Aman Sinha created DRILL-4479:
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Summary: JsonReader should pick a less restrictive type when
creating the default column
Key: DRILL-4479
URL: https://issues.apache.org/jira/browse/DRILL-4479
Project: Apache Drill
Issue Type: Bug
Components: Storage - JSON
Affects Versions: 1.5.0
Reporter: Aman Sinha
This JIRA is related to DRILL-3806 but has a narrower scope, so I decided to
create separate one.
The JsonReader has the method ensureAtLeastOneField() (see
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/vector/complex/fn/JsonReader.java#L91)
that ensures that when no columns are found, create an empty one and it
chooses to create a nullable int column. One consequence is that queries of
the following type fail:
{noformat}
select c1 from dfs.`mostlynulls.json`;
...
...
| null |
| null |
Error: DATA_READ ERROR: Error parsing JSON - You tried to write a VarChar type
when you are using a ValueWriter of type NullableIntWriterImpl.
File /Users/asinha/data/mostlynulls.json
Record 4097
{noformat}
In this file the first 4096 rows have NULL values for c1 followed by rows that
have a valid string.
It would be useful for the Json reader to choose a less restrictive type such
as varchar in order to allow more types of queries to run.
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