[GitHub] [incubator-iceberg] lxynov commented on a change in pull request #227: ORC column map fix

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lxynov commented on a change in pull request #227: ORC column map fix
URL: https://github.com/apache/incubator-iceberg/pull/227#discussion_r340374991
 
 

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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:
   > `iceberg.required` to store `"true"` if the Iceberg column is required
   Do we have a counterpart of this in Parquet?

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