[CALCITE-4303] Refactor org.apache.calcite.rel.RelInput to provide null-safe getters

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.25.0
• Component/s: core
• Assignee: Unassigned
• Reporter: Vladimir Sitnikov
• Created: 03/Oct/20 09:42
• Updated: 03/Oct/20 09:46

Description

There are several methods which might return null, however, they are used a lot as "never null" ones:

  <E extends Enum<E>> @Nullable E getEnum(String tag, Class<E> enumClass);
  @Nullable List<RexNode> getExpressionList(String tag);
  @Nullable List<String> getStringList(String tag);
  @Nullable List<Integer> getIntegerList(String tag);
  @Nullable List<List<Integer>> getIntegerListList(String tag);

It would be nice if the methods returned non-nullable values.

The suggested API is

  <E extends Enum<E>> E getEnum(String tag, Class<E> enumClass);
  List<RexNode> getExpressionList(String tag);
  List<String> getStringList(String tag);
  List<Integer> getIntegerList(String tag);
  List<List<Integer>> getIntegerListList(String tag);

  <E extends Enum<E>> @Nullable E getEnumOrNull(String tag, Class<E> enumClass);
  @Nullable List<RexNode> getExpressionListOrNull(String tag);
  @Nullable List<String> getStringListOrNull(String tag);
  @Nullable List<Integer> getIntegerListOrNull(String tag);
  @Nullable List<List<Integer>> getIntegerListListOrNull(String tag);