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Add support for array and struct literals #67

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127a60b
Support array literals
JacobHayes Sep 26, 2020
1be7d08
Support struct literals
JacobHayes Sep 26, 2020
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42 changes: 42 additions & 0 deletions pybigquery/__init__.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
from sqlalchemy.dialects.postgresql import array
from sqlalchemy.sql import expression, operators, sqltypes

__all__ = ["array", "struct"]


class STRUCT(sqltypes.Indexable, sqltypes.TypeEngine):
# NOTE: STRUCT names/types aren't currently supported.

__visit_name__ = "STRUCT"

class Comparator(sqltypes.Indexable.Comparator):
def _setup_getitem(self, index):
return operators.getitem, index, self.type

comparator_factory = Comparator


class struct(expression.ClauseList, expression.ColumnElement):
""" Create a BigQuery struct literal from a collection of named expressions/clauses.
"""
# NOTE: Struct subfields aren't currently propagated/validated.

__visit_name__ = "struct"

def __init__(self, clauses, field=None, **kw):
self.field = field
self.type = STRUCT()
super().__init__(*clauses, **kw)

def _bind_param(self, operator, obj, _assume_scalar=False, type_=None):
if operator is operators.getitem:
# TODO:
# - Validate field in clauses (or error if no clauses)
# - If the field is a sub-struct, return with all clauses, otherwise none.
return struct([], field=obj)

def self_group(self, against=None):
if not self.field and against in (operators.getitem,):
return expression.Grouping(self)
else:
return self
16 changes: 16 additions & 0 deletions pybigquery/sqlalchemy_bigquery.py
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,22 @@ def __init__(self, dialect, statement, column_keys=None,
kwargs['compile_kwargs'] = util.immutabledict({'include_table': False})
super(BigQueryCompiler, self).__init__(dialect, statement, column_keys, inline, **kwargs)

def visit_array(self, element, **kw):
return "[%s]" % self.visit_clauselist(element, **kw)

def visit_struct(self, element, within_columns_clause=True, **kw):
if element.field:
return self.preparer.quote_column(element.field)
kw["within_columns_clause"] = True
values = self.visit_clauselist(element, **kw)
return "struct(%s)" % values

def visit_getitem_binary(self, binary, operator, **kw):
return "%s.%s" % (
self.process(binary.left, **kw),
self.process(binary.right, **kw),
)

def visit_select(self, *args, **kwargs):
"""
Use labels for every column.
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