From d803c7dca98da1a487e2549dd0038801eb346b72 Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Thu, 9 Aug 2007 17:57:59 +0000
Subject: Yanked out support for fast skipping of JDBC results. JDBC drivers
 leak memory when this option is used.

---
 .../com/amazon/carbonado/repo/jdbc/JDBCCursor.java | 52 +++-------------------
 .../amazon/carbonado/repo/jdbc/JDBCStorage.java    | 17 +------
 2 files changed, 7 insertions(+), 62 deletions(-)

(limited to 'src/main')

diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
index 28b73c7..985232c 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
@@ -37,27 +37,22 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
     private final JDBCStorage<S> mStorage;
     private final Connection mConnection;
     private final PreparedStatement mStatement;
-    private final boolean mScrollInsensitiveReadOnly;
 
     private ResultSet mResultSet;
     private boolean mHasNext;
 
     /**
-     * @param scrollInsensitiveReadOnly when true, statement is
-     * TYPE_SCROLL_INSENSITIVE and CONCUR_READ_ONLY.
      * @throws SQLException from executeQuery on statement. Caller must clean
      * up when this happens by closing statement and connection.
      */
     JDBCCursor(JDBCStorage<S> storage,
                Connection con,
-               PreparedStatement statement,
-               boolean scrollInsensitiveReadOnly)
+               PreparedStatement statement)
         throws SQLException
     {
         mStorage = storage;
         mConnection = con;
         mStatement = statement;
-        mScrollInsensitiveReadOnly = scrollInsensitiveReadOnly;
         mResultSet = statement.executeQuery();
     }
 
@@ -127,48 +122,11 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
 
         int actual = 0;
 
-        if (amount > 1 && mScrollInsensitiveReadOnly) {
-            // Skip a relative amount, which is preferred.
+        while (amount > 0) {
             if (hasNext()) {
-                ResultSet rs = mResultSet;
-                try {
-                    int rowStart = rs.getRow();
-                    mHasNext = rs.relative(amount);
-                    int rowEnd = rs.getRow();
-                    if (rowEnd == 0) {
-                        // Skipped past the end. Move back to find the last row number.
-                        if (rs.previous() && (rowEnd = rs.getRow()) != 0) {
-                            rowEnd++;
-                        } else if (rs.last() && (rowEnd = rs.getRow()) != 0) {
-                            rowEnd++;
-                        } else {
-                            // No clue how many were skipped. It's at least one.
-                            rowEnd = rowStart + 1;
-                        }
-                        // Make sure ResultSet is closed below.
-                        mHasNext = false;
-                    }
-                    actual += rowEnd - rowStart;
-                } catch (SQLException e) {
-                    try {
-                        close();
-                    } catch (FetchException e2) {
-                        // Don't care.
-                    }
-                    throw mStorage.getJDBCRepository().toFetchException(e);
-                }
-                if (!mHasNext) {
-                    close();
-                }
-            }
-        } else {
-            // Call next a bunch, which is likely slower than relative skipping.
-            while (amount > 0) {
-                if (hasNext()) {
-                    actual++;
-                    amount--;
-                    mHasNext = false;
-                }
+                actual++;
+                amount--;
+                mHasNext = false;
             }
         }
 
diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
index 384f1bc..2421be7 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
@@ -488,24 +488,11 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
             boolean forUpdate = mRepository.localTxnManager().isForUpdate();
             Connection con = mRepository.getConnection();
             try {
-                boolean scrollInsensitiveReadOnly =
-                    mRepository.supportsScrollInsensitiveReadOnly();
-
-                PreparedStatement ps;
-
-                if (scrollInsensitiveReadOnly) {
-                    // Can support fast skipping.
-                    ps = con.prepareStatement
-                        (prepareSelect(values, forUpdate),
-                         ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
-                } else {
-                    // Can't support fast skipping.
-                    ps = con.prepareStatement(prepareSelect(values, forUpdate));
-                }
+                PreparedStatement ps = con.prepareStatement(prepareSelect(values, forUpdate));
 
                 try {
                     setParameters(ps, values);
-                    return new JDBCCursor<S>(JDBCStorage.this, con, ps, scrollInsensitiveReadOnly);
+                    return new JDBCCursor<S>(JDBCStorage.this, con, ps);
                 } catch (Exception e) {
                     // in case of exception, close statement
                     try {
-- 
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