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https://issues.apache.org/jira/browse/BEAM-3157?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16437561#comment-16437561
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Anton Kedin commented on BEAM-3157:
-----------------------------------

PR is merged which allows Rows generation for POJOS: 
[https://github.com/apache/beam/pull/4649/files]

Usage example: 
[https://github.com/apache/beam/blob/670c75e94795ad9da6a0690647e996dc97b60718/sdks/java/extensions/sql/src/test/java/org/apache/beam/sdk/extensions/sql/InferredRowCoderSqlTest.java#L82]
 

Caveat: `SELECT *` doesn't work correctly due to undefined order of fields.

This PR resolves this Jira for now. Bugs and extra features will go into 
separate Jiras.

PS: there's also work to convert JSON obejcts directly to Rows: 
https://github.com/apache/beam/pull/5120

> BeamSql transform should support other PCollection types
> --------------------------------------------------------
>
>                 Key: BEAM-3157
>                 URL: https://issues.apache.org/jira/browse/BEAM-3157
>             Project: Beam
>          Issue Type: Improvement
>          Components: dsl-sql
>            Reporter: Ismaël Mejía
>            Assignee: Anton Kedin
>            Priority: Major
>          Time Spent: 5h 20m
>  Remaining Estimate: 0h
>
> Currently the Beam SQL transform only supports input and output data 
> represented as a BeamRecord. This seems to me like an usability limitation 
> (even if we can do a ParDo to prepare objects before and after the transform).
> I suppose this constraint comes from the fact that we need to map 
> name/type/value from an object field into Calcite so it is convenient to have 
> a specific data type (BeamRecord) for this. However we can accomplish the 
> same by using a PCollection of JavaBean (where we know the same information 
> via the field names/types/values) or by using Avro records where we also have 
> the Schema information. For the output PCollection we can map the object via 
> a Reference (e.g. a JavaBean to be filled with the names of an Avro object).
> Note: I am assuming for the moment simple mappings since the SQL does not 
> support composite types for the moment.
> A simple API idea would be something like this:
> A simple filter:
> PCollection<MyPojo> col = BeamSql.query("SELECT * FROM .... WHERE 
> ...").from(MyPojo.class);
> A projection:
> PCollection<MyNewPojo> newCol = BeamSql.query("SELECT id, 
> name").from(MyPojo.class).as(MyNewPojo.class);
> A first approach could be to just add the extra ParDos + transform DoFns 
> however I suppose that for memory use reasons maybe mapping directly into 
> Calcite would make sense.



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