BATCH-1860: Use sub query for Derby for JdbcPagingItemReader

Order the results before the ROW_NUM restriction is applied (and make related infrastructure tests more robust)

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/support/DerbyPagingQueryProvider.java

@@ -5,7 +5,7 @@
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *      http://www.apache.org/licenses/LICENSE-2.0
+ *	  http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -26,7 +26,11 @@ import javax.sql.DataSource;
  * Derby implementation of a  {@link PagingQueryProvider} using standard SQL:2003 windowing functions.
  * These features are supported starting with Apache Derby version 10.4.1.3.
  *
+ * As the OVER() function does not support the ORDER BY clause a sub query is instead used to order the results
+ * before the ROW_NUM restriction is applied
+ *
  * @author Thomas Risberg
+ * @author David Thexton
  * @since 2.0
  */
 public class DerbyPagingQueryProvider extends SqlWindowingPagingQueryProvider {
@@ -42,23 +46,17 @@ public class DerbyPagingQueryProvider extends SqlWindowingPagingQueryProvider {
 		}
 	}
 	
-	@Override
-	protected Object getSubQueryAlias() {
-		return "AS TMP_SUB ";
-	}
-	
 	@Override
 	protected String getOverClause() {
 		return "";
 	}
-	
-	@Override
-	protected String getAfterWhereClause() {
-		if (version!=null && "10.6.1".compareTo(version) > 0) {
-			// Old behaviour retained, even though it is broken
-			return "";
-		}
-		return " " + super.getOverClause();
+
+	protected String getOverSubstituteClauseStart() {
+		return " FROM (SELECT " + getSelectClause();
+	}
+
+	protected String getOverSubstituteClauseEnd() {
+		return " " + super.getOverClause() + ") AS TMP_ORDERED";
 	}
 
 }

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/support/SqlWindowingPagingQueryProvider.java

@@ -35,16 +35,21 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 		sql.append("SELECT ").append(getSelectClause()).append(", ");
 		sql.append("ROW_NUMBER() OVER (").append(getOverClause());
 		sql.append(") AS ROW_NUMBER");
+		sql.append(getOverSubstituteClauseStart());
 		sql.append(" FROM ").append(getFromClause()).append(
 				getWhereClause() == null ? "" : " WHERE " + getWhereClause());
-		sql.append(getAfterWhereClause());
-		String alias = extractTableAlias();
-		sql.append(") ").append(getSubQueryAlias()).append("WHERE " + alias + "ROW_NUMBER <= ").append(pageSize);
+		sql.append(getOverSubstituteClauseEnd());
+		sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append(
+				"ROW_NUMBER <= ").append(pageSize);
 
 		return sql.toString();
 	}
 
-	private String extractTableAlias() {
+	protected Object getSubQueryAlias() {
+		return "AS TMP_SUB ";
+	}
+
+	protected Object extractTableAlias() {
 		String alias = "" + getSubQueryAlias();
 		if (StringUtils.hasText(alias) && alias.toUpperCase().startsWith("AS")) {
 			alias = alias.substring(3).trim() + ".";
@@ -52,10 +57,6 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 		return alias;
 	}
 
-	protected Object getSubQueryAlias() {
-		return "";
-	}
-
 	@Override
 	public String generateRemainingPagesQuery(int pageSize) {
 		StringBuilder sql = new StringBuilder();
@@ -63,6 +64,7 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 		sql.append("SELECT ").append(getSelectClause()).append(", ");
 		sql.append("ROW_NUMBER() OVER (").append(getOverClause());
 		sql.append(") AS ROW_NUMBER");
+		sql.append(getOverSubstituteClauseStart());
 		sql.append(" FROM ").append(getFromClause());
 		sql.append(" WHERE ");
 		if (getWhereClause() != null) {
@@ -77,17 +79,13 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 			sql.append(" < ");
 		}
 		sql.append(getSortKeyPlaceHolder());
-		sql.append(getAfterWhereClause());
-		String alias = extractTableAlias();
-		sql.append(") ").append(getSubQueryAlias()).append("WHERE " + alias + "ROW_NUMBER <= ").append(pageSize);
+		sql.append(getOverSubstituteClauseEnd());
+		sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append(
+				"ROW_NUMBER <= ").append(pageSize);
 
 		return sql.toString();
 	}
 
-	protected String getAfterWhereClause() {
-		return "";
-	}
-
 	@Override
 	public String generateJumpToItemQuery(int itemIndex, int pageSize) {
 		int page = itemIndex / pageSize;
@@ -101,11 +99,12 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 		sql.append("SELECT ").append(getSortKey()).append(" AS SORT_KEY, ");
 		sql.append("ROW_NUMBER() OVER (").append(getOverClause());
 		sql.append(") AS ROW_NUMBER");
-		sql.append(" FROM ").append(getFromClause()).append(
-				getWhereClause() == null ? "" : " WHERE " + getWhereClause());
-		sql.append(getAfterWhereClause());
-		String alias = extractTableAlias();
-		sql.append(") ").append(getSubQueryAlias()).append("WHERE " + alias + "ROW_NUMBER = ").append(lastRowNum);
+		sql.append(getOverSubstituteClauseStart());
+		sql.append(" FROM ").append(getFromClause());
+		sql.append(getWhereClause() == null ? "" : " WHERE " + getWhereClause());
+		sql.append(getOverSubstituteClauseEnd());
+		sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append(
+				"ROW_NUMBER = ").append(lastRowNum);
 
 		return sql.toString();
 	}
@@ -114,6 +113,14 @@ public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvi
 		return "ORDER BY " + getSortKey() + " " + getAscendingClause();
 	}
 
+	protected String getOverSubstituteClauseStart() {
+		return "";
+	}
+
+	protected String getOverSubstituteClauseEnd() {
+		return "";
+	}
+
 	private String getAscendingClause() {
 		if (isAscending()) {
 			return "ASC";

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/support/SybasePagingQueryProvider.java

@@ -37,6 +37,11 @@ public class SybasePagingQueryProvider extends SqlWindowingPagingQueryProvider {
 		return SqlPagingQueryUtils.generateTopSqlQuery(this, true, buildTopClause(pageSize));
 	}
 
+	@Override
+	protected Object getSubQueryAlias() {
+		return "";
+	}
+
 	private String buildTopClause(int pageSize) {
 		return new StringBuilder().append("TOP ").append(pageSize).toString();
 	}