Merge the implementation of timechart and chart

core/src/main/java/org/opensearch/sql/analysis/Analyzer.java

@@ -96,7 +96,6 @@
 import org.opensearch.sql.ast.tree.StreamWindow;
 import org.opensearch.sql.ast.tree.SubqueryAlias;
 import org.opensearch.sql.ast.tree.TableFunction;
-import org.opensearch.sql.ast.tree.Timechart;
 import org.opensearch.sql.ast.tree.Trendline;
 import org.opensearch.sql.ast.tree.UnresolvedPlan;
 import org.opensearch.sql.ast.tree.Values;
@@ -775,11 +774,6 @@ public LogicalPlan visitChart(Chart node, AnalysisContext context) {
     throw getOnlyForCalciteException("Chart");
   }
 
-  @Override
-  public LogicalPlan visitTimechart(Timechart node, AnalysisContext context) {
-    throw getOnlyForCalciteException("Timechart");
-  }
-
   @Override
   public LogicalPlan visitWindow(Window node, AnalysisContext context) {
     throw getOnlyForCalciteException("Window");

core/src/main/java/org/opensearch/sql/ast/AbstractNodeVisitor.java

@@ -83,7 +83,6 @@
 import org.opensearch.sql.ast.tree.StreamWindow;
 import org.opensearch.sql.ast.tree.SubqueryAlias;
 import org.opensearch.sql.ast.tree.TableFunction;
-import org.opensearch.sql.ast.tree.Timechart;
 import org.opensearch.sql.ast.tree.Trendline;
 import org.opensearch.sql.ast.tree.Values;
 import org.opensearch.sql.ast.tree.Window;
@@ -280,10 +279,6 @@ public T visitChart(Chart node, C context) {
     return visitChildren(node, context);
   }
 
-  public T visitTimechart(Timechart node, C context) {
-    return visitChildren(node, context);
-  }
-
   public T visitRegex(Regex node, C context) {
     return visitChildren(node, context);
   }

core/src/main/java/org/opensearch/sql/ast/dsl/AstDSL.java

@@ -728,7 +728,7 @@ public static Bin bin(UnresolvedExpression field, Argument... arguments) {
   }
 
   /** Get a reference to the implicit timestamp field {@code @timestamp} */
-  public static Field referImplicitTimestampField() {
+  public static Field implicitTimestampField() {
     return AstDSL.field(OpenSearchConstants.IMPLICIT_FIELD_TIMESTAMP);
   }
 }

core/src/main/java/org/opensearch/sql/ast/tree/Chart.java

@@ -5,17 +5,44 @@
 
 package org.opensearch.sql.ast.tree;
 
+import static org.opensearch.sql.ast.dsl.AstDSL.aggregate;
+import static org.opensearch.sql.ast.dsl.AstDSL.doubleLiteral;
+import static org.opensearch.sql.ast.dsl.AstDSL.eval;
+import static org.opensearch.sql.ast.dsl.AstDSL.function;
+import static org.opensearch.sql.ast.dsl.AstDSL.stringLiteral;
+import static org.opensearch.sql.ast.expression.IntervalUnit.MILLISECOND;
+import static org.opensearch.sql.ast.tree.Chart.PerFunctionRateExprBuilder.timestampadd;
+import static org.opensearch.sql.ast.tree.Chart.PerFunctionRateExprBuilder.timestampdiff;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.DIVIDE;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.MULTIPLY;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.SUM;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.TIMESTAMPADD;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.TIMESTAMPDIFF;
+
 import com.google.common.collect.ImmutableList;
 import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
 import lombok.AllArgsConstructor;
 import lombok.EqualsAndHashCode;
 import lombok.Getter;
+import lombok.RequiredArgsConstructor;
 import lombok.ToString;
 import org.opensearch.sql.ast.AbstractNodeVisitor;
 import org.opensearch.sql.ast.dsl.AstDSL;
+import org.opensearch.sql.ast.expression.AggregateFunction;
+import org.opensearch.sql.ast.expression.Alias;
 import org.opensearch.sql.ast.expression.Argument;
+import org.opensearch.sql.ast.expression.Field;
+import org.opensearch.sql.ast.expression.Function;
+import org.opensearch.sql.ast.expression.IntervalUnit;
+import org.opensearch.sql.ast.expression.Let;
 import org.opensearch.sql.ast.expression.Literal;
+import org.opensearch.sql.ast.expression.Span;
+import org.opensearch.sql.ast.expression.SpanUnit;
 import org.opensearch.sql.ast.expression.UnresolvedExpression;
+import org.opensearch.sql.calcite.utils.PlanUtils;
 
 /** AST node represent chart command. */
 @Getter
@@ -39,8 +66,8 @@ public class Chart extends UnresolvedPlan {
 
   @Override
   public UnresolvedPlan attach(UnresolvedPlan child) {
-    this.child = child;
-    return this;
+    // Transform after child attached to avoid unintentionally overriding it
+    return toBuilder().child(child).build().transformPerFunction();
   }
 
