def update_spec(expr: ibis.Expr, spec: dict):
"""
Takes in an ibis expression and a spec, updating the spec and returning a new ibis expr
"""
original_expr = expr
# iterate through transforms and move as many as we can into the ibis expression
# logic modified from
# https://github.com/vega/vega-lite-transforms2sql/blob/3b360144305a6cec79792036049e8a920e4d2c9e/transforms2sql.ts#L7
for transform in spec.get("transform", []):
groupby = transform.pop("groupby", None)
if groupby:
all_fields_exist = all(
[field in expr.columns for field in groupby])
if not all_fields_exist:
transform["groupby"] = groupby
# we referenced a field that isnt in the expression because it was an aggregate we coudnt process
continue
expr = expr.groupby(groupby)
aggregate = transform.pop("aggregate", None)
if aggregate:
expr = expr.aggregate([
vl_aggregate_to_grouping_expr(original_expr, a)
for a in aggregate
])
filter_ = transform.pop("filter", None)
if filter_:
# https://vega.github.io/vega-lite/docs/filter.html#field-predicate
field = filter_["field"]
field_expr = original_expr[field]
if "range" in filter_:
min, max = filter_["range"]
preds = [field_expr >= min, field_expr <= max]
elif "equal" in filter_:
preds = [field_expr == filter_["equal"]]
elif "gt" in filter_:
preds = [field_expr > filter_["gt"]]
elif "lt" in filter_:
preds = [field_expr < filter_["lt"]]
elif "lte" in filter_:
preds = [field_expr <= filter_["lte"]]
elif "gte" in filter_:
preds = [field_expr >= filter_["gte"]]
else:
# put filter back if we cant transform itt
transform["filter"] = filter_
continue
expr = expr.filter(preds)
# remove empty transforms
spec["transform"] = [i for i in spec.get("transform", []) if i]
# remove key if empty
if not spec["transform"]:
del spec["transform"]
return expr
def empty(expr: ibis.Expr) -> pandas.DataFrame:
"""
Creates an empty DF for a ibis expression, based on the schema
https://github.com/ibis-project/ibis/issues/1676#issuecomment-441472528
"""
return expr.schema().apply_to(pandas.DataFrame(columns=expr.columns))
def timeunit(transform: dict, expr: ibis.Expr) -> ibis.Expr:
"""
Apply a vega time unit transform to an ibis expression.
https://vega.github.io/vega/docs/transforms/timeunit/
It transforms it into the Ibis truncate expression.
https://docs.ibis-project.org/generated/ibis.expr.api.TimestampValue.truncate.html
Parameters
----------
transform: dict
A JSON-able dictionary representing the vega transform.
expr: ibis.Expr
The expression to which to apply the transform.
Returns
-------
transformed_expr: the transformed expression
"""
assert transform.pop("type") == "timeunit"
field = expr[transform.pop("field")]
as_start, as_end = transform.pop("as")
units = transform.pop("units")
if transform:
raise NotImplementedError(
f"timeunit transform: {list(transform)} keys are not supported")
if units == ["year"]:
start = field.truncate("Y")
delta = ibis.interval(years=1)
elif units == ["year", "month"]:
start = field.truncate("M")
delta = ibis.interval(months=1)
elif units == ["year", "month", "date"]:
start = field.truncate("D")
delta = ibis.interval(days=1)
elif units == ["year", "month", "date", "hours"]:
start = field.truncate("h")
delta = ibis.interval(hours=1)
elif units == ["year", "month", "date", "hours", "minutes"]:
start = field.truncate("m")
delta = ibis.interval(minutes=1)
elif units == ["year", "month", "date", "hours", "minutes", "seconds"]:
start = field.truncate("s")
delta = ibis.interval(seconds=1)
elif units == [
"year",
"month",
"date",
"hours",
"minutes",
"seconds",
"milliseconds",
]:
start = field.truncate("ms")
delta = ibis.interval(milliseconds=1)
else:
raise NotImplementedError(
f"timeunit transform: {units} units are not supported")
return expr.mutate([start.name(as_start), (start + delta).name(as_end)])
def aggregate(transform: dict, expr: ibis.Expr) -> ibis.Expr:
groupby, = transform["groupby"]
op, = transform["ops"]
field, = transform["fields"]
as_, = transform["as"]
expr = expr.group_by(groupby).aggregate(
[getattr(expr[field], _translate_op(op))().name(as_)])
return expr
def collect(transform: dict, expr: ibis.Expr) -> ibis.Expr:
fields = promote_list(transform["sort"]["field"])
orders = promote_list(transform["sort"].get("order", ["ascending"] * len(fields)))
assert len(fields) == len(orders)
rules = [
(field, (True if order == "ascending" else False))
for field, order in zip(fields, orders)
]
return expr.sort_by(rules)
def aggregate(transform: dict, expr: ibis.Expr) -> ibis.Expr:
groupby = transform["groupby"]
# It's undocumented, but an undefined "ops" value defaults to ["count"]'
# https://github.com/vega/vega/blob/4d10f9da0df0833c90ff259bbd0960f7cb05e3bf/packages/vega-transforms/src/Aggregate.js#L159-L161
ops = transform.get("ops", ["count"])
fields = transform.get("fields", [None])
as_ = transform.get("as", [None])
expr = expr.group_by(groupby).aggregate([
_aggregate(expr, field, op, as__)
for (field, op, as__) in zip(fields, ops, as_)
])
return expr
def raise_unsupported_expr_error(expr: ibis.Expr):
"""Raise an unsupported expression error for given expression.
