[CALCITE-4392] The operation of checking types equal ignoring null can be more efficient

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.27.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Liya Fan
• Reporter: Liya Fan
• Created: 11/Nov/20 12:10
• Updated: 03/Jun/21 22:32
• Resolved: 18/Nov/20 08:52

Description

Method {{SqlTypeUtil#equalSansNullability(RelDataTypeFactory, RelDataType, RelDataType) is on the hot path for many scenarios, as it compare types with nullability ignored.

In the implementation, the expensive operations are RelDataType#equals(Object) and RelDataTypeFactory#createTypeWithNullability, especially for types with multiple sub-fields.

For the current implementation, the RelDataType#equals(Object) is called at least once, and RelDataTypeFactory#createTypeWithNullability is called whenever the nullability values are different.

We can improve the implementation so that RelDataType#equals(Object) is called exactly once, and the call to RelDataTypeFactory#createTypeWithNullability can be avoided if the types are totally different (with different type names, and nullability values)

if (type1.isNullable() == type2.isNullable()) {
  return type1.equals(type2);
} else {
  return type1.equals(
        factory.createTypeWithNullability(type2, type1.isNullable()));
}

Issue Links

• links to: GitHub Pull Request #2256