AddLocalExchange.java
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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;
}
}
return false;
} else {
return false;
}
}
public static LocalExchangeType resolveExchangeType(LocalExchangeTypeRequire require,
PlanTranslatorContext translatorContext, PlanNode parent, PlanNode child) {
// Only generic RequireHash adapts to LOCAL_EXECUTION_HASH_SHUFFLE.
// Explicit RequireSpecific (GLOBAL_EXECUTION_HASH_SHUFFLE, BUCKET_HASH_SHUFFLE, etc.)
// must never be degraded — if they appear in an invalid context, the plan is wrong.
//
// Always prefer LOCAL_EXECUTION_HASH_SHUFFLE for FE-planned intra-fragment hash exchanges.
// GLOBAL_EXECUTION_HASH_SHUFFLE requires shuffle_idx_to_instance_idx which may be empty
// for fragments with non-hash sinks (UNPARTITIONED/MERGE). LOCAL_HASH is always safe
// since it partitions by local instance count without needing external shuffle maps.
if (require instanceof RequireHash) {
return LocalExchangeType.LOCAL_EXECUTION_HASH_SHUFFLE;
}
return require.preferType();
}
}