HashModShardingAlgorithm depends on shardingValue.hashCode() might cause some issues

[sandynz]

Related code:

HashModShardingAlgorithm.java

    private long hashShardingValue(final Object shardingValue) {
        return Math.abs((long) shardingValue.hashCode());
    }

Possible issue 1

java.lang.Number sub-classes might have different hashCode() implementation, e.g.

println("Integer.valueOf(-1).hashCode(): " + Integer.valueOf(-1).hashCode())
println("Long.valueOf(-1).hashCode(): " + Long.valueOf(-1).hashCode())
println("BigInteger.valueOf(-1).hashCode(): " + BigInteger.valueOf(-1).hashCode())

-- result
Integer.valueOf(-1).hashCode(): -1
Long.valueOf(-1).hashCode(): 0
BigInteger.valueOf(-1).hashCode(): -1

Eexample table: t_order.
Sharding rule:

rules:
  - !SHARDING
    autoTables:
      t_order:
        actualDataSources: ds_0,ds_1
        shardingStrategy:
          standard:
            shardingColumn: order_id
            shardingAlgorithmName: auto_mod
        keyGenerateStrategy:
          column: user_id
          keyGeneratorName: snowflake
    shardingAlgorithms:
      auto_mod:
        type: HASH_MOD
        props:
          sharding-count: 2
    
    keyGenerators:
      snowflake:
        type: SNOWFLAKE

Insert record with Integer sharding key value, then query with Long sharding key value, ResultSet return empty result.

Test code:

    @Test
    void assertHashModSetLongOnIntColumnWorks() throws SQLException {
        try (Connection connection = DriverManager.getConnection("jdbc:shardingsphere:classpath:config/driver/foo-driver-fixture.yaml")) {
            assertThat(connection, isA(ShardingSphereConnection.class));
            try (Statement statement = connection.createStatement()) {
                statement.execute("DROP TABLE IF EXISTS t_order");
                statement.execute("CREATE TABLE t_order (order_id INT PRIMARY KEY, user_id INT)");
            }
            int value = -1;
            try (PreparedStatement preparedStatement = connection.prepareStatement("INSERT INTO t_order (order_id, user_id) VALUES (?, ?)")) {
                preparedStatement.setObject(1, value); // Insert with Integer value
                preparedStatement.setObject(2, 101);
                int updatedCount = preparedStatement.executeUpdate();
                assertThat(updatedCount, is(1));
            }
            try (PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM t_order WHERE order_id = ?")) {
                preparedStatement.setObject(1, value); // Query with Integer value, related record could be queried out
                ResultSet resultSet = preparedStatement.executeQuery();
                assertTrue(resultSet.next()); // Pass
                assertThat(resultSet.getInt(1), is(value)); // Pass
                resultSet.close();
            }
            try (PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM t_order WHERE order_id = ?")) {
                preparedStatement.setObject(1, (long) value); // Query with Long value, related record could NOT be queried out
                ResultSet resultSet = preparedStatement.executeQuery();
                assertTrue(resultSet.next()); // WRONG
                assertThat(resultSet.getInt(1), is(value));
                resultSet.close();
            }
        }
    }

It was submitted in https://github.com/apache/shardingsphere/pull/37281/files

The similar test code, use raw MySQL JDBC driver, test on MySQL, it works.

Possible issue 2

If different vendors JRE or different versions of JRE have different hashCode() implementation, then when JRE vendor or version is changed, it'll cause different routing for the same sharding value.