_dbi_mysql - Private database interface for MySQL and MariaDB

Purpose:

This module contains the library’s MySQL database methods and attribute accessors; which are a specialised version of the _dbi_base._DBIBase class methods.

Platform:

Linux/Windows | Python 3.10+

Developer:

J Berendt

Email:

support@s3dev.uk

Comments:

n/a

Example:

For class-specific usage examples, please refer to the docstring for the following classes:

class _DBIMySQL(connstr: str)[source]

Bases: _DBIBase

This private class holds the methods and properties which are used for accessing MySQL-like databases, including MariaDB.

Note

This class is not designed to be interacted with directly.

Rather, please use the database.DBInterface class instead, as the proper interface class has an automatic switch for database interfaces, based on the sqlalchemy.Engine object which is created from the connection string.

Parameters:

connstr (str) – The database-specific SQLAlchemy connection string.

Example Use:

This low-level generalised class is designed to be inherited by the calling/wrapping class as:

>>> from dbilib.database import DBInterface

class MyDB(DBInterface):

    def __init__(self, connstr: str):
        super().__init__(connstr=('mysql+mysqlconnector://'
                                  '<user>:<pwd>@<host>:<port>/'
                                  '<db_name>'))
call_procedure(proc: str, params: list | tuple = None, return_status: bool = False) → DataFrame | tuple[DataFrame | bool][source]

Call a stored procedure, and return as a DataFrame.

Parameters:

  • proc (str) – Name of the stored procedure to call.

  • params (list | tuple, optional) – A list (or tuple) of parameters to pass into the procedure. Defaults to None.

  • return_status (bool, optional) – Return the method’s success status. Defaults to False.

Returns:

If the return_status argument is True, a tuple of the data and the method’s return status is returned as:

(df, status)

Otherwise, only the data is returned, as a pd.DataFrame.

Return type:

pd.DataFrame | tuple[pd.DataFrame | bool]

call_procedure_update(proc: str, params: list = None, return_id: bool = False) → bool | tuple[source]

Call an update or insert stored procedure.

Note

Results are not returned from this call, only a boolean status flag and the optional last row ID.

If results are desired, please use the call_procedure() method.

Parameters:

  • proc (str) – Name of the stored procedure to call.

  • params (list, optional) – A list of parameters to pass into the USP. Defaults to None.

  • return_id (bool, optional) – Return the ID of the last inserted row. Defaults to False.

Returns:

If return_id is False, True is returned if the procedure completed successfully, otherwise False. If return_id is True, a tuple containing the ID of the last inserted row and the execution success flag are returned as:

(id, success_flag)

Return type:

bool | tuple

call_procedure_update_many(*args, proc: str, iterable: list | tuple) → bool[source]

Call an update or insert stored procedure for an iterable.

Note

The arguments are passed into the USP in the following order:

*args, iterable_item

Ensure the USP is designed to accept the iterable item as the last parameter.

Parameters:

  • *args (str | int | float) – Positional arguments to be passed into the USP, in front of each iterable item. Note: The parameters are passed into the USP in the order received, followed by the iterable item.

  • proc (str) – Name of the stored procedure to call.

  • iterable (list | tuple) – List of items to be loaded into the database.

Returns:

True if the update was successful, otherwise False.

Return type:

bool

call_procedure_update_raw(proc: str, params: list = None)[source]

Call an update or insert stored procedure, without error handling.

Warning

This method is unprotected, perhaps use call_procedure_update() instead.

This ‘raw’ method does not contain an error handler. It is (by design) the responsibility of the caller to contain and control the errors.

The purpose of this raw method is to enable the caller method to contain and control the errors which might be generated from a USP call, for example a duplicate key error.

Parameters:

  • proc (str) – Name of the stored procedure to call.

  • params (list, optional) – A list of parameters to pass into the USP. Defaults to None.

table_exists(table_name: str, verbose: bool = False) → bool[source]

Using the engine object, test if the given table exists.

Parameters:

  • table_name (str) – Name of the table to test.

  • verbose (bool, optional) – Print a message if the table does not exist. Defaults to False.

