englefly commented on code in PR #68314:
URL: https://github.com/apache/doris/pull/68314#discussion_r4069199124
##########
fe/fe-core/src/test/java/org/apache/doris/nereids/rules/rewrite/PruneNestedColumnTest.java:
##########
@@ -1791,4 +2000,152 @@ private void assertVariantSubColumnSlotCount(String
sql, List<String> expectedSu
Assertions.assertEquals(expectedCount, actualCount);
}
+
+ /**
+ * Verify that synthetic nullability from outer join does NOT cause META
NULL paths
+ * on physically NOT NULL columns. When a NOT NULL struct sits on the
nullable side
+ * of a LEFT JOIN, the slot's {@code nullable()} returns true (from outer
join
+ * semantics), but {@code getOriginalColumn().isAllowNull()} returns false
+ * (physical column has no null map). The fix in
AccessPathExpressionCollector
+ * should suppress the {@code [s, NULL]} META path in this case.
+ */
+ @Test
+ public void testNotNullStructOnOuterJoinNullableSide() throws Exception {
+ // driving_tbl LEFT JOIN not_null_struct_tbl:
+ // not_null_struct_tbl.s is NOT NULL in the schema, but after LEFT
JOIN the
+ // slot becomes nullable (right side of LEFT JOIN →
withNullable(true)).
+ // element_at(s, 'f') IS NULL in WHERE:
+ // - s.nullable() = true (synthetic, from outer join)
+ // - s.getOriginalColumn().isAllowNull() = false (physical, no
null map)
+ // Expected: [s, f] DATA is present (field is read for IS NULL
evaluation),
+ // [s, NULL] META must NOT be present (no physical null
map).
+ assertAllAccessPathsContain(
+ "select driving_tbl.id from driving_tbl"
+ + " left join not_null_struct_tbl"
+ + " on driving_tbl.id = not_null_struct_tbl.id"
+ + " where element_at(not_null_struct_tbl.s, 'f') is
null",
+ // expect-contain: field is read (DATA path)
+ ImmutableList.of(path("s", "f")),
Review Comment:
I checked this against the real plan data before changing anything, and the
expectation is correct as written: with `path("s", "f")` the test passes
(`./run-fe-ut.sh --run
org.apache.doris.nereids.rules.rewrite.PruneNestedColumnTest` → 64 tests, 0
failures). When I first applied the suggested `metaPath("s", "f", "NULL")` the
assertion printed the complete collected set:
```
allAccessPaths=[TColumnAccessPath(type:DATA,
data_access_path:TDataAccessPath(path:[s, f]), version:1)]
```
So no field-level META path is produced for this query — the field ends up
materialized as data because the `IS NULL` is evaluated above the LEFT JOIN
rather than as a scan predicate. (The field-level META form does show up in
`testNullableFieldPreservedWithSiblingProjection`, where the null check sits
directly on the scan of a nullable struct column.)
The underlying point is fair though: this SQL never produces a root `[s,
NULL]` candidate, so the negative assertion was not really exercising the
suppression. I added `testNotNullStructIsNullOnOuterJoinNullableSide` — `select
not_null_struct_tbl.s is null from driving_tbl left join not_null_struct_tbl
...` — a direct null check on the physically NOT NULL struct, which is the
shape that reaches the `hasPhysicalNullMap` guard in `visitSlotReference`. It
asserts that the struct slot is still present in the plan and that no `[s,
NULL]` META path is emitted. It is kept in the SELECT list on purpose: in a
WHERE clause the null-rejecting predicate lets the optimizer rewrite the LEFT
JOIN into an anti join, which drops the struct from the plan and would make the
assertion vacuous again.
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