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AvroReadSupport should automatically detect file list encoding

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Active
Tech stack
java

Research direction

Look at AvroReadSupport in the parquet-avro module to understand how list structures are currently handled. The detection logic must examine the Parquet schema's repeated group patterns to distinguish three-level and two-level lists. Testing will involve reading existing Parquet files with both list encodings to ensure automatic detection works without the configuration property.

Written by the indexing model from the issue text.

Description

Type: enhancement
Describe the enhancement requested

parquet-avro currently contains opt-in support for reading and writing both "three-level" lists:

required group mylist (LIST) {
  repeated group list {
    required int32 element;
  }
}

and "two level"/"legacy"/"old" lists:

required group mylist (LIST) {
  repeated int32 array;
}

The boolean Configuration property parquet.avro.write-old-list-structure controls which structure should be written, but readers have to specify the parquet.avro.write-old-list-structure property, too, if they're either (a) supplying a custom projection, or (b) reading a Parquet file that doesn't contain the parquet.avro.schema key in its file metadata.

Ideally the reader should be able to automatically detect both types of list encoding, so that we can keep the Configuration property as a writer-side implementation detail.

Component(s)

Avro

Dominant language
Java
Stars
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Avg merge
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Merged PRs (30d)
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