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*
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* this list of conditions and the following disclaimer in the documentation
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*
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* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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package org.hsqldb;
import org.hsqldb.lib.ArrayUtil;
import org.hsqldb.lib.HashSet;
import org.hsqldb.lib.Iterator;
/**
* This class is used for grouping select results, especially for select
* statements that include group by clause and nested aggregate functions.
* It is used by the <b>Select</b> class regardless the existence of group by
* clause.
* <p>
* When a group by clause is defined, a <b>ResultGroup</b> is used to hold
* all column values and <b>AggregatingValue</b>s for each group. When a group
* by clause is not defined, one <b>ResultGroup</b> is used to hold all the
* results.<p>
*
* All <b>ResultGroup</b>s are placed in a <b>HashSet</b>. Adding a new row
* will first retrieve the corresponding group from the table, based on the
* values in the group by columns. If a group is found, then the row
* associated with the group will be returned. Otherwise a new group is
* created with the new row, and the new row is returned.
* <p>
* The <b>Select</b> can then update the values and <b>AggregatingValue</b>s
* in the returned row, rather than the original row. This approach enables
* nested aggregate functions, such as "count(id)+2, 20-count(id),
* max(id)-min(id)" support.
*
* @author Tony Lai
* @version 1.7.2
* @since 1.7.2
* @see Expression
* @see Select
*/
// fredt@users - patch 1.7.2 - mods to use new HashSet class and to separate addRow and getRow operations
class GroupedResult {
/** @todo fredt - initialise results on first use */
private Result result;
int groupBegin;
int groupEnd;
private final boolean isGrouped;
private final boolean isAggregated;
private HashSet groups;
private ResultGroup currGroup;
GroupedResult(Select select, Result.ResultMetaData meta) {
result = new Result(meta);
groupBegin = select.iResultLen;
groupEnd = groupBegin + select.iGroupLen;
isGrouped = groupBegin != groupEnd;
isAggregated = select.isAggregated;
if (isGrouped) {
groups = new HashSet();
}
}
Object[] getRow(Object[] row) {
if (isGrouped) {
ResultGroup newGroup = new ResultGroup(row);
ResultGroup group = (ResultGroup) groups.get(newGroup);
if (group != null) {
ArrayUtil.copyArray(group.row, row, row.length);
}
} else if (isAggregated) {
if (currGroup != null) {
ArrayUtil.copyArray(currGroup.row, row, row.length);
}
}
return row;
}
void addRow(Object[] row) {
if (isGrouped) {
ResultGroup newGroup = new ResultGroup(row);
currGroup = (ResultGroup) groups.get(newGroup);
if (currGroup == null) {
currGroup = newGroup;
groups.add(currGroup);
result.add(row);
} else {
System.arraycopy(row, 0, currGroup.row, 0, row.length);
}
} else if (isAggregated) {
if (currGroup == null) {
currGroup = new ResultGroup(row);
result.add(row);
} else {
System.arraycopy(row, 0, currGroup.row, 0, row.length);
}
} else {
result.add(row);
}
}
int size() {
return result.getSize();
}
Iterator iterator() {
return result.iterator();
}
Result getResult() {
return result;
}
class ResultGroup {
Object[] row;
int hashCode;
private ResultGroup(Object[] row) {
this.row = row;
hashCode = 0;
for (int i = groupBegin; i < groupEnd; i++) {
if (row[i] != null) {
hashCode += row[i].hashCode();
}
}
}
public int hashCode() {
return hashCode;
}
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj == null ||!(obj instanceof ResultGroup)) {
return false;
}
ResultGroup group = (ResultGroup) obj;
for (int i = groupBegin; i < groupEnd; i++) {
if (!equals(row[i], group.row[i])) {
return false;
}
}
return true;
}
private boolean equals(Object o1, Object o2) {
return (o1 == null) ? o2 == null
: o1.equals(o2);
}
}
}