dwsmith1983 commented on code in PR #5654:
URL: https://github.com/apache/datafusion-comet/pull/5654#discussion_r4100201193
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native/core/src/parquet/parquet_support.rs:
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@@ -162,43 +169,330 @@ impl SparkParquetOptions {
/// Spark-compatible cast implementation. Defers to DataFusion's cast where
that is known
/// to be compatible, and returns an error when a not supported and not
DF-compatible cast
-/// is requested.
+/// is requested. Resolves the nested field mapping for this one value; a
per-file caller
+/// resolves once and uses [`spark_parquet_convert_with_mapping`] for every
batch.
pub fn spark_parquet_convert(
arg: ColumnarValue,
data_type: &DataType,
parquet_options: &SparkParquetOptions,
+) -> DataFusionResult<ColumnarValue> {
+ let mapping =
+ resolve_field_mapping(&arg.data_type(), data_type,
parquet_options).map_err(spark_error)?;
+ spark_parquet_convert_with_mapping(arg, data_type, &mapping,
parquet_options)
+}
+
+/// [`spark_parquet_convert`] with a mapping already resolved for the value's
type.
+pub(crate) fn spark_parquet_convert_with_mapping(
+ arg: ColumnarValue,
+ data_type: &DataType,
+ mapping: &FieldMapping,
+ parquet_options: &SparkParquetOptions,
) -> DataFusionResult<ColumnarValue> {
match arg {
- ColumnarValue::Array(array) =>
Ok(ColumnarValue::Array(parquet_convert_array(
+ ColumnarValue::Array(array) => Ok(ColumnarValue::Array(convert_array(
array,
data_type,
+ mapping,
parquet_options,
+ None,
)?)),
ColumnarValue::Scalar(scalar) => {
// Note that normally CAST(scalar) should be fold in Spark JVM
side. However, for
// some cases e.g., scalar subquery, Spark will not fold it, so we
need to handle it
// here.
let array = scalar.to_array()?;
let scalar = ScalarValue::try_from_array(
- &parquet_convert_array(array, data_type, parquet_options)?,
+ &convert_array(array, data_type, mapping, parquet_options,
None)?,
0,
)?;
Ok(ColumnarValue::Scalar(scalar))
}
}
}
-fn parquet_convert_array(
- array: ArrayRef,
+/// Wrap a [`SparkError`] the way every native operator surfaces it to the JVM.
+pub(crate) fn spark_error(error: SparkError) -> DataFusionError {
+ DataFusionError::External(Box::new(error))
+}
+
+/// Outcome of matching one requested id or name against a struct's file
fields: the last
+/// file field that matched and whether more than one did. A plain `Copy`
value, so resolving
+/// a wide struct allocates nothing per id or per name; the matched names are
only gathered
+/// when an ambiguity is reported.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct FieldMatch {
+ pub(crate) index: usize,
+ pub(crate) ambiguous: bool,
+}
+
+impl FieldMatch {
+ pub(crate) fn new(index: usize, ambiguous: bool) -> Self {
+ Self { index, ambiguous }
+ }
+
+ /// The first file field carrying this id or name.
+ pub(crate) fn first(index: usize) -> Self {
+ Self::new(index, false)
+ }
+
+ /// A further file field carrying the same id or name: the later index
wins, as Spark's
+ /// `toMap` does for exact names, and the entry turns ambiguous.
+ pub(crate) fn also(self, index: usize) -> Self {
+ Self::new(index, true)
+ }
+}
+
+/// Record file field `index` under `key`, keeping the entry `Copy`-sized
however many fields
+/// share the key.
+pub(crate) fn record_field_match<K: Hash + Eq>(
+ matches: &mut HashMap<K, FieldMatch>,
+ key: K,
+ index: usize,
+) {
+ matches
+ .entry(key)
+ .and_modify(|m| *m = m.also(index))
+ .or_insert_with(|| FieldMatch::first(index));
+}
+
+/// Names of the fields carrying `id`, for the duplicate-id error message.
Bracketed and
+/// comma-joined the way Spark's `matchIdField` renders the list, so the
message reads
+/// `Found duplicate field(s) "1": [x, y] in id mapping mode` on both sides.
+pub(crate) fn field_names_with_id(fields: &Fields, id: i32) -> String {
+ let names = fields
+ .iter()
+ .filter(|f| field_id(f) == Some(id))
+ .map(|f| f.name().as_str())
+ .collect::<Vec<_>>()
+ .join(", ");
+ format!("[{names}]")
+}
+
+/// Which file field supplies each requested field, resolved once per file and
reused for
+/// every batch. Follows the requested type as Spark's `clipParquetSchema`
does: a struct
+/// lists one source per requested field, a list in any Arrow representation
or a map carries
+/// the mapping of its element or key and value types, and anything else is a
leaf converted
+/// by type.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub(crate) enum FieldMapping {
+ Struct(Vec<StructFieldSource>),
+ List(Box<FieldMapping>),
+ Map(Box<FieldMapping>, Box<FieldMapping>),
+ Leaf,
+}
+
+/// The file field behind one requested struct field.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub(crate) struct StructFieldSource {
+ /// Index of the file field supplying the requested field; `None`
null-fills it.
