Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/594#discussion_r101880961
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/vector/complex/fn/JsonReader.java
---
@@ -63,6 +67,12 @@
private final List<ListWriter> emptyArrayWriters = Lists.newArrayList();
/**
+ * Collection for tracking nullable fields during reading
+ * and storing them for creating default typed vectors
+ */
+ private Map<List<String>, MapWriter> fieldPathWriter = Maps.newHashMap();
--- End diff --
Actually, in JSON, all scalar types can be null. Because JSON has no
schema, any field can have any type. Drill assumes that a given field has a
single type. But, in JSON semantics, that single type can be null. That is, the
following is always valid:
{code}
{ a: 10, b: null }
{ a: null, b: "foo" }
{ a: 20 }
{code}
JSON, but not Drill, differentiates between "not present" and null.
Given this, we don't need a special map for nullable fields: all JSON
fields are nullable.
Of course, JSON allows a null map, which Drill does not handle, but let's
ignore that here...
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