def apply_filter(expr, predicates):
# This will attempt predicate pushdown in the cases where we can do it
# easily and safely, to make both cleaner SQL and fewer referential errors
# for users
op = expr.op()
if isinstance(op, ops.Selection):
return _filter_selection(expr, predicates)
elif isinstance(op, ops.Aggregation):
# Potential fusion opportunity
simplified_predicates = [
sub_for(x, [(expr, op.table)]) for x in predicates
]
if op.table._is_valid(simplified_predicates):
result = ops.Aggregation(op.table,
op.agg_exprs,
by=op.by,
having=op.having,
predicates=op.predicates +
simplified_predicates,
sort_keys=op.sort_keys)
return ir.TableExpr(result)
elif isinstance(op, ops.Join):
expr = expr.materialize()
result = ops.Selection(expr, [], predicates)
return ir.TableExpr(result)
def apply_filter(expr, predicates):
# This will attempt predicate pushdown in the cases where we can do it
# easily and safely, to make both cleaner SQL and fewer referential errors
# for users
op = expr.op()
if isinstance(op, ops.Selection):
return _filter_selection(expr, predicates)
elif isinstance(op, ops.Aggregation):
# Potential fusion opportunity
# GH1344: We can't sub in things with correlated subqueries
simplified_predicates = [
sub_for(predicate, [(expr, op.table)])
if not has_reduction(predicate) else predicate
for predicate in predicates
]
if op.table._is_valid(simplified_predicates):
result = ops.Aggregation(op.table,
op.metrics,
by=op.by,
having=op.having,
predicates=op.predicates +
simplified_predicates,
sort_keys=op.sort_keys)
return ir.TableExpr(result)
elif isinstance(op, ops.Join):
expr = expr.materialize()
result = ops.Selection(expr, [], predicates)
return ir.TableExpr(result)
def _lift_Selection(self, expr, block=None):
if block is None:
block = self.block_projection
op = expr.op()
if block and op.blocks():
# GH #549: dig no further
return expr
else:
lifted_table, unch = self._lift_arg(op.table, block=True)
lifted_selections, unch_sel = self._lift_arg(op.selections, block=True)
unchanged = unch and unch_sel
lifted_predicates, unch_sel = self._lift_arg(op.predicates, block=True)
unchanged = unch and unch_sel
lifted_sort_keys, unch_sel = self._lift_arg(op.sort_keys, block=True)
unchanged = unch and unch_sel
if not unchanged:
lifted_projection = ops.Selection(lifted_table, lifted_selections,
lifted_predicates,
lifted_sort_keys)
result = ir.TableExpr(lifted_projection)
else:
result = expr
return result
def _lift_Aggregation(self, expr, block=None):
if block is None:
block = self.block_projection
op = expr.op()
# as exposed in #544, do not lift the table inside (which may be
# filtered or otherwise altered in some way) if blocking
if block:
lifted_table = op.table
else:
lifted_table = self.lift(op.table, block=True)
unch = lifted_table is op.table
lifted_aggs, unch1 = self._lift_arg(op.metrics, block=True)
lifted_by, unch2 = self._lift_arg(op.by, block=True)
lifted_having, unch3 = self._lift_arg(op.having, block=True)
unchanged = unch and unch1 and unch2 and unch3
if not unchanged:
lifted_op = ops.Aggregation(lifted_table,
lifted_aggs,
by=lifted_by,
having=lifted_having)
result = ir.TableExpr(lifted_op)
else:
result = expr
return result
def _inject_table(self, name, schema):
if name in self.meta.tables:
table = self.meta.tables[name]
else:
table = alch.table_from_schema(name, self.meta, schema)
node = alch.AlchemyTable(table, self)
return ir.TableExpr(node)
def _filter_selection(expr, predicates):
# if any of the filter predicates have the parent expression among
# their roots, then pushdown (at least of that predicate) is not
# possible
# It's not unusual for the filter to reference the projection
# itself. If a predicate can be pushed down, in this case we must
# rewrite replacing the table refs with the roots internal to the
# projection we are referencing
#
# Assuming that the fields referenced by the filter predicate originate
# below the projection, we need to rewrite the predicate referencing
# the parent tables in the join being projected
op = expr.op()
if not op.blocks():
# Potential fusion opportunity. The predicates may need to be
# rewritten in terms of the child table. This prevents the broken
# ref issue (described in more detail in #59)
simplified_predicates = [
sub_for(x, [(expr, op.table)]) for x in predicates
]
if op.table._is_valid(simplified_predicates):
result = ops.Selection(op.table, [],
predicates=op.predicates +
simplified_predicates,
sort_keys=op.sort_keys)
return ir.TableExpr(result)
can_pushdown = _can_pushdown(op, predicates)
if can_pushdown:
simplified_predicates = [substitute_parents(x) for x in predicates]
fused_predicates = op.predicates + simplified_predicates
result = ops.Selection(op.table,
proj_exprs=op.selections,
predicates=fused_predicates,
sort_keys=op.sort_keys)
else:
result = ops.Selection(expr, proj_exprs=[], predicates=predicates)
return ir.TableExpr(result)
def apply_filter(expr, predicates):
# This will attempt predicate pushdown in the cases where we can do it
# easily and safely, to make both cleaner SQL and fewer referential errors
# for users
op = expr.op()
if isinstance(op, ops.Selection):
return _filter_selection(expr, predicates)
elif isinstance(op, ops.Aggregation):
