Re: Implementing JSON_TABLE, even hackily as a UDF?

[Gavin Ray <ra...@gmail.com>]

I think you're probably right, the functionality for reading JSON must
exist in the File adapter already
Then I'd just need to figure out how to read from "HTTP_GET" UDF as the
JSON contents

Ty, will go look at the source for the adapter

On Tue, May 31, 2022 at 6:51 PM Julian Hyde <jh...@gmail.com> wrote:

> Is there any overlap with the file adapter? The file adapter can read
> using various transports (file, http, optional compression) and various
> formats (csv, json, html tables).
>
> > On May 31, 2022, at 12:47 PM, Gavin Ray <ra...@gmail.com> wrote:
> >
> > I don't think it's SQL Standard, but essentially it takes a text value
> > containing JSON data (one record or an array) and converts it into a
> > relational table:
> >
> > https://docs.oracle.com/database/121/SQLRF/functions092.htm
> >
> > I've managed to get most of this working, now I seem to be failing to put
> > the syntax together correctly for the query
> > I currently have:
> > - A UDF ("HTTP_GET") which can make HTTP calls and return the data as a
> > String
> > - A table type for Collection<Map<String, Object>> ("MapCollectionTable")
> > - A TableFunctionImpl ("JsonTableFunction"), which takes a JSON string,
> > reads it with Jackson, and converts it into a "MapCollectionTable"
> >
> > The following work:
> >
> > SELECT HTTP_GET('https://jsonplaceholder.typicode.com/posts')
> >
> > SELECT * FROM TABLE(
> >  JSON_TABLE('[{ "id": "1", "name": "foo" }, { "id": "2", "name": "bar"
> > }]'))
> >
> > But trying to combine them fails =/
> >
> > SELECT * FROM TABLE(
> >  JSON_TABLE(HTTP_GET('https://jsonplaceholder.typicode.com/posts')))
> >
> > The TableFunctionImpl is receiving "null" for the JSON value
> > I guess it's maybe expecting static data?
> >
> > Calcite JSON_TABLE wip 2 (github.com)
> > <
> https://gist.github.com/GavinRay97/fbd16dd2b893cb59c720e6d514c5e39a#file-main-java
> >
> >
> > On Tue, May 31, 2022 at 2:44 PM Julian Hyde <jh...@apache.org> wrote:
> >
> >> What is JSON_TABLE? Is it in the SQL standard? Can you give a simple
> >> example?
> >>
> >> On Tue, May 31, 2022 at 10:03 AM Gavin Ray <ra...@gmail.com>
> wrote:
> >>>
> >>> I dug up some examples from Github of using the "TableFunctionImpl"
> >> class:
> >>>
> >>> mat-calcite-plugin/TableFunctions.java at
> >>> a57a5ba80768066714c22bd9e8a9b529d4cb9a6b · vlsi/mat-calcite-plugin
> >>> (github.com)
> >>> <
> >>
> https://github.com/vlsi/mat-calcite-plugin/blob/a57a5ba80768066714c22bd9e8a9b529d4cb9a6b/MatCalcitePlugin/src/com/github/vlsi/mat/calcite/functions/TableFunctions.java
> >>>
> >>> Calcite_sql_driver/MazeTable.java at
> >>> 6819088123e67631367ca927b112b58e4eb90829 · dream001/Calcite_sql_driver
> >>> (github.com)
> >>> <
> >>
> https://github.com/dream001/Calcite_sql_driver/blob/6819088123e67631367ca927b112b58e4eb90829/src/test/java/com/yonyou/calcite/MazeTable.java
> >>>
> >>>
> >>> Currently trying to get a TableFunction that just returns a Map<String,
> >>> Object> as a relation to work
> >>> Have the below -- calling this shows that the function IS invoked, but
> >> the
> >>> data it gives back is garbage:
> >>>
> >>> Calcite JSON_TABLE WIP (github.com)
> >>> <https://gist.github.com/GavinRay97/b42c69992a0d0c3a01f1c7e1b9ab1999>
> >>>
> >>> This is the output of main()
> >>>
> >>> json = {"id":1, "name":"John"}
> >>> json = {"id":1, "name":"John"}
> >>> json = {"id":1, "name":"John"}
> >>> EXPR$0: id
> >>> EXPR$0: id
> >>>
> >>> I'm doing something wrong here for sure, lol.
> >>>
> >>>
> >>> On Tue, May 31, 2022 at 11:35 AM Gavin Ray <ra...@gmail.com>
> >> wrote:
> >>>
> >>>> I'm interested in implementing JSON_TABLE functionality for Calcite
> >>>>
> >>>> This opens up some neat usecases, like adding HTTP request UDF's
> >>>> then using JSON_TABLE to convert the result into a table:
> >>>>
> >>>> SELECT JSON_TABLE(
> >>>> HTTP_GET('http://localhost:8080/api/v1/users/1'))
> >>>>
> >>>> Adding support for all of the functionality seems difficult,
> >>>> but I'm wondering whether this could be done as a "SqlTableFunction"
> >> UDF?
> >>>>
> >>>> I'm thinking it might be possible if the JSON_TABLE udf
> >>>> expects Map<String, Object> and does inference based on that?
> >>>>
> >>>> Something like:
> >>>>
> >>>> WITH users AS (
> >>>>    SELECT HTTP_GET('http://localhost:8080/api/v1/users')
> >>>> ) SELECT
> >>>>    id,
> >>>>    name
> >>>> FROM
> >>>>    JSON_TABLE(JSON_PATH(users, "$.0"))
> >>>>
> >>>> Does anyone have ideas or see issues with this approach?
> >>>> Thank you =)
> >>>>
> >>>>
> >>>>
> >>>>
> >>
>
>