[core] Use write null for uncompact decimal and timestamp in InternalRowSerialize

[Zouxxyy]

Purpose

This PR extracts some modifications from #5242 to the PR, thanks to zhongyujiang

The InternalRowSerializer needs to maintain the handling of null value for uncompact Decimal and timestamp types in org.apache.paimon.codegen.GenerateUtils.binaryWriterWriteNull to avoid inconsistencies in hashcode, which could lead to the inconsistencies in bucket calculation.

  def binaryWriterWriteNull(indexTerm: String, writerTerm: String, t: DataType): String =
    t.getTypeRoot match {
      // ordered by type root definition
      case DECIMAL if !Decimal.isCompact(getPrecision(t)) =>
        s"$writerTerm.writeDecimal($indexTerm, null, ${getPrecision(t)})"
      case TIMESTAMP_WITHOUT_TIME_ZONE | TIMESTAMP_WITH_LOCAL_TIME_ZONE
          if !Timestamp.isCompact(getPrecision(t)) =>
        s"$writerTerm.writeTimestamp($indexTerm, null, ${getPrecision(t)})"
      case _ =>
        s"$writerTerm.setNullAt($indexTerm)"
    }

Tests

API and Format

Documentation

[zhongyujiang]

Makes sense to me.

[JingsongLi]

+1