rdblue commented on code in PR #17433:
URL: https://github.com/apache/iceberg/pull/17433#discussion_r3779955909
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core/src/main/java/org/apache/iceberg/V4ManifestReader.java:
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@@ -292,17 +338,70 @@ private Schema readSchema(boolean hasPartitionFilter) {
if (columns != null) {
Schema selected =
caseSensitive ? fullSchema.select(columns) :
fullSchema.caseInsensitiveSelect(columns);
- return addRequiredColumns(selected, hasPartitionFilter);
+ return addRequiredColumns(fullSchema, selected, requiredStatsType,
hasPartitionFilter);
}
if (requestedProjection != null) {
- return addRequiredColumns(requestedProjection, hasPartitionFilter);
+ return addRequiredColumns(
+ fullSchema, requestedProjection, requiredStatsType,
hasPartitionFilter);
}
return fullSchema;
}
- private Schema addRequiredColumns(Schema projection, boolean
hasPartitionFilter) {
+ /** Returns the schema of everything this reader may read, including
content stats. */
+ private Schema fullSchema(Types.StructType contentStatsType) {
+ Schema base = TrackedFile.schema(unionPartitionType, contentStatsType);
+ if (contentStatsType.fields().isEmpty()) {
+ // schema uses the unknown type for empty stats, which cannot be
paired with the stats
+ // struct in the manifest, so drop the field instead of reading it as
unknown
+ base = TypeUtil.selectNot(base,
ImmutableSet.of(TrackedFile.CONTENT_STATS_ID));
+ }
+
+ // the read schema carries row_position (via BASE_TYPE) so the reader
can fill manifestPos
+ return TypeUtil.replaceFieldTypes(
+ base, ImmutableMap.of(TrackedFile.TRACKING.fieldId(),
TrackingStruct.BASE_TYPE));
+ }
+
+ /**
+ * Returns the stats type to read, which is empty when no stats are needed.
+ *
+ * <p>Stats for every field are read unless the caller narrows them with
{@link
+ * #forScanPlanning()} or {@link #projectStats(Iterable)}, because copying
entries into a new
+ * manifest needs all of them. A {@link #filter(Expression) filter}
therefore never narrows the
+ * stats that are read; it only widens a set the caller has already
narrowed.
+ */
+ private Types.StructType contentStatsType(Types.StructType
requiredStatsType) {
+ if (scanPlanning || statsProjectionForFieldIds != null) {
+ return requiredStatsType;
+ }
+
+ return StatsUtil.statsReadSchema(
+ tableSchema, TypeUtil.indexById(tableSchema.asStruct()).keySet());
+ }
+
+ /** Returns the table field IDs whose stats are read regardless of the
projection. */
+ private Set<Integer> requiredStatsProjectionForFieldIds() {
Review Comment:
This method name is very similar to the `statsProjectionForFieldIds` field,
but it returns something different -- the union of IDs that were in a filter or
requested by a user. Adding "required" doesn't imply that the user-driven field
is unioned with IDs determined by other internal state.
Another issue is that this could be static and instead it is private and
relies on fields the caller doesn't see.
I'd prefer to make this a static util and rename it:
`requiredStatsFieldIds(requestedStatsFieldIds, rowFilter)`. That way it is
clear that the required fields are based on the requested fields, plus fields
from the row filter.
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