924060929 commented on code in PR #63366:
URL: https://github.com/apache/doris/pull/63366#discussion_r3411860865


##########
fe/fe-core/src/main/java/org/apache/doris/planner/AddLocalExchange.java:
##########
@@ -0,0 +1,182 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.planner;
+
+import org.apache.doris.common.Pair;
+import org.apache.doris.nereids.glue.translator.PlanTranslatorContext;
+import org.apache.doris.nereids.trees.plans.distribute.DistributedPlan;
+import org.apache.doris.nereids.trees.plans.distribute.FragmentIdMapping;
+import org.apache.doris.nereids.trees.plans.distribute.PipelineDistributedPlan;
+import org.apache.doris.planner.LocalExchangeNode.LocalExchangeType;
+import org.apache.doris.planner.LocalExchangeNode.LocalExchangeTypeRequire;
+import org.apache.doris.planner.LocalExchangeNode.RequireHash;
+
+/**
+ * FE-side local exchange planner — inserts {@link LocalExchangeNode} into 
each fragment's
+ * plan tree so that within-fragment data redistribution is decided at 
planning time
+ * instead of at BE pipeline-build time.
+ *
+ * <h3>When this runs</h3>
+ * Invoked from {@code NereidsPlanner.addLocalExchangeAfterDistribute()} right 
after
+ * {@code DistributePlanner} has assigned instances to fragments and before 
the plan is
+ * serialized to BE.  Gated by session variable {@code 
enable_local_shuffle_planner}
+ * (default true) and {@code enable_local_shuffle}; when either is off this 
pass is
+ * skipped entirely and BE falls back to its own {@code _plan_local_exchange}. 
 The two
+ * paths are mutually exclusive: BE consults {@code 
runtime_state.h::plan_local_shuffle()}
+ * to know whether it should plan LE itself.
+ *
+ * <h3>What it changes</h3>
+ * <ul>
+ *   <li>For each fragment with {@code maxPerBeInstances > 1}, walks the plan 
tree
+ *       bottom-up via {@link PlanNode#enforceAndDeriveLocalExchange} and 
inserts
+ *       LocalExchangeNodes where children's output distribution doesn't 
satisfy the
+ *       parent's requirement.</li>
+ *   <li>May wrap the fragment root with an extra PASSTHROUGH LE so the data 
sink
+ *       (DataStreamSink / OlapTableSink) runs with the full instance count 
even when
+ *       the root operator is serial — see {@link 
#addLocalExchangeForFragment}.</li>
+ *   <li>Does NOT modify the fragment sink itself, fragment boundaries, or 
instance
+ *       assignment.</li>
+ * </ul>
+ *
+ * <h3>Per-BE instance semantics</h3>
+ * Skips fragments where every BE has at most 1 instance.  Using a global 
instance count
+ * would insert LE for "2 BEs × 1 instance" cases, which BE's own
+ * {@code _plan_local_exchange} would not — leading to pipeline task-count 
mismatch and
+ * deadlock.  See {@link #addLocalExchange}.
+ *
+ * <h3>Reading order</h3>
+ * Start with {@link PlanNode#enforceRequire} (the recursion engine), then 
individual
+ * {@code enforceAndDeriveLocalExchange} overrides on PlanNode subclasses.
+ */
+public class AddLocalExchange {
+    /** addLocalExchange with distributed plans, skipping single-instance 
fragments.
+     *  BE's _plan_local_exchange checks _num_instances which is the per-BE 
instance count.
+     *  With _num_instances<=1 all pipelines on that BE have 1 task so local 
exchange is a no-op.
+     *  We must use the same per-BE semantics: skip when every BE has at most 
1 instance.
+     *  Using global instanceCount would insert LE for fragments where 2 BEs 
each have 1 instance
+     *  (global=2, per-BE=1), causing pipeline task mismatch and deadlock. */
+    public void addLocalExchange(FragmentIdMapping<DistributedPlan> 
distributedPlans,
+            PlanTranslatorContext context) {
+        for (DistributedPlan plan : distributedPlans.values()) {
+            PipelineDistributedPlan pipePlan = (PipelineDistributedPlan) plan;
+            long maxPerBeInstances = pipePlan.getInstanceJobs().stream()
+                    .collect(java.util.stream.Collectors.groupingBy(
+                            j -> j.getAssignedWorker().id(), 
java.util.stream.Collectors.counting()))
+                    
.values().stream().mapToLong(Long::longValue).max().orElse(0);
+            if (maxPerBeInstances <= 1) {
+                continue;
+            }
+            PlanFragment fragment = pipePlan.getFragmentJob().getFragment();
+            addLocalExchangeForFragment(fragment, context);
