zuozhiw commented on code in PR #4014:
URL: https://github.com/apache/texera/pull/4014#discussion_r2485563501
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common/workflow-operator/src/main/scala/org/apache/amber/operator/sort/StableMergeSortOpExec.scala:
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@@ -225,9 +225,21 @@ class StableMergeSortOpExec(descString: String) extends
OperatorExecutor {
/**
* Compare two non-null values using their attribute type.
*
- * For DOUBLE:
- * - Uses java.lang.Double.compare (orders -Inf < ... < +Inf < NaN).
- * - Callers if desired should define how NaN interacts with ASC/DESC and
null policy.
+ * Type semantics:
+ * - INTEGER, LONG: numeric ascending via Java primitive compares.
+ * - DOUBLE: java.lang.Double.compare (orders -Inf < ... < +Inf < NaN).
+ * - BOOLEAN: false < true.
+ * - TIMESTAMP: java.sql.Timestamp#compareTo.
+ * - STRING: String#compareTo (UTF-16, lexicographic).
+ * - BINARY: unsigned lexicographic order over byte arrays:
+ * - Compare byte-by-byte treating each as 0..255 (mask 0xff).
+ * - The first differing byte decides the order.
+ * - If all compared bytes are equal, the shorter array sorts first.
+ * - Example: [] < [0x00] < [0x00,0x00] < [0x00,0x01] < [0x7F] <
[0x80] < [0xFF].
+ *
+ * Implementation note:
+ * - BINARY uses [[java.util.Arrays.compareUnsigned]] (JDK 9+). For JDK
8,
+ * replace with a manual unsigned lexicographic comparator.
Review Comment:
probably no need to mention jdk8 in comment, do we have jdk8 compat
requirements?
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