jose-torres commented on code in PR #58645:
URL: https://github.com/apache/spark/pull/58645#discussion_r4084944608
##########
sql/pipelines/src/main/scala/org/apache/spark/sql/pipelines/autocdc/Scd2VersionMap.scala:
##########
@@ -77,15 +83,69 @@ private[pipelines] object Scd2VersionMap {
/**
* Schema of the version map: `Map(String, Boolean)`.
*
- * Keys are dot-delimited paths to *leaf* columns that received a null value
in their
- * corresponding upsert event (e.g. `"address.city"`, `` "`has space`.city"
``). Paths
- * must be formatted by
[[org.apache.spark.sql.catalyst.util.QuotingUtils.quoted]] to
- * ensure segments that need quoting are back-tick escaped.
+ * Keys are compact JSON arrays of the name parts of *leaf* columns that
received a null
+ * value in their upsert event (e.g. `["address","city"]`). Keeping
+ * name parts separate distinguishes a nested path from a column whose name
contains dots
+ * and keeps persisted keys independent of SQL identifier quoting rules.
Name parts use the
+ * persisted target schema's canonical spelling.
*
- * Values indicate authorship. I.e, `true` => authored-null, `false` =>
unauthored-null.
+ * Values indicate authorship: `true` means authored-null, `false` means
unauthored-null.
+ * Null values never appear in the map.
*
* Lack of entry in the map for a null-valued leaf column implies the column
was
* schema-evolved with an unauthored-null.
*/
def mapType: MapType = MapType(StringType, BooleanType, valueContainsNull =
false)
+
+ /** Encodes a leaf path as the compact JSON string persisted as its version
map key. */
Review Comment:
Makes sense. My instinct is that it would also be a risk for the canonical
form here to diverge from the standard serialization without some sort of test
failure. Maybe it's enough for the test assertions to capture the literal
string.
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