#1760 ResultSetMetaData reports incorrect Java classes for TINYINT and SMALLINT columns

[DB]

Description

HSQLDB incorrectly reports java.lang.Integer as the Java class for both TINYINT and SMALLINT columns through ResultSetMetaData.getColumnClassName(int).

The JDBC type reported by ResultSetMetaData.getColumnType(int) is correct in both cases, but the corresponding Java class name is incorrectly reported as java.lang.Integer instead of the Java wrapper type corresponding to the JDBC type.

Reproduction

CREATE TABLE test_table (
    tinyint_col TINYINT,
    smallint_col SMALLINT
);

Then inspect the column metadata:

ResultSetMetaData metadata = resultSet.getMetaData();

for (int i = 1; i <= metadata.getColumnCount(); i++) {
    System.out.println(
        "name=" + metadata.getColumnName(i) +
        ", typeName=" + metadata.getColumnTypeName(i) +
        ", type=" + metadata.getColumnType(i) +
        ", className=" + metadata.getColumnClassName(i)
    );
}

Actual result

name=TINYINT,  typeName=TINYINT,  type=-6, className=java.lang.Integer
name=SMALLINT, typeName=SMALLINT, type=5,  className=java.lang.Integer

Expected result

name=TINYINT,  typeName=TINYINT,  type=-6, className=java.lang.Byte
name=SMALLINT, typeName=SMALLINT, type=5,  className=java.lang.Short

Environment

• HSQLDB version: 2.7.4
• Java version: JDK 17

[Fred Toussi]

The return type of Integer is correct for the two narrower types. This is listed in "JDBC 4.3 Specification • July 2017".

[DB]

Well, yes, Table B-3 clearly specifies TINYINT and SMALLINT -> Integer. However, given that the ranges of these SQL types fit within Java's byte and short ranges, respectively, wouldn't returning the more precise Java class names (Byte and Short) be a reasonable improvement rather than a deviation from the specification?

I understand that the specification defines Integer as the default mapping, but does that necessarily mean a driver should not expose a more precise class through ResultSetMetaData.getColumnClassName().

[Fred Toussi]

It returns an Integer, therefore the Java class name is "Integer".