forked from LucidDB/luciddb
/
CollapseRowsUdx.java
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/
CollapseRowsUdx.java
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/*
// Licensed to DynamoBI Corporation (DynamoBI) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. DynamoBI 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.eigenbase.applib.cursor;
import java.sql.*;
import java.util.*;
import net.sf.farrago.syslib.*;
import org.eigenbase.applib.resource.*;
/**
* Collapses one to many relationships into one to one relationships. In the
* case where A maps to B, this will result in A mapping to a concatenation of
* all Bs which previously mapped to A.
*
* @author Elizabeth Lin
* @version $Id$
*/
public abstract class CollapseRowsUdx
{
//~ Static fields/initializers ---------------------------------------------
private static final int MAX_CONCAT_LEN = 16384;
//~ Methods ----------------------------------------------------------------
public static void execute(
ResultSet inputSet,
String delimiter,
PreparedStatement resultInserter)
throws ApplibException
{
try {
ResultSetMetaData rsmd = inputSet.getMetaData();
// validate the number of input and output columns
if ((resultInserter.getParameterMetaData().getParameterCount()
!= 3)
|| (rsmd.getColumnCount() != 2))
{
throw ApplibResource.instance().InputOutputColumnError.ex();
}
// validate that parent column datatype is VARCHAR or CHAR
if (!((rsmd.getColumnType(1) == java.sql.Types.VARCHAR)
|| (rsmd.getColumnType(1) == java.sql.Types.CHAR)))
{
throw ApplibResource.instance().InvalidColumnDatatype.ex(
rsmd.getColumnLabel(1),
"VARCHAR");
}
} catch (SQLException e) {
throw ApplibResource.instance().CannotGetMetaData.ex(e);
}
String currentChildren;
int childCount;
boolean exceededLength = false;
String currentParent;
try {
// return no rows, if no rows passed in
if (!inputSet.next()) {
return;
}
currentParent = inputSet.getString(1);
String child = inputSet.getString(2);
if (child == null) {
currentChildren = null;
childCount = 0;
} else if (child.length() <= MAX_CONCAT_LEN) {
currentChildren = child;
childCount = 1;
} else {
// first item exceeds truncation limit
currentChildren = "";
childCount = 0;
exceededLength = true;
}
while (inputSet.next()) {
String parent = inputSet.getString(1);
int compare =
FarragoSyslibUtil.compareKeysUsingGroupBySemantics(
currentParent,
parent);
if (compare > 0) {
// row is out of order
throw ApplibResource.instance().InputRowsNotSorted.ex(
inputSet.getMetaData().getColumnLabel(1),
parent);
} else if (compare < 0) {
// new parent value, emit row for previous parent value
resultInserter.setString(1, currentParent);
resultInserter.setString(2, currentChildren);
resultInserter.setInt(3, childCount);
resultInserter.executeUpdate();
currentParent = parent;
child = inputSet.getString(2);
if (child == null) {
currentChildren = null;
childCount = 0;
exceededLength = false;
} else if (child.length() <= MAX_CONCAT_LEN) {
currentChildren = child;
childCount = 1;
exceededLength = false;
} else {
// first item exceeds truncation limit
currentChildren = "";
childCount = 0;
exceededLength = true;
}
} else {
// same parent value
if (exceededLength) {
continue;
}
child = inputSet.getString(2);
if (child == null) {
continue;
}
if (currentChildren == null) {
// no previous children
if (child.length() <= MAX_CONCAT_LEN) {
currentChildren = child;
childCount++;
} else {
// first item exceeds truncation limit
currentChildren = "";
childCount = 0;
exceededLength = true;
}
} else {
// append child if truncation limit not exceeded
int newLen = child.length() + delimiter.length();
if ((currentChildren.length() + newLen)
<= MAX_CONCAT_LEN)
{
currentChildren += delimiter + child;
childCount++;
} else {
exceededLength = true;
}
}
}
}
// output the last row
resultInserter.setString(1, currentParent);
resultInserter.setString(2, currentChildren);
resultInserter.setInt(3, childCount);
resultInserter.executeUpdate();
} catch (SQLException e) {
throw ApplibResource.instance().DatabaseAccessError.ex(
e.toString(),
e);
}
}
}
// End CollapseRowsUdx.java