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jackietien pushed a commit to branch ty/explain_format
in repository https://gitbox.apache.org/repos/asf/iotdb.git

commit 196df02de9d6eea8a923d3ed67a3f15872defdb3
Author: JackieTien97 <[email protected]>
AuthorDate: Thu Apr 2 12:14:20 2026 +0800

    Address review feedback for EXPLAIN FORMAT JSON feature
    
    - Fix ExplainAnalyzeOperator to only instantiate the needed drawer (TEXT or 
JSON), avoiding wasted work
    - Replace hand-concatenated JSON in mergeExplainResultsJson with Gson to 
prevent injection from unescaped CTE names
    - Add proper imports in PlanGraphJsonPrinter, replace FQN with simple class 
names
    - Use JsonArray for list-type properties instead of String.valueOf()
    - Fix ExplainAnalyze.equals()/hashCode() to include outputFormat and verbose
    - Add Javadoc to ExplainOutputFormat documenting valid formats per statement
    - Default MPPQueryContext.explainOutputFormat to TEXT instead of null
    - Mark old 5-arg ExplainAnalyzeOperator constructor @Deprecated
    - Improve testExplainInvalidFormat to assert on error message content
    - Add common pitfalls section to CLAUDE.md
    
    Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
---
 CLAUDE.md                                          | 137 +++++++++++++++++++++
 .../it/query/recent/IoTExplainJsonFormatIT.java    |  10 +-
 .../db/queryengine/common/MPPQueryContext.java     |   2 +-
 .../execution/operator/ExplainAnalyzeOperator.java |  26 ++--
 .../TableModelStatementMemorySourceVisitor.java    |  43 +++----
 .../planner/plan/node/PlanGraphJsonPrinter.java    | 116 ++++++++---------
 .../plan/relational/sql/ast/ExplainAnalyze.java    |   6 +-
 .../relational/sql/ast/ExplainOutputFormat.java    |   9 ++
 .../FragmentInstanceStatisticsJsonDrawer.java      |   1 +
 9 files changed, 254 insertions(+), 96 deletions(-)

diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 00000000000..421c68ad8ba
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,137 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with 
code in this repository.
+
+## Project Overview
+
+Apache IoTDB is a time series database for IoT data. It uses a distributed 
architecture with ConfigNodes (metadata/coordination) and DataNodes 
(storage/query). Data is stored in TsFile columnar format (separate repo: 
https://github.com/apache/tsfile). Current version is 2.0.7-SNAPSHOT.
+
+## Build Commands
+
+```bash
+# Full build (skip tests)
+mvn clean package -pl distribution -am -DskipTests
+
+# Build a specific module (e.g., datanode)
+mvn clean package -pl iotdb-core/datanode -am -DskipTests
+
+# Run unit tests for a specific module
+mvn clean test -pl iotdb-core/datanode
+
+# Run a single test class
+mvn clean test -pl iotdb-core/datanode -Dtest=ClassName
+
+# Run a single test method
+mvn clean test -pl iotdb-core/datanode -Dtest=ClassName#methodName
+
+# Format code (requires JDK 17+; auto-skipped on JDK <17)
+mvn spotless:apply
+
+# Format code in integration-test module
+mvn spotless:apply -P with-integration-tests
+
+# Check formatting without applying
+mvn spotless:check
+```
+
+## Integration Tests
+
+Integration tests live in `integration-test/` (not included in default build). 
They require the `with-integration-tests` profile:
+
+```bash
+# Build template-node first (needed once, or after code changes)
+mvn clean package -DskipTests -pl integration-test -am -P 
with-integration-tests
+
+# Run tree-model ITs (simple: 1 ConfigNode + 1 DataNode)
+mvn clean verify -DskipUTs -pl integration-test -am -P with-integration-tests
+
+# Run tree-model ITs (cluster: 1 ConfigNode + 3 DataNodes)
+mvn clean verify -DskipUTs -pl integration-test -am -PClusterIT -P 
with-integration-tests
+
+# Run table-model ITs (simple)
+mvn clean verify -DskipUTs -pl integration-test -am -PTableSimpleIT -P 
with-integration-tests
+
+# Run table-model ITs (cluster)
+mvn clean verify -DskipUTs -pl integration-test -am -PTableClusterIT -P 
with-integration-tests
+```
+
+To run integration tests from IntelliJ: enable the `with-integration-tests` 
profile in Maven sidebar, then run test cases directly.
+
+## Code Style
+
+- **Spotless** with Google Java Format (GOOGLE style). Import order: 
`org.apache.iotdb`, blank, `javax`, `java`, static.
+- **Checkstyle** is also configured (see `checkstyle.xml` at project root).
+- Java source/target level is 1.8 (compiled with `maven.compiler.release=8` on 
JDK 9+).
+
+## Architecture
+
+### Node Types
+
+- **ConfigNode** (`iotdb-core/confignode`): Manages cluster metadata, schema 
regions, data regions, partition tables. Coordinates via Ratis consensus.
+- **DataNode** (`iotdb-core/datanode`): Handles data storage, query execution, 
and client connections. The main server component.
+- **AINode** (`iotdb-core/ainode`): Python-based node for AI/ML inference 
tasks.
+
+### Dual Data Model
+
+IoTDB supports two data models operating on the same storage:
+- **Tree model**: Traditional IoT hierarchy (e.g., 
`root.ln.wf01.wt01.temperature`). SQL uses path-based addressing.
+- **Table model** (relational): SQL table semantics. Grammar lives in 
`iotdb-core/relational-grammar/`. Query plan code under 
`queryengine/plan/relational/`.
+
+### Key DataNode Subsystems (`iotdb-core/datanode`)
+
+- **queryengine**: SQL parsing, planning, optimization, and execution.
+  - `plan/parser/` - ANTLR-based SQL parser
+  - `plan/statement/` - AST statement nodes
+  - `plan/planner/` - Logical and physical planning (tree model: 
`TreeModelPlanner`, table model: under `plan/relational/`)
+  - `plan/optimization/` - Query optimization rules
+  - `execution/operator/` - Physical operators (volcano-style iterator model)
+  - `execution/exchange/` - Inter-node data exchange
+  - `execution/fragment/` - Distributed query fragment management
+- **storageengine**: Write path, memtable, flush, WAL, compaction, TsFile 
management.
+  - `dataregion/` - DataRegion lifecycle, memtable, flush, compaction
+  - `dataregion/wal/` - Write-ahead log
+  - `buffer/` - Memory buffer management
+- **schemaengine**: Schema (timeseries metadata) management.
+- **pipe**: Data sync/replication framework (source -> processor -> sink 
pipeline).
+- **consensus**: DataNode-side consensus integration.
+- **subscription**: Client subscription service for streaming data changes.
+
+### Consensus (`iotdb-core/consensus`)
+
+Pluggable consensus protocols: Simple (single-node), Ratis (Raft-based), IoT 
Consensus (optimized for IoT writes). Factory pattern via `ConsensusFactory`.
+
+### Protocol Layer (`iotdb-protocol/`)
+
+Thrift IDL definitions for RPC between nodes. Generated sources are produced 
automatically during build. Sub-modules: `thrift-commons`, `thrift-confignode`, 
`thrift-datanode`, `thrift-consensus`, `thrift-ainode`.
+
+### Client Libraries (`iotdb-client/`)
+
+- `session/` - Java Session API (primary client interface)
+- `jdbc/` - JDBC driver
+- `cli/` - Command-line client
+- `client-cpp/`, `client-go/`, `client-py/` - Multi-language clients
+- `service-rpc/` - Shared Thrift service definitions
+
+### API Layer (`iotdb-api/`)
+
+Extension point interfaces: `udf-api` (user-defined functions), `trigger-api` 
(event triggers), `pipe-api` (data sync plugins), `external-api`, 
`external-service-api`.
+
+## IDE Setup
+
+After `mvn package`, right-click the root project in IntelliJ and choose 
"Maven -> Reload Project" to add generated source roots (Thrift and ANTLR).
+
+Generated source directories that need to be on the source path:
+- `**/target/generated-sources/thrift`
+- `**/target/generated-sources/antlr4`
+
+## Common Pitfalls
+
+### Build
+
+- **Missing Thrift compiler**: The local machine may not have the `thrift` 
binary installed. Running `mvn clean package -pl <module> -am -DskipTests` will 
fail at the `iotdb-thrift` module. **Workaround**: To verify your changes 
compile, use `mvn compile -pl <module>` (without `-am` or `clean`) to leverage 
existing target caches.
+- **Pre-existing compilation errors in unrelated modules**: The datanode 
module may have pre-existing compile errors in other subsystems (e.g., pipe, 
copyto) that cause `mvn clean test -pl iotdb-core/datanode -Dtest=XxxTest` to 
fail during compilation. **Workaround**: First run `mvn compile -pl 
iotdb-core/datanode` to confirm your changed files compile successfully. If the 
errors are in files you did not modify, they are pre-existing and do not affect 
your changes.
+
+### Code Style
+
+- **Always run `mvn spotless:apply` after editing Java files**: Spotless runs 
`spotless:check` automatically during the `compile` phase. Format violations 
cause an immediate BUILD FAILURE. Make it a habit to run `mvn spotless:apply 
-pl <module>` right after editing, not at the end. For files under 
`integration-test/`, add `-P with-integration-tests`.
+- **Gson version compatibility**: `JsonObject.isEmpty()` / 
`JsonArray.isEmpty()` may not be available in the Gson version used by this 
project. Use `size() > 0` instead and add a comment explaining why.
diff --git 
a/integration-test/src/test/java/org/apache/iotdb/relational/it/query/recent/IoTExplainJsonFormatIT.java
 
