db2 changes

Author: arjopoldervaart

activejdbc/src/main/java/org/javalite/activejdbc/Configuration.java

@@ -274,6 +274,9 @@ public Dialect getDialect(String dbType){
             if(dbType.equalsIgnoreCase("Oracle")){
                 dialect = new OracleDialect();
             }
+            else if(dbType.startsWith("DB2")) {
+                dialect = new DB2Dialect();
+            }
             else if(dbType.equalsIgnoreCase("MySQL")){
                 dialect = new MySQLDialect();
             }

activejdbc/src/main/java/org/javalite/activejdbc/cache/QueryCache.java

@@ -132,7 +132,7 @@ public void purgeTableCache(MetaModel metaModel) {
      */
     public void purgeTableCache(String tableName) {
         MetaModel mm = metaModelFor(tableName);
-        if(mm != null && enabled  && mm.cached()){
+        if(mm != null && enabled && mm.cached()){
             cacheManager.flush(new CacheEvent(mm.getTableName(), getClass().getName()));
         }
     }

activejdbc/src/main/java/org/javalite/activejdbc/dialects/DB2Dialect.java

@@ -0,0 +1,60 @@
+package org.javalite.activejdbc.dialects;
+
+import org.javalite.activejdbc.MetaModel;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author William Janssen, Arjo Poldervaart
+ */
+
+public class DB2Dialect extends DefaultDialect {
+	private final List<String> EMPTY_LIST = new ArrayList<String>();
+	
+	@Override
+	public String formSelect(String tableName, String[] columns, String subQuery, List<String> orderBys, long limit, long offset) {
+		// if table name is null, sub query contains a full SQL statement
+		// we will need a more complex query if offset != -1
+		// example:
+		// SELECT * FROM (SELECT ROW_NUMBER() OVER(ORDER BY item_number) as ROWNUMBER, items.* from items WHERE  item_description like ?) as TEMP WHERE TEMP.ROWNUMBER  BETWEEN 271 AND 280
+		// select * from (select row_number() over(order by item_number) as rownumber, ORIG.* from (select * from items where item_description like '%2%') as ORIG) as TEMP WHERE TEMP.ROWNUMBER  BETWEEN 271 AND 280
+		boolean needOffset = offset != -1;
+		boolean needLimit = limit != -1;
+		StringBuilder fullQuery = new StringBuilder(subQuery == null? 0: subQuery.length());
+		
+		if (needOffset) {
+			// first create inner query without order by
+			StringBuilder innerQuery = new StringBuilder(subQuery == null? 0: subQuery.length());
+			appendSelect(innerQuery, tableName, columns, null, subQuery, EMPTY_LIST);
+			
+			fullQuery.append("SELECT * FROM (SELECT ROW_NUMBER() OVER(");
+			appendOrderBy(fullQuery, orderBys);
+			fullQuery.append(") AS ROWNUMBER, ORIG.* from (");
+			fullQuery.append(innerQuery.toString());
+			fullQuery.append(") as ORIG) as TEMP WHERE TEMP.ROWNUMBER ");
+			if (needLimit) {
+				fullQuery.append(" BETWEEN ");
+				fullQuery.append(offset+1);
+				fullQuery.append(" AND ");
+				fullQuery.append(offset+limit);
+			} else {
+				fullQuery.append(" > ");
+				fullQuery.append(offset);
+			}
+			
+		} else {
+			appendSelect(fullQuery, tableName, columns, null, subQuery, orderBys);
+			if (needLimit) {
+				fullQuery.append(" FETCH FIRST ").append(limit).append(" ROWS ONLY");
+			}
+		}
+		
+		return fullQuery.toString();
+	}
+	
+    @Override
+    protected void appendEmptyRow(MetaModel metaModel, StringBuilder query) {
+        query.append('(').append(metaModel.getIdName()).append(") VALUES (DEFAULT)");
+    }
+}