+        }
+    }
+
+    private void addLocalExchangeForFragment(PlanFragment fragment, 
PlanTranslatorContext context) {
+        DataSink sink = fragment.getSink();
+        LocalExchangeTypeRequire require = sink == null
+                ? LocalExchangeTypeRequire.noRequire() : 
sink.getLocalExchangeTypeRequire();
+        PlanNode root = fragment.getPlanRoot();
+        context.setHasSerialAncestorInPipeline(root, false);
+        Pair<PlanNode, LocalExchangeType> output = root
+                .enforceAndDeriveLocalExchange(context, null, require);
+        PlanNode newRoot = output.first;
+        // The fragment data sink (DataStreamSink, OlapTableSink) runs in the 
same pipeline
+        // as the root. If the root will be serial on BE, the sink pipeline 
has 1 task —
+        // only instance 0 sends data, others hang or miss writes.
+        // Insert PASSTHROUGH fan-out so sink runs with _num_instances tasks.
+        // This matches BE-native's default required_data_distribution():
+        //   _child->is_serial_operator() ? PASSTHROUGH : NOOP
+        if (newRoot.isSerialOperatorOnBe(context.getConnectContext())) {
+            newRoot = new LocalExchangeNode(context.nextPlanNodeId(), newRoot,
+                    LocalExchangeType.PASSTHROUGH, null);
+        }
+        if (newRoot != root) {
+            fragment.setPlanRoot(newRoot);
+        }
+        validateNoSerialWithoutLocalExchange(fragment.getPlanRoot(), 
context.getConnectContext());
+    }
+
+    /**
+     * In a local-shuffle fragment, the root check above guarantees the root 
pipeline
+     * has N tasks. Any serial operator reduces its pipeline to 1 task. If 
this serial
+     * operator feeds into a non-serial parent without LocalExchangeNode in 
between,
+     * some pipelines have 1 task while others have N → shared_state mismatch, 
data loss.
+     *
+     * Serial→serial chains are fine (all at 1 task, consistent). Only the 
transition
+     * from serial to non-serial needs LE to restore parallelism.
+     */
+    private void validateNoSerialWithoutLocalExchange(PlanNode node,
+            org.apache.doris.qe.ConnectContext context) {
+        for (PlanNode child : node.getChildren()) {
+            validateNoSerialWithoutLocalExchange(child, context);
+            if (child.isSerialOperatorOnBe(context)
+                    && !(child instanceof LocalExchangeNode)
+                    && !(node instanceof LocalExchangeNode)
+                    && !(node instanceof ExchangeNode)
+                    && !node.isSerialOperatorOnBe(context)) {
+                
org.apache.logging.log4j.LogManager.getLogger(AddLocalExchange.class).warn(
+                        "Serial " + child.getClass().getSimpleName() + "(id=" 
+ child.getId()
+                        + ") feeds into non-serial " + 
node.getClass().getSimpleName()
+                        + "(id=" + node.getId() + ") without LocalExchangeNode"
+                        + " in fragment " + node.getFragment().getFragmentId()
+                        + ". FE should insert LocalExchangeNode to restore 
parallelism.");
+            }
+        }
+    }
+
+    public static boolean isColocated(PlanNode plan) {
+        if (plan instanceof AggregationNode) {
+            return ((AggregationNode) plan).isColocate() && 
isColocated(plan.getChild(0));
+        } else if (plan instanceof OlapScanNode) {
+            return true;
+        } else if (plan instanceof SelectNode) {
+            return isColocated(plan.getChild(0));
+        } else if (plan instanceof HashJoinNode) {
+            return ((HashJoinNode) plan).isColocate()
+                    && (isColocated(plan.getChild(0)) || 
isColocated(plan.getChild(1)));
+        } else if (plan instanceof SetOperationNode) {
+            if (!((SetOperationNode) plan).isColocate()) {
+                return false;
+            }
+            for (PlanNode child : plan.getChildren()) {
+                if (isColocated(child)) {
+                    return true;
+                }

Review Comment:
   Done — removed all three unused params 
(`translatorContext`/`parent`/`child`); 
`resolveExchangeType(LocalExchangeTypeRequire require)` now reads only 
`require`. Updated all call sites + the unit test (this also resolves the 
`SetOperationNode` null-`firstChild` note below).
   



