Document unsigned numeric type MySQL/MariaDB to Trino mapping

[willshen]

Description

Document how unsigned numeric types from MySQL and MariaDB are mapped to Trino.

Additional context and related issues

As discussed in #14679

trino/plugin/trino-mariadb/src/main/java/io/trino/plugin/mariadb/MariaDbClient.java

Lines 616 to 634 in 1be256c

	private static Optional<ColumnMapping> getUnsignedMapping(JdbcTypeHandle typeHandle)
	{
	if (typeHandle.getJdbcTypeName().isEmpty()) {
	return Optional.empty();
	}
	String typeName = typeHandle.getJdbcTypeName().get();
	if (typeName.equalsIgnoreCase("tinyint unsigned")) {
	return Optional.of(smallintColumnMapping());
	}
	if (typeName.equalsIgnoreCase("smallint unsigned")) {
	return Optional.of(integerColumnMapping());
	}
	if (typeName.equalsIgnoreCase("int unsigned")) {
	return Optional.of(bigintColumnMapping());
	}
	if (typeName.equalsIgnoreCase("bigint unsigned")) {
	return Optional.of(decimalColumnMapping(createDecimalType(20)));
	}

trino/plugin/trino-mysql/src/main/java/io/trino/plugin/mysql/MySqlClient.java

Lines 371 to 379 in 1be256c

	switch (jdbcTypeName.toLowerCase(ENGLISH)) {
	case "tinyint unsigned":
	return Optional.of(smallintColumnMapping());
	case "smallint unsigned":
	return Optional.of(integerColumnMapping());
	case "int unsigned":
	return Optional.of(bigintColumnMapping());
	case "bigint unsigned":
	return Optional.of(decimalColumnMapping(createDecimalType(20)));

Release notes

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# Section
* Fix some things. ({issue}`issuenumber`)

[willshen]

FYI @mosabua I followed the precedent set in https://github.com/trinodb/trino/blob/master/docs/src/main/sphinx/connector/memsql.rst#type-mapping to create a new row after BIGINT for BIGINT UNSIGNED.

[mosabua]

Thank you so much. Can you please confirm that this is technically accurate @ebyhr.

Looking at getUnsignedMapping (see

trino/plugin/trino-mariadb/src/main/java/io/trino/plugin/mariadb/MariaDbClient.java

Line 616 in e3bbf6c

private static Optional<ColumnMapping> getUnsignedMapping(JdbcTypeHandle typeHandle)

) we should maybe also document the unsigned variants of tinyint, smallint and int. At least for MariaDB ..

Just checked.. MySql is the same logic but different code structure..

[mosabua]

That was fast @willshen .. looks good to me. Once @ebyhr or another engineer confirm .. this looks good to go from my point of view.