I would also not unnest arrays nested in arrays just the top-level array of the specified fields.
On Wed, 13 Jan 2021 at 20:58, Reuven Lax <re...@google.com> wrote: > Nested fields are not part of standard SQL AFAIK. Beam goes further and > supports array of array, etc. > > On Wed, Jan 13, 2021 at 11:42 AM Kenneth Knowles <k...@apache.org> wrote: > >> Just the fields specified, IMO. When in doubt, copy SQL. (and I mean SQL >> generally, not just Beam SQL) >> >> Kenn >> >> On Wed, Jan 13, 2021 at 11:17 AM Reuven Lax <re...@google.com> wrote: >> >>> Definitely could be a top-level transform. Should it automatically >>> unnest all arrays, or just the fields specified? >>> >>> We do have to define the semantics for nested arrays as well. >>> >>> On Wed, Jan 13, 2021 at 10:57 AM Robert Bradshaw <rober...@google.com> >>> wrote: >>> >>>> Ah, thanks for the clarification. UNNEST does sound like what you want >>>> here, and would likely make sense as a top-level relational transform as >>>> well as being supported by SQL. >>>> >>>> On Wed, Jan 13, 2021 at 10:53 AM Tao Li <t...@zillow.com> wrote: >>>> >>>>> @Kyle Weaver <kcwea...@google.com> sure thing! So the input/output >>>>> definition for the Flatten.Iterables >>>>> <https://beam.apache.org/releases/javadoc/2.25.0/org/apache/beam/sdk/transforms/Flatten.Iterables.html> >>>>> is: >>>>> >>>>> >>>>> >>>>> Input: PCollection<Iterable<T> >>>>> >>>>> Output: PCollection<T> >>>>> >>>>> >>>>> >>>>> The input/output for a explode transform would look like this: >>>>> >>>>> Input: PCollection<Row> The row schema has a field which is an array >>>>> of T >>>>> >>>>> Output: PCollection<Row> The array type field from input schema is >>>>> replaced with a new field of type T. The elements from the array type >>>>> field >>>>> are flattened into multiple rows in the new table (other fields of input >>>>> table are just duplicated. >>>>> >>>>> >>>>> >>>>> Hope this clarification helps! >>>>> >>>>> >>>>> >>>>> *From: *Kyle Weaver <kcwea...@google.com> >>>>> *Reply-To: *"user@beam.apache.org" <user@beam.apache.org> >>>>> *Date: *Tuesday, January 12, 2021 at 4:58 PM >>>>> *To: *"user@beam.apache.org" <user@beam.apache.org> >>>>> *Cc: *Reuven Lax <re...@google.com> >>>>> *Subject: *Re: Is there an array explode function/transform? >>>>> >>>>> >>>>> >>>>> @Reuven Lax <re...@google.com> yes I am aware of that transform, but >>>>> that’s different from the explode operation I was referring to: >>>>> https://spark.apache.org/docs/latest/api/sql/index.html#explode >>>>> <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspark.apache.org%2Fdocs%2Flatest%2Fapi%2Fsql%2Findex.html%23explode&data=04%7C01%7Ctaol%40zillow.com%7C1226a5d9efee43fc7d5508d8b75e5bfd%7C033464830d1840e7a5883784ac50e16f%7C0%7C0%7C637460963191408293%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=IjXWhmHTGsbpgbxa1gJ5LcOFI%2BoiGIDYBwXPnukQfxk%3D&reserved=0> >>>>> >>>>> >>>>> >>>>> How is it different? It'd help if you could provide the signature >>>>> (input and output PCollection types) of the transform you have in mind. >>>>> >>>>> >>>>> >>>>> On Tue, Jan 12, 2021 at 4:49 PM Tao Li <t...@zillow.com> wrote: >>>>> >>>>> @Reuven Lax <re...@google.com> yes I am aware of that transform, but >>>>> that’s different from the explode operation I was referring to: >>>>> https://spark.apache.org/docs/latest/api/sql/index.html#explode >>>>> <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspark.apache.org%2Fdocs%2Flatest%2Fapi%2Fsql%2Findex.html%23explode&data=04%7C01%7Ctaol%40zillow.com%7C1226a5d9efee43fc7d5508d8b75e5bfd%7C033464830d1840e7a5883784ac50e16f%7C0%7C0%7C637460963191418249%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=XuUUmNB3fgBasjDj0Dq1Z2g6%2Bc5fbvluf%2BnAp2m8cuE%3D&reserved=0> >>>>> >>>>> >>>>> >>>>> *From: *Reuven Lax <re...@google.com> >>>>> *Reply-To: *"user@beam.apache.org" <user@beam.apache.org> >>>>> *Date: *Tuesday, January 12, 2021 at 2:04 PM >>>>> *To: *user <user@beam.apache.org> >>>>> *Subject: *Re: Is there an array explode function/transform? >>>>> >>>>> >>>>> >>>>> Have you tried Flatten.iterables >>>>> >>>>> >>>>> >>>>> On Tue, Jan 12, 2021, 2:02 PM Tao Li <t...@zillow.com> wrote: >>>>> >>>>> Hi community, >>>>> >>>>> >>>>> >>>>> Is there a beam function to explode an array (similarly to spark sql’s >>>>> explode())? I did some research but did not find anything. >>>>> >>>>> >>>>> >>>>> BTW I think we can potentially use FlatMap to implement the explode >>>>> functionality, but a Beam provided function would be very handy. >>>>> >>>>> >>>>> >>>>> Thanks a lot! >>>>> >>>>>
