ClickHouse / ClickHouse/clickhouse-java

Regression in JDBC 0.9.8 when reading Array(Tuple(...)) with named tuple elements.

Open
#3,045 0 comments 0 reactions 0 assignees View on GitHub
area:data-type area:jdbc-read bug jdbc-v2
Dominant language
Java
Stars
1.6k
Forks
636
Avg merge
2d 16h
Merged PRs (30d)
28

Description

## Description
Regression in JDBC 0.9.8 when reading Array(Tuple(...)) with named tuple elements.

With the official ClickHouse JDBC driver 0.9.8, IntelliJ IDEA displays Array(Tuple(id UUID)) values as:
`com.clickhouse.jdbc.types.Array@54c3b772`
instead of the array contents.

The same query works correctly with JDBC 0.6.0.
The issue only affects named tuples. Arrays of unnamed tuples are displayed correctly.

### Steps to reproduce
1. Connect to ClickHouse using clickhouse-jdbc:0.9.8.
2. Execute `SELECT [('550e8400-e29b-41d4-a716-446655440000')];` Result is displayed correctly.
3. Execute `SELECT [('550e8400-e29b-41d4-a716-446655440000')::Tuple(id UUID)];` Result is displayed as com.clickhouse.jdbc.types.Array@...
### Error Log or Exception StackTrace
No exception is thrown.

The value is rendered as:
```
com.clickhouse.jdbc.types.Array@54c3b772
```

### Expected Behaviour
Array(Tuple(id UUID)) should be returned through JDBC in a way that clients can display its contents, the same as in JDBC 0.6.0 and the same as Array(Tuple(UUID))

### Code Example

```sql
SELECT [('550e8400-e29b-41d4-a716-446655440000')];

SELECT [('550e8400-e29b-41d4-a716-446655440000')::Tuple(id UUID)];

```

### Configuration

#### Client Configuration
Default JDBC configuration.
```java

```

#### Environment
* [ ] Cloud
* Client version: clickhouse-jdbc 0.9.8
* Language version: N/A (observed in IntelliJ Database Viewer)
* OS: macOS
* IDE: IntelliJ IDEA 2026.2.0.1

#### ClickHouse Server
* ClickHouse Server version: 26.3.17.56
* ClickHouse Server non-default settings, if any: None
* `CREATE TABLE` statements for tables involved: Not required (reproducible with literal values only)
* Sample data for all these tables, use [clickhouse-obfuscator](https://github.com/ClickHouse/ClickHouse/blob/master/programs/obfuscator/Obfuscator.cpp#L42-L80) if necessary

It is unclear whether this is a JDBC driver regression or an incompatibility with IntelliJ’s database viewer, but the behavior changed between JDBC 0.6.0 and 0.9.8 and is reproducible with the SQL above.

Contributor guide

Open the contributing guide

Research direction

Start by reproducing the two SQL queries with clickhouse-jdbc 0.9.8, then compare the returned Array(Tuple(...)) value with JDBC 0.6.0 and the unnamed-tuple case. Check whether the driver or IntelliJ Database Viewer controls rendering; done means named tuple arrays expose their contents consistently with the expected cases.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
database
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
52/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.