Method getQueryProcessingStage

src/Storages/StorageLoop.cpp:22–32

    }

    QueryProcessingStage::Enum StorageLoop::getQueryProcessingStage(
        ContextPtr, QueryProcessingStage::Enum, const StorageSnapshotPtr &, SelectQueryInfo &) const
    {
        /// `LoopSource` always materialises the inner select with
        /// `QueryProcessingStage::Complete`, so the chunks it emits are plain column
        /// data. Delegating to `inner_storage` here could advertise `WithMergeableState`
        /// (e.g. when the inner storage is `Distributed`) and make the outer planner add
        /// a `MergingAggregatedStep`, which then trips on the missing chunk info — see
        /// issue #104863.
        return QueryProcessingStage::FetchColumns;
    }

    void StorageLoop::read(
            QueryPlan & query_plan,