b/integration-test/src/test/java/org/apache/iotdb/relational/it/query/recent/IoTExplainJsonFormatIT.java
index 94ed692ab64..e023d6ce386 100644
--- 
a/integration-test/src/test/java/org/apache/iotdb/relational/it/query/recent/IoTExplainJsonFormatIT.java
+++ 
b/integration-test/src/test/java/org/apache/iotdb/relational/it/query/recent/IoTExplainJsonFormatIT.java
@@ -239,13 +239,19 @@ public class IoTExplainJsonFormatIT {
     }
   }
 
-  @Test(expected = SQLException.class)
-  public void testExplainInvalidFormat() throws SQLException {
+  @Test
+  public void testExplainInvalidFormat() {
     String sql = "EXPLAIN (FORMAT XML) SELECT * FROM testtb";
     try (Connection conn = 
EnvFactory.getEnv().getConnection(BaseEnv.TABLE_SQL_DIALECT);
         Statement statement = conn.createStatement()) {
       statement.execute("USE " + DATABASE_NAME);
       statement.executeQuery(sql);
+      fail("Expected SQLException for invalid format");
+    } catch (SQLException e) {
+      Assert.assertTrue(
+          "Error message should mention the invalid format",
+          e.getMessage().toUpperCase().contains("FORMAT")
+              || e.getMessage().toUpperCase().contains("XML"));
     }
   }
 }
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
index 43b214f226c..8f248c29363 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
@@ -109,7 +109,7 @@ public class MPPQueryContext implements IAuditEntity {
   // - EXPLAIN: Show the logical and physical query plan without execution
   // - EXPLAIN_ANALYZE: Execute the query and collect detailed execution 
statistics
   private ExplainType explainType = ExplainType.NONE;
-  private ExplainOutputFormat explainOutputFormat = null;
+  private ExplainOutputFormat explainOutputFormat = ExplainOutputFormat.TEXT;
   private boolean verbose = false;
 
   private QueryPlanStatistics queryPlanStatistics = null;
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/ExplainAnalyzeOperator.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/ExplainAnalyzeOperator.java
index 52af0bb7455..9676c94844a 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/ExplainAnalyzeOperator.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/ExplainAnalyzeOperator.java
@@ -82,15 +82,14 @@ public class ExplainAnalyzeOperator implements 
ProcessOperator {
   private final List<FragmentInstance> instances;
   private final ExplainOutputFormat outputFormat;
 
