rdblue commented on a change in pull request #227: ORC column map fix
URL: https://github.com/apache/incubator-iceberg/pull/227#discussion_r326395231
 
 

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 File path: site/docs/spec.md
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 @@ -489,7 +489,7 @@ Lists must use the [3-level 
representation](https://github.com/apache/parquet-fo
 
 One of the interesting challenges with this is how to map Iceberg’s schema 
evolution (id based) on to ORC’s (name based). In theory, we could use 
Iceberg’s column ids as the column and field names, but that would suck from a 
user’s point of view. 
 
-The column ids would be stored in ORC’s user metadata as `iceberg.column.id` 
with a comma separated list of the ids.
+The column IDs must be stored in ORC type attributes using the key 
`iceberg.id`, and `iceberg.required` to store `"true"` if the Iceberg column is 
required, otherwise it will be optional.
 
 Review comment:
   I think this is fine. There's no need to use more ID names than necessary. 
Avro uses several properties because it can't store properties with every type.

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