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https://issues.apache.org/jira/browse/SPARK-26964?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16774783#comment-16774783
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Huon Wilson commented on SPARK-26964:
-------------------------------------
We wish to store columns as columns within a {{binary}}-based database (HBase),
meaning encoding individual fields. JSON represents a non-horrible way of
encoding values into the database, e.g. it allows handling from many
languages/environments (and is even human readable), and is very convenient to
handle with DataFrames. I don't know of another way to extract byte
representations of individual columns that satisfies those constraints.
Looking at the source code, it seems like all of these types have support in
JacksonGenerator and JacksonParser, and so most of the work will be surfacing
that, rather than entirely new code. Is there something you expect to be more
intricate than additions to JsonToStructs and StructsToJson (and tests)? I'm
considering having a look at this myself, but if your intuition implies that
this is going to be a dead end, I will not.
> to_json/from_json do not match JSON spec due to not supporting scalars
> ----------------------------------------------------------------------
>
> Key: SPARK-26964
> URL: https://issues.apache.org/jira/browse/SPARK-26964
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.3.2, 2.4.0
> Reporter: Huon Wilson
> Priority: Major
>
> Spark SQL's {{to_json}} and {{from_json}} currently support arrays and
> objects, but not the scalar/primitive types. This doesn't match the JSON spec
> on https://www.json.org/ or [RFC8259|https://tools.ietf.org/html/rfc8259]: a
> JSON document ({{json: element}}) consists of a value surrounded by
> whitespace ({{element: ws value ws}}), where a value is an object or array
> _or_ a number or string etc.:
> {code:none}
> value
> object
> array
> string
> number
> "true"
> "false"
> "null"
> {code}
> Having {{to_json}} and {{from_json}} support scalars would make them flexible
> enough for a library I'm working on, where an arbitrary (user-supplied)
> column needs to be turned into JSON.
> NB. these newer specs differ to the original [RFC4627|
> https://tools.ietf.org/html/rfc4627] (which is now obsolete) that
> (essentially) had {{value: object | array}}.
> This is related to SPARK-24391 and SPARK-25252, which added support for
> arrays of scalars.
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