-  private final FragmentInstanceStatisticsDrawer 
fragmentInstanceStatisticsDrawer =
-      new FragmentInstanceStatisticsDrawer();
-  private final FragmentInstanceStatisticsJsonDrawer 
fragmentInstanceStatisticsJsonDrawer =
-      new FragmentInstanceStatisticsJsonDrawer();
+  private final FragmentInstanceStatisticsDrawer 
fragmentInstanceStatisticsDrawer;
+  private final FragmentInstanceStatisticsJsonDrawer 
fragmentInstanceStatisticsJsonDrawer;
 
   private final ScheduledFuture<?> logRecordTask;
   private final IClientManager<TEndPoint, SyncDataNodeInternalServiceClient> 
clientManager;
   private final MPPQueryContext mppQueryContext;
 
+  @Deprecated
   public ExplainAnalyzeOperator(
       OperatorContext operatorContext,
       Operator child,
@@ -118,8 +117,16 @@ public class ExplainAnalyzeOperator implements 
ProcessOperator {
     QueryExecution queryExecution = (QueryExecution) 
coordinator.getQueryExecution(queryId);
     this.instances = queryExecution.getDistributedPlan().getInstances();
     mppQueryContext = queryExecution.getContext();
-    fragmentInstanceStatisticsDrawer.renderPlanStatistics(mppQueryContext);
-    fragmentInstanceStatisticsJsonDrawer.renderPlanStatistics(mppQueryContext);
+
+    if (outputFormat == ExplainOutputFormat.JSON) {
+      this.fragmentInstanceStatisticsDrawer = null;
+      this.fragmentInstanceStatisticsJsonDrawer = new 
FragmentInstanceStatisticsJsonDrawer();
+      
fragmentInstanceStatisticsJsonDrawer.renderPlanStatistics(mppQueryContext);
+    } else {
+      this.fragmentInstanceStatisticsDrawer = new 
FragmentInstanceStatisticsDrawer();
+      this.fragmentInstanceStatisticsJsonDrawer = null;
+      fragmentInstanceStatisticsDrawer.renderPlanStatistics(mppQueryContext);
+    }
 
     // The time interval guarantees the result of EXPLAIN ANALYZE will be 
printed at least three
     // times.
@@ -146,8 +153,11 @@ public class ExplainAnalyzeOperator implements 
ProcessOperator {
       return null;
     }
 
-    fragmentInstanceStatisticsDrawer.renderDispatchCost(mppQueryContext);
-    fragmentInstanceStatisticsJsonDrawer.renderDispatchCost(mppQueryContext);
+    if (outputFormat == ExplainOutputFormat.JSON) {
+      fragmentInstanceStatisticsJsonDrawer.renderDispatchCost(mppQueryContext);
+    } else {
+      fragmentInstanceStatisticsDrawer.renderDispatchCost(mppQueryContext);
+    }
 
     // fetch statics from all fragment instances
     TsBlock result = buildResult();
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/execution/memory/TableModelStatementMemorySourceVisitor.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/execution/memory/TableModelStatementMemorySourceVisitor.java
index c6a7692395a..2633805074d 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/execution/memory/TableModelStatementMemorySourceVisitor.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/execution/memory/TableModelStatementMemorySourceVisitor.java
@@ -41,6 +41,11 @@ import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Node;
 import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.ShowDevice;
 import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Table;
 
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
 import org.apache.tsfile.enums.TSDataType;
 import org.apache.tsfile.read.common.block.TsBlock;
 import org.apache.tsfile.utils.Pair;
@@ -60,6 +65,8 @@ import static 
org.apache.iotdb.db.queryengine.plan.execution.memory.StatementMem
 public class TableModelStatementMemorySourceVisitor
     extends AstVisitor<StatementMemorySource, 
TableModelStatementMemorySourceContext> {
 
+  private static final Gson GSON = new 
GsonBuilder().setPrettyPrinting().create();
+
   @Override
   public StatementMemorySource visitNode(
       final Node node, final TableModelStatementMemorySourceContext context) {
@@ -170,36 +177,18 @@ public class TableModelStatementMemorySourceVisitor
       return mainExplainResult;
     }
 
