Concepts ======== If you are relatively new to BTrDB, then there are a few things you should be aware of about interacting with the server. First of all, time series databases such as BTrDB are not relational databases and so they behave differently, have different access methods, and provide different guarantees. The following sections provide insight into the high level objects and aspects of their behavior which will allow you to use them effectively. .. note:: Data requests are fully materialized at this time. A future release will include the option to process data using generators to save on memory usage. BTrDB Server ------------ Like most time series databases, the BTrDB server contains multiple streams of data in which each stream contains a data point at a given time. However, BTrDB focuses on univariate data which opens a host of benefits and is one of the reasons BTrDB is able to process incredibly large amounts of data quickly and easily. .. _Points Described: Points ------------ Points of data within a time series make up the smallest objects you will be dealing with when making calls to the database. Because there are different types of interactions with the database, there are different types of points that could be returned to you: :code:`RawPoint` and :code:`StatPoint`. RawPoint ^^^^^^^^^^^^ The RawPoint represents a single time/value pair and is the simpler of the two types of points. This is most useful when you need to process every single value within the stream. .. code-block:: python >>> # view time and value of a single point in the stream >>> point.time 1547241923338098176 >>> point.value 120.5 StatPoint ^^^^^^^^^^^^ The StatPoint provides statistics about multiple points and gives aggregation values such as :code:`min`, :code:`max`, :code:`mean`, :code:`count` and :code:`stddev` (standard deviation). This is most useful when you don't need to touch every individual value such as when you only need the count of the values over a range of time. These statistical queries execute in time proportional to the number of results, not the number of underlying points (i.e logarithmic time) and so you can attain valuable data in a fraction of the time when compared with retrieving all of the individual values. Due to the internal data structures, :code:`BTrDB` does not need to read the underlying points to return these statistics! .. code-block:: python >>> # view aggregate values for points in a stream >>> point.time 1547241923338098176 >>>point.min 42.1 >>> point.mean 78.477 >>> point.max 122.4 >>> point.count 18600 >>> point.stddev 3.4 Tabular Data ------------ In addition to working with the :code:`RawPoint` or :code:`StatPoint` objects, newer versions of the platform now natively support some tabular data formats as well. This is enabled for commercial customers and are available using the :code:`stream.arrow_` or :code:`streamset.arrow_` methods. Refer to the :ref:`arrow enabled queries page ` and the :ref:`API docs ` Streams ------------ :code:`Stream` s represent a single series of time/value pairs. As such, the database can hold an almost unlimited amount of individual streams. Each stream has a :code:`collection` which is similar to a "path" or grouping for multiple streams. Each steam will also have a :code:`name` as well as a :code:`uuid` which is guaranteed to be unique across streams. :code:`BTrDB` data is versioned such that changes to a given stream (time series) will result in a new version for the stream. In this manner, you can pin your interactions to a specific version ensuring the values do not change over the course of your interactions. .. note:: If you want to work with the most recent version/data then specify a version of :code:`0` (the default). Each stream has a number of attributes and methods available and these are documented within the :ref:`API Reference ` section of this publication. But the most common interactions by users are to access the :code:`UUID`, :code:`tags`, :code:`annotations`, :code:`version`, and underlying data. Each stream uses a :code:`UUID` as its unique identifier which can also be used when querying for streams. Metadata is provided by :code:`tags` and :code:`annotations` which are both provided as dictionaries of data. :code:`tags` are used internally and have very specific keys while :code:`annotations` are more free-form and can be used by you to store your own metadata. .. code-block:: python >>> # retrieve stream's UUID >>> stream.uuid UUID("0d22a53b-e2ef-4e0a-ab89-b2d48fb2592a") >>> # retrieve stream's current version >>> stream.version() 244 >>> # retrieve stream tags >>> stream.tags() {'name': 'L1MAG', 'unit': 'volts', 'ingress': ''} >>> # retrieve stream annotations >>> stream.annotations() ({'poc': 'Salvatore McFesterson', 'region': 'northwest', 'state': 'WA'}, 23) >>> # loop through points in the stream >>> for point, _ in stream.values(end=1547241923338098176, version=133): >>> print(point) RawPoint(1500000000100000000, 2.4) RawPoint(1500000000200000000, 2.8) RawPoint(1500000000300000000, 3.6) ... StreamSets ------------ Often you will want to query and work with multiple streams instead of just an individual stream - :code:`StreamSets` allow you to do this effectively. It is a light wrapper around a list of :code:`Stream` objects with convenience methods provided to help you work with multiple streams of data. As an example, you can filter the stream data with a single method call and then easily transform the data into other data types such as a pandas DataFrame or to disk as a CSV file. See the examples below for a quick sample and then visit our API docs to see the full list of features provided to you. .. note:: :code:`StreamSet` methods that filter and operate on the :code:`StreamSet` object (like :code:`StreamSet.filter` ) return new copies of the :code:`StreamSet` itself rather than modifying in place. Similar to how most :code:`pandas.DataFrame` methods return a new :code:`DataFrame` object. This lets you compose multiple functions in a single call, which can improve readability, but can be tricky if you are not expecting this behavior. Lets explore a common use-case, filtering a streamset. .. code-block:: python >>> # create a streamset and apply a few filters >>> streamset = btrdb.stream.StreamSet(list_of_streams) >>> print(f"Total streams: {len(streamset)}") Total streams: 89 >>> streamset.filter(units="Volts") >>> print(f"Total streams: {len(streamset)}") Total streams: 89 >>> filtered_streamset = streamset.filter(units="Volts") >>> print(f"Total streams: {len(filtered_streamset)}") Total streams: 23 >>> multiple_filters_streamset = (streamset.filter(unit="Volts") >>> .filter(name="Sensor 1") >>> .filter(annotations={"phase":"A"}) >>> ) >>> print(f"Total streams: {len(multiple_filters_streamset)}") Total streams: 1 .. code-block:: python >>> # establish database connection and query for streams by UUID >>> db = connect() >>> uuid_list = ["0d22a53b-e2ef-4e0a-ab89-b2d48fb2592a", ...] >>> streams = db.streams(*uuid_list) >>> streams.filter(start=1500000000000000000).to_csv("data.csv") >>> streams.filter(start=1500000000000000000).to_dataframe() time NW/stream0 NW/stream1 0 1500000000000000000 NaN 1.0 1 1500000000100000000 2.0 NaN 2 1500000000200000000 NaN 3.0 3 1500000000300000000 4.0 NaN 4 1500000000400000000 NaN 5.0 5 1500000000500000000 6.0 NaN 6 1500000000600000000 NaN 7.0 7 1500000000700000000 8.0 NaN 8 1500000000800000000 NaN 9.0 9 1500000000900000000 10.0 NaN Apache-Arrow Accelerated Methods -------------------------------- * Refer to :ref:`Arrow Page`