Liu created FLINK-39195:
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Summary: ObjectPath should implement Comparable
Key: FLINK-39195
URL: https://issues.apache.org/jira/browse/FLINK-39195
Project: Flink
Issue Type: Improvement
Components: Table SQL / API
Reporter: Liu
h2. Motivation
ObjectPath is a core value object in Flink's Table/SQL API that represents a
database name and object (table/view/function) name combo in a catalog. It
already
implements equals() and hashCode(), and is widely used as a Map key throughout
the
codebase (e.g., GenericInMemoryCatalog has 8 Map<ObjectPath, ...> fields).
However, ObjectPath does not implement Comparable<ObjectPath>, which causes
issues
in several scenarios:
1. *Jackson JSON Serialization Failure*: Flink Planner's CompiledPlanSerdeUtil
enables SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS (line 110), which
requires
Map keys to implement Comparable. Any object containing Map<ObjectPath, ...>
fields
that goes through compilePlan().toJson() will fail with:
\{code}
java.lang.ClassCastException: class
org.apache.flink.table.catalog.ObjectPath
cannot be cast to class java.lang.Comparable
\{code}
2. *Value Object Completeness*: As a widely-used identifier class, ObjectPath
has a
natural ordering semantic (databaseName + objectName, both Strings).
Implementing
Comparable is a standard practice for value objects in Java (similar to
java.io.File,
java.net.URI, java.nio.file.Path).
3. *Usability*: Users cannot currently use ObjectPath with TreeMap, TreeSet, or
Collections.sort(), which limits its utility in scenarios requiring sorted
output
(logging, debugging, deterministic serialization).
h2. Proposed Change
Add Comparable<ObjectPath> to ObjectPath:
{code:java}
@PublicEvolving
public class ObjectPath implements Serializable, Comparable<ObjectPath> {
// ... existing code unchanged ...
@Override
public int compareTo(ObjectPath other) {
int cmp = this.databaseName.compareTo(other.databaseName);
if (cmp != 0) {
return cmp;
}
return this.objectName.compareTo(other.objectName);
}
}
{code}
The comparison uses lexicographic ordering: first by databaseName, then by
objectName.
This is consistent with the format returned by getFullName()
("databaseName.objectName").
h2. Compatibility
* *API Compatible*: Only adds a new interface implementation; no existing
method
signatures are changed.
* *Behavior Compatible*: equals/hashCode behavior is unchanged.
* *Binary Compatible*: Adding a new method does not break existing bytecode.
h2. Impact
* Fixes Jackson serialization failure for any Map<ObjectPath, ...> in the
Compiled
Plan JSON serialization path.
* Enables ObjectPath to be used with TreeMap/TreeSet/sorted collections.
* Zero risk to existing functionality.
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