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Allow Parquet map key to be optional #17

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Merged
Avogar merged 1 commit into from
Mar 29, 2023
Merged

Allow Parquet map key to be optional #17

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13 changes: 13 additions & 0 deletions cpp/src/parquet/arrow/schema.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -548,10 +548,23 @@ Status MapToSchemaField(const GroupNode& group, LevelInfo current_levels,
return Status::Invalid("Key-value map node must have 1 or 2 child elements. Found: ",
key_value.field_count());
}

/*
* If Parquet file was written by Flink, key type of map column is allowed to be optional, like this:
* optional group event_info (MAP) {
* repeated group key_value {
* optional binary key (UTF8);
* optional binary value (UTF8);
* }
* }
*
* Refer to: https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/table/types/#constructured-data-types
const Node& key_node = *key_value.field(0);
if (!key_node.is_required()) {
return Status::Invalid("Map keys must be annotated as required.");
}
*/

// Arrow doesn't support 1 column maps (i.e. Sets). The options are to either
// make the values column nullable, or process the map as a list. We choose the latter
// as it is simpler.
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