Hello Wes,
Thanks for the info! I'm working to better understand Parquet/Arrow design and
development processes. No hurry for LARGE_BYTE_ARRAY.
-Brian
On 4/26/19, 11:14 AM, "Wes McKinney" <wesmck...@gmail.com> wrote:
EXTERNAL
hi Brian,
I doubt that such a change could be made on a short time horizon.
Collecting feedback and building consensus (if it is even possible)
with stakeholders would take some time. The appropriate place to have
the discussion is here on the mailing list, though
Thanks
On Mon, Apr 8, 2019 at 1:37 PM Brian Bowman <brian.bow...@sas.com> wrote:
>
> Hello Wes/all,
>
> A new LARGE_BYTE_ARRAY type in Parquet would satisfy SAS' needs without
resorting to other alternatives. Is this something that could be done in
Parquet over the next few months? I have a lot of experience with file
formats/storage layer internals and can contribute for Parquet C++.
>
> -Brian
>
> On 4/5/19, 3:44 PM, "Wes McKinney" <wesmck...@gmail.com> wrote:
>
> EXTERNAL
>
> hi Brian,
>
> Just to comment from the C++ side -- the 64-bit issue is a limitation
> of the Parquet format itself and not related to the C++
> implementation. It would be possibly interesting to add a
> LARGE_BYTE_ARRAY type with 64-bit offset encoding (we are discussing
> doing much the same in Apache Arrow for in-memory)
>
> - Wes
>
> On Fri, Apr 5, 2019 at 2:11 PM Ryan Blue <rb...@netflix.com.invalid>
wrote:
> >
> > I don't think that's what you would want to do. Parquet will
eventually
> > compress large values, but not after making defensive copies and
attempting
> > to encode them. In the end, it will be a lot more overhead, plus
the work
> > to make it possible. I think you'd be much better of compressing
before
> > storing in Parquet if you expect good compression rates.
> >
> > On Fri, Apr 5, 2019 at 11:29 AM Brian Bowman <brian.bow...@sas.com>
wrote:
> >
> > > My hope is that these large ByteArray values will encode/compress
to a
> > > fraction of their original size. FWIW, cpp/src/parquet/
> > > column_writer.cc/.h has int64_t offset and length fields all over
the
> > > place.
> > >
> > > External file references to BLOBS is doable but not the elegant,
> > > integrated solution I was hoping for.
> > >
> > > -Brian
> > >
> > > On Apr 5, 2019, at 1:53 PM, Ryan Blue <rb...@netflix.com> wrote:
> > >
> > > *EXTERNAL*
> > > Looks like we will need a new encoding for this:
> > > https://github.com/apache/parquet-format/blob/master/Encodings.md
> > >
> > > That doc specifies that the plain encoding uses a 4-byte length.
That's
> > > not going to be a quick fix.
> > >
> > > Now that I'm thinking about this a bit more, does it make sense
to support
> > > byte arrays that are more than 2GB? That's far larger than the
size of a
> > > row group, let alone a page. This would completely break memory
management
> > > in the JVM implementation.
> > >
> > > Can you solve this problem using a BLOB type that references an
external
> > > file with the gigantic values? Seems to me that values this large
should go
> > > in separate files, not in a Parquet file where it would destroy
any benefit
> > > from using the format.
> > >
> > > On Fri, Apr 5, 2019 at 10:43 AM Brian Bowman
<brian.bow...@sas.com> wrote:
> > >
> > >> Hello Ryan,
> > >>
> > >> Looks like it's limited by both the Parquet implementation and
the Thrift
> > >> message methods. Am I missing anything?
> > >>
> > >> From cpp/src/parquet/types.h
> > >>
> > >> struct ByteArray {
> > >> ByteArray() : len(0), ptr(NULLPTR) {}
> > >> ByteArray(uint32_t len, const uint8_t* ptr) : len(len),
ptr(ptr) {}
> > >> uint32_t len;
> > >> const uint8_t* ptr;
> > >> };
> > >>
> > >> From cpp/src/parquet/thrift.h
> > >>
> > >> inline void DeserializeThriftMsg(const uint8_t* buf, uint32_t*
len, T*
> > >> deserialized_msg) {
> > >> inline int64_t SerializeThriftMsg(T* obj, uint32_t len,
OutputStream*
> > >> out)
> > >>
> > >> -Brian
> > >>
> > >> On 4/5/19, 1:32 PM, "Ryan Blue" <rb...@netflix.com.INVALID>
wrote:
> > >>
> > >> EXTERNAL
> > >>
> > >> Hi Brian,
> > >>
> > >> This seems like something we should allow. What imposes the
current
> > >> limit?
> > >> Is it in the thrift format, or just the implementations?
> > >>
> > >> On Fri, Apr 5, 2019 at 10:23 AM Brian Bowman
<brian.bow...@sas.com>
> > >> wrote:
> > >>
> > >> > All,
> > >> >
> > >> > SAS requires support for storing varying-length character
and
> > >> binary blobs
> > >> > with a 2^64 max length in Parquet. Currently, the
ByteArray len
> > >> field is
> > >> > a unint32_t. Looks this the will require incrementing
the Parquet
> > >> file
> > >> > format version and changing ByteArray len to uint64_t.
> > >> >
> > >> > Have there been any requests for this or other Parquet
developments
> > >> that
> > >> > require file format versioning changes?
> > >> >
> > >> > I realize this a non-trivial ask. Thanks for considering
it.
> > >> >
> > >> > -Brian
> > >> >
> > >>
> > >>
> > >> --
> > >> Ryan Blue
> > >> Software Engineer
> > >> Netflix
> > >>
> > >>
> > >>
> > >
> > > --
> > > Ryan Blue
> > > Software Engineer
> > > Netflix
> > >
> > >
> >
> > --
> > Ryan Blue
> > Software Engineer
> > Netflix
>
>
