Release Notes¶

New Expressions¶

• Add a shift() expression for shifting data backwards or forwards by N rows (#1266).

Improved Expressions¶

New Backends¶

• Initial support for dask.dataframe has been added, see (#1317). Please send feedback via an issue or pull request if we missed any expressions you need.

Improved Backends¶

• Adds support for tail() in the sql backend (#1289).

• Blaze Server now supports dynamically adding datasets (#1329).

• Two new keyword only arguments are added to compute() for use when computing against a Client object:

  1. compute_kwargs: This is a dictionary to send to the server to use as keyword arguments when calling compute on the server.
  2. odo_kwargs: This is a dictionary to send to the server to use as keyword arguments when calling odo on the server.

  This extra information is completely optional and will have different meanings based on the backend of the data on the server (#1342).

• Can now point Data() to URLs of CSVs (#1336).

Experimental Features¶

• There is now support for joining tables from multiple sources. This is very experimental right now, so use it at your own risk. It currently only works with things that fit in memory (#1282).
• Foreign columns in database tables that have foreign key relationships can now be accessed with a more concise syntax (#1192).

API Changes¶

• Removed support for Python 2.6 (#1267).
• Removed support for Python 3.3 (#1270).
• When a CSV file consists of all strings, you must pass has_header=True when using the Data constructor (#1254).
• Comparing date and datetime datashaped things to the empty string now raises a TypeError (#1308).
• Like expressions behave like a predicate, and operate on columns, rather than performing the selection for you on a table (#1333, #1340).
• blaze.server.Server.run() no longer retries binding to a new port by default. Also, positional arguments are no longer forwarded to the inner flask app’s run method. All keyword arguments not consumed by the blaze server run are still forwarded (#1316).
• Server represents datashapes in a canonical form with consistent linebreaks for use by non-Python clients (#1361).

Bug Fixes¶

• Fixed a bug where Merge expressions would unpack option types in their fields. This could cause you to have a table where expr::{a: int32} but expr.a::?int32. Note that the dotted access is an option (#1262).
• Explicitly set Node.__slots__ and Expr.__slots__ to (). This ensures instances of slotted subclasses like Join do not have a useless empty __dict__ attribute (#1274 and #1268).
• Fixed a bug that prevented creating a InteractiveSymbol that wrapped nan if the dshape was datetime. This now correctly coerces to NaT (#1272).
• Fixed an issue where blaze client/server could not use isin expressions because the frozenset failed to serialize. This also added support for rich serialization over json for things like datetimes (#1255).
• Fixed a bug where len would fail on an interactive expression whose resources were sqlalchemy objects (#1273).
• Use aliases instead of common table expressions (CTEs) because MySQL doesn’t have CTEs (#1278).
• Fixed a bug where we couldn’t display an empty string identifier in interactive mode (#1279).
• Fixed a bug where comparisons with optionals that should have resulted in optionals did not (#1292).
• Fixed a bug where Join.schema would not always be instantiated (#1288).
• Fixed a bug where comparisons to a empty string magically converted the empty string to None (#1308).
• Fix the retry kwarg to the blaze server. When retry is False, an exception is now properly raised if the port is in use. (#1316).
• Fixed a bug where leaves that only appeared in the predicate of a selection would not be in scope in time to compute the predicate. This would cause whole expressions like a[a > b] to fail because b was not in scope (#1275).
• Fix a broken test on machines that don’t allow postgres to read from the local filesystem (#1323).
• Updated a test to reflect changes from odo #366 (#1323).
• Fixed pickling of blaze expressions with interactive symbols (#1319).
• Fixed repring partials in blaze expression to show keyword arguments (#1319).
• Fixed a memory leak that would preserve the lifetime of any blaze expression that had cached an attribute access (#1335).
• Fixed a bug where common_subexpression() gave the wrong answer (#1325, #1338).
• BinaryMath operations without numba installed were failing (#1343).
• win32 tests were failing for hypot and atan2 due to slight differences in numpy vs numba implementations of those functions (#1343).
• Only start up a ThreadPool when using the h5py backend (#1347, #1331).
• Fix return type for sum and mean reductions whose children have a Decimal dshape.

Miscellaneous¶

• blaze.server.Server.run() now uses warnings.warn() instead of print when it fails to bind to a port and is retrying (#1316).
• Make expressions (subclasses of Expr) weak referencable (:issue:`1319).
• Memoize dshape and schema methods (#1319).
• Use pandas.DataFrame.sort_values() with pandas version >= 0.17.0 (#1321).

New Expressions¶

• Adds Tail which acts as an opposite to head. This is exposed throught the tail() function. This returns the last n elements from a collection. (#1187)
• Adds notnull returning an indicator of whether values in a field are null (#697, #733)

Improved Expressions¶

• Distinct expressions now support an on parameter to allow distinct on a subset of columns (#1159)
• Reduction instances are now named as their class name if their _child attribute is named '_' (#1198)
• Join expressions now promotes the types of the fields being joined on. This allows us to join things like int32 and int64 and have the result be an int64. This also allows us to join any type a with ?a. (#1193, #1218).

