Datasets:

Nacryos
/

ancient-scripts-datasets

Converting the 5 largest TSV files to Parquet format (columnar, compressed, typed)
Adding a YAML frontmatter dataset card to README.md with named configs pointing to the Parquet files
Preserving all original TSV files as legacy backups (no data removed)

Why Parquet?

The HuggingFace datasets library v4.0 removed support for custom loading scripts (they cause RuntimeError). YAML-based configs pointing to Parquet files are the recommended replacement.
Parquet enables: columnar reads (load only needed columns), predicate pushdown (filter without full scan), proper null handling, typed schemas.
TSV sentinel values (- for missing data) are converted to proper nulls.

2. Scripts Used

Script	Lines	Purpose
`scripts/convert_to_parquet.py`	~100	Read TSV via pyarrow, force all columns to string on initial read, convert `-` sentinels to null, cast typed columns (int/float), write Parquet with ZSTD compression

Key Implementation Details

Type safety: All columns initially read as pa.string() to avoid pyarrow type inference issues (e.g., Score column auto-detected as double conflicting with - sentinel)
Null handling: All - values converted to proper Parquet nulls via pc.if_else(pc.equal(col, "-"), None, col)
Compression: ZSTD (Zstandard) — best compression ratio for this data profile
Column casting: Int columns (Tree_Distance, MRCA_Depth) cast to pa.int32(), float columns (Score) cast to pa.float64()

3. Data Sources

No new external data. This change only converts existing TSV files already in the dataset.

Input Files (preserved as legacy)

File	Rows	TSV Size
`cognate_pairs_inherited.tsv`	22.9M	2.2 GB
`cognate_pairs_similarity.tsv`	465K	49.9 MB
`cognate_pairs_borrowing.tsv`	17K	1.9 MB
`phylo_pairs.tsv`	386K	24.7 MB
`languages.tsv`	1,177	39.3 KB

4. Source Reputability

N/A — format conversion only, no new external data. All data integrity preserved from source TSVs.

5. Methodology

Conversion Process

Read TSV with pyarrow.csv.read_csv(), forcing all columns to pa.string() schema
For each column, replace - sentinel with null
Cast numeric columns to proper types (int32, float64)
Write Parquet with pq.write_table(table, path, compression='zstd')

YAML Dataset Card

Added to README.md frontmatter:

configs:
  - config_name: cognate_pairs_inherited
    data_files:
      - split: train
        path: data/training/cognate_pairs/cognate_pairs_inherited.parquet
  - config_name: cognate_pairs_borrowing
    data_files:
      - split: train
        path: data/training/cognate_pairs/cognate_pairs_borrowing.parquet
  # ... (5 total configs)

Why NOT a Loading Script

HuggingFace datasets v4.0 (released late 2025) removed custom loading script support entirely. Any repo with a *.py loading script triggers RuntimeError. YAML-based configuration is the official replacement.

6. Tests Performed

Row count verification: Each Parquet file verified to have identical row count to source TSV
Schema verification: Column names and types match expected schema
Random sample verification: 10 random rows from each Parquet file compared byte-for-byte against corresponding TSV rows
Null handling: Verified - sentinels are proper nulls (not empty strings) in Parquet
LFS integrity: Verified no LFS pointer files were accidentally converted (detected and re-pulled cognate_pairs_borrowing.tsv which was a 3-line LFS pointer)
HuggingFace API verification: Confirmed https://huggingface.co/api/datasets/Nacryos/ancient-scripts-datasets returns all 5 configs

7. Cross-Referencing

Parquet file sizes verified to be strictly smaller than TSV (compression working correctly)
Column count matches: 14 columns for cognate pairs, 9 for phylo_pairs, 5 for languages
HuggingFace Dataset Viewer activated and showing data correctly

8. Output Summary

File	TSV Size	Parquet Size	Compression Ratio
`cognate_pairs_inherited.parquet`	2.2 GB	23.6 MB	93.8x
`cognate_pairs_similarity.parquet`	49.9 MB	5.0 MB	10.0x
`cognate_pairs_borrowing.parquet`	1.9 MB	487 KB	4.0x
`phylo_pairs.parquet`	24.7 MB	416 KB	59.3x
`languages.parquet`	39.3 KB	13.7 KB	2.9x
Total	2.28 GB	29.5 MB	77.2x

9. Legacy Preservation

All original TSV files are preserved in their original locations. The Parquet files are stored alongside them:

data/training/cognate_pairs/cognate_pairs_inherited.tsv (original, kept)
data/training/cognate_pairs/cognate_pairs_inherited.parquet (new, added)

No data was removed or modified. The Parquet files are a read-optimized mirror.

10. SDK Package

A companion Python SDK (ancient-scripts-data) was also created in a separate repo (Project-Phaistos/ancient-scripts-datasets-NEW) to provide typed APIs for accessing this data. See that repo's README for API documentation.