Remove Expr.visit. (#10437)

* Remove Expr.visit.

It isn't used and doesn't have tests.

* Remove Visitor too.

core/src/main/java/org/apache/druid/math/expr/BinaryOperatorExpr.java

@@ -46,14 +46,6 @@ abstract class BinaryOpExprBase implements Expr
     this.right = right;
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    left.visit(visitor);
-    right.visit(visitor);
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {

core/src/main/java/org/apache/druid/math/expr/ConstantExpr.java

@@ -57,12 +57,6 @@ abstract class ConstantExpr implements Expr
     return true;
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {

core/src/main/java/org/apache/druid/math/expr/Expr.java

@@ -112,12 +112,6 @@ public interface Expr
    */
   String stringify();
 
-  /**
-   * Programmatically inspect the {@link Expr} tree with a {@link Visitor}. Each {@link Expr} is responsible for
-   * ensuring the {@link Visitor} can visit all of its {@link Expr} children before visiting itself
-   */
-  void visit(Visitor visitor);
-
   /**
    * Programatically rewrite the {@link Expr} tree with a {@link Shuttle}. Each {@link Expr} is responsible for
    * ensuring the {@link Shuttle} can visit all of its {@link Expr} children, as well as updating its children
@@ -252,25 +246,15 @@ public interface Expr
     <T> T[] getObjectVector(String name);
 
     long[] getLongVector(String name);
+
     double[] getDoubleVector(String name);
+
     @Nullable
     boolean[] getNullVector(String name);
 
     int getCurrentVectorSize();
   }
 
-  /**
-   * Mechanism to inspect an {@link Expr}, implementing a {@link Visitor} allows visiting all children of an
-   * {@link Expr}
-   */
-  interface Visitor
-  {
-    /**
-     * Provide the {@link Visitor} with an {@link Expr} to inspect
-     */
-    void visit(Expr expr);
-  }
-
   /**
    * Mechanism to rewrite an {@link Expr}, implementing a {@link Shuttle} allows visiting all children of an
    * {@link Expr}, and replacing them as desired.

core/src/main/java/org/apache/druid/math/expr/ExprMacroTable.java

@@ -111,13 +111,6 @@ public class ExprMacroTable
       analyzeInputsSupplier = Suppliers.memoize(this::supplyAnalyzeInputs);
     }
 
-    @Override
-    public void visit(final Visitor visitor)
-    {
-      arg.visit(visitor);
-      visitor.visit(this);
-    }
-
     @Override
     public BindingAnalysis analyzeInputs()
     {
@@ -184,15 +177,6 @@ public class ExprMacroTable
       );
     }
 
-    @Override
-    public void visit(final Visitor visitor)
-    {
-      for (Expr arg : args) {
-        arg.visit(visitor);
-      }
-      visitor.visit(this);
-    }
-
     @Override
     public BindingAnalysis analyzeInputs()
     {

core/src/main/java/org/apache/druid/math/expr/FunctionalExpr.java

@@ -101,13 +101,6 @@ class LambdaExpr implements Expr
     return StringUtils.format("(%s) -> %s", ARG_JOINER.join(getIdentifiers()), expr.stringify());
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    expr.visit(visitor);
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {
@@ -201,15 +194,6 @@ class FunctionExpr implements Expr
     return StringUtils.format("%s(%s)", name, ARG_JOINER.join(args.stream().map(Expr::stringify).iterator()));
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    for (Expr child : args) {
-      child.visit(visitor);
-    }
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {
@@ -338,16 +322,6 @@ class ApplyFunctionExpr implements Expr
     );
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    lambdaExpr.visit(visitor);
-    for (Expr arg : argsExpr) {
-      arg.visit(visitor);
-    }
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {

core/src/main/java/org/apache/druid/math/expr/IdentifierExpr.java

@@ -131,12 +131,6 @@ class IdentifierExpr implements Expr
     return StringUtils.format("\"%s\"", StringEscapeUtils.escapeJava(binding));
   }
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {

core/src/main/java/org/apache/druid/math/expr/UnaryOperatorExpr.java

@@ -45,13 +45,6 @@ abstract class UnaryExpr implements Expr
 
   abstract UnaryExpr copy(Expr expr);
 
-  @Override
-  public void visit(Visitor visitor)
-  {
-    expr.visit(visitor);
-    visitor.visit(this);
-  }
-
   @Override
   public Expr visit(Shuttle shuttle)
   {

processing/src/main/java/org/apache/druid/query/expression/TrimExprMacro.java

@@ -282,14 +282,6 @@ public abstract class TrimExprMacro implements ExprMacroTable.ExprMacro
       return StringUtils.format("%s(%s, %s)", mode.getFnName(), stringExpr.stringify(), charsExpr.stringify());
     }
 
-    @Override
-    public void visit(final Visitor visitor)
-    {
-      stringExpr.visit(visitor);
-      charsExpr.visit(visitor);
-      visitor.visit(this);
-    }
-
     @Override
     public Expr visit(Shuttle shuttle)
     {