sql2mongo 0.1.0

A CLI tool to transpile SQL to MongoDB Query Language

SQL to MongoDB Transpiler

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Table of Contents

• Project Overview
• Folder Structure
• Intended SQL Subset
• Architecture Flow Diagram
• Technologies Used
• Work Done So Far
• How to Run

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Project Overview

This project aims to build a SQL-to-MongoDB transpiler that converts basic SQL queries into their equivalent MongoDB queries. The current implementation focuses on the lexical analysis (tokenizer) phase using the PLY (Python Lex-Yacc) library.

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Folder Structure

sql-to-mongodb-transpiler/
├── ast/
│ └── ast_nodes.py # AST node definitions (for future use)
├── lexer/
│ ├── init.py
│ ├── lexer.py # PLY lexer implementation
│ └── tokens.py # Token definitions & reserved keywords
├── parser/
│ └── parser.py # Placeholder for parser (future)
├── tests/
│ └── test_lexer.py # Unit test for lexer
├── pycache/
├── .gitignore
├── README.md
└── requirements.txt

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Intended SQL Subset

The transpiler is designed to support the following subset of SQL:

• SELECT
• FROM
• WHERE
• Comparisons (=, !=, <, >, <=, >=)
• Logical operators: AND, OR, NOT
• ORDER BY
• LIMIT
• Aggregation functions (e.g., COUNT, SUM, AVG, MIN, MAX)

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Architecture flow diagram:

+--------------------+
|    SQL Query       |
| (User Input)       |
+--------------------+
          |
          v
+--------------------+
|   Lexical Analyzer |
|   (PLY Lexer)      |
|                    |
| - Keywords         |
| - Identifiers      |
| - Literals         |
| - Operators        |
+--------------------+
          |
          v
+--------------------+
|   Token Stream     |
| (Type, Value,      |
|  Line, Position)   |
+--------------------+
          |
          v
+----------------------------+
|   Syntax Analyzer (Parser) |
|   - SQL Grammar Rules      |
|   - Parse Tree / AST       |
+----------------------------+
          |
          v
+----------------------------+
| Intermediate Code          |
| Generation                 |
| - Logical Query Structure  |
| - Query Representation    |
+----------------------------+
          |
          v
+----------------------------+
| MongoDB Query Translation  |
| - find() / projection      |
| - filter conditions        |
+----------------------------+
          |
          v
+----------------------------+
| MongoDB Query Output       |
+----------------------------+

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Technologies Used

• Python
• PLY (Python Lex-Yacc)
• sqlparse (for testing and comparison)

---

Work Done So Far

• Implemented a lexer using PLY to tokenize SQL queries.
• Supported SQL keywords: SELECT, FROM, WHERE.
• Identified tokens for:
  • Identifiers (table names, column names)
  • Numeric literals
  • String literals
  • Relational operators (=, <, >, <=, >=, !=)
  • Comma and semicolon
• Implemented case-insensitive keyword recognition.
• Added line number tracking and error handling for illegal characters.
• Developed a testing script - test_lexer.py to compare PLY-generated tokens with tokens produced by the sqlparse library.

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How to Run

Before cloning create venv environment and enter in it.as,

python3 -m venv venv
source venv/bin/activate

1. Clone the repository:

git clone "https://github.com/MANDADI-PRANATHI/SQL_to_MongoDB_Transpiler.git"

cd SQL-to-MongoDB-Transpiler

pip install -r requirements.txt
pip install ply

To test the lexer implementated until now,in the sql-to-mongodb-transpiler folder

python3 main.py
cd SQL_to_MongoDB_Transpiler-main

2. Install the CLI Tool globally via pip:

pip install .

3. Run the tool using the mapped console command:

sql2mongo --schema custom_schema.json --query "SELECT * FROM users;" --pretty

You can also use the interactive shell:

sql2mongo shell --schema custom_schema.json