the begginning

utils/funcexp/func_rand.cpp

@@ -0,0 +1,98 @@
+/* Copyright (C) 2014 InfiniDB, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+/****************************************************************************
+* $Id: func_rand.cpp 3495 2013-01-21 14:09:51Z rdempsey $
+*
+*
+****************************************************************************/
+
+#include <cstdlib>
+#include <string>
+#include <sstream>
+using namespace std;
+
+#include "functor_export.h"
+#include "funchelpers.h"
+#include "functioncolumn.h"
+#include "rowgroup.h"
+#include "constantcolumn.h"
+using namespace execplan;
+
+#include "dataconvert.h"
+
+
+namespace funcexp
+{
+uint64_t maxValue = 0x3FFFFFFFL;
+
+/**
+ * Follow MySQL's rand() implementation in item_func.cpp to guarantee compatibility
+ */
+double Func_rand::getRand()
+{
+	uint64_t fSeed1_save = fSeed1;
+	fSeed1 = (fSeed1 * 3 + fSeed2) % maxValue;
+	// prevent the seed to repeat itself. e.g. seed1 = 1073741790; seed2 = 66;
+	if (fSeed1_save == fSeed1)
+		fSeed1 += 23;
+  fSeed2 = (fSeed1 + fSeed2 + 33) % maxValue;
+  return (((double) fSeed1) / (double)maxValue);
+}
+
+CalpontSystemCatalog::ColType Func_rand::operationType( FunctionParm& fp, CalpontSystemCatalog::ColType& resultType )
+{
+	return resultType;
+}
+
+
+double Func_rand::getDoubleVal(rowgroup::Row& row,
+						FunctionParm& parm,
+						bool& isNull,
+						execplan::CalpontSystemCatalog::ColType& op_ct)
+{
+	int64_t seedParm = 0;
+	// rand with parameter. if the parm is constanct, then a column is attached for fetching
+	if (parm.size() == 1 || parm.size() == 2)
+	{
+		execplan::ConstantColumn *cc = dynamic_cast<execplan::ConstantColumn*>(parm[0].get()->data());
+		if (!fSeedSet || !cc)
+		{
+			/* Copied from item_func.cpp */
+			seedParm = parm[0]->data()->getIntVal(row, isNull);
+			fSeed1 = (uint64_t)(seedParm*0x10001L+55555555L);
+			fSeed2 = (uint64_t)(seedParm*0x10000001L);
+			fSeedSet = true;
+		}
+	}
+	// rand without parameter. thd->rand are passed in. The 3rd is a simple column for fetching
+	else
+	{
+		idbassert(parm.size() == 3);
+		if (fSeed1 == 0)
+		{
+			fSeed1 = parm[0]->data()->getIntVal(row, isNull);
+			fSeed2 = parm[1]->data()->getIntVal(row, isNull);
+			fSeedSet = true;
+		}
+	}
+	return getRand();
+}
+
+
+} // namespace funcexp
+// vim:ts=4 sw=4: