[GitHub] kaspersorensen commented on a change in pull request #208: the result of column.getNativeType() may be null and add pagination function to the Hive sql.

[GitBox <gi...@apache.org>]

kaspersorensen commented on a change in pull request #208:  the result of column.getNativeType() may be null and add pagination function to the Hive sql.
URL: https://github.com/apache/metamodel/pull/208#discussion_r259643332
 
 

 ##########
 File path: jdbc/src/main/java/org/apache/metamodel/jdbc/dialects/HiveQueryRewriter.java
 ##########
 @@ -18,18 +18,46 @@
  */
 package org.apache.metamodel.jdbc.dialects;
 
+import java.util.List;
+import org.apache.metamodel.MetaModelException;
 import org.apache.metamodel.jdbc.JdbcDataContext;
+import org.apache.metamodel.query.FromItem;
+import org.apache.metamodel.query.Query;
+import org.apache.metamodel.query.SelectItem;
 import org.apache.metamodel.schema.ColumnType;
 
 /**
  * Query rewriter for Apache Hive
  */
-public class HiveQueryRewriter extends DefaultQueryRewriter {
+public class HiveQueryRewriter extends RowNumberQueryRewriter {
 
     public HiveQueryRewriter(JdbcDataContext dataContext) {
         super(dataContext);
     }
 
+    @Override
+    public String rewriteQuery(Query query) {
+
+        Integer maxRows = query.getMaxRows();
+        Integer firstRow = query.getFirstRow();
+
+        if (maxRows == null && (firstRow == null || firstRow.intValue() == 1)) {
+            return super.rewriteQuery(query);
+        }
+
+        if ((firstRow == null || firstRow.intValue() == 1) && maxRows != null && maxRows > 0) {
+            // We prefer to use the "LIMIT n" approach, if
+            // firstRow is not specified.
+            return super.rewriteQuery(query) + " LIMIT " + maxRows;
+        } else {
+            return getRowNumberSql(query, maxRows, firstRow);
+        }
+
+    }
+
+
 
 Review comment:
   No need for the 4 line breaks

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