tree b740440be689370598e1b694615d0cf0209e7ab9
parent a944afb8925ca710caa9e590e0bcb4a2d1a66ab5
author Paul Rogers <par0328@yahoo.com> 1577773806 -0800
committer Volodymyr Vysotskyi <vvovyk@gmail.com> 1578579865 +0200

DRILL-7502: Invalid codegen for typeof() with UNION

Also fixes DRILL-6362: typeof() reports NULL for primitive
columns with a NULL value.

typeof() is meant to return "NULL" if a UNION has a NULL
value, but the column type when known, such as for non-UNION
columns.

Also fixes DRILL-7499: sqltypeof() function with an array returns
"ARRAY", not type. This was due to treating REPEATED like LIST.

Handling of the Union vector in code gen is problematic
with about three special cases. Existing code handled two
of the cases. This change handles the third case.

Figuring out the change required poking around quite a bit
of unclear code. Added comments and restructuring to make
that code a bit more clear.

The fix modified code gen for the Union Holder. It can now
"go back in time" to add the union reader at the point we
need it.

closes #1945