Convert comparisons with current-datetime, current-date, and current-time to applicable index searches as though they were constants

Change-Id: Ied64276873afcfbdd31dac313009e47429d8f9b0
Reviewed-on: https://asterix-gerrit.ics.uci.edu/367
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Yingyi Bu <buyingyi@gmail.com>
diff --git a/asterix-app/src/test/resources/optimizerts/queries/btree-index/btree-datetime-02.aql b/asterix-app/src/test/resources/optimizerts/queries/btree-index/btree-datetime-02.aql
new file mode 100644
index 0000000..8a5fe07
--- /dev/null
+++ b/asterix-app/src/test/resources/optimizerts/queries/btree-index/btree-datetime-02.aql
@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+/*
+ *  Description     : This test is intended to verify that the primary BTree index is used 
+ *                  : for an invocation of current-datetime()
+ *  Expected Result : Success
+ *  Date            : 27th Aug 2015
+ *	Author			: Steven Jacobs
+ */
+
+drop dataverse emergencyTest if exists;
+create dataverse emergencyTest;
+use dataverse emergencyTest;
+create type CHPReport as {
+        "id":int,
+	"timestamp":datetime,
+        "title":string,
+        "message":string
+}
+create dataset CHPReports(CHPReport)
+primary key timestamp;
+
+for $emergency in dataset CHPReports
+let $time := current-datetime() - day-time-duration("PT10H")
+where $emergency.timestamp >= $time
+return $emergency;
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