From be484c39bfb5666a20578ed3fe3371aa02d256e0 Mon Sep 17 00:00:00 2001
From: Lukas Eder <lukas.eder@gmail.com>
Date: Mon, 4 Feb 2013 19:08:07 +0100
Subject: [PATCH] [#1974] Optimise various Executor.fetchOne() methods, which
 consume the whole ResultSet before throwing an InvalidResultException

---
 .../org/jooq/impl/AbstractResultQuery.java    | 12 +----------
 .../src/main/java/org/jooq/impl/Executor.java | 12 +++++------
 jOOQ/src/main/java/org/jooq/impl/Utils.java   | 20 +++++++++++++++++++
 3 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/jOOQ/src/main/java/org/jooq/impl/AbstractResultQuery.java b/jOOQ/src/main/java/org/jooq/impl/AbstractResultQuery.java
index 664b24e3f4..6fda7ce90b 100644
--- a/jOOQ/src/main/java/org/jooq/impl/AbstractResultQuery.java
+++ b/jOOQ/src/main/java/org/jooq/impl/AbstractResultQuery.java
@@ -70,7 +70,6 @@ import org.jooq.ResultQuery;
 import org.jooq.SQLDialect;
 import org.jooq.Table;
 import org.jooq.exception.DataTypeException;
-import org.jooq.exception.InvalidResultException;
 import org.jooq.tools.Convert;
 import org.jooq.tools.JooqLogger;
 
@@ -409,16 +408,7 @@ abstract class AbstractResultQuery<R extends Record> extends AbstractQuery imple
 
     @Override
     public final R fetchOne() {
-        Result<R> r = fetch();
-
-        if (r.size() == 1) {
-            return r.get(0);
-        }
-        else if (r.size() > 1) {
-            throw new InvalidResultException("Query returned more than one result");
-        }
-
-        return null;
+        return Utils.fetchOne(fetchLazy());
     }
 
     @Override
diff --git a/jOOQ/src/main/java/org/jooq/impl/Executor.java b/jOOQ/src/main/java/org/jooq/impl/Executor.java
index 8fa20f41d5..a205f8047d 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Executor.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Executor.java
@@ -1316,7 +1316,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final Record fetchOne(ResultSet rs) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetchLazy(rs).fetch());
+        return Utils.fetchOne(fetchLazy(rs));
     }
 
     /**
@@ -1335,7 +1335,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final Record fetchOne(ResultSet rs, Field<?>... fields) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetchLazy(rs, fields).fetch());
+        return Utils.fetchOne(fetchLazy(rs, fields));
     }
 
     /**
@@ -1354,7 +1354,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final Record fetchOne(ResultSet rs, DataType<?>... types) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetchLazy(rs, types).fetch());
+        return Utils.fetchOne(fetchLazy(rs, types));
     }
 
     /**
@@ -1373,7 +1373,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final Record fetchOne(ResultSet rs, Class<?>... types) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetchLazy(rs, types).fetch());
+        return Utils.fetchOne(fetchLazy(rs, types));
     }
 
     /**
@@ -4163,7 +4163,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final <R extends Record> R fetchOne(Table<R> table) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetch(table));
+        return Utils.fetchOne(fetchLazy(table));
     }
 
     /**
@@ -4180,7 +4180,7 @@ public class Executor implements Configuration {
      */
     @Support
     public final <R extends Record> R fetchOne(Table<R> table, Condition condition) throws DataAccessException, InvalidResultException {
-        return Utils.filterOne(fetch(table, condition));
+        return Utils.fetchOne(fetchLazy(table, condition));
     }
 
     /**
diff --git a/jOOQ/src/main/java/org/jooq/impl/Utils.java b/jOOQ/src/main/java/org/jooq/impl/Utils.java
index ec4d2cfd5a..2422184928 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Utils.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Utils.java
@@ -84,6 +84,7 @@ import org.jooq.AttachableInternal;
 import org.jooq.BindContext;
 import org.jooq.Configuration;
 import org.jooq.Converter;
+import org.jooq.Cursor;
 import org.jooq.DataType;
 import org.jooq.EnumType;
 import org.jooq.ExecuteContext;
@@ -450,6 +451,25 @@ final class Utils {
         return null;
     }
 
+    /**
+     * Get the only element from a cursor or <code>null</code>, or throw an
+     * exception
+     *
+     * @param cursor The cursor
+     * @return The only element from the cursor or <code>null</code>
+     * @throws InvalidResultException Thrown if the cursor returns more than one
+     *             element
+     */
+    static <R extends Record> R fetchOne(Cursor<R> cursor) throws InvalidResultException {
+        R record = cursor.fetchOne();
+
+        if (cursor.hasNext()) {
+            throw new InvalidResultException("Cursor returned more than one result");
+        }
+
+        return record;
+    }
+
     /**
      * Render and bind a list of {@link QueryPart} to plain SQL
      * <p>