-    // For JSON format with CTEs, wrap everything in a combined JSON object
-    StringBuilder sb = new StringBuilder();
-    sb.append("{\n");
-    sb.append("  \"cteQueries\": [\n");
-    int cteIndex = 0;
-    int cteSize = cteExplainResults.size();
+    JsonObject wrapper = new JsonObject();
+    JsonArray cteArray = new JsonArray();
     for (Map.Entry<NodeRef<Table>, Pair<Integer, List<String>>> entry :
         cteExplainResults.entrySet()) {
-      sb.append("    {\n");
-      sb.append("      \"name\": 
\"").append(entry.getKey().getNode().getName()).append("\",\n");
-      sb.append("      \"plan\": ");
-      // Each CTE's plan is already a JSON string
-      for (String line : entry.getValue().getRight()) {
-        sb.append(line);
-      }
-      sb.append("\n    }");
-      if (++cteIndex < cteSize) {
-        sb.append(",");
-      }
-      sb.append("\n");
-    }
-    sb.append("  ],\n");
-    sb.append("  \"mainQuery\": ");
-    for (String line : mainExplainResult) {
-      sb.append(line);
+      JsonObject cte = new JsonObject();
+      cte.addProperty("name", entry.getKey().getNode().getName());
+      cte.add("plan", 
JsonParser.parseString(entry.getValue().getRight().get(0)));
+      cteArray.add(cte);
     }
-    sb.append("\n}");
+    wrapper.add("cteQueries", cteArray);
+    wrapper.add("mainQuery", JsonParser.parseString(mainExplainResult.get(0)));
 
-    List<String> result = new ArrayList<>();
-    result.add(sb.toString());
-    return result;
+    return Collections.singletonList(GSON.toJson(wrapper));
   }
 }
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/PlanGraphJsonPrinter.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/PlanGraphJsonPrinter.java
index e35c23d4660..97e7d88328f 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/PlanGraphJsonPrinter.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/PlanGraphJsonPrinter.java
@@ -19,12 +19,21 @@
 
 package org.apache.iotdb.db.queryengine.plan.planner.plan.node;
 
+import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.AggregationNode;
 import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.DeviceTableScanNode;
 import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.ExchangeNode;
 import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.ExplainAnalyzeNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.FilterNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.JoinNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.LimitNode;
+import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.MergeSortNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.OffsetNode;
 import org.apache.iotdb.db.queryengine.plan.relational.planner.node.OutputNode;
+import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.ProjectNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.SortNode;
 import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.TableScanNode;
 import 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.TreeDeviceViewScanNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.UnionNode;
 
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
@@ -59,6 +68,7 @@ public class PlanGraphJsonPrinter {
     jsonNode.addProperty("id", nodeId);
 
     JsonObject properties = buildProperties(node);
+    // JsonObject.isEmpty() is not available in all Gson versions
     if (properties.size() > 0) {
       jsonNode.add("properties", properties);
     }
@@ -80,71 +90,68 @@ public class PlanGraphJsonPrinter {
 
