rdblue commented on a change in pull request #2952:
URL: https://github.com/apache/iceberg/pull/2952#discussion_r693534089
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File path: api/src/main/java/org/apache/iceberg/types/TypeUtil.java
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@@ -42,6 +42,45 @@
private TypeUtil() {
}
+ /**
+ * Project extracts particular fields from a schema. Unlike
+ * {@link TypeUtil#select(Schema, Set)}, project will pick out only
+ * the fields enumerated, this means no sub fields will be selected
+ * unless they are explicitly requested.
+ * @param schema to project fields from
+ * @param fieldIds list of explicit fields to extract
+ * @return the schema with all fields fields not selected removed
+ */
+ public static Schema project(Schema schema, Set<Integer> fieldIds) {
+ Preconditions.checkNotNull(schema, "Schema cannot be null");
+
+ Types.StructType result = project(schema.asStruct(), fieldIds);
+ if (Objects.equals(schema.asStruct(), result)) {
+ return schema;
+ } else if (result != null) {
+ if (schema.getAliases() != null) {
+ return new Schema(result.fields(), schema.getAliases());
+ } else {
+ return new Schema(result.fields());
+ }
+ }
+ return new Schema();
+ }
+
+ public static Types.StructType project(Types.StructType struct, Set<Integer>
fieldIds) {
+ Preconditions.checkNotNull(struct, "Struct cannot be null");
+ Preconditions.checkNotNull(fieldIds, "Field ids cannot be null");
+
+ Type result = visit(struct, new PruneColumns(fieldIds, false));
+ if (struct == result) {
Review comment:
Should this be `.equals`? We used to use identity, but there are build
warnings so now we just use `equals`.
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