From b896e55af15eb31009bfb2e3c58fa5e7b0d52de6 Mon Sep 17 00:00:00 2001
From: Rob Bygrave <robin.bygrave@gmail.com>
Date: Thu, 7 Nov 2013 23:07:39 +1300
Subject: [PATCH] Fix for Issue 56 - Using findIterate with MySQL streams the
 entire result set at once

---
 .../ebeaninternal/server/query/CQuery.java    | 21 ++++++++++++++++++-
 .../server/query/CQueryEngine.java            |  2 +-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/main/java/com/avaje/ebeaninternal/server/query/CQuery.java b/src/main/java/com/avaje/ebeaninternal/server/query/CQuery.java
index 20f036e07..0ad5c619c 100644
--- a/src/main/java/com/avaje/ebeaninternal/server/query/CQuery.java
+++ b/src/main/java/com/avaje/ebeaninternal/server/query/CQuery.java
@@ -343,7 +343,21 @@ public class CQuery<T> implements DbReadContext, CancelableQuery {
     }
   }
 
+  /**
+   * Prepare bind and execute query with Forward only hints.
+   */
+  public boolean prepareBindExecuteQueryForwardOnly() throws SQLException {
+    return prepareBindExecuteQueryWithOption(true);
+  }
+
+  /**
+   * Prepare bind and execute the query normally.
+   */
   public boolean prepareBindExecuteQuery() throws SQLException {
+    return prepareBindExecuteQueryWithOption(false);
+  }
+
+  private boolean prepareBindExecuteQueryWithOption(boolean forward) throws SQLException {
 
     synchronized (this) {
       if (cancelled || query.isCancelled()) {
@@ -357,7 +371,12 @@ public class CQuery<T> implements DbReadContext, CancelableQuery {
       // prepare
       SpiTransaction t = request.getTransaction();
       Connection conn = t.getInternalConnection();
-      pstmt = conn.prepareStatement(sql);
+      if (forward) {
+        // Hints required for mysql for large resultset processing (Issue 56)
+        pstmt = conn.prepareStatement(sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
+      } else {
+        pstmt = conn.prepareStatement(sql);        
+      }
 
       if (query.getTimeout() > 0) {
         pstmt.setQueryTimeout(query.getTimeout());
diff --git a/src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java b/src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java
index af3ea921e..844f26af9 100644
--- a/src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java
+++ b/src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java
@@ -122,7 +122,7 @@ public class CQueryEngine {
 
     try {
 
-      if (!cquery.prepareBindExecuteQuery()) {
+      if (!cquery.prepareBindExecuteQueryForwardOnly()) {
         // query has been cancelled already
         logger.trace("Future fetch already cancelled");
         return null;