     if (node instanceof OutputNode) {
       OutputNode n = (OutputNode) node;
-      properties.addProperty("OutputColumns", 
String.valueOf(n.getOutputColumnNames()));
-      properties.addProperty("OutputSymbols", 
String.valueOf(n.getOutputSymbols()));
+      properties.add("OutputColumns", toJsonArray(n.getOutputColumnNames()));
+      properties.add("OutputSymbols", toJsonArray(n.getOutputSymbols()));
     } else if (node instanceof ExplainAnalyzeNode) {
       ExplainAnalyzeNode n = (ExplainAnalyzeNode) node;
-      properties.addProperty("ChildPermittedOutputs", 
String.valueOf(n.getChildPermittedOutputs()));
+      properties.add("ChildPermittedOutputs", 
toJsonArray(n.getChildPermittedOutputs()));
     } else if (node instanceof TableScanNode) {
       buildTableScanProperties(properties, (TableScanNode) node);
     } else if (node instanceof ExchangeNode) {
       // No extra properties needed
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.AggregationNode) {
-      buildAggregationProperties(
-          properties,
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.AggregationNode) 
node);
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.FilterNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.FilterNode 
n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.FilterNode) node;
+    } else if (node instanceof AggregationNode) {
+      buildAggregationProperties(properties, (AggregationNode) node);
+    } else if (node instanceof FilterNode) {
+      FilterNode n = (FilterNode) node;
       properties.addProperty("Predicate", String.valueOf(n.getPredicate()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.ProjectNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.ProjectNode 
n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.ProjectNode) node;
-      properties.addProperty("OutputSymbols", 
String.valueOf(n.getOutputSymbols()));
-      properties.addProperty("Expressions", 
String.valueOf(n.getAssignments().getMap().values()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.LimitNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.LimitNode n 
=
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.LimitNode) node;
-      properties.addProperty("Count", String.valueOf(n.getCount()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.OffsetNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.OffsetNode 
n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.OffsetNode) node;
-      properties.addProperty("Count", String.valueOf(n.getCount()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.SortNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.SortNode n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.SortNode) node;
+    } else if (node instanceof ProjectNode) {
+      ProjectNode n = (ProjectNode) node;
+      properties.add("OutputSymbols", toJsonArray(n.getOutputSymbols()));
+      properties.add("Expressions", 
toJsonArray(n.getAssignments().getMap().values()));
+    } else if (node instanceof LimitNode) {
+      LimitNode n = (LimitNode) node;
+      properties.addProperty("Count", n.getCount());
+    } else if (node instanceof OffsetNode) {
+      OffsetNode n = (OffsetNode) node;
+      properties.addProperty("Count", n.getCount());
+    } else if (node instanceof SortNode) {
+      SortNode n = (SortNode) node;
       properties.addProperty("OrderBy", String.valueOf(n.getOrderingScheme()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.MergeSortNode) {
-      
org.apache.iotdb.db.queryengine.plan.relational.planner.node.MergeSortNode n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.MergeSortNode) 
node;
+    } else if (node instanceof MergeSortNode) {
+      MergeSortNode n = (MergeSortNode) node;
       properties.addProperty("OrderBy", String.valueOf(n.getOrderingScheme()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.JoinNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.JoinNode n =
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.JoinNode) node;
+    } else if (node instanceof JoinNode) {
+      JoinNode n = (JoinNode) node;
       properties.addProperty("JoinType", String.valueOf(n.getJoinType()));
-      properties.addProperty("Criteria", String.valueOf(n.getCriteria()));
-      properties.addProperty("OutputSymbols", 
String.valueOf(n.getOutputSymbols()));
-    } else if (node
-        instanceof 
org.apache.iotdb.db.queryengine.plan.relational.planner.node.UnionNode) {
-      org.apache.iotdb.db.queryengine.plan.relational.planner.node.UnionNode n 
=
-          
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.UnionNode) node;
-      properties.addProperty("OutputSymbols", 
String.valueOf(n.getOutputSymbols()));
+      properties.add("Criteria", toJsonArray(n.getCriteria()));
+      properties.add("OutputSymbols", toJsonArray(n.getOutputSymbols()));
+    } else if (node instanceof UnionNode) {
+      UnionNode n = (UnionNode) node;
+      properties.add("OutputSymbols", toJsonArray(n.getOutputSymbols()));
     }
 
     return properties;
   }
 
+  private static <T> JsonArray toJsonArray(java.util.Collection<T> items) {
+    JsonArray array = new JsonArray();
+    for (T item : items) {
+      array.add(String.valueOf(item));
+    }
+    return array;
+  }
+
+  private static <T> JsonArray toJsonArray(List<T> items) {
+    JsonArray array = new JsonArray();
+    for (T item : items) {
+      array.add(String.valueOf(item));
+    }
+    return array;
+  }
+
   private static void buildTableScanProperties(JsonObject properties, 
TableScanNode node) {
     properties.addProperty("QualifiedTableName", 
node.getQualifiedObjectName().toString());
-    properties.addProperty("OutputSymbols", 
String.valueOf(node.getOutputSymbols()));
+    properties.add("OutputSymbols", toJsonArray(node.getOutputSymbols()));
 
     if (node instanceof DeviceTableScanNode) {
       DeviceTableScanNode deviceNode = (DeviceTableScanNode) node;
@@ -182,15 +189,12 @@ public class PlanGraphJsonPrinter {
     }
   }
 
