NeuroCard

NeuroCard is a neural cardinality estimator for multi-table join queries.

NeuroCard's philosophy is to learn as much correlation as possible across tables, thereby achieving high accuracy.

Technical details can be found in the VLDB 2021 paper, NeuroCard: One Cardinality Estimator for All Tables [bibtex].

Quick start | Main modules | Running experiments | Contributors | Citation

Quick start

Set up a conda environment with depedencies installed:

# On Ubuntu/Debian
sudo apt install build-essential
# Install Python environment
conda env create -f environment.yml
conda activate neurocard
# Run commands below inside this directory.
cd neurocard

Download the IMDB dataset as CSV files and place under datasets/job:

# Download size 1.2GB.
bash scripts/download_imdb.sh

# If you already have the CSVs or can export from a
# database, simply link to an existing directory.
# ln -s <existing_dir_with_csvs> datasets/job
# Run the following if the existing CSVs are without headers.
# python scripts/prepend_imdb_headers.py

Launch a short test run:

python run.py --run test-job-light

Main modules

Module	Description
run	Main script to train and evaluate
experiments	Registry of experiment configurations
common	Abstractions for columns, tables, joined relations; column factorization
factorized_sampler	Unbiased join sampler
estimators	Cardinality estimators: probabilistic inference for density models; inference for column factorization
datasets	Registry of datasets and schemas
Models: made, transformer	Deep autoregressive models: ResMADE & Transformer

Running experiments

Launch training and evaluation using a single script:

# 'name' is a config registered in experiments.py.
python run.py --run <name>

Registered configs. Hyperparameters are statically declared in experiments.py. New experiments (e.g., changing query files; running hparam tuning) can be specified there.

Configs for evaluation on pretrained checkpoints and full training runs:

Benchmark	Config (reload pretrained ckpt)	Config (re-train)	Model	Num Params
JOB-light	job-light-reload	job-light	ResMADE	1.0M
JOB-light-ranges	job-light-ranges-reload	job-light-ranges	ResMADE	1.1M
	job-light-ranges-large-reload	job-light-ranges-large	Transformer	5.4M
JOB-M	job-m-reload	job-m	ResMADE	7.2M
	-	job-m-large (launch with --gpus=4 or lower the batch size)	Transformer	107M

The reload configs load pretrained checkpoints and run evaluation only. Normal configs start training afresh and also run evaluation.

Metrics & Monitoring. The key metrics to track are

• Cardinality estimation accuracy (Q-errors): fact_psample_<num_psamples>_<quantile>
• Quality of the density model: train_bits (negative log-likelihood in bits-per-tuple; lower is better).

The standard output prints these metrics and can be piped into a log file. If TensorBoard is installed, use the following to visualize:

python -m tensorboard.main --logdir ~/ray_results/

Contributors

This repo was written by

• Frank Luan
• Amog Kamsetty
• Eric Liang
• Zongheng Yang

Citation

@article{neurocard,
  title={NeuroCard: One Cardinality Estimator for All Tables},
  author={Yang, Zongheng and Kamsetty, Amog and Luan, Sifei and Liang, Eric and Duan, Yan and Chen, Xi and Stoica, Ion},
  journal={arXiv preprint arXiv:2006.08109},
  year={2020}
}

Related projects. NeuroCard builds on top of Naru and Variable Skipping.