That's right. Shrinking happens here: https://github.com/apache/parquet-cpp/blob/master/src/parquet/arrow/writer.cc#L808-L809
On Thu, Apr 19, 2018 at 9:40 AM Wes McKinney <wesmck...@gmail.com> wrote: > We do "shrink" the input 128-bit decimals to the smallest number of > bytes that fits, though, is that right? > > > https://github.com/apache/parquet-cpp/blob/c405bf36506ec584e8009a6d53349277e600467d/src/parquet/arrow/schema.cc#L635 > > On Thu, Apr 19, 2018 at 8:09 AM, Phillip Cloud <cpcl...@gmail.com> wrote: > > Hi Colin, > > > > Only 128 bit decimal writing is supported right now. Feel free to open a > > JIRA about this. > > > > On Wed, Apr 18, 2018, 19:10 Wes McKinney <wesmck...@gmail.com> wrote: > > > >> hi Colin, > >> > >> Phillip Cloud is the expert on this topic, but I believe we only > >> support writing decimals to FIXED_LEN_BYTE_ARRAY physical type in > >> Parquet right now > >> > >> > >> > https://github.com/apache/parquet-cpp/blob/master/src/parquet/arrow/writer.cc#L798 > >> > >> The size of the type depends on the decimal precision, so if we can > >> write to 32- or 64-bit, then we do that. Writing to INT32 or INT64 > >> would be more complicated and require some work in parquet-cpp > >> > >> - Wes > >> > >> On Wed, Apr 18, 2018 at 7:04 PM, Colin Nichols <co...@narrativ.com> > wrote: > >> > Hi all, > >> > > >> > Any thoughts on the below? I did a little more code browsing and I'm > not > >> > sure this is supported right now, should I open a Jira ticket? > >> > > >> > - Colin > >> > > >> > On Tue, Apr 17, 2018 at 11:11 PM, Colin Nichols <co...@narrativ.com> > >> wrote: > >> > > >> >> Hi there, > >> >> > >> >> I know (py)arrow has the decimal128() type, and using this type it's > >> easy > >> >> to take an array of Python Decimals, convert to a pa.array, and write > >> out > >> >> to Parquet. > >> >> > >> >> In the absence (afaict) of decimal32 and decimal64 types, is it > possible > >> >> to go from an array of Decimals (with compatible precision/scale) and > >> write > >> >> them to a parquet column of 32- or 64- bit width? > >> >> > >> >> Relevant parquet spec -- https://github.com/apache/ > >> >> parquet-format/blob/master/LogicalTypes.md#decimal > >> >> > >> >> I'm looking to add this functionality to the project Spectrify, as > AWS > >> >> Redshift Spectrum will not query unnecessarily-wide DECIMAL columns > -- > >> >> https://github.com/hellonarrativ/spectrify/issues/14 > >> >> > >> >> Thanks, > >> >> Colin > >> >> > >> >> > >> >
