[jira] [Created] (FLINK-15266) NPE in blink planner code gen

[Shang Yuanchun (Jira)]

Benchao Li created FLINK-15266:
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             Summary: NPE in blink planner code gen
                 Key: FLINK-15266
                 URL: https://issues.apache.org/jira/browse/FLINK-15266
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / Runtime
    Affects Versions: 1.9.1
            Reporter: Benchao Li


`cast` function in blink planner and old planner are different:

in legacy planner:
cast('' as int)  ->  throw NumberFormatException
cast(null as int) -> throw NullPointerException
cast('abc' as int)  -> throw NumberFormatException

but in blink planner:
cast('' as int)  ->  return null
cast(null as int) -> return null
cast('abc' as int)  -> return null

A step forward:
```
create table source {
  age int,
  id varchar
};
select case when age < 20 then cast(id as bigint) else 0 end from source;
```
queries like above will throw NPE because we will try assign a `null` to a `long` field.



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