Oracle does the same: "The *scale* must be less than or equal to the precision." (see https://docs.oracle.com/javadb/10.6.2.1/ref/rrefsqlj15260.html).
Il giorno mer 9 gen 2019 alle ore 05:31 Wenchen Fan <cloud0...@gmail.com> ha scritto: > Some more thoughts. If we support unlimited negative scale, why can't we > support unlimited positive scale? e.g. 0.0001 can be decimal(1, 4) instead > of (4, 4). I think we need more references here: how other databases deal > with decimal type and parse decimal literals? > > On Mon, Jan 7, 2019 at 10:36 PM Wenchen Fan <cloud0...@gmail.com> wrote: > >> I'm OK with it, i.e. fail the write if there are negative-scale decimals >> (we need to document it though). We can improve it later in data source v2. >> >> On Mon, Jan 7, 2019 at 10:09 PM Marco Gaido <marcogaid...@gmail.com> >> wrote: >> >>> In general we can say that some datasources allow them, others fail. At >>> the moment, we are doing no casting before writing (so we can state so in >>> the doc). But since there is ongoing discussion for DSv2, we can maybe add >>> a flag/interface there for "negative scale intollerant" DS and try and cast >>> before writing to them. What do you think about this? >>> >>> Il giorno lun 7 gen 2019 alle ore 15:03 Wenchen Fan <cloud0...@gmail.com> >>> ha scritto: >>> >>>> AFAIK parquet spec says decimal scale can't be negative. If we want to >>>> officially support negative-scale decimal, we should clearly define the >>>> behavior when writing negative-scale decimals to parquet and other data >>>> sources. The most straightforward way is to fail for this case, but maybe >>>> we can do something better, like casting decimal(1, -20) to decimal(20, 0) >>>> before writing. >>>> >>>> On Mon, Jan 7, 2019 at 9:32 PM Marco Gaido <marcogaid...@gmail.com> >>>> wrote: >>>> >>>>> Hi Wenchen, >>>>> >>>>> thanks for your email. I agree adding doc for decimal type, but I am >>>>> not sure what you mean speaking of the behavior when writing: we are not >>>>> performing any automatic casting before writing; if we want to do that, we >>>>> need a design about it I think. >>>>> >>>>> I am not sure if it makes sense to set a min for it. That would break >>>>> backward compatibility (for very weird use case), so I wouldn't do that. >>>>> >>>>> Thanks, >>>>> Marco >>>>> >>>>> Il giorno lun 7 gen 2019 alle ore 05:53 Wenchen Fan < >>>>> cloud0...@gmail.com> ha scritto: >>>>> >>>>>> I think we need to do this for backward compatibility, and according >>>>>> to the discussion in the doc, SQL standard allows negative scale. >>>>>> >>>>>> To do this, I think the PR should also include a doc for the decimal >>>>>> type, like the definition of precision and scale(this one >>>>>> <https://stackoverflow.com/questions/35435691/bigdecimal-precision-and-scale> >>>>>> looks pretty good), and the result type of decimal operations, and the >>>>>> behavior when writing out decimals(e.g. we can cast decimal(1, -20) to >>>>>> decimal(20, 0) before writing). >>>>>> >>>>>> Another question is, shall we set a min scale? e.g. shall we allow >>>>>> decimal(1, -10000000)? >>>>>> >>>>>> On Thu, Oct 25, 2018 at 9:49 PM Marco Gaido <marcogaid...@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> Hi all, >>>>>>> >>>>>>> a bit more than one month ago, I sent a proposal for handling >>>>>>> properly decimals with negative scales in our operations. This is a long >>>>>>> standing problem in our codebase as we derived our rules from Hive and >>>>>>> SQLServer where negative scales are forbidden, while in Spark they are >>>>>>> not. >>>>>>> >>>>>>> The discussion has been stale for a while now. No more comments on >>>>>>> the design doc: >>>>>>> https://docs.google.com/document/d/17ScbMXJ83bO9lx8hB_jeJCSryhT9O_HDEcixDq0qmPk/edit#heading=h.x7062zmkubwm >>>>>>> . >>>>>>> >>>>>>> So I am writing this e-mail in order to check whether there are more >>>>>>> comments on it or we can go ahead with the PR. >>>>>>> >>>>>>> Thanks, >>>>>>> Marco >>>>>>> >>>>>>
