[IMPALA-3060] Supports IS [NOT] NULL feature for complex types

[Jin Chul Kim]

Hi,

I would like to get your advice before implementing the feature
https://issues.apache.org/jira/browse/IMPALA-3060

Let me start with struct type of complex types. Would you please answer the
questions? Thanks.

1. Does StructType have getSlotSize? If your answer is yes, do you think
the following code piece is fine to you? Here is a initial code for
StructType.

  @Override
  public int getSlotSize() {
    int slotSize = 0;
    for (StructField f: fields_) slotSize += f.getType().getSlotSize();
    slotSize += (slotSize % 8); // For 8 byte alignment
    return slotSize;
  }

2. I think we should consider materialized path for struct type, but it
seems struct type might not be described in
SlotDescriptor.getMaterialzedPath() due to the guidance of the function:
"Assembles the absolute materialized path to this slot starting from the
schema root.
The materialized path points to the first non-struct schema element along
the path starting
from the parent's tuple path to this slot's path."

Can we determine materialized path for complex types?

Best regards,
Jinchul