Github user bitblender commented on a diff in the pull request:
https://github.com/apache/drill/pull/837#discussion_r120198724
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/record/BatchSchema.java ---
@@ -157,4 +158,26 @@ private boolean majorTypeEqual(MajorType t1, MajorType
t2) {
return true;
}
+ /**
+ * Merge two schema to produce a new, merged schema. The caller is
responsible
+ * for ensuring that column names are unique. The order of the fields in
the
+ * new schema is the same as that of this schema, with the other
schema's fields
+ * appended in the order defined in the other schema. The resulting
selection
+ * vector mode is the same as this schema. (That is, this schema is
assumed to
+ * be the main part of the batch, possibly with a selection vector, with
the
+ * other schema representing additional, new columns.)
+ * @param otherSchema the schema to merge with this one
+ * @return the new, merged, schema
+ */
+
+ public BatchSchema merge(BatchSchema otherSchema) {
+ if (otherSchema.selectionVectorMode != SelectionVectorMode.NONE &&
+ selectionVectorMode != otherSchema.selectionVectorMode) {
+ throw new IllegalArgumentException("Left schema must carry the
selection vector mode");
+ }
+ List<MaterializedField> mergedFields = new ArrayList<>();
--- End diff --
List<MaterializedField> mergedFields = new ArrayList(this.fields.size() +
otherSchema.fields.size()) would avoid having to potentially grow the ArrayList
twice.
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