[client-v2] Enum type parsing accepts duplicate ordinals and duplicate labels: Enum8('a' = 1, 'b' = 1) silently stores 'b' as 'a'

Beginne in clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseEnum.java, wo der Konstruktor Collection<String> (etwa Zeilen 37-53) und der Konstruktor (String[], int[]) (etwa Zeilen 55-65) doppelte Ordinalwerte und Labels akzeptieren. Füge in beiden Konstruktoren eine Prüfung hinzu, die IllegalArgumentException mit Nennung des Typs wirft, wenn ein Ordinalwert oder Label sich wiederholt. Fertig ist es, wenn ClickHouseColumn.parse Enum8('a' = 1, 'b' = 1) und Enum8('a' = 1, 'a' = 2) ablehnt und Enum8('a' = 200, 'b' = 1) weiterhin geparst wird.

Description

ClickHouseColumn.parse(...) / ClickHouseEnum accept an Enum type definition in which two members share an ordinal (Enum8('a' = 1, 'b' = 1)) or share a label (Enum8('a' = 1, 'a' = 2)). The server rejects both (Code: 62 ... Duplicate values in enum / Duplicate names in enum).

com.clickhouse.data.ClickHouseEnum stores the members in two parallel arrays and does no uniqueness check at all:

• ClickHouseEnum(Collection<String> params) (clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseEnum.java:37-53) only validates that each entry contains =.
• value(String name) / name(int value) (lines 87-115) are first-match linear scans.

Consequence for a duplicate ordinal: value("a") == value("b") == 1, so both labels serialize to the same byte in SerializerUtils.serializeEnumData (client-v2/src/main/java/com/clickhouse/client/api/data_formats/internal/SerializerUtils.java:858-880), and name(1) only ever returns "a" — "b" is unreachable.

This is reachable whenever the application supplies the column type itself rather than letting the client probe the server: a TableSchema built from ClickHouseColumn.parse(...) and passed to Client.register(Class, TableSchema), then used for a RowBinary insert. The insert succeeds with no error and the wrong value lands in the table.

Impact is low — the server never emits such a type, so reads and server-probed insert schemas are unaffected. But the failure mode is silent data corruption rather than an error.

Found while checking whether ClickHouse/clickhouse-cs#731 also applies here. Distinct from #3304 (non-member integer / Enum.ordinal()).

ClickHouse server version

26.10.3.7 (verified against a running server; client built from main, version 0.12.0-rc1-SNAPSHOT).

The server rejects the type on every version:

SELECT CAST('a' AS Enum8('a' = 1, 'b' = 1))
Code: 62. DB::Exception: Duplicate values in enum: 'b' = 1 and 'a' ... (SYNTAX_ERROR)

Reproduction

client-v2/src/test/java/com/clickhouse/client/insert/EnumDupOrdinalTest.java:

package com.clickhouse.client.insert;

import com.clickhouse.client.api.Client;
import com.clickhouse.client.api.insert.InsertResponse;
import com.clickhouse.client.api.insert.InsertSettings;
import com.clickhouse.client.api.metadata.TableSchema;
import com.clickhouse.client.api.query.GenericRecord;
import com.clickhouse.data.ClickHouseColumn;
import org.testng.annotations.Test;

import java.util.ArrayList;
import java.util.List;

public class EnumDupOrdinalTest {

    public static class Row {
        private short id;
        private String e;

        public short getId() { return id; }
        public void setId(short id) { this.id = id; }
        public String getE() { return e; }
        public void setE(String e) { this.e = e; }
    }

    @Test
    public void duplicateOrdinalIsAccepted() throws Exception {
        ClickHouseColumn c = ClickHouseColumn.parse("e Enum8('a' = 1, 'b' = 1)").get(0);
        System.out.println("parsed OK (duplicate ordinal): " + c.getOriginalTypeName());
        System.out.println("  value('a') = " + c.getEnumConstants().value("a"));
        System.out.println("  value('b') = " + c.getEnumConstants().value("b"));
        System.out.println("  name(1)    = " + c.getEnumConstants().name(1));

        ClickHouseColumn c2 = ClickHouseColumn.parse("e Enum8('a' = 1, 'a' = 2)").get(0);
        System.out.println("parsed OK (duplicate label): " + c2.getOriginalTypeName());
        System.out.println("  value('a') = " + c2.getEnumConstants().value("a"));

        try (Client client = new Client.Builder().addEndpoint("http://localhost:8123")
                .setUsername("default").setPassword("").compressServerResponse(false).build()) {

            String table = "enum_dup_ordinal_test";
            client.execute("DROP TABLE IF EXISTS " + table).get();
            client.execute("CREATE TABLE " + table
                    + " (id UInt8, e Enum8('a' = 1, 'b' = 2)) ENGINE = Memory").get();

            // application-supplied schema, with a type the server would reject
            TableSchema schema = new TableSchema(table, null, "default",
                    ClickHouseColumn.parse("id UInt8, e Enum8('a' = 1, 'b' = 1)"));
            client.register(Row.class, schema);

            List<Object> data = new ArrayList<>();
            Row r1 = new Row(); r1.setId((short) 1); r1.setE("a");
            Row r2 = new Row(); r2.setId((short) 2); r2.setE("b");
            data.add(r1);
            data.add(r2);

            try (InsertResponse resp = client.insert(table, data, new InsertSettings()).get()) {
                System.out.println("insert succeeded, rows written = " + resp.getWrittenRows());
            }

            for (GenericRecord rec : client.queryAll(
                    "SELECT concat(toString(id), '|', toString(e), '|', toString(toInt16(e))) AS r FROM "
                            + table + " ORDER BY id")) {
                System.out.println("  row: " + rec.getString("r"));
            }
            client.execute("DROP TABLE IF EXISTS " + table).get();
        }
    }
}

Run: mvn -pl client-v2 -Dtest=EnumDupOrdinalTest test

Actual output (target/surefire-reports/...-output.txt):

parsed OK (duplicate ordinal): Enum8('a' = 1, 'b' = 1)
  value('a') = 1
  value('b') = 1
  name(1)    = a
parsed OK (duplicate label): Enum8('a' = 1, 'a' = 2)
  value('a') = 1
server version: 26.10.3.7
server rejected: SELECT CAST('a' AS Enum8('a' = 1, 'b' = 1))   <- server refuses the same type
insert succeeded, rows written = 2
  row: 1|a|1
  row: 2|a|1        <- 'b' was written as ordinal 1 and reads back as 'a'

Expected: ClickHouseColumn.parse / the ClickHouseEnum constructor reject both type strings with an exception naming the offending type, as the server does. The row written as 'b' should either fail or be stored as 'b'.

Suggested fix

In com.clickhouse.data.ClickHouseEnum (clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseEnum.java), validate in the Collection<String> constructor (lines 37-53) and in the (String[], int[]) constructor (lines 55-65) that no ordinal and no label repeats, throwing IllegalArgumentException that names the type, e.g. Enum declares the ordinal 1 more than once / Enum declares the label 'a' more than once.

Note the contrast case that must keep working: an explicit out-of-range ordinal (Enum8('a' = 200, 'b' = 1)) is accepted and wrapped by older servers, so no range check should be added here.

Link

Relayed from https://github.com/ClickHouse/clickhouse-cs/issues/731
Tracking: https://github.com/ClickHouse/integrations-ai-playground/issues/693