shirshanka commented on a change in pull request #2806: GOBBLIN-957: Add
recursion eliminating converter for Avro
URL: https://github.com/apache/incubator-gobblin/pull/2806#discussion_r346610906
##########
File path: gobblin-utility/src/main/java/org/apache/gobblin/util/AvroUtils.java
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@@ -935,4 +941,141 @@ public static Schema overrideNameAndNamespace(Schema
input, String nameOverride,
return newSchema;
}
+ @Builder
+ @ToString
+ public static class SchemaEntry {
+ @Getter
+ final String fieldName;
+ final Schema schema;
+ String fullyQualifiedType() {
+ return schema.getFullName();
+ }
+ }
+
+ /**
+ * Drop recursive fields from a Schema. Recursive fields are fields that
refer to types that are part of the
+ * parent tree.
+ * e.g. consider this Schema for a User
+ * {
+ * "type": "record",
+ * "name": "User",
+ * "fields": [
+ * {"name": "name", "type": "string",
+ * {"name": "friend", "type": "User"}
+ * ]
+ * }
+ * the friend field is a recursive field. After recursion has been
eliminated we expect the output Schema to look like
+ * {
+ * "type": "record",
+ * "name": "User",
+ * "fields": [
+ * {"name": "name", "type": "string"}
+ * ]
+ * }
+ *
+ * @param schema
+ * @return a Pair of (The transformed schema with recursion eliminated, A
list of @link{SchemaEntry} objects which
+ * represent the fields that were removed from the original schema)
+ */
+ public static Pair<Schema, List<SchemaEntry>> dropRecursiveFields(Schema
schema) {
+ List<SchemaEntry> recursiveFields = new ArrayList<>();
+ return new Pair(dropRecursive(new SchemaEntry(null, schema),
Collections.EMPTY_LIST, recursiveFields),
+ recursiveFields);
+ }
+
+ /**
+ * Inner recursive method called by {@link #dropRecursiveFields(Schema)}
+ * @param schemaEntry
+ * @param parents
+ * @param fieldsWithRecursion
+ * @return the transformed Schema, null if schema is recursive w.r.t parent
schema traversed so far
+ */
+ private static Schema dropRecursive(SchemaEntry schemaEntry,
List<SchemaEntry> parents, List<SchemaEntry> fieldsWithRecursion) {
+ Schema schema = schemaEntry.schema;
+ // ignore primitive fields
+ switch (schema.getType()) {
+ case UNION:{
+ List<Schema> unionTypes = schema.getTypes();
+ List<Schema> copiedUnionTypes = new ArrayList<Schema>();
+ for (Schema unionSchema: unionTypes) {
+ SchemaEntry unionSchemaEntry = new SchemaEntry(
+ schemaEntry.fieldName, unionSchema);
+ copiedUnionTypes.add(dropRecursive(unionSchemaEntry, parents,
fieldsWithRecursion));
+ }
+ if (copiedUnionTypes.stream().anyMatch(x -> x == null)) {
+ // one or more types in the union are referring to a parent type
(directly recursive),
+ // entire union must be dropped
+ return null;
+ }
+ else {
+ Schema copySchema = Schema.createUnion(copiedUnionTypes);
+ copyProperties(schema, copySchema);
+ return copySchema;
+ }
+ }
+ case RECORD:{
+ // check if the type of this schema matches any in the parents list
+ if (parents.stream().anyMatch(parent ->
parent.fullyQualifiedType().equals(schemaEntry.fullyQualifiedType()))) {
+ fieldsWithRecursion.add(schemaEntry);
+ return null;
+ }
+ List<SchemaEntry> newParents = new ArrayList<>(parents);
+ newParents.add(schemaEntry);
+ List<Schema.Field> copiedSchemaFields = new ArrayList<>();
+ for (Schema.Field field: schema.getFields()) {
+ String fieldName = schemaEntry.fieldName != null ?
schemaEntry.fieldName + "." + field.name() : field.name();
+ SchemaEntry fieldSchemaEntry = new SchemaEntry(fieldName,
field.schema());
+ Schema copiedFieldSchema = dropRecursive(fieldSchemaEntry,
newParents, fieldsWithRecursion);
+ if (copiedFieldSchema == null) {
+ } else {
+ Schema.Field copiedField =
+ new Schema.Field(field.name(), copiedFieldSchema, field.doc(),
field.defaultValue(), field.order());
+ copyFieldProperties(field, copiedField);
+ copiedSchemaFields.add(copiedField);
+ }
+ }
+ if (copiedSchemaFields.size() > 0) {
+ Schema copiedRecord = Schema.createRecord(schema.getName(),
schema.getDoc(), schema.getNamespace(),
+ schema.isError());
+ copiedRecord.setFields(copiedSchemaFields);
+ copyProperties(schema, copiedRecord);
+ return copiedRecord;
+ } else {
+ return null;
+ }
+ }
+ case ARRAY: {
+ Schema itemSchema = schema.getElementType();
+ SchemaEntry itemSchemaEntry = new SchemaEntry(schemaEntry.fieldName,
itemSchema);
+ Schema copiedItemSchema = dropRecursive(itemSchemaEntry, parents,
fieldsWithRecursion);
+ if (copiedItemSchema == null) {
+ return null;
+ } else {
+ Schema copiedArraySchema = Schema.createArray(copiedItemSchema);
+ copyProperties(schema, copiedArraySchema);
+ return copiedArraySchema;
+ }
+ }
+ case MAP: {
+ Schema valueSchema = schema.getValueType();
+ SchemaEntry valueSchemaEntry = new SchemaEntry(schemaEntry.fieldName,
valueSchema);
+ Schema copiedValueSchema = dropRecursive(valueSchemaEntry, parents,
fieldsWithRecursion);
+ if (copiedValueSchema == null) {
+ return null;
+ } else {
+ Schema copiedMapSchema = Schema.createMap(copiedValueSchema);
+ copyProperties(schema, copiedMapSchema);
+ return copiedMapSchema;
+ }
+ }
+ default: {
+ return schema;
+ }
+ }
+ }
+
+ private static void copyFieldProperties(Schema.Field field, Schema.Field
copiedField) {
Review comment:
those are not copyable... they need to be provided when you create the
field.
You'll see that in the code above where I do:
Schema.Field copiedField =
new Schema.Field(field.name(), copiedFieldSchema,
field.doc(), field.defaultValue(), field.order());
Will add javadoc on this method to make this clearer.
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