def _validate_join_predicates(self, predicates):
for pred in predicates:
op = pred.op()
if not isinstance(op, ops.Equals):
raise com.TranslationError('Non-equality join predicates are '
'not supported')
left_on, right_on = op.args
if left_on.get_name() != right_on.get_name():
raise com.TranslationError('Joining on different column names '
'is not supported')
def selection(op, expr):
plan = translate(op.table)
selections = []
for expr in op.selections or [op.table]:
# TODO(kszucs) it would be nice if we wouldn't need to handle the
# specific cases in the backend implementations, we could add a
# new operator which retrieves all of the TableExpr columns
# (.e.g. Asterisk) so the translate() would handle this
# automatically
if isinstance(expr, ir.TableExpr):
for name in expr.columns:
column = expr.get_column(name)
field = translate(column)
selections.append(field)
elif isinstance(expr, ir.ValueExpr):
field = translate(expr)
selections.append(field)
else:
raise com.TranslationError(
"DataFusion backend is unable to compile selection with "
f"expression type of {type(expr)}")
plan = plan.select(*selections)
if op.predicates:
predicates = map(translate, op.predicates)
predicate = functools.reduce(operator.and_, predicates)
plan = plan.filter(predicate)
if op.sort_keys:
sort_keys = map(translate, op.sort_keys)
plan = plan.sort(*sort_keys)
return plan
def filter_by_time_context(df: DataFrame,
timecontext: Optional[TimeContext] = None
) -> DataFrame:
""" Filter a Dataframe by given time context
Parameters
----------
df : pyspark.sql.dataframe.DataFrame
timecontext: TimeContext
Returns
-------
filtered Spark Dataframe
"""
if not timecontext:
return df
if TIME_COL in df.columns:
# For py3.8, underlying spark type converter calls utctimetuple()
# and will throw excpetion for Timestamp type if tz is set.
# See https://github.com/pandas-dev/pandas/issues/32174
# Dropping tz will cause spark to interpret begin, end with session
# timezone & os env TZ. We convert Timestamp to pydatetime to
# workaround.
begin, end = timecontext
return df.filter((F.col(TIME_COL) >= begin.to_pydatetime())
& (F.col(TIME_COL) < end.to_pydatetime()))
else:
raise com.TranslationError(
"'time' column missing in Dataframe {}."
"To use time context, a Timestamp column name 'time' must"
"present in the table. ".format(df))
def _validate_join_predicates(self, predicates):
for pred in predicates:
op = pred.op()
if (not isinstance(op, ops.Equals)
and not self._non_equijoin_supported):
raise com.TranslationError('Non-equality join predicates, '
'i.e. non-equijoins, are not '
'supported')
def compile_variance(t, expr, scope, context=None, **kwargs):
how = expr.op().how
if how == 'sample':
fn = F.var_samp
elif how == 'pop':
fn = F.var_pop
else:
raise com.TranslationError(
"Unexpected 'how' in translation: {}".format(how))
return compile_aggregator(t, expr, scope, fn, context)
def _adapt_expr(expr):
# Non-table expressions need to be adapted to some well-formed table
# expression, along with a way to adapt the results to the desired
# arity (whether array-like or scalar, for example)
#
# Canonical case is scalar values or arrays produced by some reductions
# (simple reductions, or distinct, say)
if isinstance(expr, ir.Table):
return expr, toolz.identity
if isinstance(expr, ir.Scalar):
if not expr.has_name():
expr = expr.name('tmp')
if L.is_scalar_reduction(expr):
table_expr = L.reduction_to_aggregation(expr)
return table_expr, _get_scalar(expr.get_name())
else:
return expr, _get_scalar(expr.get_name())
elif isinstance(expr, ir.Analytic):
return expr.to_aggregation(), toolz.identity
elif isinstance(expr, ir.Column):
op = expr.op()
if isinstance(op, ops.TableColumn):
table_expr = op.table[[op.name]]
result_handler = _get_column(op.name)
else:
if not expr.has_name():
expr = expr.name('tmp')
table_expr = expr.to_projection()
result_handler = _get_column(expr.get_name())
return table_expr, result_handler
else:
raise com.TranslationError(
f'Do not know how to execute: {type(expr)}')
def filter_by_time_context(df: DataFrame,
timecontext: Optional[TimeContext] = None
) -> DataFrame:
""" Filter a Dataframe by given time context
Parameters
----------
df : pyspark.sql.dataframe.DataFrame
timecontext: TimeContext
Returns
-------
filtered Spark Dataframe
"""
if not timecontext:
return df
begin, end = timecontext
if TIME_COL in df.columns:
return df.filter((F.col(TIME_COL) >= begin) & (F.col(TIME_COL) < end))
else:
raise com.TranslationError(
"'time' column missing in Dataframe {}."
"To use time context, a Timestamp column name 'time' must"
"present in the table. ".format(df))
def _adapt_expr(expr):
# Non-table expressions need to be adapted to some well-formed table
# expression, along with a way to adapt the results to the desired
# arity (whether array-like or scalar, for example)
#
# Canonical case is scalar values or arrays produced by some reductions
# (simple reductions, or distinct, say)
if isinstance(expr, ir.TableExpr):
return expr, toolz.identity
def _get_scalar(field):
def scalar_handler(results):
return results[field][0]
return scalar_handler
if isinstance(expr, ir.ScalarExpr):
if L.is_scalar_reduction(expr):
table_expr, name = L.reduction_to_aggregation(
expr, default_name='tmp'
)
return table_expr, _get_scalar(name)
else:
base_table = ir.find_base_table(expr)
if base_table is None:
# exprs with no table refs
# TODO(phillipc): remove ScalarParameter hack
if isinstance(expr.op(), ops.ScalarParameter):
name = expr.get_name()
assert (
name is not None
), f'scalar parameter {expr} has no name'
return expr, _get_scalar(name)
return expr.name('tmp'), _get_scalar('tmp')
raise NotImplementedError(repr(expr))
elif isinstance(expr, ir.AnalyticExpr):
return expr.to_aggregation(), toolz.identity
elif isinstance(expr, ir.ColumnExpr):
op = expr.op()
def _get_column(name):
def column_handler(results):
return results[name]
return column_handler
if isinstance(op, ops.TableColumn):
table_expr = op.table[[op.name]]
result_handler = _get_column(op.name)
else:
# Something more complicated.
base_table = L.find_source_table(expr)
if isinstance(op, ops.DistinctColumn):
expr = op.arg
try:
name = op.arg.get_name()
except Exception:
name = 'tmp'
table_expr = base_table.projection(
[expr.name(name)]
).distinct()
result_handler = _get_column(name)
else:
table_expr = base_table.projection([expr.name('tmp')])
result_handler = _get_column('tmp')
return table_expr, result_handler
else:
raise com.TranslationError(
f'Do not know how to execute: {type(expr)}'
)
