[CALCITE-2714] Make BasicSqlType immutable, and now createWithNullability re-uses existing type if possible

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 1.18.0
• Assignee: Julian Hyde
• Reporter: Ruben Q L
• Created: 28/Nov/18 10:59
• Updated: 23/Dec/18 00:12
• Resolved: 02/Dec/18 17:25

Description

As it is done in the parent implementation RelDataTypeFactoryImpl#createTypeWithNullability where the parameter 'type' is directly used as 'newType' if nullable matches:

public RelDataType createTypeWithNullability(final RelDataType type, final boolean nullable) {
  RelDataType newType;
  if (type.isNullable() == nullable) {
    newType = type;
  } else ...

I think that SqlTypeFactoryImpl#createTypeWithNullability should be modified in the same way when handling a BasicSqlType, to avoid calling BasicSqlType#createWithNullability (which internally executes a clone) if nullable matches:

public RelDataType createTypeWithNullability(final RelDataType type, final boolean nullable) {
  RelDataType newType;
  if (type instanceof BasicSqlType) {
    if (type.isNullable() == nullable) { // new piece of code
      newType = type;
    } else { // previously, this block was always executed
      BasicSqlType sqlType = (BasicSqlType) type;
      newType = sqlType.createWithNullability(nullable);
    }
  } else ...

I have verified, and Calcite Core unit tests run fine with this modification.

Issue Links

• links to: PR#947