Adding JMCR-Stable version

[Benchmarks_CSolver.git] / JMCR-Stable / real-world application / derby-10.3.2.1 / java / engine / org / apache / derby / catalog / types / StatisticsImpl.java

diff --git a/JMCR-Stable/real-world application/derby-10.3.2.1/java/engine/org/apache/derby/catalog/types/StatisticsImpl.java b/JMCR-Stable/real-world application/derby-10.3.2.1/java/engine/org/apache/derby/catalog/types/StatisticsImpl.java
new file mode 100644 (file)
index 0000000..743bc74
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+++ b/JMCR-Stable/real-world application/derby-10.3.2.1/java/engine/org/apache/derby/catalog/types/StatisticsImpl.java
@@ -0,0 +1,123 @@
+/*\r
+\r
+   Derby - Class org.apache.derby.catalog.types.StatisticsImpl\r
+\r
+   Licensed to the Apache Software Foundation (ASF) under one or more\r
+   contributor license agreements.  See the NOTICE file distributed with\r
+   this work for additional information regarding copyright ownership.\r
+   The ASF licenses this file to You under the Apache License, Version 2.0\r
+   (the "License"); you may not use this file except in compliance with\r
+   the License.  You may obtain a copy of the License at\r
+\r
+      http://www.apache.org/licenses/LICENSE-2.0\r
+\r
+   Unless required by applicable law or agreed to in writing, software\r
+   distributed under the License is distributed on an "AS IS" BASIS,\r
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
+   See the License for the specific language governing permissions and\r
+   limitations under the License.\r
+\r
+ */\r
+\r
+package org.apache.derby.catalog.types;\r
+\r
+import org.apache.derby.catalog.Statistics;\r
+import org.apache.derby.iapi.services.io.Formatable;\r
+import org.apache.derby.iapi.services.io.StoredFormatIds;\r
+import org.apache.derby.iapi.services.io.FormatableHashtable;\r
+import org.apache.derby.iapi.services.io.FormatableLongHolder;\r
+\r
+import java.io.ObjectOutput;\r
+import java.io.ObjectInput;\r
+import java.io.IOException;\r
+\r
+public class StatisticsImpl    implements Statistics, Formatable\r
+{\r
+       /* total count of rows for which this statistic was created-- this\r
+          is not the same as the total number of rows in the conglomerate\r
+          currently, but a snapshot; i.e the  number of rows when this\r
+          statistic was created/updated.\r
+       */\r
+\r
+       private long numRows;\r
+       \r
+       /* total count of unique values for the keys \r
+        */\r
+       private long numUnique;\r
+\r
+       /**\r
+        * Constructor for StatisticsImpl.\r
+        * \r
+        * @param numRows       number of rows in the conglomerate for which\r
+        * this statistic is being created.\r
+        * @param numUnique number of unique values in the key for which\r
+        * this statistic is being created.\r
+        */\r
+       public StatisticsImpl(long numRows, long numUnique)\r
+       {\r
+               this.numRows = numRows;\r
+               this.numUnique = numUnique;\r
+       }\r
+\r
+       /** Zero argument constructor for Formatable Interface */\r
+       public StatisticsImpl()\r
+       {}\r
+\r
+       /** @see Statistics#selectivity */\r
+       public double selectivity(Object[] predicates)\r
+       {\r
+               if (numRows == 0.0)\r
+                       return 0.1;\r
+\r
+               /* xxxSTATresolve: for small values of numRows, should we do something\r
+                * special? \r
+                */\r
+               return (double)(1/(double)numUnique);\r
+       }\r
+\r
+       /*------------------ Externalizable Interface ------------------*/\r
+       \r
+       /**\r
+        * @see java.io.Externalizable#readExternal\r
+        */\r
+       public void readExternal(ObjectInput in) \r
+               throws IOException, ClassNotFoundException\r
+       {\r
+               FormatableHashtable fh = (FormatableHashtable)in.readObject();\r
+               numRows = fh.getLong("numRows");\r
+               numUnique = fh.getLong("numUnique");\r
+       }\r
+\r
+       /**\r
+        * Write this object to a stream of stored objects.\r
+        *\r
+        * @param out write bytes here.\r
+        *\r
+        * @exception IOException               thrown on error\r
+        */\r
+       public void writeExternal(ObjectOutput out)\r
+                throws IOException\r
+       {\r
+               FormatableHashtable fh = new FormatableHashtable();\r
+               fh.putLong("numRows", numRows);\r
+               fh.putLong("numUnique", numUnique);\r
+               out.writeObject(fh);\r
+       }\r
+               \r
+       /*------------------- Formatable Interface ------------------*/\r
+       /**\r
+        * @return the format id which corresponds to this class.\r
+        */\r
+       public int getTypeFormatId()\r
+       {\r
+               return StoredFormatIds.STATISTICS_IMPL_V01_ID;\r
+       }\r
+\r
+       \r
+       /** @see java.lang.Object#toString */\r
+       public String toString()\r
+       {\r
+               return "numunique= " + numUnique + " numrows= " + numRows;\r
+       }\r
+       \r
+}\r