Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/incubator-phoenix/pull/30#discussion_r12057845
--- Diff:
phoenix-core/src/it/java/org/apache/phoenix/end2end/FirstByLastByFunctionIT.java
---
@@ -0,0 +1,557 @@
+/*
+ * Copyright 2014 The Apache Software Foundation
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.phoenix.end2end;
+
+import static org.junit.Assert.*;
+import java.sql.*;
+import org.junit.Test;
+
+/**
+ *
+ * @author tzolkincz
+ */
+public class FirstByLastByFunctionIT extends BaseHBaseManagedTimeIT {
+
+ private void prepareTable() throws Exception {
+ Connection conn = DriverManager.getConnection(getUrl());
+ String ddl = "CREATE TABLE IF NOT EXISTS firstBy "
+ + "(id INTEGER NOT NULL PRIMARY KEY, page_id
INTEGER,"
+ + " date INTEGER, \"value\" INTEGER)";
+ conn.createStatement().execute(ddl);
+
+ //in value column will be 0, 2, 4, 6, 8, so 8 is the biggest
+ for (int i = 0; i < 5; i++) {
+ conn.createStatement().execute("UPSERT INTO firstBy
(id, page_id, date, \"value\")"
+ + " VALUES (" + i + ", 8, " + 100 * i +
", " + i * 2 + ")");
+ }
+
+ conn.commit();
+ }
+
+ @Test
+ public void testFirst() throws Exception {
+ prepareTable();
+ Connection conn = DriverManager.getConnection(getUrl());
+
+ ResultSet rs = conn.createStatement().executeQuery(
+ "SELECT FIRST_BY(\"value\", date) FROM firstBy
GROUP BY page_id");
--- End diff --
First, thank you very much for these new built-in functions, @tzolkincz -
these are definitely generally useful. Perhaps we can imitate what SQL server
and others do, but only support a limited subset for now. I don't think this
would require any changes to your implementation - this would be a parser only
change, as you'd still compile down to the same built-in function expression
that you created:
(FIRST_VALUE | LAST_VALUE) ( [scalar_expression )
OVER ( [ partition_by_clause ] order_by_clause rows_range_clause )
We wouldn't yet support a partition_by_clause and the only
rows_range_clause we'd support would be to specify the Nth row (i.e. your
offset argument) which would be a bit non standard. The order_by_clause would
map to your second argument and if DESC is used instead of ASC, you'd just need
to wrap this in a call to the INVERT built-in function.
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