mrhhsg commented on code in PR #68606:
URL: https://github.com/apache/doris/pull/68606#discussion_r4129411160
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be/src/exprs/aggregate/aggregate_function_simple_factory.cpp:
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@@ -123,7 +122,6 @@ AggregateFunctionSimpleFactory&
AggregateFunctionSimpleFactory::instance() {
register_aggregate_function_avg_weighted(instance);
register_aggregate_function_histogram(instance);
register_aggregate_function_linear_histogram(instance);
- register_aggregate_function_map_agg(instance);
Review Comment:
Thanks for the analysis. The failure mode you describe is accurate, and we
are accepting it on purpose. This PR does not add a compatibility path.
- Scope decision: the maintainers decided to remove `map_agg_v1` completely,
BE implementation included, without keeping upgrade compatibility. `map_agg_v2`
was added in #51343, and `map_agg` has resolved to it in FE since then. Keeping
`AggregateFunctionMapAgg` in BE just to read old states would leave the v1 code
in the tree, and removing that code is the purpose of this PR.
- As you note, the v1 and v2 intermediate encodings differ: v1 serializes
key/value pairs one at a time, while v2 serializes whole columns. Because of
that, a name alias from `map_agg_v1` to `map_agg_v2` would silently misread old
data. Failing visibly with `DataTypeAggState function get failed` is the safer
outcome, so the lookup is left to fail instead of being aliased.
- The break is documented in the PR description and release note:
`agg_state` columns (and sync MVs) built on the old `map_agg` implementation
are no longer readable and must be rebuilt before or after the upgrade. The
same applies to mixed-version fragments during a rolling upgrade from an FE
that still plans `map_agg_v1`.
No code change for this thread; resolving it as by design.
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