Returns:

True if the given table exists, otherwise False.

Return type:

bool

_create_engine() → sqlalchemy.engine.base.Engine

Create a database engine using the provided environment.

Returns:

A sqlalchemy database engine object.

Return type:

sqlalchemy.engine.base.Engine

static _is_dangerous(stmt: str) → bool

Perform a dirty security check for injection attempts.

Parameters:

stmt (str) – SQL statement to be potentially executed.

Raises:

SecurityWarning – If there are multiple semi-colons (;) in the statement, or any comment delimiters (--).

Returns:

False if the checks pass.

Return type:

bool

_report_sa_error(msg: str, error: sqlalchemy.exc.SQLAlchemyError)

Report SQLAlchemy error to the terminal.

Parameters:

  • msg (str) – Additional error to be displayed. This message will be automatically prefixed with ‘[DatabaseError]: ‘

  • error (sqlalchemy.exc.SQLAlchemyError) – Caught error object from the try/except block.

static _result_to_df__cursor(result: sqlalchemy.engine.cursor.CursorResult) → DataFrame

Convert a CursorResult object to a DataFrame.

If the cursor did not return results, an empty DataFrame containing the column names only, is returned.

Parameters:

result (sqlalchemy.engine.cursor.CursorResult) – Object to be converted.

Returns:

A pandas.DataFrame object containing the cursor’s data.

Return type:

pd.DataFrame

static _result_to_df__stored(result: object) → DataFrame

Convert a MySQLCursor.stored_results object to a DataFrame.

Parameters:

  • result (object) – The cursor.stored_results() object from

  • call. (a sqlalchemy or mysql.connector procedure)

Returns:

A DataFrame containing the results from the procedure call.

Return type:

pd.DataFrame

property database_name

Accessor to the database name used by the engine object.

property engine

Accessor to the sqlalchemy.engine.base.Engine object.

execute_query(stmt: str, params: dict = None, *, raw: bool = True, flat: bool = False, commit: bool = True, ignore_unsafe: bool = False) → list | DataFrame | None

Execute a query statement.

Important

The following are not allowed to be executed by this method:

  • Statements containing multiple semi-colons (;).

  • Statements containing a comment delimiter (--).

If found, a SecurityWarning will be raised by the _is_dangerous() method.

Parameters:

  • stmt (str) – Statement to be executed. The parameter bindings are to be written in colon format.

  • params (dict, optional) – Parameter key/value bindings as a dictionary, if applicable. Defaults to None.

  • raw (bool, optional) – Return the data in ‘raw’ (tuple) format rather than as a formatted DataFrame. Defaults to True for efficiency.

  • flat (bool, optional) – Flatten the response. This is useful if the expected response is a collection of single elements. If True, this will return a flattened tuple of elements, rather than a list of tuples, as is the default behaviour. Note (1): If true, and the return is a list of multi-value tuples, only the first element in each tuple will be returned. Note (2): This argument should only be used if raw=True. Defaults to False.

  • commit (bool, optional) – Call COMMIT after the transaction is complete. Defaults to True (for backwards compatibility).

  • ignore_unsafe (bool, optional) –

    Bypass the ‘is dangerous’ check and the run query anyway. This may be required if a script contains multiple statements. Defaults to False.

    WARNING: HC SVNT DRACONES

If the query did not return results and the raw argument is False, an empty DataFrame containing the column names only, is returned.

Note

In the SQL query, the bind parameters are specified by name, using the format :bind_name. The params dictionary argument must contain the associated parameter name/value bindings.

Warning

  1. Generally, whatever statement is passed into this method will be executed, and may have destructive implications.

  2. This method contains a commit call, and the option to disable the COMMIT.

If a statement is passed into this method, and the user has the appropriate permissions - the change will be committed.

… HC SVNT DRACONES.

Returns:

If the raw parameter is True, a list of tuples containing values is returned. Otherwise, a pandas.DataFrame object containing the returned data is returned.

If this method is called with a script which does not return results, for example a CREATE script, None is returned; regardless of the value passed to the raw parameter.

Return type:

list | pd.DataFrame | None