etseidl commented on code in PR #9700:
URL: https://github.com/apache/arrow-rs/pull/9700#discussion_r3096432061
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parquet/src/arrow/arrow_writer/mod.rs:
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@@ -4813,18 +4890,56 @@ mod tests {
let col0_meta = metadata.row_group(0).column(0);
let col1_meta = metadata.row_group(0).column(1);
- let get_dict_page_size = move |meta: &ColumnChunkMetaData| {
- let mut reader =
- SerializedPageReader::new(Arc::new(data.clone()), meta, 0,
None).unwrap();
- let page = reader.get_next_page().unwrap().unwrap();
- match page {
- Page::DictionaryPage { buf, .. } => buf.len(),
- _ => panic!("expected DictionaryPage"),
- }
- };
+ assert_eq!(get_dict_page_size(col0_meta, data.clone()), 1024 * 1024);
+ assert_eq!(get_dict_page_size(col1_meta, data.clone()), 1024 * 1024 *
4);
+ }
+
+ #[test]
+ fn test_dict_page_size_decided_by_compression_fallback() {
+ // Generate values that are well dispersed across a range
approximating (0..256 * 1024)
+ let array = Arc::new(Int32Array::from_iter(
+ (0i32..1024 * 1024).map(|x| x.wrapping_mul(163019) % 262139),
+ ));
+ let schema = Arc::new(Schema::new(vec![Field::new(
+ "col0",
+ arrow_schema::DataType::Int32,
+ false,
+ )]));
+ let batch = arrow_array::RecordBatch::try_new(schema.clone(),
vec![array]).unwrap();
+
+ let props = WriterProperties::builder()
+ .set_dictionary_page_size_limit(1024 * 1024)
+ .build();
+ let mut writer = ArrowWriter::try_new(Vec::new(), schema.clone(),
Some(props)).unwrap();
+ writer.write(&batch).unwrap();
+ let data = Bytes::from(writer.into_inner().unwrap());
+
+ println!("file length, dictionary: {}", data.len());
+
+ let mut metadata = ParquetMetaDataReader::new();
+ metadata.try_parse(&data).unwrap();
+ let metadata = metadata.finish().unwrap();
+ let full_dict_meta = metadata.row_group(0).column(0);
+ assert_eq!(get_dict_page_size(full_dict_meta, data.clone()),
1_048_576);
+
+ let props = WriterProperties::builder()
+ .set_dictionary_page_size_limit(1024 * 1024)
+ .set_column_dictionary_fallback(
+ ColumnPath::from("col0"),
+ DictionaryFallback::OnUnfavorableAfter(8192),
Review Comment:
If this is set to a value larger than a page (30000 say), then fallback
occurs only after the dictionary gets too large.
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