-  private static void buildAggregationProperties(
-      JsonObject properties,
-      
org.apache.iotdb.db.queryengine.plan.relational.planner.node.AggregationNode 
node) {
-    properties.addProperty("OutputSymbols", 
String.valueOf(node.getOutputSymbols()));
+  private static void buildAggregationProperties(JsonObject properties, 
AggregationNode node) {
+    properties.add("OutputSymbols", toJsonArray(node.getOutputSymbols()));
 
     JsonArray aggregators = new JsonArray();
     int i = 0;
-    for 
(org.apache.iotdb.db.queryengine.plan.relational.planner.node.AggregationNode.Aggregation
-        aggregation : node.getAggregations().values()) {
+    for (AggregationNode.Aggregation aggregation : 
node.getAggregations().values()) {
       JsonObject agg = new JsonObject();
       agg.addProperty("index", i++);
       agg.addProperty("function", 
aggregation.getResolvedFunction().toString());
@@ -204,10 +208,10 @@ public class PlanGraphJsonPrinter {
     }
     properties.add("Aggregators", aggregators);
 
-    properties.addProperty("GroupingKeys", 
String.valueOf(node.getGroupingKeys()));
+    properties.add("GroupingKeys", toJsonArray(node.getGroupingKeys()));
     if (node.isStreamable()) {
       properties.addProperty("Streamable", true);
-      properties.addProperty("PreGroupedSymbols", 
String.valueOf(node.getPreGroupedSymbols()));
+      properties.add("PreGroupedSymbols", 
toJsonArray(node.getPreGroupedSymbols()));
     }
     properties.addProperty("Step", String.valueOf(node.getStep()));
   }
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainAnalyze.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainAnalyze.java
index dc7798967e4..b824705df18 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainAnalyze.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainAnalyze.java
@@ -86,7 +86,7 @@ public class ExplainAnalyze extends Statement {
 
   @Override
   public int hashCode() {
-    return Objects.hash(statement, verbose);
+    return Objects.hash(statement, verbose, outputFormat);
   }
 
   @Override
@@ -98,7 +98,9 @@ public class ExplainAnalyze extends Statement {
       return false;
     }
     ExplainAnalyze o = (ExplainAnalyze) obj;
-    return Objects.equals(statement, o.statement);
+    return Objects.equals(statement, o.statement)
+        && verbose == o.verbose
+        && outputFormat == o.outputFormat;
   }
 
   @Override
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainOutputFormat.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainOutputFormat.java
index 9dba3649a7f..d7d1fc08bb3 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainOutputFormat.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/ExplainOutputFormat.java
@@ -19,6 +19,15 @@
 
 package org.apache.iotdb.db.queryengine.plan.relational.sql.ast;
 
+/**
+ * Output format for EXPLAIN and EXPLAIN ANALYZE statements.
+ *
+ * <ul>
+ *   <li>{@link #GRAPHVIZ} - Box-drawing plan visualization. Valid for EXPLAIN 
only (default).
+ *   <li>{@link #TEXT} - Text-based output. Valid for EXPLAIN ANALYZE only 
(default).
+ *   <li>{@link #JSON} - Structured JSON output. Valid for both EXPLAIN and 
EXPLAIN ANALYZE.
+ * </ul>
+ */
 public enum ExplainOutputFormat {
   GRAPHVIZ,
   TEXT,
diff --git 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/statistics/FragmentInstanceStatisticsJsonDrawer.java
 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/statistics/FragmentInstanceStatisticsJsonDrawer.java
index 3c6ff7bfb41..2b00d6191fe 100644
--- 
a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/statistics/FragmentInstanceStatisticsJsonDrawer.java
+++ 
b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/statistics/FragmentInstanceStatisticsJsonDrawer.java
@@ -345,6 +345,7 @@ public class FragmentInstanceStatisticsJsonDrawer {
           childrenArray.add(childJson);
         }
       }
+      // JsonArray.isEmpty() is not available in all Gson versions
       if (childrenArray.size() > 0) {
         operatorJson.add("children", childrenArray);
       }

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