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https://issues.apache.org/jira/browse/BEAM-7610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17066875#comment-17066875
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Kenneth Knowles commented on BEAM-7610:
---------------------------------------

Still an issue? Still working on this?

> SELECT COALESCE(...) isn't inferred as non-nullable field
> ---------------------------------------------------------
>
>                 Key: BEAM-7610
>                 URL: https://issues.apache.org/jira/browse/BEAM-7610
>             Project: Beam
>          Issue Type: Bug
>          Components: dsl-sql
>    Affects Versions: 2.13.0
>            Reporter: Gleb Kanterov
>            Assignee: Kirill Kozlov
>            Priority: Major
>
> In Calcite, Coalesce is described as:
> {code}
> ReturnTypes.cascade(ReturnTypes.LEAST_RESTRICTIVE,
>             SqlTypeTransforms.LEAST_NULLABLE)
> {code}
> However, giving non-null constant as an argument doesn't result in a 
> non-nullable expression:
> {code}
>     Schema inputSchema = Schema.of(
>         Schema.Field.of("name", Schema.FieldType.STRING.withNullable(true)));
>     PCollection<Row> input = p.apply(Create.of(ImmutableList.<Row>of())
>         .withCoder(SchemaCoder.of(inputSchema)));
>     Schema outputSchema = input
>         .apply(SqlTransform.query("SELECT COALESCE(name, 'unknown') as name 
> FROM PCOLLECTION"))
>         .getSchema();
>     assertEquals(
>         Schema.builder().addStringField("name").build(),
>         outputSchema);
> {code}
> Not sure if it's a problem in Calcite or Beam SQL.
> There are no other functions that can be used to produce a non-nullable field.



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