distributed-curator 0.1.2

Partition-aware MinHash LSH deduplication for large-scale text data curation on Apache Spark

distributed-curator

Partition-aware MinHash LSH deduplication library for large-scale text data curation on Apache Spark.

Headline

2.53 billion documents deduplicated on a 63-node EMR cluster for ~$500 using partition-aware MinHash LSH — zero shuffle during local deduplication.

Quick Start

pip install distributed-curator

from distributed_curator import partition_aware_deduplicate, get_jar_path
from pyspark.sql import SparkSession

spark = SparkSession.builder \
    .config("spark.jars", get_jar_path()) \
    .getOrCreate()

# input_df must have a "doc_id" column and a text column
result = partition_aware_deduplicate(
    spark=spark,
    input_df=df,
    text_column="text",
    similarity_threshold=0.8,
    num_partitions=1000,
)

# result has original columns + "representative_id" and "is_duplicate"
unique_docs = result.filter(~result.is_duplicate)

How It Works

The pipeline assigns documents to partitions based on LSH band hashes so that similar documents are co-located. All comparisons happen locally within partitions with no shuffle, then a two-phase union-find merges components across partition boundaries.

Step	What happens	Shuffle?
1. MinHash	Cython/NumPy SIMD computes signatures via pandas_udf	No
2. Partition assignment	Scala UDF maps LSH bands to partition IDs	No
3. Identity repartition	Documents move to assigned partitions	Yes (once)
4. Local dedup	Scala mapPartitions finds similar pairs within each partition	No
5a. Local union-find	Scala partition-local connected components	No
5b. Global union-find	Driver-side union-find with Eclipse Collections LongLongHashMap	No
6. Mark duplicates	Join results back to input	Yes (once)

For a detailed architecture walkthrough, see docs/architecture.md.

Benchmark Results

All benchmarks run on Common Crawl WET files (CC-MAIN-2024-22) with similarity_threshold=0.9, num_hashes=64, num_bands=8.

Scale	Documents	Duplicates	Rate	Cluster	Time	Cost
9K WET	253M	55M	21.82%	9× r5ad.8xlarge	~1.5 hr	~$50
90K WET	2.53B	827.7M	32.76%	63× r6gd.8xlarge	~4.5 hr	~$500

Configuration

partition_aware_deduplicate(
    spark,                          # SparkSession
    input_df,                       # DataFrame with doc_id + text columns
    text_column="text",             # name of the text column
    similarity_threshold=0.8,       # Jaccard similarity threshold (0.0–1.0)
    num_hashes=64,                  # MinHash signature length
    num_bands=8,                    # LSH bands (num_hashes must be divisible by num_bands)
    num_partitions=1000,            # number of partitions for dedup
    ngram=9,                        # character n-gram size for shingling
    checkpoint_path=None,           # [optional] S3/HDFS path to cache intermediate results
    enable_diagnostics=False,       # [optional] enable driver memory logging and heap capture
)

When to tune:

• similarity_threshold: lower catches more near-duplicates, higher is stricter. 0.8–0.9 is typical for web text.
• num_partitions: set to spark.sql.shuffle.partitions. More partitions = less memory per partition but more overhead.
• num_bands / num_hashes: controls the LSH probability curve. More bands = higher recall but more comparisons. num_hashes must be divisible by num_bands.
• checkpoint_path: recommended for runs over 1K WET files. Saves MinHash signatures so you don't recompute on retry.
• ngram: 9 works well for English web text. Shorter n-grams increase recall but reduce precision.

Version Compatibility

Component	Supported	Planned
PySpark	3.5.x	4.0+
Python	3.9, 3.10, 3.11, 3.12
Scala	2.12
AWS EMR	7.5–7.12 (Spark 3.5)
Java	8, 11, 17 (runtime)

The Scala UDF JAR is compiled against Spark 3.5. Spark 4.0 support requires recompilation due to breaking API changes in StructType.

Documentation

• Architecture — detailed pipeline walkthrough, design decisions, and performance characteristics
• EMR Deployment — Terraform setup, bootstrap configuration, and spark-submit examples
• Contributing — development setup, running tests, and how to submit changes

License

Apache License 2.0 — see LICENSE for details.