null for String values

[Deepanwita Roy]

When I ingest data through ClickHouse Kafka for a column name Fee of type String. If the json I pass is Foo:null, Kafka Engine fails to parse it and ClickHouse "
{} <Error> void DB::StorageKafka::streamThread(): Code: 26, e.displayText() = DB::Exception: Cannot parse JSON string:". For successful parsing of JsonEachRow message I have to specifically pass Foo:"". Is there a better way of dealing with null values

[Mikhail Filimonov]

If you need to have null - insert into Nullable column.

If you inserting in regular (not null) String field you need to convert all null to empty strings before.

create temporary table str_nullable ( a Nullable(String), b String);


insert into str_nullable format JSONEachRow {"a":null}

Ok.
1 rows in set. Elapsed: 0.002 sec.


SELECT * FROM str_nullable

┌─a────┬─b─┐
│ ᴺᵁᴸᴸ │   │
└──────┴───┘
1 rows in set. Elapsed: 0.001 sec.


insert into str_nullable format JSONEachRow {"b":null}

Exception on client:
Code: 26. DB::Exception: Cannot parse JSON string: expected opening quote: (while read the value of key b): (at row 1)