voonhous commented on code in PR #19691:
URL: https://github.com/apache/hudi/pull/19691#discussion_r3838207600
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hudi-spark-datasource/hudi-spark/src/test/scala/org/apache/spark/sql/hudi/dml/schema/TestVariantDataType.scala:
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@@ -977,6 +978,78 @@ class TestVariantDataType extends HoodieSparkSqlTestBase {
}
}
+ test("Test Spark 3.x schema-on-read reads of a variant table with a
committed internal schema") {
+ // #18021: hoodie.schema.on.read.enable resolves the schema through the
InternalSchema round
+ // trip, whose sentinel detection restores the VARIANT logical type - the
exact input
+ // HoodieSparkSchemaConverters rejects on Spark 3.x. Verified 2026-08-20:
every leg fails
+ // LOUDLY with the same actionable error as the plain auto-resolve path;
there is no silent
+ // wrong data and no obscure secondary failure. Notably that includes the
documented
+ // struct-DDL compat mode, which works on this same table with the conf
off (pinned below)
+ // but breaks once it is on, because internal-schema resolution overrides
the user's DDL.
+ // Real support is #18285; until then Spark 3.x compat-mode readers must
keep
Review Comment:
Right - `DefaultSource` sets `userSchema = None` under `isUsingHiveCatalog`,
so the struct DDL never reaches the relation and HMS throws with the conf off
too. Scoped the note in 88545658: keeping the conf off is necessary but only
sufficient off a Hive catalog, and this test runs on the in-memory catalog so
it pins that half only. HMS stays out of scope for the pin.
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