Should Unnest be allowed to specify multiple array fields, or just one? On Wed, Jan 13, 2021 at 11:59 PM Manninger, Matyas < [email protected]> wrote:
> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> >>>> 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 <[email protected]> wrote: >>>>> >>>>>> @Kyle Weaver <[email protected]> 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 <[email protected]> >>>>>> *Reply-To: *"[email protected]" <[email protected]> >>>>>> *Date: *Tuesday, January 12, 2021 at 4:58 PM >>>>>> *To: *"[email protected]" <[email protected]> >>>>>> *Cc: *Reuven Lax <[email protected]> >>>>>> *Subject: *Re: Is there an array explode function/transform? >>>>>> >>>>>> >>>>>> >>>>>> @Reuven Lax <[email protected]> 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 <[email protected]> wrote: >>>>>> >>>>>> @Reuven Lax <[email protected]> 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 <[email protected]> >>>>>> *Reply-To: *"[email protected]" <[email protected]> >>>>>> *Date: *Tuesday, January 12, 2021 at 2:04 PM >>>>>> *To: *user <[email protected]> >>>>>> *Subject: *Re: Is there an array explode function/transform? >>>>>> >>>>>> >>>>>> >>>>>> Have you tried Flatten.iterables >>>>>> >>>>>> >>>>>> >>>>>> On Tue, Jan 12, 2021, 2:02 PM Tao Li <[email protected]> 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! >>>>>> >>>>>>
