ipython-polypheny 0.1.1

Access Polypheny via IPython magics

Polypheny Extension for IPython

This IPython extension adds %poly magics for querying a Polypheny polystore.
The extension was heavily inspired by the wonderful IPython SQL Extension.

Installation

Get it via PyPI

The recommended way to install the package is with pip:

pip install ipython-polypheny

Building & Installing the Package From Source

If you do not want to use pip, you can download the code and build it manually.

From the top level directory, first execute python -m build.
This should create a .tar.gz and .whl file in dist/.
Now you can install the built package with python -m pip install ./dist/<file-name>.whl.

For Development

Since installation of a package is usually not needed for development, it can be installed in editable mode:
Execute python -m pip install -e . from the top level folder of the project.

Changes to the codebase should now be reflected immediately after reloading the extension.
It is useful to have autoreload running, to automatically reload the extension:

%load_ext autoreload
%autoreload 2

%load_ext poly

Usage

First, the extension needs to be loaded:

%load_ext poly

Both line magics (lines starting with %poly) and cell magics (cells starting with%%poly) can be used.
Following the magic keyword, a command must be specified.

Here is a basic example:

# Print help
%poly help

If a command expects an argument, then it must be separated with a colon (:):

# Specify the http-interface address of a running Polypheny instance.
%poly db: http://localhost:13137

The colon can also be replaced by a line break when using cell magics. This is the ideal syntax for querying the database, where the command specifies the query language:

%%poly sql
SELECT * FROM emps

The result is automatically printed as a nicely formatted table.

Storing the result in a variable:

result = _

# Or when using line magics (note the required colon that separates the query from the command):
result = %poly sql: SELECT * FROM emps

Additionally to the query language, a namespace can be specified. It is also possible to set flags. The -c flag deactivates the cache for this query:

%%poly mql mynamespace -c
db.emps.find({})

Working With the Result

The result object provides useful ways to work with the retrieved data.

result = %poly sql: SELECT * FROM emps

Getting the raw ResultSet:

result.result_set

The data can be accessed like a two-dimensional list:

# get the value of the element in the first row and second column
result[0][1]

Iterate over the rows as dicts:

for employee in result.dicts():
    print(employee['name'], employee['salary'])

Provided Pandas is installed, it is possible to transform the result into a DataFrame:

df = result.as_df()

Advanced Features

It is possible to expand variables defined in the local namespace into a query. For this to work, the --template (shorter: -t) flag must be set:

key = 'salary'
x = 10000

%% poly -t sql: SELECT * FROM emps WHERE ${key} > ${x}

# is equal to
%% poly sql: SELECT * FROM emps WHERE salary > 10000

Be careful to not accidentally inject unwanted queries, as the values are not escaped.

Data Types

Many file types supported by Polypheny are automatically casted to corresponding Python data types:

Type in Polypheny	Type in Python
BIGINT, INTEGER, SMALLINT, TINYINT	int
DECIMAL, DOUBLE, REAL	float
BOOLEAN	bool
DOCUMENT, JSON, NODE, PATH	dict
ARRAY	list

Any other types are stored as str. The same is true for values where the casting does not succeed.

If the raw data as a nested list of str is required, one can get it from the ResultSet:

raw_data = result.result_set['data']

Limitations

Working with (multimedia) file types is currently not supported. While it does not result in an error, only the identifier for a given file is stored, not the actual file content.

License

The Apache 2.0 License