##########
fe/fe-core/src/main/java/org/apache/doris/planner/AddLocalExchange.java:
##########
@@ -0,0 +1,182 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.planner;
+
+import org.apache.doris.common.Pair;
+import org.apache.doris.nereids.glue.translator.PlanTranslatorContext;
+import org.apache.doris.nereids.trees.plans.distribute.DistributedPlan;
+import org.apache.doris.nereids.trees.plans.distribute.FragmentIdMapping;
+import org.apache.doris.nereids.trees.plans.distribute.PipelineDistributedPlan;
+import org.apache.doris.planner.LocalExchangeNode.LocalExchangeType;
+import org.apache.doris.planner.LocalExchangeNode.LocalExchangeTypeRequire;
+import org.apache.doris.planner.LocalExchangeNode.RequireHash;
+
+/**
+ * FE-side local exchange planner — inserts {@link LocalExchangeNode} into 
each fragment's
+ * plan tree so that within-fragment data redistribution is decided at 
planning time
+ * instead of at BE pipeline-build time.
+ *
+ * <h3>When this runs</h3>
+ * Invoked from {@code NereidsPlanner.addLocalExchangeAfterDistribute()} right 
after
+ * {@code DistributePlanner} has assigned instances to fragments and before 
the plan is
+ * serialized to BE.  Gated by session variable {@code 
enable_local_shuffle_planner}
+ * (default true) and {@code enable_local_shuffle}; when either is off this 
pass is
+ * skipped entirely and BE falls back to its own {@code _plan_local_exchange}. 
 The two
+ * paths are mutually exclusive: BE consults {@code 
runtime_state.h::plan_local_shuffle()}
+ * to know whether it should plan LE itself.
+ *
+ * <h3>What it changes</h3>
+ * <ul>
+ *   <li>For each fragment with {@code maxPerBeInstances > 1}, walks the plan 
tree
+ *       bottom-up via {@link PlanNode#enforceAndDeriveLocalExchange} and 
inserts
+ *       LocalExchangeNodes where children's output distribution doesn't 
satisfy the
+ *       parent's requirement.</li>
+ *   <li>May wrap the fragment root with an extra PASSTHROUGH LE so the data 
sink
+ *       (DataStreamSink / OlapTableSink) runs with the full instance count 
even when
+ *       the root operator is serial — see {@link 
#addLocalExchangeForFragment}.</li>
+ *   <li>Does NOT modify the fragment sink itself, fragment boundaries, or 
instance
+ *       assignment.</li>
+ * </ul>
+ *
+ * <h3>Per-BE instance semantics</h3>
+ * Skips fragments where every BE has at most 1 instance.  Using a global 
instance count
+ * would insert LE for "2 BEs × 1 instance" cases, which BE's own
+ * {@code _plan_local_exchange} would not — leading to pipeline task-count 
mismatch and
+ * deadlock.  See {@link #addLocalExchange}.
+ *
+ * <h3>Reading order</h3>
+ * Start with {@link PlanNode#enforceRequire} (the recursion engine), then 
individual
+ * {@code enforceAndDeriveLocalExchange} overrides on PlanNode subclasses.
+ */
+public class AddLocalExchange {
+    /** addLocalExchange with distributed plans, skipping single-instance 
fragments.
+     *  BE's _plan_local_exchange checks _num_instances which is the per-BE 
instance count.
+     *  With _num_instances<=1 all pipelines on that BE have 1 task so local 
exchange is a no-op.
+     *  We must use the same per-BE semantics: skip when every BE has at most 
1 instance.
+     *  Using global instanceCount would insert LE for fragments where 2 BEs 
each have 1 instance
