Having problems with Langchain and SQLDatabaseToolkit: 'sql_db_list_tables' and others doesn't work

[arturgomesc]

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Example Code

from langchain.sql_database import SQLDatabase

mysql = f"mysql+mysqlconnector://{db_user}:{db_password}@{db_host}:3306/{db_name}"

database = SQLDatabase.from_uri(mysql, schema="my_schema", view_support=True)
print(database.dialect)
print(database.get_usable_table_names())
print(database.table_info)
database.run("SHOW FULL TABLES FROM db;")

# Result:
# mysql
# []


# "[(bytearray(b'first_table'), bytearray(b'BASE TABLE')), (bytearray(b'second_table'), bytearray(b'BASE TABLE')), (bytearray(b'third_table'), bytearray(b'BASE TABLE'))"

Description

Hello, everyone. I'm trying to query a MySQL database using Python and Langchain. However, some features seem to return nothing, while others work. sql_db_list_tables, get,usable_table_names, table_info and others do not work, while other features like sql_db_query work. I've tried the same code with a postgresql database with read and write permissions and I didn´t get this trouble, just worked fine. This MySQL databse just have the read permissions.

Does anyone know what the problem could be?

I tried to make my database schema explicit, updated the libraries, but nothing helped.

System Info

pip install langchain==2.6.0

[dosubot[bot]]

Hello, @arturgomesc! I'm here to assist you with any bugs, questions, or contributions you may have. Let's work together to resolve the issue you're facing.

The issue you're encountering with sql_db_list_tables, get_usable_table_names, and table_info in Langchain is likely due to problems with table reflection and metadata handling in your MySQL database. These methods rely on SQLAlchemy's reflection capabilities, which can fail due to permissions, unsupported features, or specific database configurations. Since your MySQL database only has read permissions, this might be causing the reflection process to fail.

On the other hand, sql_db_query works because it directly executes SQL commands without relying on the reflection process.

Here is a relevant code snippet showing how table reflection is handled:

self._metadata.reflect(
    views=view_support,
    bind=self._engine,
    only=list(self._usable_tables),
    schema=self._schema,
)

If the reflection process fails, it can cause methods like get_usable_table_names and table_info to not function correctly. This is not an issue for sql_db_query as it does not depend on this process.

Additionally, the get_table_info method in the SQLDatabase class is used to get column information and sample data from the table, which is crucial for methods like table_info. If there are issues with this method, it can also affect the functionality of these methods.

To resolve this, you might need to ensure that your MySQL user has the necessary permissions to access metadata. You can try granting the required permissions:

GRANT SHOW DATABASES, SHOW TABLES, SHOW COLUMNS ON db_freterapid2.* TO 'your_user'@'your_host';

After granting the permissions, try running your code again. If the issue persists, you might need to check for any specific configurations or limitations in your MySQL setup that could be affecting the reflection process.

For more details, you can refer to the relevant source code in Langchain:

• libs/community/langchain_community/utilities/sql_database.py ^[1]
• libs/langchain/langchain/chains/sql_database/query.py ^[2]
• libs/community/langchain_community/tools/sql_database/tool.py ^[3]

To continue talking to Dosu, mention @dosu.