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langchain/langchain/sql_database.py

75 lines
2.7 KiB
Python

"""SQLAlchemy wrapper around a database."""
from typing import Any, Iterable, List, Optional
from sqlalchemy import create_engine, inspect
from sqlalchemy.engine import Engine
class SQLDatabase:
"""SQLAlchemy wrapper around a database."""
def __init__(
self,
engine: Engine,
ignore_tables: Optional[List[str]] = None,
include_tables: Optional[List[str]] = None,
):
"""Create engine from database URI."""
self._engine = engine
if include_tables and ignore_tables:
raise ValueError("Cannot specify both include_tables and ignore_tables")
self._inspector = inspect(self._engine)
self._all_tables = self._inspector.get_table_names()
self._include_tables = include_tables or []
if self._include_tables:
missing_tables = set(self._include_tables).difference(self._all_tables)
if missing_tables:
raise ValueError(
f"include_tables {missing_tables} not found in database"
)
self._ignore_tables = ignore_tables or []
if self._ignore_tables:
missing_tables = set(self._ignore_tables).difference(self._all_tables)
if missing_tables:
raise ValueError(
f"ignore_tables {missing_tables} not found in database"
)
@classmethod
def from_uri(cls, database_uri: str, **kwargs: Any) -> "SQLDatabase":
"""Construct a SQLAlchemy engine from URI."""
return cls(create_engine(database_uri), **kwargs)
@property
def dialect(self) -> str:
"""Return string representation of dialect to use."""
return self._engine.dialect.name
def _get_table_names(self) -> Iterable[str]:
if self._include_tables:
return self._include_tables
return set(self._all_tables) - set(self._ignore_tables)
@property
def table_info(self) -> str:
"""Information about all tables in the database."""
template = "Table '{table_name}' has columns: {columns}."
tables = []
for table_name in self._get_table_names():
columns = []
for column in self._inspector.get_columns(table_name):
columns.append(f"{column['name']} ({str(column['type'])})")
column_str = ", ".join(columns)
table_str = template.format(table_name=table_name, columns=column_str)
tables.append(table_str)
return "\n".join(tables)
def run(self, command: str) -> str:
"""Execute a SQL command and return a string of the results."""
try:
result = self._engine.execute(command).fetchall()
except Exception as e:
result = e
return str(result)