+     *  (global=2, per-BE=1), causing pipeline task mismatch and deadlock. */
+    public void addLocalExchange(FragmentIdMapping<DistributedPlan> 
distributedPlans,
+            PlanTranslatorContext context) {
+        for (DistributedPlan plan : distributedPlans.values()) {
+            PipelineDistributedPlan pipePlan = (PipelineDistributedPlan) plan;
+            long maxPerBeInstances = pipePlan.getInstanceJobs().stream()
+                    .collect(java.util.stream.Collectors.groupingBy(
+                            j -> j.getAssignedWorker().id(), 
java.util.stream.Collectors.counting()))
+                    
.values().stream().mapToLong(Long::longValue).max().orElse(0);
+            if (maxPerBeInstances <= 1) {
+                continue;
+            }
+            PlanFragment fragment = pipePlan.getFragmentJob().getFragment();
+            addLocalExchangeForFragment(fragment, context);
+        }
+    }
+
+    private void addLocalExchangeForFragment(PlanFragment fragment, 
PlanTranslatorContext context) {
+        DataSink sink = fragment.getSink();
+        LocalExchangeTypeRequire require = sink == null
+                ? LocalExchangeTypeRequire.noRequire() : 
sink.getLocalExchangeTypeRequire();
+        PlanNode root = fragment.getPlanRoot();
+        context.setHasSerialAncestorInPipeline(root, false);
+        Pair<PlanNode, LocalExchangeType> output = root
+                .enforceAndDeriveLocalExchange(context, null, require);
+        PlanNode newRoot = output.first;
+        // The fragment data sink (DataStreamSink, OlapTableSink) runs in the 
same pipeline
+        // as the root. If the root will be serial on BE, the sink pipeline 
has 1 task —
+        // only instance 0 sends data, others hang or miss writes.
+        // Insert PASSTHROUGH fan-out so sink runs with _num_instances tasks.
+        // This matches BE-native's default required_data_distribution():
+        //   _child->is_serial_operator() ? PASSTHROUGH : NOOP
+        if (newRoot.isSerialOperatorOnBe(context.getConnectContext())) {
+            newRoot = new LocalExchangeNode(context.nextPlanNodeId(), newRoot,
+                    LocalExchangeType.PASSTHROUGH, null);
+        }
+        if (newRoot != root) {
+            fragment.setPlanRoot(newRoot);
+        }
+        validateNoSerialWithoutLocalExchange(fragment.getPlanRoot(), 
context.getConnectContext());
+    }
+
+    /**
+     * In a local-shuffle fragment, the root check above guarantees the root 
pipeline
+     * has N tasks. Any serial operator reduces its pipeline to 1 task. If 
this serial
+     * operator feeds into a non-serial parent without LocalExchangeNode in 
between,
+     * some pipelines have 1 task while others have N → shared_state mismatch, 
data loss.
+     *
+     * Serial→serial chains are fine (all at 1 task, consistent). Only the 
transition
+     * from serial to non-serial needs LE to restore parallelism.
+     */
+    private void validateNoSerialWithoutLocalExchange(PlanNode node,
+            org.apache.doris.qe.ConnectContext context) {
+        for (PlanNode child : node.getChildren()) {
+            validateNoSerialWithoutLocalExchange(child, context);
+            if (child.isSerialOperatorOnBe(context)
+                    && !(child instanceof LocalExchangeNode)