Parameters
----------
expr : ibis.Expr
Raises
------
com.UnsupportedOperationError
"""
msg = "OmniSciDB backend doesn't support {} operation!"
op = expr.op()
raise com.UnsupportedOperationError(msg.format(type(op)))
def maybe_add_random_sort(
self, data_client: ibis.client, table: ibis.Expr
) -> ibis.Expr:
"""Return a randomly sorted query if it is supported for the client."""
if type(data_client) in RANDOM_SORT_SUPPORTS:
return table.sort_by(
RandomSortKey(RANDOM_SORT_SUPPORTS[type(data_client)]).to_expr()
)
if type(data_client) != TeradataClient:
# Teradata 'SAMPLE' is random by nature and does not require a sort by
logging.warning(
"Data Client %s Does Not Enforce Random Sort on Sample",
str(type(data_client)),
)
return table
def apply(expr: ibis.Expr, transforms: Any) -> ibis.Expr:
"""Apply transform or transforms to the expression.
Parameters
----------
expr: ibis.Expr
transform: list
A transform specification or list of transform specifications.
Each specification must be valid according to Vega's transform
schema.
Returns
-------
expr_transformed : ibis.expr
The transformed dataframe.
"""
if transforms is None:
return expr
transforms = promote_list(transforms)
# First traverse list of transforms, and find any that create bins
# The resulting bin fields, we create as the source fields,
# Because, for some reason, the filter happens before
# the binning, but it refers to the field created by the binning
# See the signals in https://vega.github.io/editor/#/gist/9c7d4dee819450e59cf7381f4d47fee0/example.vl.json
# as an example
# TODO: Bring this up with Dominik and see why this is
for t in transforms:
if t["type"] == "bin":
expr = expr.mutate(expr[t["field"]].name(t["as"][0]))
# Have extra processing for extents that create signals
# can probably remove once https://github.com/vega/vega-lite/issues/5320 is fixed.
signal_mapping = {}
for t in transforms:
if t["type"] == "extent":
assert {"field", "signal_", "type"} == t.keys()
signal_mapping[t["signal_"]] = t["field"]
continue
# Change binning that reference signal extent with actual value
if "extent" in t and "signal" in t["extent"]:
t["extent"] = signal_mapping.pop(t["extent"]["signal"])
expr = _delegate_transform(t, expr)
return expr
def formula(transform: dict, expr: ibis.Expr) -> ibis.Expr:
"""
Apply a vega formula transform to an ibis expression.
https://vega.github.io/vega/docs/transforms/formula/
This transform evaluates a vega expression, which is not fully
implemented. Not every expression will work.
Parameters
----------
transform: dict
A JSON-able dictionary representing the vega transform.
expr: ibis.Expr
The expression to which to apply the transform.
Returns
-------
transformed_expr: the transformed expression
"""
col = transform["as"]
calc = transform["expr"]
new_col = eval_vegajs(calc, expr).name(col)
return expr.mutate(new_col)
def bin(transform: BinTransform, expr: ibis.Expr) -> ibis.Expr:
"""
Apply a vega bin transform to an ibis expression.
https://vega.github.io/vega/docs/transforms/bin/
"""
field = expr[transform["field"]]
as_left, as_right = transform["as"]
maxbins = transform["maxbins"]
extent = expr[transform["extent"]]
# Precompute min/max or else we get
# "Expression 'xxx' is not being grouped"
# errors
with tracer.start_span("bin_transform:min") as span:
min_expr = extent.min()
span.log_kv({"sql": min_expr.compile()})
min_ = min_expr.execute()
with tracer.start_span("bin_transform:max") as span:
max_expr = extent.max()
span.log_kv({"sql": max_expr.compile()})
max_ = max_expr.execute()
# Cast these to floats to work around
# https://github.com/ibis-project/ibis/issues/1934
binwidth = (max_ - min_) / maxbins
bin_ = (((field / _float(binwidth)) - _float(min_ / binwidth))).floor()
left = (min_ + (bin_ * binwidth)).name(as_left)
right = (((min_ + binwidth) + (bin_ * binwidth))).name(as_right)
# add the two new fields and remove the initial column
return expr.mutate(
[left, right]
# + [c for c in expr.columns if c not in {transform["field"], as_left, as_right}]
)
def collect(transform: dict, expr: ibis.Expr) -> ibis.Expr:
"""
Apply a vega collect transform to an ibis expression.
https://vega.github.io/vega/docs/transforms/collect/
Parameters
----------
transform: dict
A JSON-able dictionary representing the vega transform.
expr: ibis.Expr
The expression to which to apply the transform.
Returns
-------
transformed_expr: the transformed expression
"""
fields = promote_list(transform["sort"]["field"])
orders = promote_list(transform["sort"].get("order",
["ascending"] * len(fields)))
assert len(fields) == len(orders)
rules = [(field, (True if order == "ascending" else False))
for field, order in zip(fields, orders)]
return expr.sort_by(rules)
def formula(transform: dict, expr: ibis.Expr) -> ibis.Expr:
col = transform["as"]
calc = transform["expr"]
new_col = eval_vegajs(calc, expr).name(col)
return expr.mutate(new_col)
def vl_aggregate_to_grouping_expr(expr: ibis.Expr, a: dict) -> ibis.Expr:
if "field" in a:
expr = expr[a["field"]]
op = translate_op(a["op"])
expr = getattr(expr, op)()
return expr.name(a["as"])
def get_client(expr: ibis.Expr) -> ibis.client.Client:
return expr.op().table.op().source
def filter(transform: dict, expr: ibis.Expr) -> ibis.Expr:
calc = transform["expr"]
return expr.filter(eval_vegajs(calc, expr))
