test: add performance test for "reused vs non-reused at client side" …

…prepared statements

TL;DR: the difference is not significant

Benchmark                                              (columnIndexType)  (getter)  (ncols)  (nrows)  (reuseStatement)  (type)  (unique)  Mode  Cnt    Score      Error   Units
ProcessResultSet.bindExecuteFetch                                  INDEX      BEST        1        1              true     INT     false  avgt   10   38,899 ±    0,508   us/op
ProcessResultSet.bindExecuteFetch:·gc.alloc.rate.norm              INDEX      BEST        1        1              true     INT     false  avgt   10  464,069 ±    0,228    B/op
ProcessResultSet.bindExecuteFetch                                  INDEX      BEST        1        1             false     INT     false  avgt   10   39,724 ±    0,454   us/op
ProcessResultSet.bindExecuteFetch:·gc.alloc.rate.norm              INDEX      BEST        1        1             false     INT     false  avgt   10  752,070 ±    0,232    B/op

ubenchmark/src/main/java/org/postgresql/benchmark/statement/ProcessResultSet.java

@@ -79,8 +79,14 @@ public enum GetterType {
   @Param({"NAME"})
   public ColumnIndexType columnIndexType;
 
+  // Reuse == false is in line with what most applications do. They never reuse PreparedStatement objects
+  @Param({"false"})
+  public boolean reuseStatement;
+
   private Connection connection;
 
+  private PreparedStatement ps;
+
   private String sql;
 
   private int cntr;
@@ -89,6 +95,10 @@ public enum GetterType {
 
   @Setup(Level.Trial)
   public void setUp() throws SQLException {
+    if (reuseStatement && unique) {
+      System.out.println("It does not make sense to test reuseStatement && unique combination. Terminating to save time");
+      System.exit(-1);
+    }
     if (type == FieldType.TIMESTAMP) {
       System.out.println(
           "TimeZone.getDefault().getDisplayName() = " + TimeZone.getDefault().getDisplayName());
@@ -124,6 +134,9 @@ public void setUp() throws SQLException {
     }
     sb.append(" from generate_series(1, ?) as t(x)");
     sql = sb.toString();
+    if (reuseStatement) {
+      this.ps = connection.prepareStatement(sql);
+    }
   }
 
   @TearDown(Level.Trial)
@@ -137,7 +150,8 @@ public Statement bindExecuteFetch(Blackhole b) throws SQLException {
     if (unique) {
       sql += " -- " + cntr++;
     }
-    PreparedStatement ps = connection.prepareStatement(sql);
+
+    PreparedStatement ps = reuseStatement ? this.ps : connection.prepareStatement(sql);
     ps.setInt(1, nrows);
     ResultSet rs = ps.executeQuery();
     while (rs.next()) {
@@ -150,7 +164,9 @@ public Statement bindExecuteFetch(Blackhole b) throws SQLException {
       }
     }
     rs.close();
-    ps.close();
+    if (!reuseStatement) {
+      ps.close();
+    }
     return ps;
   }