   @Override
@@ -52,4 +79,131 @@ public List<UnresolvedPlan> getChild() {
   public <T, C> T accept(AbstractNodeVisitor<T, C> nodeVisitor, C context) {
     return nodeVisitor.visitChart(this, context);
   }
+
+  /**
+   * Transform per function to eval-based post-processing on sum result by chart. Specifically,
+   * calculate how many seconds are in the time bucket based on the span option dynamically, then
+   * divide the aggregated sum value by the number of seconds to get the per-second rate.
+   *
+   * <p>For example, with span=5m per_second(field): per second rate = sum(field) / 300 seconds
+   *
+   * @return eval+chart if per function present, or the original chart otherwise.
+   */
+  private UnresolvedPlan transformPerFunction() {
+    Optional<PerFunction> perFuncOpt = PerFunction.from(aggregationFunction);
+    if (perFuncOpt.isEmpty()) {
+      return this;
+    }
+
+    PerFunction perFunc = perFuncOpt.get();
+    // For chart, the rowSplit should contain the span information
+    UnresolvedExpression spanExpr = rowSplit;
+    if (rowSplit instanceof Alias) {
+      spanExpr = ((Alias) rowSplit).getDelegated();
+    }
+    if (!(spanExpr instanceof Span)) {
+      return this; // Cannot transform without span information
+    }
+
+    Span span = (Span) spanExpr;
+    Field spanStartTime = AstDSL.implicitTimestampField();
+    Function spanEndTime = timestampadd(span.getUnit(), span.getValue(), spanStartTime);
+    Function spanMillis = timestampdiff(MILLISECOND, spanStartTime, spanEndTime);
+    final int SECOND_IN_MILLISECOND = 1000;
+    return eval(
+        chart(AstDSL.alias(perFunc.aggName, PerFunctionRateExprBuilder.sum(perFunc.aggArg))),
+        let(perFunc.aggName)
+            .multiply(perFunc.seconds * SECOND_IN_MILLISECOND)
+            .dividedBy(spanMillis));
+  }
+
+  private Chart chart(UnresolvedExpression newAggregationFunction) {
+    return this.toBuilder().aggregationFunction(newAggregationFunction).build();
+  }
+
+  @RequiredArgsConstructor
+  static class PerFunction {
+    private static final Map<String, Integer> UNIT_SECONDS =
+        Map.of(
+            "per_second", 1,
+            "per_minute", 60,
+            "per_hour", 3600,
+            "per_day", 86400);
+    private final String aggName;
+    private final UnresolvedExpression aggArg;
+    private final int seconds;
+
+    static Optional<PerFunction> from(UnresolvedExpression aggExpr) {
+      if (aggExpr instanceof Alias) {
+        return from(((Alias) aggExpr).getDelegated());
+      }
+      ;
+      if (!(aggExpr instanceof AggregateFunction)) {
+        return Optional.empty();
+      }
+
+      AggregateFunction aggFunc = (AggregateFunction) aggExpr;
+      String aggFuncName = aggFunc.getFuncName().toLowerCase(Locale.ROOT);
+      if (!UNIT_SECONDS.containsKey(aggFuncName)) {
+        return Optional.empty();
+      }
+
+      String aggName = toAggName(aggFunc);
+      return Optional.of(
+          new PerFunction(aggName, aggFunc.getField(), UNIT_SECONDS.get(aggFuncName)));
+    }
+
+    private static String toAggName(AggregateFunction aggFunc) {
+      String fieldName =
+          (aggFunc.getField() instanceof Field)
+              ? ((Field) aggFunc.getField()).getField().toString()
+              : aggFunc.getField().toString();
+      return String.format(Locale.ROOT, "%s(%s)", aggFunc.getFuncName(), fieldName);
+    }
+  }
+
+  private PerFunctionRateExprBuilder let(String fieldName) {
+    return new PerFunctionRateExprBuilder(AstDSL.field(fieldName));
+  }
+
+  /** Fluent builder for creating Let expressions with mathematical operations. */
+  static class PerFunctionRateExprBuilder {
+    private final Field field;
+    private UnresolvedExpression expr;
+
+    PerFunctionRateExprBuilder(Field field) {
+      this.field = field;
+      this.expr = field;
+    }
+
+    PerFunctionRateExprBuilder multiply(Integer multiplier) {
+      // Promote to double literal to avoid integer division in downstream
+      this.expr =
+          function(
+              MULTIPLY.getName().getFunctionName(), expr, doubleLiteral(multiplier.doubleValue()));
+      return this;
+    }
+
+    Let dividedBy(UnresolvedExpression divisor) {
+      return AstDSL.let(field, function(DIVIDE.getName().getFunctionName(), expr, divisor));
+    }
+
+    static UnresolvedExpression sum(UnresolvedExpression field) {
+      return aggregate(SUM.getName().getFunctionName(), field);
+    }
+
+    static Function timestampadd(
+        SpanUnit unit, UnresolvedExpression value, UnresolvedExpression timestampField) {
+      UnresolvedExpression intervalUnit =
+          stringLiteral(PlanUtils.spanUnitToIntervalUnit(unit).toString());
+      return function(
+          TIMESTAMPADD.getName().getFunctionName(), intervalUnit, value, timestampField);
+    }
+
+    static Function timestampdiff(
+        IntervalUnit unit, UnresolvedExpression start, UnresolvedExpression end) {
+      return function(
+          TIMESTAMPDIFF.getName().getFunctionName(), stringLiteral(unit.toString()), start, end);
+    }
+  }
 }