+ pub(crate) from_index: Option<usize>,
+ /// Mapping of the requested field's own type.
+ pub(crate) nested: FieldMapping,
+}
+
+impl FieldMapping {
+ /// Mapping of a list's element type. A `Leaf` list converts its elements
by type alone,
+ /// as the adapter hands one to every column whose type holds no struct.
+ pub(crate) fn list_element(&self) -> DataFusionResult<&FieldMapping> {
+ match self {
+ FieldMapping::List(inner) => Ok(inner),
+ FieldMapping::Leaf => Ok(&FieldMapping::Leaf),
+ other => Err(DataFusionError::Internal(format!(
+ "list column resolved to a non-list field mapping: {other:?}"
+ ))),
+ }
+ }
+
+ /// Mappings of a map's key and value types; see
[`FieldMapping::list_element`].
+ pub(crate) fn map_entries(&self) -> DataFusionResult<(&FieldMapping,
&FieldMapping)> {
+ match self {
+ FieldMapping::Map(key, value) => Ok((key, value)),
+ FieldMapping::Leaf => Ok((&FieldMapping::Leaf,
&FieldMapping::Leaf)),
+ other => Err(DataFusionError::Internal(format!(
+ "map column resolved to a non-map field mapping: {other:?}"
+ ))),
+ }
+ }
+
+ /// True when every requested field reads the file field at its own
position, so a
+ /// metadata-only relabel of the file array already yields the requested
layout.
+ pub(crate) fn is_positional(&self) -> bool {
+ match self {
+ FieldMapping::Struct(sources) => sources
+ .iter()
+ .enumerate()
+ .all(|(i, s)| s.from_index == Some(i) &&
s.nested.is_positional()),
+ FieldMapping::List(inner) => inner.is_positional(),
+ FieldMapping::Map(key, value) => key.is_positional() &&
value.is_positional(),
+ FieldMapping::Leaf => true,
+ }
+ }
+}
+
+/// The element field of a list in any Arrow representation. One place decides
which types
+/// are lists, so the mapping resolver, the struct-holding walk in the schema
adapter, and
+/// [`convert_array`] agree.
+pub(crate) fn list_element_field(data_type: &DataType) -> Option<&FieldRef> {
+ match data_type {
+ DataType::List(f)
+ | DataType::LargeList(f)
+ | DataType::FixedSizeList(f, _)
+ | DataType::ListView(f)
+ | DataType::LargeListView(f) => Some(f),
+ _ => None,
+ }
+}
+
+/// Resolve how `to_type` reads from `from_type`, recursing through struct,
list, and map
+/// types. Raises the ambiguity Spark reports from `clipParquetGroupFields`
when a requested
+/// id or case-insensitive name matches more than one file field at any level.
+pub(crate) fn resolve_field_mapping(
+ from_type: &DataType,
to_type: &DataType,
parquet_options: &SparkParquetOptions,
-) -> DataFusionResult<ArrayRef> {
- parquet_convert_array_impl(array, to_type, parquet_options, None)
+) -> Result<FieldMapping, SparkError> {
+ use DataType::*;
+ // Dictionary encoding is a physical detail: resolve against the value
type it wraps.
+ // Parquet dictionary encoding only wraps a leaf type, so this mirrors the
adapter's
+ // conversion check and never changes which mapping is built.
+ if let Dictionary(_, value_type) = from_type {
+ return resolve_field_mapping(value_type, to_type, parquet_options);
+ }
+ // The element mapping is the same whichever list representation either
side uses.
