[jira] [Created] (CALCITE-4311) Add non-nullable experimental accessors side by side with their nullable counterparts

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

Vladimir Sitnikov created CALCITE-4311:
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             Summary: Add non-nullable experimental accessors side by side with their nullable counterparts
                 Key: CALCITE-4311
                 URL: https://issues.apache.org/jira/browse/CALCITE-4311
             Project: Calcite
          Issue Type: Sub-task
    Affects Versions: 1.25.0
            Reporter: Vladimir Sitnikov


Certain APIs are declared to return nullable values, however, they are often used in "I know this must be non-null" context.

For instance: {{Wrapper#unwrap(Class)}}.
It happens so that {{.unwrap(Table.class)}} is quite common.
For instance:
{code:java}
            final Table leftTable = leftRelOptTable.unwrap(Table.class);
            final int leftCount = leftRelOptTable.getRowType().getFieldCount();
{code}

It would be nice if unwrap could fail with a proper message like "oh, I can't find Table in ...", so the end users would get better error messages, and the code would be way easier to read.

For instance:
{code:java}
// unwrapNonNull can be declared as a default implementation
            final Table leftTable = leftRelOptTable.unwrapNonNull(Table.class);
            final int leftCount = leftRelOptTable.getRowType().getFieldCount();
{code}

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Another case is {{org.apache.calcite.sql.SqlSelect#getSelectList}}. The method returns a nullable value, however, it is often used as if it was non-nullable.


Initially, I thought of adding static helper methods to utility classes/interfaces, however, now I'm inlined to adding non-nullable getters right to the original classes/interfaces.
That would make the code easier to read and write.



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