Copilot commented on code in PR #15662:
URL: https://github.com/apache/iotdb/pull/15662#discussion_r2321167671


##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/ir/PredicateWithUncorrelatedScalarSubqueryReconstructor.java:
##########
@@ -0,0 +1,171 @@
+/*
+ * 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.iotdb.db.queryengine.plan.relational.planner.ir;
+
+import org.apache.iotdb.commons.exception.IoTDBException;
+import org.apache.iotdb.db.protocol.session.SessionManager;
+import org.apache.iotdb.db.queryengine.common.MPPQueryContext;
+import org.apache.iotdb.db.queryengine.plan.Coordinator;
+import org.apache.iotdb.db.queryengine.plan.execution.ExecutionResult;
+import org.apache.iotdb.db.queryengine.plan.planner.LocalExecutionPlanner;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.BinaryLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.BooleanLiteral;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.ComparisonExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.DoubleLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Expression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Identifier;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Literal;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.LogicalExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.LongLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.NotExpression;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.SubqueryExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.parser.SqlParser;
+import org.apache.iotdb.rpc.TSStatusCode;
+
+import org.apache.tsfile.block.column.Column;
+import org.apache.tsfile.read.common.block.TsBlock;
+
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+public class PredicateWithUncorrelatedScalarSubqueryReconstructor {
+
+  private static final SqlParser relationSqlParser = new SqlParser();
+
+  private static final Coordinator coordinator = Coordinator.getInstance();
+
+  private PredicateWithUncorrelatedScalarSubqueryReconstructor() {
+    // utility class
+  }
+
+  public static void reconstructPredicateWithUncorrelatedScalarSubquery(
+      Expression expression, MPPQueryContext context) {
+    if (expression instanceof LogicalExpression) {
+      LogicalExpression logicalExpression = (LogicalExpression) expression;
+      for (Expression term : logicalExpression.getTerms()) {
+        reconstructPredicateWithUncorrelatedScalarSubquery(term, context);
+      }
+    } else if (expression instanceof NotExpression) {
+      NotExpression notExpression = (NotExpression) expression;
+      
reconstructPredicateWithUncorrelatedScalarSubquery(notExpression.getValue(), 
context);
+    } else if (expression instanceof ComparisonExpression) {
+      ComparisonExpression comparisonExpression = (ComparisonExpression) 
expression;
+      Expression left = comparisonExpression.getLeft();
+      Expression right = comparisonExpression.getRight();
+      if (left instanceof Identifier && right instanceof SubqueryExpression) {
+        Optional<Literal> result =
+            fetchUncorrelatedSubqueryResultForPredicate((SubqueryExpression) 
right, context);
+        // If the subquery result is not present, we cannot reconstruct the 
predicate.
+        if (result.isPresent()) {
+          right = result.get();
+        }
+      } else if (right instanceof Identifier && left instanceof 
SubqueryExpression) {
+        Optional<Literal> result =
+            fetchUncorrelatedSubqueryResultForPredicate((SubqueryExpression) 
left, context);
+        if (result.isPresent()) {
+          left = result.get();
+        }
+      }
+      comparisonExpression.setLeft(left);
+      comparisonExpression.setRight(right);

Review Comment:
   [nitpick] The code duplicates the logic for handling subquery expressions on 
left and right sides. Consider extracting the common logic into a helper method 
to reduce duplication.



