Stop rewriting item/index variables inside foreach

Although it is not the goal, this could improve performance when there are many foreach iterations.

Author: harawata

src/main/java/org/apache/ibatis/scripting/xmltags/DynamicContext.java

@@ -45,7 +45,6 @@ public class DynamicContext {
 
   protected final ContextMap bindings;
   private final StringJoiner sqlBuilder = new StringJoiner(" ");
-  private int uniqueNumber = 0;
 
   private final Configuration configuration;
   private final Object parameterObject;
@@ -91,10 +90,6 @@ public String getSql() {
     return sqlBuilder.toString().trim();
   }
 
-  public int getUniqueNumber() {
-    return uniqueNumber++;
-  }
-
   public List<ParameterMapping> getParameterMappings() {
     return tokenHandler == null ? new ArrayList<>() : tokenHandler.getParameterMappings();
   }

src/main/java/org/apache/ibatis/scripting/xmltags/ForEachSqlNode.java

@@ -20,14 +20,12 @@
 import java.util.Optional;
 
 import org.apache.ibatis.mapping.ParameterMapping;
-import org.apache.ibatis.parsing.GenericTokenParser;
 import org.apache.ibatis.session.Configuration;
 
 /**
  * @author Clinton Begin
  */
 public class ForEachSqlNode implements SqlNode {
-  public static final String ITEM_PREFIX = "__frch_";
 
   private final ExpressionEvaluator evaluator;
   private final String collectionExpression;
@@ -44,14 +42,16 @@ public class ForEachSqlNode implements SqlNode {
    * @deprecated Since 3.5.9, use the {@link #ForEachSqlNode(Configuration, SqlNode, String, Boolean, String, String, String, String, String)}.
    */
   @Deprecated
-  public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, String index, String item, String open, String close, String separator) {
+  public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, String index,
+      String item, String open, String close, String separator) {
     this(configuration, contents, collectionExpression, null, index, item, open, close, separator);
   }
 
   /**
    * @since 3.5.9
    */
-  public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, Boolean nullable, String index, String item, String open, String close, String separator) {
+  public ForEachSqlNode(Configuration configuration, SqlNode contents, String collectionExpression, Boolean nullable,
+      String index, String item, String open, String close, String separator) {
     this.evaluator = new ExpressionEvaluator();
     this.collectionExpression = collectionExpression;
     this.nullable = nullable;
@@ -68,7 +68,7 @@ public ForEachSqlNode(Configuration configuration, SqlNode contents, String coll
   public boolean apply(DynamicContext context) {
     Map<String, Object> bindings = context.getBindings();
     final Iterable<?> iterable = evaluator.evaluateIterable(collectionExpression, bindings,
-      Optional.ofNullable(nullable).orElseGet(configuration::isNullableOnForEach));
+        Optional.ofNullable(nullable).orElseGet(configuration::isNullableOnForEach));
     if (iterable == null || !iterable.iterator().hasNext()) {
       return true;
     }
@@ -82,18 +82,17 @@ public boolean apply(DynamicContext context) {
       } else {
         scopedContext = new PrefixedContext(context, separator);
       }
-      int uniqueNumber = scopedContext.getUniqueNumber();
       // Issue #709
       if (o instanceof Map.Entry) {
         @SuppressWarnings("unchecked")
         Map.Entry<Object, Object> mapEntry = (Map.Entry<Object, Object>) o;
-        applyIndex(scopedContext, mapEntry.getKey(), uniqueNumber);
-        applyItem(scopedContext, mapEntry.getValue(), uniqueNumber);
+        applyIndex(scopedContext, mapEntry.getKey());
+        applyItem(scopedContext, mapEntry.getValue());
       } else {
-        applyIndex(scopedContext, i, uniqueNumber);
-        applyItem(scopedContext, o, uniqueNumber);
+        applyIndex(scopedContext, i);
+        applyItem(scopedContext, o);
       }
-      contents.apply(new FilteredDynamicContext(configuration, scopedContext, index, item, uniqueNumber));
+      contents.apply(scopedContext);
       if (first) {
         first = !((PrefixedContext) scopedContext).isPrefixApplied();
       }
@@ -103,17 +102,15 @@ public boolean apply(DynamicContext context) {
     return true;
   }
 
-  private void applyIndex(DynamicContext context, Object o, int i) {
+  private void applyIndex(DynamicContext context, Object o) {
     if (index != null) {
       context.bind(index, o);
-      context.bind(itemizeItem(index, i), o);
     }
   }
 
-  private void applyItem(DynamicContext context, Object o, int i) {
+  private void applyItem(DynamicContext context, Object o) {
     if (item != null) {
       context.bind(item, o);
-      context.bind(itemizeItem(item, i), o);
     }
   }
 
@@ -129,55 +126,6 @@ private void applyClose(DynamicContext context) {
     }
   }
 
-  private static String itemizeItem(String item, int i) {
-    return ITEM_PREFIX + item + "_" + i;
-  }
-
-  private static class FilteredDynamicContext extends DynamicContext {
-    private final DynamicContext delegate;
-    private final int index;
-    private final String itemIndex;
-    private final String item;
-
-    public FilteredDynamicContext(Configuration configuration,DynamicContext delegate, String itemIndex, String item, int i) {
-      super(configuration, delegate.getParameterObject(), delegate.getParameterType(), delegate.isParamExists());
-      this.delegate = delegate;
-      this.index = i;
-      this.itemIndex = itemIndex;
-      this.item = item;
-      this.bindings.putAll(delegate.getBindings());
-    }
-
-    @Override
-    public String getSql() {
-      return delegate.getSql();
-    }
-
-    @Override
-    public void appendSql(String sql) {
-      GenericTokenParser parser = new GenericTokenParser("#{", "}", content -> {
-        String newContent = content.replaceFirst("^\\s*" + item + "(?![^.,:\\s])", itemizeItem(item, index));
-        if (itemIndex != null && newContent.equals(content)) {
-          newContent = content.replaceFirst("^\\s*" + itemIndex + "(?![^.,:\\s])", itemizeItem(itemIndex, index));
-        }
-        return "#{" + newContent + "}";
-      });
-
-      delegate.appendSql(parser.parse(sql));
-    }
-
-    @Override
-    public int getUniqueNumber() {
-      return delegate.getUniqueNumber();
-    }
-
-    @Override
-    public List<ParameterMapping> getParameterMappings() {
-      return delegate.getParameterMappings();
-    }
-  }
-
-
   private class PrefixedContext extends DynamicContext {
     private final DynamicContext delegate;
     private final String prefix;
@@ -209,11 +157,6 @@ public String getSql() {
       return delegate.getSql();
     }
 
-    @Override
-    public int getUniqueNumber() {
-      return delegate.getUniqueNumber();
-    }
-
     @Override
     public List<ParameterMapping> getParameterMappings() {
       return delegate.getParameterMappings();

src/main/java/org/apache/ibatis/scripting/xmltags/TrimSqlNode.java

@@ -94,11 +94,6 @@ public void applyAll() {
       delegate.appendSql(sqlBuffer.toString());
     }
 
-    @Override
-    public int getUniqueNumber() {
-      return delegate.getUniqueNumber();
-    }
-
     @Override
     public void appendSql(String sql) {
       sqlBuffer.append(sql);