small speed enhancement using a column factory

source/net/yacy/kelondro/index/Column.java

@@ -31,7 +31,7 @@ import java.io.Serializable;
 
 import net.yacy.kelondro.util.kelondroException;
 
-public final class Column implements Serializable {
+public final class Column implements Cloneable, Serializable {
 
     private static final long serialVersionUID=6558500565023465301L;
 
@@ -60,7 +60,7 @@ public final class Column implements Serializable {
         this.nickname = nickname;
         this.description = description;
     }
-
+    
     public Column(String celldef) {
         // define column with column syntax
         // example: <UDate-3>
@@ -196,6 +196,24 @@ public final class Column implements Serializable {
         }
     }
 
+    /**
+     * th clone method is useful to produce a similiar column with a different cell width
+     * @return the cloned Column
+     */
+    public Object clone() {
+    	return new Column(this.nickname, this.celltype, this.encoder, this.cellwidth, this.description);
+    }
+
+    /**
+     * a column width may change when the object was not yet used.
+     * this applies to clones of Column objects which are used as Column producers
+     * @param cellwidth
+     */
+    public void setCellwidth(int cellwidth) {
+    	assert this.celltype == celltype_string || this.celltype == celltype_binary;
+    	this.cellwidth = cellwidth;
+    }
+
     @Override
     public final String toString() {
         final StringBuilder s = new StringBuilder(20);

source/net/yacy/kelondro/index/RowCollection.java

@@ -169,10 +169,10 @@ public class RowCollection implements Sortable<Row.Entry>, Iterable<Row.Entry>,
         return (int) (time / day) - 10957;
     }
 
-    private static Column exportColumn0, exportColumn1, exportColumn2, exportColumn3, exportColumn4;
+    private static Column exportColumn0, exportColumn1, exportColumn2, exportColumn3, exportColumn4, collectionColumnProducer;
 
     protected static final long exportOverheadSize = 14;
-
+    
     private static Row exportRow(final int chunkcachelength) {
         /*
         return new Row(
@@ -191,15 +191,17 @@ public class RowCollection implements Sortable<Row.Entry>, Iterable<Row.Entry>,
         if (exportColumn2 == null) exportColumn2 = new Column("short lastwrote-2 {b256}");
         if (exportColumn3 == null) exportColumn3 = new Column("byte[] orderkey-2");
         if (exportColumn4 == null) exportColumn4 = new Column("int orderbound-4 {b256}");
+        if (collectionColumnProducer == null) collectionColumnProducer = new Column("byte[] collection-1");
         /*
          * because of a strange bug these objects cannot be initialized as normal
          * static final. If I try that, they are not initialized and are assigned null. why?
          */
-        final StringBuilder colName = new StringBuilder(30);
-        colName.append("byte[] collection-").append(Integer.toString(chunkcachelength));
+        
+        Column collectionColumn = (Column) collectionColumnProducer.clone();
+        collectionColumn.setCellwidth(chunkcachelength);
         final Row er = new Row(new Column[]{
                     exportColumn0, exportColumn1, exportColumn2, exportColumn3, exportColumn4,
-                    new Column(colName.toString())
+                    collectionColumn
                 },
                 NaturalOrder.naturalOrder
         );