EnricoMi commented on code in PR #45411:
URL: https://github.com/apache/arrow/pull/45411#discussion_r2012077997
##########
docs/source/cpp/parquet.rst:
##########
@@ -585,6 +585,51 @@ More specifically, Parquet C++ supports:
* EncryptionWithFooterKey and EncryptionWithColumnKey modes.
* Encrypted Footer and Plaintext Footer modes.
+Configuration
+~~~~~~~~~~~~~
+
+Parquet encryption uses a ``parquet::encryption::CryptoFactory`` that has
access to a
+Key Management System (KMS), which stores actual encryption keys, referenced
by key ids.
+The Parquet encryption configuration only uses key ids, no actual keys.
+
+Parquet metadata encryption is configured via
``parquet::encryption::EncryptionConfiguration``:
+
+.. literalinclude:: ../../../cpp/examples/arrow/parquet_column_encryption.cc
+ :language: cpp
+ :start-at: // Set write options with encryption configuration
+ :end-before: encryption_config->column_keys
+ :dedent: 2
+
+All columns are encrypted with the same key as the Parquet metadata when above
+``encryption_config->uniform_encryption`` is set ``true``.
+
+Individual columns are encrypted with individual keys as configured via
``encryption_config->column_keys``.
+This field expects a string of the format
``"columnKeyID:colName,colName;columnKeyID:colName..."``.
+
+.. literalinclude:: ../../../cpp/examples/arrow/parquet_column_encryption.cc
+ :language: cpp
+ :start-at: // Set write options with encryption configuration
+ :end-before: auto parquet_encryption_config
+ :emphasize-lines: 4-5
+ :dedent: 2
+
+See the full `Parquet column encryption example
<examples/parquet_column_encryption.html>`_.
+
+.. note::
+
+ Encrypting columns that have nested fields (struct, map, or even list data
types)
+ requires column keys for the inner fields, not the column itself.
+ Configuring a column key for the column itself causes this error (here
column name is ``col``):
Review Comment:
I find `nested column` ambiguous, it sounds like the inner column, the
nested field.
What about `outer column` instead of `nested column`?
```suggestion
Encrypting columns that have nested fields (struct, map, or even list
data types)
requires column keys for the inner fields, not the outer column itself.
Configuring a column key for the outer column causes this error (here
column name is ``col``):
```
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