huaxingao commented on code in PR #18885:
URL: https://github.com/apache/iceberg/pull/18885#discussion_r4575232373
##########
core/src/main/java/org/apache/iceberg/SchemaUpdate.java:
##########
@@ -506,22 +506,33 @@ private TableMetadata
applyChangesToMetadata(TableMetadata metadata) {
// Transform the metrics if they exist
if (base != null && base.properties() != null) {
- Schema newSchema = newMetadata.schema();
- List<String> deletedColumns =
-
deletes.stream().map(schema::findColumnName).collect(Collectors.toList());
- Map<String, String> renamedColumns =
- updates.keySet().stream()
- .filter(id -> !addedNameToId.containsValue(id)) // remove added
columns
- .filter(id ->
!schema.findColumnName(id).equals(newSchema.findColumnName(id)))
- .collect(Collectors.toMap(schema::findColumnName,
newSchema::findColumnName));
+ Map<Integer, String> newIdToName = newMetadata.schema().idToName();
+ List<String> deletedColumns = Lists.newArrayList();
+ Map<String, String> renamedColumns = Maps.newHashMap();
+ // compare all fields so that nested fields of a deleted or renamed
struct are included
+ schema
+ .idToName()
Review Comment:
+1, this sounds simpler. Schema lookups only happen for keys with a column
property prefix, and since the key already names the column, nested fields and
renamed/dropped parents are handled directly.
One small thing I noticed while looking into the cost: `Schema` already
builds `idToName` in its constructor (for `highestFieldId`), so
`idToName()`/`findColumnName()` are just lookups and don't trigger any new
schema indexing.
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