New Backends¶

Improved Backends¶

• Blaze now tries a bit harder to avoid generating ScalarSelects when using the SQL backend (#1201, #1205)
• ReLabel expressions on the SQL backend are now flattened (#1217).

API Changes¶

• Serialization format in blaze server is now passed in as a mimetype (#1176)

• We only allow and use HTTP POST requests when sending a computation to Blaze server for consistency with the HTTP spec (#1172)

• Allow Client objects to explicitly disable verification of ssl certificates by passing verify_ssl=False. (#1170)

• Enable basic auth for the blaze server. The server now accepts an authorization keyword which must be a callable that accepts an object holding the username and password, or None if no auth was given and returns a bool indicating if the request should be allowed. Client objects can pass an optional auth keyword which should be a tuple of (username, password) to send to the server. (#1175)

• We now allow Distinct expressions on ColumnElement to be more general and let things like sa.sql.elements.Label objects through (#1212)

• Methods now take priority over field names when using attribute access for Field instances to fix a bug that prevented accessing the method at all (#1204). Here’s an example of how this works:

  >>> from blaze import symbol
  >>> t = symbol('t', 'var * {max: float64, isin: int64, count: int64}')
  >>> t['count'].max()
  t.count.max()
  >>> t.count()  # calls the count method on t
  t.count()
  >>> t.count.max()  # AttributeError
  Traceback (most recent call last):
     ...
  AttributeError: ...
  

Bug Fixes¶

• Upgrade versioneer so that our version string is now PEP 440 compliant (#1171)
• Computed columns (e.g., the result of a call to transform()) can now be accessed via standard attribute access when using the SQL backend (#1201)
• Fixed a bug where blaze server was depending on an implementation detail of CPython regarding builtins (#1196)
• Fixed incorrect SQL generated by count on a subquery (#1202).
• Fixed an ImportError generated by an API change in dask.
• Fixed an issue where columns were getting trampled if there were column name collisions in a sql join. (#1208)
• Fixed an issue where arithmetic in a Merge expression wouldn’t work because arithmetic wasn’t defined on sa.sql.Select objects (#1207)
• Fixed a bug where the wrong value was being passed into time() (#1213)
• Fixed a bug in sql relabel that prevented relabeling anything that generated a subselect. (#1216)
• Fixed a bug where methods weren’t accessible on fields with the same name (#1204)
• Fixed a bug where optimized expressions going into a pandas group by were incorrectly assigning extra values to the child DataFrame (#1221)
• Fixed a bug where multiple same-named operands caused incorrect scope to be constructed ultimately resulting in incorrect results on expressions like x + x + x (#1227). Thanks to @llllllllll and @jcrist for discussion around solving the issue.
• Fixed a bug where minute() and Minute were not being exported which made them unusable from the blaze server (#1232).
• Fixed a bug where repr was being called on data resources rather than string, which caused massive slowdowns on largish expressions running against blaze server (#1240, #1247).
• Skip a test on Win32 + Python 3.4 and PyTables until this gets sorted out on the library side (#1251).

Miscellaneous¶

• We now run tests against pandas master to catch incompatibility issues (#1243).

Bug Fixes¶

• Fix broken sdist tarball

New Expressions¶

• String arithmetic is now possible across the numpy and pandas backends via the + (concatenation) and * (repeat) operators (#1058).
• Datetime arithmetic is now available (#1112).
• Add a Concat expression that implements Union-style operations (#1128).
• Add a Coerce expression that casts expressions to a different datashape. This maps to astype in numpy and cast in SQL (#1137).

Improved Expressions¶

• ReLabel expressions repr differently depending on whether the existing column names are valid Python variable names (#1070).

New Backends¶

None

Improved Backends¶

API Changes¶

• Remove old ExprClient(). Use Client instead (#1154).

• Make sort + slice and sort + slice semantics of the SQL backend reflect those of numpy (#1125).

• The following syntax is no longer allowed for Blaze server (#1154):

  >>> Data('blaze://localhost::accounts')  # raises an error 
  

  Use this syntax instead:

  >>> Data('blaze://localhost').accounts  # valid 
  

Bug Fixes¶

• Handle SQLAlchemy API churn around reference of ColumnElement objects in the 1.0.x series (#1071, #1076).
• Obscure hashing bug when passing in both a pandas Timestamp and a datetime.datetime object. Both objects hash to the same value but don’t necessarily compare equal; this makes Python call __eq__ which caused an Eq expression to be constructed (#1097).
• Properly handle And expressions that involve the same field in MongoDB (#1099).
• Handle Dask API changes (#1114).
• Use the date function in SQLAlchemy when getting the date attribute of a datetime dshaped expression. Previously this was calling extract, which is incorrect for the postgres backend (#1120).
• Fix API compatibility with different versions of psutil (#1136).
• Use explicit int64 comparisons on Windows, since the default values may be different (#1148).
• Fix name attribute propagation in pandas Series objects (#1152).
• Raise a more informative error when trying to subset with an unsupported expression in the MongoDB backend (#1155).