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synced 2026-05-06 07:56:41 -04:00
Factor out the column resolution into helper func.
This commit is contained in:
Charles Leifer
@@ -8016,6 +8016,97 @@ def safe_python_value(conv_func):
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return validate
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def _resolve_model_columns(cursor, model, select):
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"""Resolve cursor columns against a model's selected nodes.
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Returns ``(columns, fields, converters, no_convert, convert)``:
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``columns`` and ``fields`` are aligned per-column lists, ``converters``
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is a per-column ``python_value`` callable or ``None``, and
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``no_convert``/``convert`` are the index partitions of ``converters``.
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"""
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combined = model._meta.combined
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table = model._meta.table
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description = cursor.description
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ncols = len(description)
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columns = []
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converters = [None] * ncols
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fields = [None] * ncols
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for idx, description_item in enumerate(description):
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column = orig_column = description_item[0]
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# Try to clean-up messy column descriptions when people do not
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# provide an alias. The idea is that we take something like:
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# SUM("t1"."price") -> "price") -> price
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dot_index = column.rfind('.')
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if dot_index != -1:
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column = column[dot_index + 1:]
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column = column.strip('()"`')
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columns.append(column)
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# Now we'll see what they selected and see if we can improve the
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# column-name being returned - e.g. by mapping it to the selected
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# field's name.
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try:
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raw_node = select[idx]
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except IndexError:
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if column in combined:
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raw_node = node = combined[column]
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else:
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continue
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else:
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node = raw_node.unwrap()
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# If this column was given an alias, then we will use whatever
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# alias was returned by the cursor.
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is_alias = raw_node.is_alias()
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if is_alias:
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columns[idx] = orig_column
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# Heuristics used to attempt to get the field associated with a
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# given SELECT column, so that we can accurately convert the value
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# returned by the database-cursor into a Python object.
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if isinstance(node, Field):
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if raw_node._coerce:
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converters[idx] = node.python_value
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fields[idx] = node
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if not is_alias:
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columns[idx] = node.name
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elif isinstance(node, ColumnBase) and raw_node._converter:
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converters[idx] = raw_node._converter
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elif isinstance(node, Function) and node._coerce:
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if node._python_value is not None:
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converters[idx] = node._python_value
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elif node.arguments and isinstance(node.arguments[0], Node):
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# If the first argument is a field or references a column
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# on a Model, try using that field's conversion function.
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# This usually works, but we use "safe_python_value()" so
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# that if a TypeError or ValueError occurs during
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# conversion we can just fall-back to the raw cursor value.
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first = node.arguments[0].unwrap()
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if isinstance(first, Entity):
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path = first._path[-1] # Try to look-up by name.
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first = combined.get(path)
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if isinstance(first, Field):
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converters[idx] = safe_python_value(first.python_value)
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elif column in combined:
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if node._coerce:
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converters[idx] = combined[column].python_value
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if isinstance(node, Column) and node.source == table:
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fields[idx] = combined[column]
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no_convert = []
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convert = []
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for i in range(ncols):
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if converters[i] is not None:
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convert.append(i)
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else:
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no_convert.append(i)
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return columns, fields, converters, no_convert, convert
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class BaseModelCursorWrapper(DictCursorWrapper):
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def __init__(self, cursor, model, columns):
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super(BaseModelCursorWrapper, self).__init__(cursor)
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@@ -8023,85 +8114,10 @@ class BaseModelCursorWrapper(DictCursorWrapper):
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self.select = columns or []
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def initialize(self):
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combined = self.model._meta.combined
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table = self.model._meta.table
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description = self.cursor.description
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self.ncols = len(self.cursor.description)
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self.columns = []
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self.converters = converters = [None] * self.ncols
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self.fields = fields = [None] * self.ncols
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for idx, description_item in enumerate(description):
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column = orig_column = description_item[0]
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# Try to clean-up messy column descriptions when people do not
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# provide an alias. The idea is that we take something like:
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# SUM("t1"."price") -> "price") -> price
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dot_index = column.rfind('.')
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if dot_index != -1:
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column = column[dot_index + 1:]
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column = column.strip('()"`')
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self.columns.append(column)
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# Now we'll see what they selected and see if we can improve the
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# column-name being returned - e.g. by mapping it to the selected
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# field's name.
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try:
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raw_node = self.select[idx]
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except IndexError:
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if column in combined:
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raw_node = node = combined[column]
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else:
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continue
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else:
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node = raw_node.unwrap()
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# If this column was given an alias, then we will use whatever
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# alias was returned by the cursor.
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is_alias = raw_node.is_alias()
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if is_alias:
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self.columns[idx] = orig_column
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# Heuristics used to attempt to get the field associated with a
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# given SELECT column, so that we can accurately convert the value
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# returned by the database-cursor into a Python object.
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if isinstance(node, Field):
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if raw_node._coerce:
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converters[idx] = node.python_value
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fields[idx] = node
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if not is_alias:
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self.columns[idx] = node.name
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elif isinstance(node, ColumnBase) and raw_node._converter:
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converters[idx] = raw_node._converter
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elif isinstance(node, Function) and node._coerce:
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if node._python_value is not None:
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converters[idx] = node._python_value
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elif node.arguments and isinstance(node.arguments[0], Node):
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# If the first argument is a field or references a column
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# on a Model, try using that field's conversion function.
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# This usually works, but we use "safe_python_value()" so
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# that if a TypeError or ValueError occurs during
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# conversion we can just fall-back to the raw cursor value.
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first = node.arguments[0].unwrap()
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if isinstance(first, Entity):
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path = first._path[-1] # Try to look-up by name.
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first = combined.get(path)
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if isinstance(first, Field):
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converters[idx] = safe_python_value(first.python_value)
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elif column in combined:
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if node._coerce:
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converters[idx] = combined[column].python_value
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if isinstance(node, Column) and node.source == table:
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fields[idx] = combined[column]
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self.no_convert = []
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self.convert = []
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for i in range(self.ncols):
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if converters[i] is not None:
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self.convert.append(i)
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else:
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self.no_convert.append(i)
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(self.columns, self.fields, self.converters,
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self.no_convert, self.convert) = _resolve_model_columns(
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self.cursor, self.model, self.select)
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self.ncols = len(self.columns)
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def process_row(self, row):
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raise NotImplementedError
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