > > >>>> I think both Wes's suggestion of FixedSizeBinary and Andrew's of > > > >> composing > > > >>>> the with a struct are good stop-gaps. These obviously have > different > > > >>>> trade-offs. Ultimately, it would be good to define common > extension > > > >> types > > > >>>> that can represent this use-case if there really is demand for it > (if > > > it > > > >>>> doesn't become a top level type). > > > >>>> > > > >>>> [1] > > > >>>> > > > >> > > > > https://docs.microsoft.com/en-us/sql/odbc/reference/appendixes/interval-data-types?view=sql-server-ver15 > > > >>>> > > > >>>> -Micah > > > >>>> > > > >>>> On Wed, Feb 17, 2021 at 2:05 PM Andrew Lamb <al...@influxdata.com > > > > > >> wrote: > > > >>>> > > > >>>>> That is a great suggestion Wes, thank you. > > > >>>>> > > > >>>>> I wonder if we could get away with a 128 bit representation that > is > > > the > > > >>>>> concatenation of the two existing interval types > > > (YearMonth)(DayTime). > > > >> Or > > > >>>>> maybe even define a `struct` type with those fields that is used > by > > > >>>>> DataFusion. > > > >>>>> > > > >>>>> Basically, given our reading of the Arrow spec[1], it is > currently > > > not > > > >>>>> possible to precisely represent an interval that has both > monthly and > > > >>>>> sub-montly granularity. > > > >>>>> > > > >>>>> As Dmtry says, if you have an interval seemingly simple like 1 > > > month, > > > >> 1 > > > >>>>> day > > > >>>>> > > > >>>>> Using IntervalUnit(YEAR_MONTH) can't represent the 1 day > > > >>>>> Using IntervalUnit(DAY_TIME) can't represent the month as > different > > > >> months > > > >>>>> have different numbers of days > > > >>>>> > > > >>>>> [1] > > > >>>>> > > > >> > https://github.com/apache/arrow/blob/master/format/Schema.fbs#L249-L260 > > > >>>>> > > > >>>>> > > > >>>>> On Wed, Feb 17, 2021 at 5:01 PM Wes McKinney < > wesmck...@gmail.com> > > > >> wrote: > > > >>>>> > > > >>>>>> On Wed, Feb 17, 2021 at 3:46 PM <t...@dmtry.me> wrote: > > > >>>>>>> > > > >>>>>>>> It's unclear to me that this needs to be introduced into the > > > >>>>> top-level > > > >>>>>>> > > > >>>>>>> Similar thing to columnar format, How to store interval like 1 > > > month > > > >> 1 > > > >>>>>> day 1 hour? It’s not possible to do it without converting 1 > month to > > > >> 30 > > > >>>>>> days, which is a bad way. > > > >>>>>>> > > > >>>>>> > > > >>>>>> Presumably you can represent a complex interval in a fixed > number of > > > >>>>>> bytes, and then embed the data in a FixedSizeBinary type. You > can > > > >>>>>> adorn this type with extension type metadata so that DataFusion > can > > > >>>>>> then apply Interval semantics to it. This could also serve as an > > > >>>>>> interim strategy for you to proceed with implementation while > > > >>>>>> proposing a top-level type to the Arrow format (which may or > may not > > > >>>>>> be accepting) so you aren't blocked on acceptance of changes > into > > > >>>>>> Schema.fbs. > > > >>>>>> > > > >>>>>>>> On 17 Feb 2021, at 21:02, Wes McKinney <wesmck...@gmail.com> > > > wrote: > > > >>>>>>>> > > > >>>>>>>> It's unclear to me that this needs to be introduced into the > > > >>>>> top-level > > > >>>>>>>> columnar format without more analysis — have you considered > > > >>>>>>>> implementing this for DataFusion as an extension type for the > time > > > >>>>>>>> being? > > > >>>>>>>> > > > >>>>>>>> On Wed, Feb 17, 2021 at 11:59 AM t...@dmtry.me <mailto: > > > >> t...@dmtry.me > > > >>>>>> > > > >>>>>> <t...@dmtry.me <mailto:t...@dmtry.me>> wrote: > > > >>>>>>>>> > > > >>>>>>>>> Hi, > > > >>>>>>>>> > > > >>>>>>>>> For now, There are only two types of IntervalUnit inside > Arrow: > > > >>>>>>>>> > > > >>>>>>>>> - YearMonth - month stored as int32 > > > >>>>>>>>> - DayTime - days as int32 and time in milliseconds as in32. > > > Total > > > >>>>>> (64 bites) > > > >>>>>>>>> > > > >>>>>>>>> Since DF is using Arrow, It’s not possible to store “Complex” > > > >>>>>> intervals such 1 MONTH 1 DAY 1 HOUR. > > > >>>>>>>>> I think, the best way to understand the problem will be to > read a > > > >>>>>> comment from DF codebase: > > > >>>>>> > > > >>>>> > > > >> > > > > https://github.com/apache/arrow/blob/bca7d2fe84ccd8fc1129cb4d85448eb0779c52c3/rust/datafusion/src/sql/planner.rs#L1148 > > > >>>>>>>>> > > > >>>>>>>>> // Interval is tricky thing > > > >>>>>>>>> // 1 day is not 24 hours because timezones, 1 year > != > > > >>>>> 365/364! > > > >>>>>> 30 days != 1 month > > > >>>>>>>>> // The true way to store and calculate intervals is > to > > > >> store > > > >>>>>> it as it defined > > > >>>>>>>>> // Due the fact that Arrow supports only two types > > > >> YearMonth > > > >>>>>> (month) and DayTime (day, time) > > > >>>>>>>>> // It's not possible to store complex intervals > > > >>>>>>>>> // It's possible to do select (NOW() + INTERVAL '1 > > > year') + > > > >>>>>> INTERVAL '1 day'; as workaround > > > >>>>>>>>> if result_month != 0 && (result_days != 0 || > > > result_millis > > > >> != > > > >>>>>> 0) { > > > >>>>>>>>> return > Err(DataFusionError::NotImplemented(format!( > > > >>>>>>>>> "DF does not support intervals that have > both a > > > >>>>>> Year/Month part as well as Days/Hours/Mins/Seconds: {:?}. Hint: > try > > > >>>>>> breaking the interval into two parts, one with Year/Month and > the > > > >> other > > > >>>>>> with Days/Hours/Mins/Seconds - e.g. (NOW() + INTERVAL '1 year') > + > > > >>>>> INTERVAL > > > >>>>>> '1 day'", > > > >>>>>>>>> value > > > >>>>>>>>> ))); > > > >>>>>>>>> } > > > >>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>>> I prepared a PR > https://github.com/apache/arrow/pull/9516/files > > > < > > > >>>>>> https://github.com/apache/arrow/pull/9516/files> < > > > >>>>>> https://github.com/apache/arrow/pull/9516/files < > > > >>>>>> https://github.com/apache/arrow/pull/9516/files>> that > introduce a > > > >> new > > > >>>>>> type for IntervalUnit called Complex, that store both YearMonth > and > > > >>>>> DayTime > > > >>>>>> to support complex interval. > > > >>>>>>>>> I didn’t find any page/documentation on how to do RFC in > Arrow > > > >>>>>> protocol, so can anyone point me to it or PR with email will be > > > >> enough? > > > >>>>>>>>> > > > >>>>>>>>> Thanks. > > > >>>>>>> > > > >>>>>> > > > >>>>> > > > >>>> > > > >> > > > > > > > >
