szehon-ho commented on code in PR #17957:
URL: https://github.com/apache/iceberg/pull/17957#discussion_r4237378072
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spark/v4.2/spark/src/main/java/org/apache/iceberg/spark/source/SparkTable.java:
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@@ -158,6 +173,118 @@ public Set<TableCapability> capabilities() {
return capabilities;
}
+ @Override
+ public boolean supportsColumnChange(TableChange.ColumnChange change) {
+ if (isMapKeyChange(change)) {
+ return false;
+ }
+
+ if (change instanceof TableChange.AddColumn) {
+ TableChange.AddColumn add = (TableChange.AddColumn) change;
+ if (!add.isNullable() || add.defaultValue() != null) {
+ return false;
+ }
+
+ Type type = tryConvert(add.dataType());
+ return type != null && isSupportedAtFormatVersion(type);
+ } else if (change instanceof TableChange.UpdateColumnType) {
+ return supportsTypeUpdate((TableChange.UpdateColumnType) change);
+ } else if (change instanceof TableChange.UpdateColumnNullability) {
+ return supportsNullabilityUpdate((TableChange.UpdateColumnNullability)
change);
+ } else if (change instanceof TableChange.DeleteColumn) {
+ return supportsDeleteColumn((TableChange.DeleteColumn) change);
+ } else {
+ return change instanceof TableChange.RenameColumn
+ || change instanceof TableChange.UpdateColumnComment
+ || change instanceof TableChange.UpdateColumnPosition;
+ }
+ }
+
+ private Set<Integer> mapKeyFieldIds() {
+ if (mapKeyFieldIds == null) {
+ this.mapKeyFieldIds = mapKeyFieldIds(schema);
+ }
+
+ return mapKeyFieldIds;
+ }
+
+ private static Set<Integer> mapKeyFieldIds(Schema schema) {
+ Set<Integer> keyFieldIds = Sets.newHashSet();
+ for (Types.NestedField field :
TypeUtil.indexById(schema.asStruct()).values()) {
+ if (field.type().isMapType()) {
+ Types.MapType map = field.type().asMapType();
+
keyFieldIds.addAll(TypeUtil.indexById(Types.StructType.of(map.fields().get(0))).keySet());
+ }
+ }
+
+ return keyFieldIds;
+ }
+
+ private boolean isMapKeyChange(TableChange.ColumnChange change) {
+ String[] fieldNames = change.fieldNames();
+ int pathLength =
+ change instanceof TableChange.AddColumn ? fieldNames.length - 1 :
fieldNames.length;
+ if (pathLength == 0) {
+ return false;
+ }
+
+ Types.NestedField field =
+ schema.findField(String.join(".", Arrays.copyOf(fieldNames,
pathLength)));
+ return field != null && mapKeyFieldIds().contains(field.fieldId());
+ }
+
+ private boolean supportsTypeUpdate(TableChange.UpdateColumnType update) {
+ Types.NestedField field = schema.findField(String.join(".",
update.fieldNames()));
+ if (field == null) {
+ return false;
+ }
+
+ Type newType = tryConvert(update.newDataType());
+ return newType != null
+ && newType.isPrimitiveType()
+ && TypeUtil.isPromotionAllowed(field.type(), newType.asPrimitiveType())
+ && SparkSchemaUtil.convert(newType).equals(update.newDataType());
+ }
+
+ private boolean
supportsNullabilityUpdate(TableChange.UpdateColumnNullability update) {
+ Types.NestedField field = schema.findField(String.join(".",
update.fieldNames()));
+ return update.nullable() && field != null &&
!containsIdentifierField(field);
+ }
+
+ private boolean supportsDeleteColumn(TableChange.DeleteColumn delete) {
+ Types.NestedField field = schema.findField(String.join(".",
delete.fieldNames()));
+ if (field == null) {
+ return false;
+ }
+
+ // Iceberg rejects dropping an identifier field or a field whose subtree
contains one
+ return !containsIdentifierField(field);
Review Comment:
Nit: Could we return false when deleting a list element or map value itself,
and add unit coverage? For example, `items.element` and `m.value` currently
return true, but `SchemaUpdate.apply()` rejects both. Spark 4.2 only generates
additions and type updates today, so this is a hook-contract edge case.
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