Description

when attempting to make a union select statement of a form similar to:

SELECT *
FROM test_table
UNION DISTINCT
SELECT *
FROM test_table

Steps to reproduce

1. make a prepared statement using the above query
2. executeQuery

Error Log or Exception StackTrace

line 1:31 mismatched input 'DISTINCT' expecting ALL

Expected Behaviour

a union of distinct elements is performed on the given select statements. (it looks like the antlr grammar specifically defines a union statement as 2 selects UNION ALL)

Code Example

 String sql = "SELECT * FROM " + TABLE_NAME + " UNION DISTINCT SELECT * FROM " + TABLE_NAME;
       // try to get all results with a union distinct 
        try (PreparedStatement pstmt = connection.prepareStatement(sql)) {
            try (Statement stmt = connection.createStatement();
                ResultSet rs = stmt.executeQuery(sql)) {
                while (rs.next()) {
                    System.out.println("id: " + rs.getInt("id") + ", Name: " + rs.getString("NameCol") + ", Attributes: " + rs.getString("MapCol") + ", TimeStamp: " + rs.getString("TimeCol") + ", Value: " + rs.getDouble("Value"));
                }
            }
        }

Configuration

tested with a local docker container at clickhouse:8123

Environment

• Client version: 0.9.0
• Language version: Java 17.0.6
• OS: CentOS 8 (also seen on Rocky9)

ClickHouse Server

• ClickHouse Server version: 25.5.2
• ClickHouse Server non-default settings, if any: N/A
• CREATE TABLE statements for tables involved:
  CREATE TABLE IF NOT EXISTS test_table (
  id UInt64,
  NameCol String,
  MapCol Map(LowCardinality(String), String),
  TimeCol TIMESTAMP,
  Value Float
  ) ENGINE = MergeTree()
  ORDER BY id
• Sample data for all these tables, use clickhouse-obfuscator if necessary