[jira] [Created] (CALCITE-5148) BasicSqlType.generateTypeString() should use equals() to compare collation instead of == by reference

["Yingyu Wang (Jira)" <ji...@apache.org>]

Yingyu Wang created CALCITE-5148:
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             Summary: BasicSqlType.generateTypeString() should use equals() to compare collation instead of == by reference
                 Key: CALCITE-5148
                 URL: https://issues.apache.org/jira/browse/CALCITE-5148
             Project: Calcite
          Issue Type: Bug
            Reporter: Yingyu Wang


Currently in {{{}BasicSqlType{}}}, 

{{generateTypeString(StringBuilder sb, boolean withDetail)}} method compares collation field against static 

{{SqlCollation.IMPLICIT}} by reference. I.e.
{code:java}
if (collation != null
    && collation != SqlCollation.IMPLICIT && collation != SqlCollation.COERCIBLE) { {code}
This will cause type that constructed with a collation instance that equals to {{SqlCollation.IMPLICIT}} or {{SqlCollation.COERCIBLE}} (e.g. collation instance is constructed during deserialization) to generate different type string. 

The following test can demonstrate the problem. 
{code:java}
@Test void testCreateSqlTypeWithCollation() {
  final RelDataTypeFactory typeFactory =
      new SqlTypeFactoryImpl(RelDataTypeSystem.DEFAULT);
  final RelDataType varchar =
      typeFactory.createSqlType(SqlTypeName.VARCHAR);

  final SqlCollation myImplicitCollation = new SqlCollation(SqlCollation.Coercibility.IMPLICIT);

  final RelDataType myVarchar = typeFactory.createTypeWithCharsetAndCollation(
      typeFactory.createSqlType(SqlTypeName.VARCHAR),
      typeFactory.getDefaultCharset(),
      myImplicitCollation);

  assertTrue(myImplicitCollation.equals(SqlCollation.IMPLICIT));
  assertTrue(myVarchar.equals(varchar));

  assertEquals("VARCHAR NOT NULL", varchar.getFullTypeString());
  assertEquals("VARCHAR NOT NULL", myVarchar.getFullTypeString());
}{code}
Here {{myImplicitCollation}} is constructed with the same coercibility as the static instance {{SqlCollation.IMPLICIT}} so {{myImplicitCollation}} equals to {{{}SqlCollation.IMPLICIT{}}}.

 

However due to the issue with {{BasicSqlType.generateTypeString()}} where collation is compared by reference, these 2 assert will fail:
{code:java}
assertTrue(myVarchar.equals(varchar)); 
//myVarchar.digest = VARCHAR COLLATE "ISO-8859-1$en_US$primary" NOT NULL
//varchar.digest = VARCHAR NOT NULL

assertEquals("VARCHAR NOT NULL", myVarchar.getFullTypeString());
//myVarchar.getFullTypeString() = VARCHAR COLLATE "ISO-8859-1$en_US$primary" NOT NULL{code}
The fix would be using equals to compare collation instance in BasicSqlType.generateTypeString(). I.e.
{code:java}
if (collation != null
    && !collation.equals(SqlCollation.IMPLICIT) && !collation.equals(SqlCollation.COERCIBLE)) { {code}



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