Review Comment:
   Removed the method entirely (commit `3630071a131`) rather than adding a 
throw/DCHECK/metric — see the longer reply on the [P1] thread at 
`AddLocalExchange:132`. Short version: the invariant is self-referential (it 
reads the same `isSerialOperatorOnBe` flag it validates), so it can't catch the 
one bug class that matters, and it false-fires on legitimate 
serial→{TableFunction, NLJ, Agg} plans. The regression suite + RQG differential 
are the actual guard.
   



##########
fe/fe-core/src/main/java/org/apache/doris/planner/SetOperationNode.java:
##########
@@ -193,4 +198,52 @@ public int getNumInstances() {
     public boolean isBucketShuffle() {
         return distributionMode.equals(DistributionMode.BUCKET_SHUFFLE);
     }
+
+    public boolean isColocate() {
+        return isColocate;
+    }
+
+    @Override
+    public Pair<PlanNode, LocalExchangeType> 
enforceAndDeriveLocalExchange(PlanTranslatorContext translatorContext,
+            PlanNode parent, LocalExchangeTypeRequire parentRequire) {
+        LocalExchangeTypeRequire requireChild;
+        LocalExchangeType outputType;
+        PlanNode firstChild = children.isEmpty() ? null : children.get(0);
+        if (this instanceof UnionNode) {
+            // Propagate parent's hash requirement to children ONLY when a 
downstream operator
+            // requires shuffle for correctness (not just performance 
optimization). Matches BE's

Review Comment:
   Resolved by removing the unused `child` param from `resolveExchangeType` — 
`SetOperationNode` no longer passes `firstChild` (only `requireChild` at 
`SetOperationNode.java:222/239`), so no null can reach it.
   



##########
be/src/exec/pipeline/pipeline_fragment_context.cpp:
##########
@@ -690,6 +716,199 @@ Status 
PipelineFragmentContext::_build_pipelines(ObjectPool* pool, const Descrip
     return Status::OK();
 }
 
+Status PipelineFragmentContext::_create_deferred_local_exchangers() {
+    for (auto& info : _deferred_exchangers) {
+        // DANGER ZONE — do not "fix" this line without reading the history.
+        //
+        // sender_count seeds Exchanger::_running_sink_operators, which the 
source side
+        // waits to reach 0 via sub_running_sink_operators on each sink 
LocalState close.
+        // The correct value is THIS pipeline-instance's sink task count, 
which is exactly
+        // info.upstream_pipe->num_tasks() — one PipelineTask per task, one 
close per task.
+        //
+        // Tempting wrong fix #1: `std::max(num_tasks, _num_instances)` to 
mirror the
+        //   BE-planned path in _add_local_exchange_impl (~line 1023).  THIS 
BREAKS the
+        //   common FE-planned shape of `serial scan → LE(PT) → ...`: 
upstream_pipe
+        //   genuinely has num_tasks=1, only 1 close arrives, but seed becomes
+        //   _num_instances so _running_sink_operators never reaches 0 — 
downstream
+        //   sources hang on SHUFFLE_DATA_DEPENDENCY (e.g. MTMV refresh from
+        //   mtmv_up_down_job_p0/load.groovy stays at Status=RUNNING; build 
949402
+        //   regressed exactly this way).  BE-planned mode uses max() because 
its
+        //   `cur_pipe` is the source-side pipeline (always raised to 
_num_instances by
+        //   add_pipeline) — not analogous to our `upstream_pipe` here, which 
is the
+        //   sink-side pipeline that may legitimately stay at 1 for serial 
sources.
+        //
+        // Tempting wrong fix #2: multiply by _num_instances on the theory 
shared_state
+        //   is shared across all instances.  Same hang — each 
fragment-instance
+        //   PipelineFragmentContext has its OWN _op_id_to_shared_state map, 
so the
+        //   exchanger is per-instance, not per-BE.  num_tasks() is already 
the right
+        //   close-count for one instance.
+        //
+        // If a hang shows up with `_running_sink_operators < 0`, the bug is 
upstream:
+        // _propagate_local_exchange_num_tasks left num_tasks too low (or too 
high) for
+        // this fragment shape.  Fix THAT pass, not this seed value.
+        const int sender_count = info.upstream_pipe->num_tasks();

Review Comment:
   Replaced the two iterative `while (changed)` passes in 
`_propagate_local_exchange_num_tasks()` with a single Kahn topological sweep 
over the pipeline DAG (commit `a97d3347789`): each pipeline is visited once, 
after all of its upstreams, so `num_tasks` is set in one pass and the loop 
can't run unbounded. Added a cycle `DCHECK` instead of a max-iteration guard.
   



##########
be/src/exec/pipeline/pipeline_fragment_context.h:
##########
@@ -320,8 +322,11 @@ class PipelineFragmentContext : public 
TaskExecutionContext {
 
     std::mutex _state_map_lock;
 
-    int _operator_id = 0;
-    int _sink_operator_id = 0;
+    // Start from -1 so all operator IDs are negative. This avoids collision 
with

Review Comment:
   Thanks — confirmed. Operator IDs are only used as map keys / `dest_id` 
equality and printed as-is in profiles; nothing enumerates them expecting 
non-negative. The only hardcoded `0` was the unpaired sink `dest_id=0`, which 
is exactly the collision the `-1` start avoids. No change needed.
   



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