+ if let (Some(from_item), Some(to_item)) =
+ (list_element_field(from_type), list_element_field(to_type))
+ {
+ return Ok(FieldMapping::List(Box::new(resolve_field_mapping(
+ from_item.data_type(),
+ to_item.data_type(),
+ parquet_options,
+ )?)));
+ }
+ match (from_type, to_type) {
+ (Struct(from_fields), Struct(to_fields)) => {
+ resolve_struct_mapping(from_fields, to_fields, parquet_options)
+ }
+ (Map(from_entries, from_ordered), Map(to_entries, to_ordered))
+ if from_ordered == to_ordered =>
+ {
+ match (from_entries.data_type(), to_entries.data_type()) {
+ (Struct(from_kv), Struct(to_kv)) if from_kv.len() == 2 &&
to_kv.len() == 2 => {
+ let key = resolve_field_mapping(
+ from_kv[0].data_type(),
+ to_kv[0].data_type(),
+ parquet_options,
+ )?;
+ let value = resolve_field_mapping(
+ from_kv[1].data_type(),
+ to_kv[1].data_type(),
+ parquet_options,
+ )?;
+ Ok(FieldMapping::Map(Box::new(key), Box::new(value)))
+ }
+ _ => Ok(FieldMapping::Leaf),
+ }
+ }
+ _ => Ok(FieldMapping::Leaf),
+ }
}
-fn parquet_convert_array_impl(
+/// Match `to` (requested) struct fields to `from` (file) fields. Mirrors
Spark's
+/// `clipParquetGroupFields`: when the requested struct carries Parquet field
ids anywhere,
+/// id-bearing requested fields match only by id and the rest by name;
otherwise every field
+/// matches by name.
+fn resolve_struct_mapping(
+ from_fields: &Fields,
+ to_fields: &Fields,
+ parquet_options: &SparkParquetOptions,
+) -> Result<FieldMapping, SparkError> {
+ let should_match_by_id =
+ parquet_options.use_field_id && to_fields.iter().any(|f|
field_id(f).is_some());
+
+ let mut id_matches: HashMap<i32, FieldMatch> = HashMap::new();
+ if should_match_by_id {
+ for (i, field) in from_fields.iter().enumerate() {
+ if let Some(id) = field_id(field) {
+ record_field_match(&mut id_matches, id, i);
+ }
+ }
+ }
+
+ // Fold the file and requested names once via the same
`toLowerCase(Locale.ROOT)` the
+ // top-level schema adapter uses, so nested case-insensitive matching
agrees with it.
+ let mut all_names: Vec<&str> = Vec::with_capacity(from_fields.len() +
to_fields.len());
+ all_names.extend(from_fields.iter().map(|f| f.name().as_str()));
+ all_names.extend(to_fields.iter().map(|f| f.name().as_str()));
+ let all_folded = fold_names(&all_names, parquet_options.case_sensitive)
+ .map_err(|e| SparkError::Internal(e.to_string()))?;
+ let (from_folded, to_folded) = all_folded.split_at(from_fields.len());
+
+ let mut name_matches: HashMap<&str, FieldMatch> = HashMap::new();
+ for (i, folded) in from_folded.iter().enumerate() {
+ record_field_match(&mut name_matches, folded.as_str(), i);
+ }
+
+ let mut sources = Vec::with_capacity(to_fields.len());
+ for (to_pos, to_field) in to_fields.iter().enumerate() {
+ let from_index = match (should_match_by_id, field_id(to_field)) {
+ // A missing id match is a missing column, never a name match.
+ (true, Some(id)) => match id_matches.get(&id) {
+ Some(m) if m.ambiguous => {
+ return Err(SparkError::DuplicateFieldByFieldId {
+ required_id: id,
+ matched_fields: field_names_with_id(from_fields, id),
+ });
+ }
+ Some(m) => Some(m.index),
+ None => None,
+ },
+ _ => match name_matches.get(to_folded[to_pos].as_str()) {
+ // Spark's `matchCaseInsensitiveField` raises
`_LEGACY_ERROR_TEMP_2093` for a
+ // requested name that folds onto more than one file field,
whether the siblings
+ // differ by case or are byte-identical. In case-sensitive
mode the fold is
+ // identity, so a collision means byte-identical siblings.
Spark's
+ // `matchCaseSensitiveField` builds its map with `toMap` there
and the last field
+ // wins silently. Comet refuses instead of picking one, with
the error every
+ // other path raises for a duplicate the decoder cannot
represent.
+ Some(m) if m.ambiguous => {
+ let matched: Vec<&str> = from_folded
+ .iter()
+ .zip(from_fields.iter())
+ .filter(|(folded, _)| *folded == &to_folded[to_pos])
+ .map(|(_, f)| f.name().as_str())
+ .collect();
+ if parquet_options.case_sensitive {
+ return
Err(SparkError::Internal(duplicate_parquet_field_message(
Review Comment:
The resolver is back to main's `match_struct_fields` with its
`DataFusionResult`, so a requested nested duplicate name raises the same
execution error main raises, and nothing is cached per field. The only addition
there is the duplicate-id arm, which raises
`SparkError::DuplicateFieldByFieldId` the way the root check does.
`CometNativeReaderSuite` `duplicate Parquet field names fail clearly` now
asserts that the cause chain holds a `CometNativeException` and no
`INTERNAL_ERROR`, so the nested and root paths cannot drift apart again.
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