##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/ir/PredicateWithUncorrelatedScalarSubqueryReconstructor.java:
##########
@@ -0,0 +1,171 @@
+/*
+ * 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.iotdb.db.queryengine.plan.relational.planner.ir;
+
+import org.apache.iotdb.commons.exception.IoTDBException;
+import org.apache.iotdb.db.protocol.session.SessionManager;
+import org.apache.iotdb.db.queryengine.common.MPPQueryContext;
+import org.apache.iotdb.db.queryengine.plan.Coordinator;
+import org.apache.iotdb.db.queryengine.plan.execution.ExecutionResult;
+import org.apache.iotdb.db.queryengine.plan.planner.LocalExecutionPlanner;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.BinaryLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.BooleanLiteral;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.ComparisonExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.DoubleLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Expression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Identifier;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.Literal;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.LogicalExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.LongLiteral;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.ast.NotExpression;
+import 
org.apache.iotdb.db.queryengine.plan.relational.sql.ast.SubqueryExpression;
+import org.apache.iotdb.db.queryengine.plan.relational.sql.parser.SqlParser;
+import org.apache.iotdb.rpc.TSStatusCode;
+
+import org.apache.tsfile.block.column.Column;
+import org.apache.tsfile.read.common.block.TsBlock;
+
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+public class PredicateWithUncorrelatedScalarSubqueryReconstructor {
+
+  private static final SqlParser relationSqlParser = new SqlParser();
+
+  private static final Coordinator coordinator = Coordinator.getInstance();
+
+  private PredicateWithUncorrelatedScalarSubqueryReconstructor() {
+    // utility class
+  }
+
+  public static void reconstructPredicateWithUncorrelatedScalarSubquery(
+      Expression expression, MPPQueryContext context) {
+    if (expression instanceof LogicalExpression) {
+      LogicalExpression logicalExpression = (LogicalExpression) expression;
+      for (Expression term : logicalExpression.getTerms()) {
+        reconstructPredicateWithUncorrelatedScalarSubquery(term, context);
+      }
+    } else if (expression instanceof NotExpression) {
+      NotExpression notExpression = (NotExpression) expression;
+      
reconstructPredicateWithUncorrelatedScalarSubquery(notExpression.getValue(), 
context);
+    } else if (expression instanceof ComparisonExpression) {
+      ComparisonExpression comparisonExpression = (ComparisonExpression) 
expression;
+      Expression left = comparisonExpression.getLeft();
+      Expression right = comparisonExpression.getRight();
+      if (left instanceof Identifier && right instanceof SubqueryExpression) {
+        Optional<Literal> result =
+            fetchUncorrelatedSubqueryResultForPredicate((SubqueryExpression) 
right, context);
+        // If the subquery result is not present, we cannot reconstruct the 
predicate.
+        if (result.isPresent()) {
+          right = result.get();
+        }
+      } else if (right instanceof Identifier && left instanceof 
SubqueryExpression) {
+        Optional<Literal> result =
+            fetchUncorrelatedSubqueryResultForPredicate((SubqueryExpression) 
left, context);
+        if (result.isPresent()) {
+          left = result.get();
+        }
+      }
+      comparisonExpression.setLeft(left);
+      comparisonExpression.setRight(right);
+    }
+  }
+
+  /**
+   * @return an Optional containing the result of the uncorrelated scalar 
subquery. Returns
+   *     Optional.empty() if the subquery cannot be executed in advance or if 
it does not return a
+   *     valid result.
+   */
+  private static Optional<Literal> fetchUncorrelatedSubqueryResultForPredicate(
+      SubqueryExpression subqueryExpression, MPPQueryContext context) {
+    final long queryId = SessionManager.getInstance().requestQueryId();
+    Throwable t = null;
+
+    try {
+      final ExecutionResult executionResult =
+          coordinator.executeForTableModel(
+              subqueryExpression.getQuery(),
+              relationSqlParser,
+              SessionManager.getInstance().getCurrSession(),
+              queryId,
+              SessionManager.getInstance()
+                  
.getSessionInfoOfTableModel(SessionManager.getInstance().getCurrSession()),
+              "Try to Fetch Uncorrelated Scalar Subquery Result for Predicate",
+              LocalExecutionPlanner.getInstance().metadata,
+              context.getTimeOut(),
+              false);
+
+      // This may occur when the subquery cannot be executed in advance (for 
example, with
+      // correlated scalar subqueries).
+      // Since we cannot determine the subquery's validity beforehand, we must 
submit the subquery.
+      // This approach may slow down filter involving correlated scalar 
subqueries.
+      if (executionResult.status.getCode() != 
TSStatusCode.SUCCESS_STATUS.getStatusCode()) {
+        return Optional.empty();
+      }
+
+      while (coordinator.getQueryExecution(queryId).hasNextResult()) {
+        final Optional<TsBlock> tsBlock;
+        try {
+          tsBlock = coordinator.getQueryExecution(queryId).getBatchResult();
+        } catch (final IoTDBException e) {
+          t = e;
+          throw new RuntimeException("Failed to Fetch Subquery Result.", e);
+        }
+        if (!tsBlock.isPresent() || tsBlock.get().isEmpty()) {
+          continue;
+        }
+        final Column[] columns = tsBlock.get().getValueColumns();
+        checkArgument(columns.length == 1, "Scalar Subquery result should only 
have one column.");
+        checkArgument(
+            tsBlock.get().getPositionCount() == 1 && 
!tsBlock.get().getColumn(0).isNull(0),
+            "Scalar Subquery result should only have one row.");
+        switch (columns[0].getDataType()) {
+          case INT32:
+          case DATE:
+            return Optional.of(new 
LongLiteral(Long.toString(columns[0].getInt(0))));
+          case INT64:
+          case TIMESTAMP:
+            return Optional.of(new 
LongLiteral(Long.toString(columns[0].getLong(0))));
+          case FLOAT:
+            return Optional.of(new 
DoubleLiteral(Double.toString(columns[0].getFloat(0))));
+          case DOUBLE:
+            return Optional.of(new 
DoubleLiteral(Double.toString(columns[0].getDouble(0))));
+          case BOOLEAN:
+            return Optional.of(new 
BooleanLiteral(Boolean.toString(columns[0].getBoolean(0))));

Review Comment:
   Converting primitive values to strings and then back to literals is 
inefficient. Consider using the constructor overloads that accept primitive 
values directly instead of string conversion.
   ```suggestion
               return Optional.of(new LongLiteral(columns[0].getInt(0)));
             case INT64:
             case TIMESTAMP:
               return Optional.of(new LongLiteral(columns[0].getLong(0)));
             case FLOAT:
               return Optional.of(new DoubleLiteral(columns[0].getFloat(0)));
             case DOUBLE:
               return Optional.of(new DoubleLiteral(columns[0].getDouble(0)));
             case BOOLEAN:
               return Optional.of(new BooleanLiteral(columns[0].getBoolean(0)));
   ```



##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/predicate/ConvertPredicateToTimeFilterVisitor.java:
##########
@@ -225,6 +226,13 @@ protected Filter visitBetweenPredicate(BetweenPredicate 
node, Void context) {
   }
 
   public static long getLongValue(Expression expression) {
-    return ((LongLiteral) expression).getParsedValue();
+    if (expression instanceof LongLiteral) {
+      return ((LongLiteral) expression).getParsedValue();
+    } else if (expression instanceof DoubleLiteral) {
+      return (long) ((DoubleLiteral) expression).getValue();
+    } else {
+      throw new IllegalArgumentException(
+          "Expression should be LongLiteral or DoubleLiteral, but got: " + 
expression.getClass());
+    }

Review Comment:
   The cast from double to long on line 232 may result in precision loss or 
unexpected behavior for large double values. Consider adding validation or 
documentation about the expected range of double values.



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