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243 lines
9.3 KiB
Python
243 lines
9.3 KiB
Python
"""SQLAlchemy wrapper around a database."""
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from __future__ import annotations
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import warnings
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from typing import Any, Iterable, List, Optional
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from sqlalchemy import MetaData, create_engine, inspect, select, text
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from sqlalchemy.engine import Engine
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from sqlalchemy.exc import ProgrammingError, SQLAlchemyError
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from sqlalchemy.schema import CreateTable
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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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metadata: Optional[MetaData] = 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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custom_table_info: Optional[dict] = None,
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view_support: Optional[bool] = False,
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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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# including view support by adding the views as well as tables to the all
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# tables list if view_support is True
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self._all_tables = set(
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self._inspector.get_table_names(schema=schema)
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+ (self._inspector.get_view_names(schema=schema) if view_support else [])
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)
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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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usable_tables = self.get_usable_table_names()
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self._usable_tables = set(usable_tables) if usable_tables else self._all_tables
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if not isinstance(sample_rows_in_table_info, int):
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raise TypeError("sample_rows_in_table_info must be an integer")
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self._sample_rows_in_table_info = sample_rows_in_table_info
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self._custom_table_info = custom_table_info
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if self._custom_table_info:
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if not isinstance(self._custom_table_info, dict):
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raise TypeError(
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"table_info must be a dictionary with table names as keys and the "
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"desired table info as values"
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)
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# only keep the tables that are also present in the database
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intersection = set(self._custom_table_info).intersection(self._all_tables)
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self._custom_table_info = dict(
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(table, self._custom_table_info[table])
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for table in self._custom_table_info
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if table in intersection
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)
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self._metadata = metadata or MetaData()
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# including view support if view_support = true
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self._metadata.reflect(
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views=view_support,
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bind=self._engine,
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only=self._usable_tables,
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schema=self._schema,
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)
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@classmethod
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def from_uri(
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cls, database_uri: str, engine_args: Optional[dict] = None, **kwargs: Any
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) -> SQLDatabase:
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"""Construct a SQLAlchemy engine from URI."""
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_engine_args = engine_args or {}
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return cls(create_engine(database_uri, **_engine_args), **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_usable_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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def get_table_names(self) -> Iterable[str]:
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"""Get names of tables available."""
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warnings.warn(
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"This method is deprecated - please use `get_usable_table_names`."
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)
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return self.get_usable_table_names()
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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_usable_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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meta_tables = [
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tbl
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for tbl in self._metadata.sorted_tables
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if tbl.name in set(all_table_names)
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and not (self.dialect == "sqlite" and tbl.name.startswith("sqlite_"))
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]
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tables = []
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for table in meta_tables:
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if self._custom_table_info and table.name in self._custom_table_info:
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tables.append(self._custom_table_info[table.name])
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continue
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# add create table command
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create_table = str(CreateTable(table).compile(self._engine))
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if self._sample_rows_in_table_info:
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# build the select command
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command = select([table]).limit(self._sample_rows_in_table_info)
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# save the columns in string format
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columns_str = "\t".join([col.name for col in table.columns])
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try:
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# get the sample rows
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with self._engine.connect() as connection:
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sample_rows = connection.execute(command)
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# shorten values in the sample rows
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sample_rows = list(
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map(lambda ls: [str(i)[:100] for i in ls], sample_rows)
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)
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# save the sample rows in string format
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sample_rows_str = "\n".join(["\t".join(row) for row in sample_rows])
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# in some dialects when there are no rows in the table a
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# 'ProgrammingError' is returned
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except ProgrammingError:
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sample_rows_str = ""
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table_info = (
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f"{create_table.rstrip()}\n"
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f"/*\n"
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f"{self._sample_rows_in_table_info} rows from {table.name} table:\n"
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f"{columns_str}\n"
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f"{sample_rows_str}\n"
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f"*/"
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)
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# build final info for table
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tables.append(table_info)
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else:
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tables.append(create_table)
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final_str = "\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.execute(text(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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def get_table_info_no_throw(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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try:
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return self.get_table_info(table_names)
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except ValueError as e:
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"""Format the error message"""
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return f"Error: {e}"
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def run_no_throw(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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If the statement throws an error, the error message is returned.
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"""
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try:
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return self.run(command, fetch)
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except SQLAlchemyError as e:
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"""Format the error message"""
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return f"Error: {e}"
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