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"""SQLAlchemy wrapper around a database."""
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from __future__ import annotations
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import ast
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from typing import Any, Iterable, List, Optional
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from sqlalchemy import create_engine, inspect
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from sqlalchemy.engine import Engine
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_TEMPLATE_PREFIX = """Table data will be described in the following format:
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Table 'table name' has columns: {
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column1 name: (column1 type, [list of example values for column1]),
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column2 name: (column2 type, [list of example values for column2]),
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...
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}
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These are the tables you can use, together with their column information:
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"""
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class SQLDatabase:
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"""SQLAlchemy wrapper around a database."""
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def __init__(
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self,
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engine: Engine,
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schema: Optional[str] = None,
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ignore_tables: Optional[List[str]] = None,
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include_tables: Optional[List[str]] = None,
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sample_rows_in_table_info: int = 3,
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):
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"""Create engine from database URI."""
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self._engine = engine
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self._schema = schema
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if include_tables and ignore_tables:
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raise ValueError("Cannot specify both include_tables and ignore_tables")
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self._inspector = inspect(self._engine)
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self._all_tables = set(self._inspector.get_table_names(schema=schema))
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self._include_tables = set(include_tables) if include_tables else set()
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if self._include_tables:
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missing_tables = self._include_tables - self._all_tables
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if missing_tables:
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raise ValueError(
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f"include_tables {missing_tables} not found in database"
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)
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self._ignore_tables = set(ignore_tables) if ignore_tables else set()
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if self._ignore_tables:
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missing_tables = self._ignore_tables - self._all_tables
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if missing_tables:
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raise ValueError(
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f"ignore_tables {missing_tables} not found in database"
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)
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self._sample_rows_in_table_info = sample_rows_in_table_info
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@classmethod
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def from_uri(cls, database_uri: str, **kwargs: Any) -> SQLDatabase:
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"""Construct a SQLAlchemy engine from URI."""
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return cls(create_engine(database_uri), **kwargs)
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@property
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def dialect(self) -> str:
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"""Return string representation of dialect to use."""
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return self._engine.dialect.name
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def get_table_names(self) -> Iterable[str]:
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"""Get names of tables available."""
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if self._include_tables:
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return self._include_tables
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return self._all_tables - self._ignore_tables
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@property
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def table_info(self) -> str:
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"""Information about all tables in the database."""
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return self.get_table_info()
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def get_table_info(self, table_names: Optional[List[str]] = None) -> str:
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"""Get information about specified tables.
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Follows best practices as specified in: Rajkumar et al, 2022
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(https://arxiv.org/abs/2204.00498)
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If `sample_rows_in_table_info`, the specified number of sample rows will be
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appended to each table description. This can increase performance as
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demonstrated in the paper.
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"""
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all_table_names = self.get_table_names()
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if table_names is not None:
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missing_tables = set(table_names).difference(all_table_names)
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if missing_tables:
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raise ValueError(f"table_names {missing_tables} not found in database")
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all_table_names = table_names
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tables = []
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for table_name in all_table_names:
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columns = []
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create_table = self.run(
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(
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"SELECT sql FROM sqlite_master WHERE "
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f"type='table' AND name='{table_name}'"
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),
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fetch="one",
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)
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for column in self._inspector.get_columns(table_name, schema=self._schema):
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columns.append(column["name"])
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if self._sample_rows_in_table_info:
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select_star = (
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f"SELECT * FROM '{table_name}' LIMIT "
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f"{self._sample_rows_in_table_info}"
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)
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sample_rows = self.run(select_star)
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sample_rows_ls = ast.literal_eval(sample_rows)
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sample_rows_ls = list(
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map(lambda ls: [str(i)[:100] for i in ls], sample_rows_ls)
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)
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columns_str = " ".join(columns)
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sample_rows_str = "\n".join([" ".join(row) for row in sample_rows_ls])
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tables.append(
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create_table
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+ "\n\n"
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+ select_star
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+ "\n"
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+ columns_str
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+ "\n"
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+ sample_rows_str
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)
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else:
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tables.append(create_table)
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final_str = "\n\n\n".join(tables)
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return final_str
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def run(self, command: str, fetch: str = "all") -> str:
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"""Execute a SQL command and return a string representing the results.
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If the statement returns rows, a string of the results is returned.
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If the statement returns no rows, an empty string is returned.
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"""
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with self._engine.begin() as connection:
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if self._schema is not None:
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connection.exec_driver_sql(f"SET search_path TO {self._schema}")
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cursor = connection.exec_driver_sql(command)
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if cursor.returns_rows:
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if fetch == "all":
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result = cursor.fetchall()
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elif fetch == "one":
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result = cursor.fetchone()[0]
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else:
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raise ValueError("Fetch parameter must be either 'one' or 'all'")
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return str(result)
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return ""
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