SOLR-9720: Use the new MapWriter and IteratorWriter interface

solr/solrj/src/java/org/apache/solr/client/solrj/io/Tuple.java

@@ -16,14 +16,15 @@
  */
 package org.apache.solr.client.solrj.io;
 
+import java.io.IOException;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
-import java.util.Map;
 import java.util.List;
+import java.util.Map;
 
-import org.apache.solr.common.MapSerializable;
+import org.apache.solr.common.MapWriter;
 
 /**
  *  A simple abstraction of a record containing key/value pairs.
@@ -32,7 +33,7 @@ import org.apache.solr.common.MapSerializable;
  *
 **/
 
-public class Tuple implements Cloneable, MapSerializable {
+public class Tuple implements Cloneable, MapWriter {
 
   /**
    *  When EOF field is true the Tuple marks the end of the stream.
@@ -90,7 +91,7 @@ public class Tuple implements Cloneable, MapSerializable {
     }
   }
 
-  // Convenience method since Booleans can be pased around as Strings.
+  // Convenience method since Booleans can be passed around as Strings.
   public Boolean getBool(Object key) {
     Object o = this.fields.get(key);
 
@@ -196,7 +197,13 @@ public class Tuple implements Cloneable, MapSerializable {
   }
 
   @Override
-  public Map toMap(Map<String, Object> map) {
-    return fields;
+  public void writeMap(EntryWriter ew) throws IOException {
+    fields.forEach((k, v) -> {
+      try {
+        ew.put((String)k,v);
+      } catch (IOException e) {
+        throw new RuntimeException(e);
+      }
+    });
   }
 }

solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/TupleStream.java

@@ -19,21 +19,19 @@ package org.apache.solr.client.solrj.io.stream;
 import java.io.Closeable;
 import java.io.IOException;
 import java.io.Serializable;
-import java.util.Collections;
-import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
 import java.util.UUID;
 
 import org.apache.solr.client.solrj.io.Tuple;
 import org.apache.solr.client.solrj.io.comp.StreamComparator;
 import org.apache.solr.client.solrj.io.stream.expr.Explanation;
 import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
-import org.apache.solr.common.MapSerializable;
+import org.apache.solr.common.IteratorWriter;
+import org.apache.solr.common.MapWriter;
 import org.apache.solr.common.SolrException;
 
 
-public abstract class TupleStream implements Closeable, Serializable, MapSerializable {
+public abstract class TupleStream implements Closeable, Serializable, MapWriter {
 
   private static final long serialVersionUID = 1;
   
@@ -42,15 +40,6 @@ public abstract class TupleStream implements Closeable, Serializable, MapSeriali
   public TupleStream() {
 
   }
-/*
-  public static void writeStreamOpen(Writer out) throws IOException {
-    out.write("{\"docs\":[");
-  }
-
-  public static void writeStreamClose(Writer out) throws IOException {
-    out.write("]}");
-  }*/
-
   public abstract void setStreamContext(StreamContext context);
 
   public abstract List<TupleStream> children();
@@ -69,41 +58,25 @@ public abstract class TupleStream implements Closeable, Serializable, MapSeriali
     return 0;
   }
 
-  private boolean isOpen = false;
-
   @Override
-  public Map toMap(Map<String, Object> map) {
-    try {
-      if (!isOpen) {
-        open();
-        isOpen = true;
-      }
-    } catch (IOException e) {
-      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, e);
-    }
-    return Collections.singletonMap("docs", new Iterator<Tuple>() {
-      Tuple tuple;
-      boolean isEOF = false;
-
-      @Override
-      public boolean hasNext() {
-        if (isEOF) return false;
-        if (tuple != null) return true;
-        try {
-          tuple = read();
-          if(tuple != null && tuple.EOF) close();
-          return tuple != null;
-        } catch (IOException e) {
-          throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, e);
+  public void writeMap(EntryWriter ew) throws IOException {
+    open();
+    ew.put("docs", (IteratorWriter) iw -> {
+      try {
+        for (; ; ) {
+          Tuple tuple = read();
+          if (tuple != null) {
+            iw.add(tuple);
+            if (tuple.EOF) {
+              close();
+              break;
+            }
+          } else {
+            break;
+          }
         }
-      }
-
-      @Override
-      public Tuple next() {
-        Tuple tmp = tuple;
-        tuple = null;
-        isEOF = tmp == null || tmp.EOF;
-        return tmp;
+      } catch (IOException e) {
+        throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, e);
       }
     });
   }

solr/solrj/src/java/org/apache/solr/common/IteratorWriter.java

@@ -25,12 +25,14 @@ import java.io.IOException;
  */
 public interface IteratorWriter {
   /**
-   * @param w after this method returns , the EntryWriter Object is invalid
+   * @param iw after this method returns , the EntryWriter Object is invalid
    *          Do not hold a reference to this object
    */
-  void writeIter(ItemWriter w) throws IOException;
+  void writeIter(ItemWriter iw) throws IOException;
 
   interface ItemWriter {
+    /**The item could be any supported type
+     */
     ItemWriter add(Object o) throws IOException;
 
     default ItemWriter add(int v) throws IOException {

solr/solrj/src/java/org/apache/solr/common/MapWriter.java

@@ -22,7 +22,9 @@ import java.io.IOException;
 import java.util.Map;
 
 /**
- * Use this class if the Map size is not known
+ * Use this class to push all entries of a Map into an output.
+ * This avoids creating map instances and is supposed to be memory efficient.
+ * If the entries are primitives, unnecessary boxing is also avoided
  */
 public interface MapWriter extends MapSerializable {
 
@@ -45,8 +47,14 @@ public interface MapWriter extends MapSerializable {
 
   void writeMap(EntryWriter ew) throws IOException;
 
+  /**
+   * An interface to push one entry at a time to the output
+   */
   interface EntryWriter {
-    /**Writes a key value into the map
+
+    /**
+     * Writes a key value into the map
+     *
      * @param k The key
      * @param v The value can be any supported object
      */
@@ -69,11 +77,12 @@ public interface MapWriter extends MapSerializable {
       return this;
     }
 
-    default EntryWriter put(String k, double v) throws IOException{
+    default EntryWriter put(String k, double v) throws IOException {
       put(k, (Double) v);
       return this;
     }
-    default EntryWriter put(String k, boolean v) throws IOException{
+
+    default EntryWriter put(String k, boolean v) throws IOException {
       put(k, (Boolean) v);
       return this;
     }