---
license: apache-2.0
pipeline_tag: text-ranking
library_name: transformers
tags:
- text-to-sql
- llm
- schema-filtering
- graph-reranker
- qwen3
---

# GRAST-SQL: Scaling Text2SQL via LLM-efficient Schema Filtering with Functional Dependency Graph Rerankers

The **GRAST-SQL** model was introduced in the paper [Scaling Text2SQL via LLM-efficient Schema Filtering with Functional Dependency Graph Rerankers](https://huggingface.co/papers/2512.16083).

**Authors:** Thanh Dat Hoang, Thanh Tam Nguyen, Thanh Trung Huynh, Hongzhi Yin, Quoc Viet Hung Nguyen

GRAST-SQL is an open-source, LLM-efficient schema filtering framework designed to scale Text2SQL systems to real-world, large databases that often exceed LLM context limits. It compacts Text2SQL prompts by employing a multi-step approach:
(i) ranking columns with a query-aware LLM encoder enriched with values and metadata,
(ii) reranking inter-connected columns via a lightweight graph transformer over functional dependencies, and
(iii) selecting a connectivity-preserving sub-schema with a Steiner-tree heuristic.

This framework achieves near-perfect recall and higher precision than existing methods (CodeS, SchemaExP, Qwen rerankers, embedding retrievers), maintains sub-second median latency, scales to schemas with 23,000+ columns, and significantly reduces prompt tokens while often improving accuracy in end-to-end systems.

For more details on the project, including training and full evaluation scripts, visit the [GitHub repository](https://github.com/thanhdath/grast-sql).

## Sample Usage

GRAST-SQL models are often served via `vLLM` for efficient embedding generation, as suggested by the project's GitHub repository. The following example demonstrates how to set up a `vLLM` server and use the model to generate embeddings for text inputs. This is a crucial step for the ranking and filtering pipeline described in the paper.

First, ensure you have `vLLM` installed. You can typically install it via pip:
```bash
pip install vllm
```

### Step 1: Start the vLLM Server

Start the `vLLM` server for the GRAST-SQL model in a separate terminal or background process. This command specifies using `griffith-bigdata/GRAST-SQL-0.6B-BIRD-Reranker` as the model, enabling embedding generation.

```bash
CUDA_VISIBLE_DEVICES=0,1 vllm serve griffith-bigdata/GRAST-SQL-0.6B-BIRD-Reranker \
  --port 8000 \
  --max-model-len 8192 \
  --tensor-parallel-size 2 \
  --task embedding \
  --gpu-memory-utilization 0.8
```

### Step 2: Generate Embeddings using Python

Once the `vLLM` server is running, you can connect to it and generate embeddings programmatically:

```python
from vllm import LLM, SamplingParams

# Ensure the vLLM server is running at the specified port.
# Replace with the actual path to your GRAST-SQL model checkpoint if different.
model_path = "griffith-bigdata/GRAST-SQL-0.6B-BIRD-Reranker"
llm = LLM(
    model=model_path,
    tensor_parallel_size=1, # Adjust based on your GPU setup
    dtype="auto",
    max_model_len=8192,
    enforce_eager=True,
    trust_remote_code=True,
    gpu_memory_utilization=0.8,
    task="embedding", # Essential for embedding models
)

# Example texts for which to generate embeddings
text_list = [
    "List all tables related to user activity.",
    "Find columns for product price and description."
]

# Generate embeddings
# The `llm.encode` method is used when the vLLM server is started with --task embedding.
embeddings = llm.encode(texts=text_list)

for i, text in enumerate(text_list):
    print(f"Text: '{text}'")
    print(f"Embedding shape: {embeddings[i].shape}")
    print(f"First 5 embedding dimensions: {embeddings[i][:5]}
")

# These embeddings can then be utilized by the GRAST-SQL framework
# for tasks like column ranking and schema filtering.
```

## Datasets

The GRAST-SQL framework was evaluated on the following datasets:
-   **Spider**: [Spider Evaluation Dataset](https://huggingface.co/datasets/griffith-bigdata/GRAST-SQL-Spider)
-   **BIRD**: [BIRD Training/Evaluation Dataset](https://huggingface.co/datasets/griffith-bigdata/GRAST-SQL-BIRD)
-   **Spider-2.0-lite**: [Spider 2.0-lite Eval Dataset](https://huggingface.co/datasets/griffith-bigdata/GRAST-SQL-Spider2.0-lite)

## Models

Other GRAST-SQL models available on the Hugging Face Hub:
-   **GRAST-SQL 0.6B**: [GRAST-SQL 0.6B BIRD](https://huggingface.co/griffith-bigdata/GRAST-SQL-0.6B-BIRD-Reranker)
-   **GRAST-SQL 4B**: [GRAST-SQL 4B BIRD](https://huggingface.co/griffith-bigdata/GRAST-SQL-4B-BIRD-Reranker)
-   **GRAST-SQL 8B**: [GRAST-SQL 8B BIRD](https://huggingface.co/griffith-bigdata/GRAST-SQL-8B-BIRD-Reranker)

More models can be found in the [Huggingface collection](https://huggingface.co/collections/griffith-bigdata/grast-sql).

## System Flow

![GRAST-SQL main flow](https://raw.githubusercontent.com/thanhdath/grast-sql/main/figures/main-flow.png)

## Citation

If you find this work useful for your research, please cite the paper:

```bibtex
@misc{hoang2025scalingtext2sqlllmefficientschema,
      title={Scaling Text2SQL via LLM-efficient Schema Filtering with Functional Dependency Graph Rerankers}, 
      author={Thanh Dat Hoang and Thanh Tam Nguyen and Thanh Trung Huynh and Hongzhi Yin and Quoc Viet Hung Nguyen},
      year={2025},
      eprint={2512.16083},
      archivePrefix={arXiv},
      primaryClass={cs.DB},
      url={https://arxiv.org/abs/2512.16083}, 
}
```