# Potential fusion opportunity
# GH1344: We can't sub in things with correlated subqueries
simplified_predicates = [
# Originally this line tried substituting op.table in for expr, but
# that is too aggressive in the presence of filters that occur
# after aggregations.
#
# See https://github.com/ibis-project/ibis/pull/3341 for details
sub_for(predicate, [(op.table, expr)])
if not has_reduction(predicate)
else predicate
for predicate in predicates
]
if op.table._is_valid(simplified_predicates):
result = ops.Aggregation(
op.table,
op.metrics,
by=op.by,
having=op.having,
predicates=op.predicates + simplified_predicates,
sort_keys=op.sort_keys,
)
return ir.TableExpr(result)
result = ops.Selection(expr, [], predicates)
return ir.TableExpr(result)
def _wrap_new_table(self, qualified_name, persist):
if persist:
t = self.table(qualified_name)
else:
schema = self._get_table_schema(qualified_name)
node = ImpalaTemporaryTable(qualified_name, schema, self)
t = ir.TableExpr(node)
# Compute number of rows in table for better default query planning
cardinality = t.count().execute()
set_card = ("alter table {0} set tblproperties('numRows'='{1}', "
"'STATS_GENERATED_VIA_STATS_TASK' = 'true')".format(
qualified_name, cardinality))
self._execute(set_card)
return t
def sql(self, query):
"""
Convert a SQL query to an Ibis table expression
Parameters
----------
Returns
-------
table : TableExpr
"""
# Get the schema by adding a LIMIT 0 on to the end of the query. If
# there is already a limit in the query, we find and remove it
limited_query = 'SELECT * FROM ({}) t0 LIMIT 0'.format(query)
schema = self._get_schema_using_query(limited_query)
node = ops.SQLQueryResult(query, schema, self)
return ir.TableExpr(node)
def table(self, name, database=None):
"""
Create a table expression that references a particular table in the
database
Parameters
----------
name : string
database : string, optional
Returns
-------
table : TableExpr
"""
qualified_name = self._fully_qualified_name(name, database)
schema = self._get_table_schema(qualified_name)
node = ops.DatabaseTable(qualified_name, schema, self)
return ir.TableExpr(node)
def _lift_Projection(self, expr, block=None):
if block is None:
block = self.block_projection
op = expr.op()
if block:
lifted_table = op.table
unch = True
else:
lifted_table, unch = self._lift_arg(op.table, block=True)
lifted_selections, unch_sel = self._lift_arg(op.selections, block=True)
unchanged = unch and unch_sel
if not unchanged:
lifted_projection = ops.Projection(lifted_table, lifted_selections)
result = ir.TableExpr(lifted_projection)
else:
result = expr
return result
def _lift_Join(self, expr, block=None):
op = expr.op()
left_lifted = self.lift(op.left, block=block)
right_lifted = self.lift(op.right, block=block)
unchanged = (left_lifted is op.left and right_lifted is op.right)
# Fix predicates
lifted_preds = []
for x in op.predicates:
subbed = self._sub(x, block=True)
if subbed is not x:
unchanged = False
lifted_preds.append(subbed)
if not unchanged:
lifted_join = type(op)(left_lifted, right_lifted, lifted_preds)
result = ir.TableExpr(lifted_join)
else:
result = expr
return result
def _lift_Aggregation(self, expr, block=None):
if block is None:
block = self.block_projection
op = expr.op()
lifted_table = self.lift(op.table, block=True)
unch = lifted_table is op.table
lifted_aggs, unch1 = self._lift_arg(op.agg_exprs, block=True)
lifted_by, unch2 = self._lift_arg(op.by, block=True)
lifted_having, unch3 = self._lift_arg(op.having, block=True)
unchanged = unch and unch1 and unch2 and unch3
if not unchanged:
lifted_op = ops.Aggregation(lifted_table,
lifted_aggs,
by=lifted_by,
having=lifted_having)
result = ir.TableExpr(lifted_op)
else:
result = expr
return result
