englefly commented on code in PR #69340:
URL: https://github.com/apache/doris/pull/69340#discussion_r4332426708
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/AccessPathExpressionCollector.java:
##########
@@ -576,11 +576,32 @@ public Void visitArrayMap(ArrayMap arrayMap,
CollectorContext context) {
Expression argument = arrayMap.getArgument(0);
if ((argument instanceof Lambda)) {
- return collectArrayPathInLambda((Lambda) argument, context);
+ Lambda lambda = (Lambda) argument;
+ return collectArrayMapPathInLambda(lambda, context);
}
return visit(arrayMap, context);
}
+ private Void collectArrayMapPathInLambda(Lambda lambda, CollectorContext
context) {
+ if (context.getType() == ColumnAccessPathType.META) {
+ // A metadata requirement on the ARRAY_MAP result (OFFSET for
cardinality(), NULL for
+ // IS NULL) describes the output ARRAY container, not the lambda
elements. The output
+ // container is shaped by the input arrays: array_map copies the
first input's offsets
+ // and its null map is the union of all inputs' null maps. Pushing
that context into
+ // the lambda body would attach the metadata to the element layer
instead, producing
+ // e.g. `arr.*.OFFSET`, which the BE rejects for a struct element
(OFFSET metadata is
+ // only supported at array/map/string level). Route the container
metadata to the
+ // input arrays, and collect the element paths the lambda actually
reads with a fresh
+ // data context so that the elements stay available to the lambda
body.
+ for (ArrayItemReference lambdaArgument :
lambda.getLambdaArguments()) {
+ continueCollectAccessPath(lambdaArgument.getArrayExpression(),
copyContext(context));
Review Comment:
Fixed in 5d0d5dc6f36. The finding was correct and reproducible on a local
FE/BE cluster.
- Added `isRootContainerMetadata`: only an unprefixed `[OFFSET]` / `[NULL]`
request describes the ARRAY_MAP result's own container and is routed to the
input arrays.
- A prefixed request such as the `[*, OFFSET]` of
`cardinality(element_at(array_map(...), 1))` keeps the previous
`collectArrayPathInLambda` traversal, which drops the unrepresentable metadata
and preserves the lambda payload.
- Added unit case `testArrayMapResultElementMetadataKeepsLambdaPayloadOnly`
and regression cases `array_map_result_element_cardinality` /
`array_map_result_element_is_null` (plus two explain guards) with a selected
ARRAY_MAP result whose element type differs from the input.
Verification for `a ARRAY<STRUCT<v:INT>>` and
`cardinality(element_at(array_map(x -> array(x.v), a), 1))`:
```
before: all access paths: [a.*.v, a.*.OFFSET] -> [E-3110] Invalid META
access path ... OFFSET metadata is not supported at this level
after: all access paths: [a.*.v] -> 1, NULL, NULL (same as
nested column pruning disabled)
```
Root-container cases are unchanged (`[a.*, a.OFFSET]`, `[s.arr.*,
s.arr.OFFSET]`, `[m.KEYS, m.VALUES.*, m.VALUES.OFFSET]`, `[a.*, a.NULL]`).
`PruneNestedColumnTest` passes 79/79 and the whole
`nereids_rules_p0/column_pruning` directory (16 suites) passes.
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