[Performance] Large Object's Input Stream (BlobInputStream) takes a lot of time due to read one by one in application level

pgjdbc/src/main/java/org/postgresql/largeobject/BlobInputStream.java

@@ -178,6 +178,36 @@ public synchronized void reset() throws IOException {
     }
   }
 
+  /**
+   * Buffered read on Application Level.
+   */
+  @Override
+  public int read(byte[] buf, int off, int len) throws IOException {
+
+    if (bpos != 0) {
+      return super.read(buf,off,len);
+    }
+
+    LargeObject lo = getLo();
+    try {
+
+      if (limit > 0 && apos >= limit) {
+        return -1;
+      }
+
+      if (limit > 0 && limit - apos < len) {
+        len = (int) (limit - apos);
+      }
+
+      int result =  lo.read(buf, off, len);
+      apos += result;
+
+      return result == 0 ? -1 : result;
+    } catch (SQLException se) {
+      throw new IOException(se.toString());
+    }
+  }
+
   /**
    * Tests if this input stream supports the <code>mark</code> and <code>reset</code> methods. The
    * <code>markSupported</code> method of <code>InputStream</code> returns <code>false</code>.

pgjdbc/src/test/java/org/postgresql/test/jdbc2/BlobTest.java

@@ -16,6 +16,7 @@
 import org.postgresql.test.TestUtil;
 
 import org.junit.After;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -262,6 +263,62 @@ public void testLargeLargeObject() throws Exception {
     assertEquals(length, lob.length());
   }
 
+  @Test
+  public void testLargeObjectBufferedRead() throws Exception {
+    String fileName = "/test-file.xml";
+    long loid = uploadFile("/test-file.xml", LOOP);
+    LargeObjectManager lom = ((org.postgresql.PGConnection) con).getLargeObjectAPI();
+
+    InputStream fis = getClass().getResourceAsStream(fileName);
+
+    InputStream lois = lom.open(loid).getInputStream();
+
+    for (byte[] fileBuffer = new byte[10], loBuffer = new byte[10]; (fis.read(fileBuffer)) != -1;) {
+      lois.read(loBuffer);
+      Assert.assertArrayEquals(fileBuffer, loBuffer);
+    }
+
+    fis.close();
+    lois.close();
+  }
+
+  @Test
+  public void testLargeObjectBufferedReadWithLimit() throws Exception {
+    long loid = uploadFile("/test-file.xml", LOOP);
+    LargeObjectManager lom = ((org.postgresql.PGConnection) con).getLargeObjectAPI();
+    int limit = 35;
+    InputStream lois = lom.open(loid).getInputStream(limit);
+    byte[] loBuffer = new byte[10];
+    int totalReadBytes = 0;
+
+    for (int countBytes; (countBytes = lois.read(loBuffer)) != -1;) {
+      totalReadBytes += countBytes;
+    }
+
+    Assert.assertEquals(limit, totalReadBytes);
+    lois.close();
+  }
+
+  @Test
+  public void testLargeObjectBufferedReadPlusSingleWithLimit() throws Exception {
+    long loid = uploadFile("/test-file.xml", LOOP);
+    LargeObjectManager lom = ((org.postgresql.PGConnection) con).getLargeObjectAPI();
+    int limit = 35;
+    InputStream lois = lom.open(loid).getInputStream(limit);
+    byte[] loBuffer = new byte[10];
+    int totalReadBytes = 0;
+
+    for (int countBytes; (countBytes = lois.read(loBuffer)) != -1;) {
+      totalReadBytes += countBytes;
+      if (lois.read() != -1) {
+        ++totalReadBytes;
+      }
+    }
+
+    Assert.assertEquals(limit, totalReadBytes);
+    lois.close();
+  }
+
   /*
    * Helper - uploads a file into a blob using old style methods. We use this because it always
    * works, and we can use it as a base to test the new methods.