Fokko commented on code in PR #4685:
URL: https://github.com/apache/iceberg/pull/4685#discussion_r871846400
##########
python/src/iceberg/schema.py:
##########
@@ -497,31 +530,78 @@ def index_name_by_id(schema_or_type) -> Dict[int, str]:
return indexer.by_id()
-class _BuildPositionAccessors(SchemaVisitor[Dict[int, "Accessor"]]):
- """A schema visitor for generating a field ID to accessor index"""
+Position = int
- def __init__(self) -> None:
- self._index: Dict[int, Accessor] = {}
- def schema(self, schema, result: Dict[int, Accessor]) -> Dict[int,
Accessor]:
- return self._index
+class _BuildPositionAccessors(SchemaVisitor[Dict[Position, Accessor]]):
+ """A schema visitor for generating a field ID to accessor index
- def struct(self, struct, result: List[Dict[int, Accessor]]) -> Dict[int,
Accessor]:
- # TODO: Populate the `self._index` dictionary where the key is the
field ID and the value is an accessor for that field.
- # The equivalent java logic can be found here:
https://github.com/apache/iceberg/blob/master/api/src/main/java/org/apache/iceberg/Accessors.java#L213-L230
- return self._index
+ Example:
+ >>> from iceberg.schema import Schema
+ >>> from iceberg.types import *
+ >>> schema = Schema(
+ ... NestedField(field_id=2, name="id", field_type=IntegerType(),
is_optional=False),
+ ... NestedField(field_id=1, name="data", field_type=StringType(),
is_optional=True),
+ ... NestedField(
+ ... field_id=3,
+ ... name="location",
+ ... field_type=StructType(
+ ... NestedField(field_id=5, name="latitude",
field_type=FloatType(), is_optional=False),
+ ... NestedField(field_id=6, name="longitude",
field_type=FloatType(), is_optional=False),
+ ... ),
+ ... is_optional=True,
+ ... ),
+ ... schema_id=1,
+ ... identifier_field_ids=[1],
+ ... )
+ >>> result = build_position_accessors(schema)
+ >>> expected = {
+ ... 2: Accessor(position=0, inner=None),
+ ... 1: Accessor(position=1, inner=None),
+ ... 5: Accessor(position=2, inner=Accessor(position=0,
inner=None)),
+ ... 6: Accessor(position=2, inner=Accessor(position=1,
inner=None)),
+ ... }
+ >>> result == expected
+ True
+ """
- def field(self, field: NestedField, result: Dict[int, Accessor]) ->
Dict[int, Accessor]:
- return self._index
+ @staticmethod
+ def _wrap_leaves(result: Dict[Position, Accessor], position: Position = 0)
-> Dict[Position, Accessor]:
+ return {field_id: Accessor(position, inner=inner) for field_id, inner
in result.items()}
- def list(self, list_type: ListType, result: Dict[int, Accessor]) ->
Dict[int, Accessor]:
- return self._index
+ def schema(self, schema: Schema, result: Dict[Position, Accessor]) ->
Dict[Position, Accessor]:
+ return result
- def map(self, map_type: MapType, key_result: Dict[int, Accessor],
value_result: Dict[int, Accessor]) -> Dict[int, Accessor]:
- return self._index
+ def struct(self, struct: StructType, field_results: List[Dict[Position,
Accessor]]) -> Dict[Position, Accessor]:
+ result = {}
- def primitive(self, primitive: PrimitiveType) -> Dict[int, Accessor]:
- return self._index
+ for position, field in enumerate(struct.fields):
+ if field_results[position]:
Review Comment:
This is Python:
```python
➜ python3
Python 3.9.12 (main, Mar 26 2022, 15:44:31)
[Clang 13.1.6 (clang-1316.0.21.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> if {}:
... print('if')
... else:
... print('else')
...
else
```
> I think that is correct (if `{}` uses the else branch) but I don't think
there's a need to return accessors for fields inside maps or lists because we
don't really know how to handle repeated elements. We could extend this later
so that a repeated layer returns a tuple of the values, but right now we don't
really need that.
So you only want to support structs (including nested structs), but discard
support for lists and maps?
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