[chore](expr) decouple Expr from unnecessary class

fe/fe-core/src/main/java/org/apache/doris/analysis/ArithmeticExpr.java

@@ -102,11 +102,9 @@ protected ArithmeticExpr(ArithmeticExpr other) {
     @Override
     public String toString() {
         if (children.size() == 1) {
-            return op.toString() + " " + getChild(0).accept(ExprToSqlVisitor.INSTANCE, ToSqlParams.WITH_TABLE);
+            return op.toString() + " " + getChild(0);
         } else {
-            return "(" + getChild(0).accept(ExprToSqlVisitor.INSTANCE, ToSqlParams.WITH_TABLE)
-                    + " " + op.toString()
-                    + " " + getChild(1).accept(ExprToSqlVisitor.INSTANCE, ToSqlParams.WITH_TABLE) + ")";
+            return "(" + getChild(0) + " " + op.toString() + " " + getChild(1) + ")";
         }
     }
 

fe/fe-core/src/main/java/org/apache/doris/analysis/ExprToThriftVisitor.java

@@ -26,6 +26,7 @@
 import org.apache.doris.common.ErrorCode;
 import org.apache.doris.common.ErrorReport;
 import org.apache.doris.qe.ConnectContext;
+import org.apache.doris.thrift.TAggregateExpr;
 import org.apache.doris.thrift.TBoolLiteral;
 import org.apache.doris.thrift.TCaseExpr;
 import org.apache.doris.thrift.TColumnRef;
@@ -493,7 +494,7 @@ public Void visitFunctionCallExpr(FunctionCallExpr expr, TExprNode msg) {
             if (aggParams == null) {
                 aggParams = expr.getFnParams();
             }
-            msg.setAggExpr(aggParams.createTAggregateExpr(expr.isMergeAggFn()));
+            msg.setAggExpr(createTAggregateExprFromFunctionParams(aggParams, expr.isMergeAggFn()));
         } else {
             msg.node_type = TExprNodeType.FUNCTION_CALL;
         }
@@ -504,6 +505,20 @@ public Void visitFunctionCallExpr(FunctionCallExpr expr, TExprNode msg) {
         return null;
     }
 
+    public TAggregateExpr createTAggregateExprFromFunctionParams(FunctionParams functionParams, boolean isMergeAggFn) {
+        List<TTypeDesc> paramTypes = new ArrayList<>();
+        if (functionParams.exprs() != null) {
+            for (Expr expr : functionParams.exprs()) {
+                TTypeDesc desc = expr.getType().toThrift();
+                desc.setIsNullable(expr.isNullable());
+                paramTypes.add(desc);
+            }
+        }
+        TAggregateExpr aggExpr = new TAggregateExpr(isMergeAggFn);
+        aggExpr.setParamTypes(paramTypes);
+        return aggExpr;
+    }
+
     @Override
     public Void visitLambdaFunctionCallExpr(LambdaFunctionCallExpr expr, TExprNode msg) {
         msg.node_type = TExprNodeType.LAMBDA_FUNCTION_CALL_EXPR;

fe/fe-core/src/main/java/org/apache/doris/analysis/FunctionParams.java

@@ -20,13 +20,9 @@
 
 package org.apache.doris.analysis;
 
-import org.apache.doris.thrift.TAggregateExpr;
-import org.apache.doris.thrift.TTypeDesc;
-
 import com.google.common.base.Preconditions;
 import com.google.gson.annotations.SerializedName;
 
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 
@@ -74,20 +70,6 @@ public FunctionParams clone(List<Expr> children) {
         return new FunctionParams(isDistinct(), children);
     }
 
-    public TAggregateExpr createTAggregateExpr(boolean isMergeAggFn) {
-        List<TTypeDesc> paramTypes = new ArrayList<>();
-        if (exprs != null) {
-            for (Expr expr : exprs) {
-                TTypeDesc desc = expr.getType().toThrift();
-                desc.setIsNullable(expr.isNullable());
-                paramTypes.add(desc);
-            }
-        }
-        TAggregateExpr aggExpr = new TAggregateExpr(isMergeAggFn);
-        aggExpr.setParamTypes(paramTypes);
-        return aggExpr;
-    }
-
     public boolean isStar() {
         return isStar;
     }

fe/fe-core/src/main/java/org/apache/doris/analysis/OrderByElement.java

@@ -75,13 +75,14 @@ public static List<Expr> getOrderByExprs(List<OrderByElement> src) {
         return result;
     }
 
-    public String toSql() {
+    @Override
+    public String toString() {
         StringBuilder strBuilder = new StringBuilder();
-        strBuilder.append(expr.accept(ExprToSqlVisitor.INSTANCE, ToSqlParams.WITH_TABLE));
+        strBuilder.append(expr);
         strBuilder.append(isAsc ? " ASC" : " DESC");
 
         // When ASC and NULLS LAST or DESC and NULLS FIRST, we do not print NULLS FIRST/LAST
-        // because it is the default behavior and we want to avoid printing NULLS FIRST/LAST
+        // because it is the default behavior. we want to avoid printing NULLS FIRST/LAST
         // whenever possible as it is incompatible with Hive (SQL compatibility with Hive is
         // important for views).
         if (nullsFirstParam != null) {
@@ -97,11 +98,6 @@ public String toSql() {
         return strBuilder.toString();
     }
 
-    @Override
-    public String toString() {
-        return toSql();
-    }
-
     @Override
     public boolean equals(Object obj) {
         if (obj == null) {

fe/fe-core/src/main/java/org/apache/doris/planner/AnalyticEvalNode.java

@@ -126,7 +126,7 @@ public String getNodeExplainString(String prefix, TExplainLevel detailLevel) {
             strings.clear();
 
             for (OrderByElement element : orderByElements) {
-                strings.add(element.toSql());
+                strings.add(orderByElementToSql(element));
             }
 
             output.append(Joiner.on(", ").join(strings));
@@ -146,6 +146,29 @@ public String getNodeExplainString(String prefix, TExplainLevel detailLevel) {
         return output.toString();
     }
 
+
+    private String orderByElementToSql(OrderByElement orderByElement) {
+        StringBuilder strBuilder = new StringBuilder();
+        strBuilder.append(orderByElement.getExpr().accept(ExprToSqlVisitor.INSTANCE, ToSqlParams.WITH_TABLE));
+        strBuilder.append(orderByElement.getIsAsc() ? " ASC" : " DESC");
+
+        // When ASC and NULLS LAST or DESC and NULLS FIRST, we do not print NULLS FIRST/LAST
+        // because it is the default behavior and we want to avoid printing NULLS FIRST/LAST
+        // whenever possible as it is incompatible with Hive (SQL compatibility with Hive is
+        // important for views).
+        if (orderByElement.getNullsFirstParam() != null) {
+            if (orderByElement.getIsAsc() && orderByElement.getNullsFirstParam()) {
+                // If ascending, nulls are last by default, so only add if nulls first.
+                strBuilder.append(" NULLS FIRST");
+            } else if (!orderByElement.getIsAsc() && !orderByElement.getNullsFirstParam()) {
+                // If descending, nulls are first by default, so only add if nulls last.
+                strBuilder.append(" NULLS LAST");
+            }
+        }
+
+        return strBuilder.toString();
+    }
+
     /**
      * If `partitionExprs` is empty, the result must be output by single instance.
      *