Select from map with LowCardinality keys returns ClickHouseUnknownException: ClickHouse exception, message: Parse exception: ByteFragment

[vmnikulin]

Hello,

My setup
Clickhouse server version 21.9.4 revision 54449
Clickhouse client version 21.9.4.35
JDBC version 0.3.1

Native client works

CREATE TABLE lcmap (m Map(LowCardinality(String), Int32)) ENGINE=Memory;
//...
INSERT INTO lcmap(m) VALUES ({'key1':1});

//...
select * from lcmap;
//...
┌─m──────────┐
│ {'key1':1} │
└────────────

But when I try to execute select * from lcmap; in Datagrip I get

<failed to load>
ru.yandex.clickhouse.except.ClickHouseUnknownException: ClickHouse exception, message: Parse exception: ByteFragment{[{'key1':1}], start=0, len=10}; null
	at ru.yandex.clickhouse.response.ClickHouseResultSet.getObject(ClickHouseResultSet.java:648)
	in JdbcHelperImpl.getObject(JdbcHelperImpl.java:321)
Caused by: java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:221)
	at ru.yandex.clickhouse.response.parser.ClickHouseMapParser.parse(ClickHouseMapParser.java:119)
	at ru.yandex.clickhouse.response.parser.ClickHouseMapParser.parse(ClickHouseMapParser.java:17)
	at ru.yandex.clickhouse.response.ClickHouseResultSet.getObject(ClickHouseResultSet.java:749)
	at ru.yandex.clickhouse.response.ClickHouseResultSet.getObject(ClickHouseResultSet.java:642)
	... 21 more

[zhicwu]

Thanks for reporting the issue. The driver does not support nested data types very well at this point. It understands Map(String, Int32) but not Map(LowCardinality(String), Int32), Map(String, Nullable(Int32)), or Map<String, Tuple(Int32, Array())>. Actually these cases work in an in-development version, so I believe this will be addressed in next release.

[vmnikulin]

Thank you for your answer.
That is great.

I have tried to build 0.3.2-SNAPSHOT from develop with mvn package -DskipTests=true and use clickhouse-jdbc-0.3.2-SNAPSHOT-shaded.jar in Datagrip. And I have got the same exception.
Could you please give some advice on how to build the in-development version?

[zhicwu]

Sorry I'm in the middle of merging new gRPC client into develop branch. After which, I'll create another pull request by updating JDBC driver, clickhouse-jdbc module to be more specific, to use the new client in order to support more data types.

If you're familiar with Java, you may play with the new client in these two days to explore what's coming next.

[vmnikulin]

Great, thank you!
I am looking forward to the new version to see what is coming.

By the way, I made a quick fix in ClickHouseColumnInfo.splitArgs locally to fix the issue.

[zhicwu]

Tried the query on DBeaver, it works using the new JDBC driver.