app.py

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from fastapi.responses import JSONResponse

# Initialize FastAPI app
app = FastAPI()

# Load the tokenizer and model
tokenizer = AutoTokenizer.from_pretrained("chatdb/natural-sql-7b")
model = AutoModelForCausalLM.from_pretrained(
    "chatdb/natural-sql-7b",
    device_map="cpu",
    torch_dtype=torch.float32,
)

schema = """
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    manager_id INTEGER,
    first_name VARCHAR(100) NOT NULL,
    last_name VARCHAR(100) NOT NULL,
    designation VARCHAR(100),
    email VARCHAR(100) UNIQUE NOT NULL,
    phone VARCHAR(15) UNIQUE NOT NULL,
    password TEXT NOT NULL,
    role VARCHAR(50) NOT NULL, -- employee, manager, hr
    country VARCHAR(50) NOT NULL, -- pakistan, uae, uk
    fcm_token VARCHAR(255),
    image VARCHAR(255) DEFAULT '',
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE leaves_balances (
    id SERIAL PRIMARY KEY,
    sick_available FLOAT NOT NULL,
    casual_available FLOAT NOT NULL,
    wfh_available FLOAT NOT NULL,
    sick_taken FLOAT NOT NULL,
    casual_taken FLOAT NOT NULL,
    wfh_taken FLOAT NOT NULL,
    user_id INTEGER UNIQUE REFERENCES users(id) ON DELETE CASCADE,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE leaves (
    id SERIAL PRIMARY KEY,
    user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
    manager_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
    username VARCHAR(100) NOT NULL,
    type VARCHAR(50) NOT NULL, -- sick, casual, wfh
    from_date TIMESTAMP NOT NULL,
    to_date TIMESTAMP NOT NULL,
    comments TEXT,
    status VARCHAR(50) DEFAULT 'pending', -- pending, approved, rejected
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE user_otps (
    id SERIAL PRIMARY KEY,
    user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
    otp INTEGER NOT NULL,
    otp_expiry TIMESTAMP NOT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);
"""

# Define the request body model using Pydantic
class QuestionRequest(BaseModel):
    question: str

@app.get("/")
async def root():    
    return{"message":"Hello, World!"}

@app.post('/generate-sql')
async def generate_sql(request: QuestionRequest):
    """
    Endpoint to generate a SQL query based on a given question.
    The schema is defined within the code (in the `schema` variable).
    """
    question = request.question
    if not question:
        raise HTTPException(status_code=400, detail="No question provided")

    prompt = f"""
    ### Task

    Generate a SQL query to answer the following question: `{question}`

    ### PostgreSQL Database Schema
    The query will run on a database with the following schema:
    {schema}

    ### Answer
    Here is the SQL query that answers the question: `{question}`
    ```sql
    """

    # Generate SQL query
    inputs = tokenizer(prompt, return_tensors="pt").to("cpu")
    generated_ids = model.generate(
        **inputs,
        num_return_sequences=1,
        eos_token_id=100001,
        pad_token_id=100001,
        max_new_tokens=400,
        do_sample=False,
        num_beams=1,
    )

    outputs = tokenizer.batch_decode(generated_ids, skip_special_tokens=True)
    sql_query = outputs[0].split("```sql")[-1].strip()

    return JSONResponse(content={'sql_query': sql_query})