private Column undeclaredHKeyColumn(HKeyColumn hKeyColumn) {
Column undeclaredHKeyColumn = null;
int rootMostDepth = rootMostTable().getDepth();
List<Column> equivalentColumns = hKeyColumn.equivalentColumns();
switch (getJoinType()) {
case LEFT:
// use a rootward bias, but no more rootward than the rootmost table
for (Column equivalentColumn : equivalentColumns) {
int equivalentColumnDepth = equivalentColumn.getTable().getDepth();
if (undeclaredHKeyColumn == null && equivalentColumnDepth >= rootMostDepth) {
undeclaredHKeyColumn = equivalentColumn;
}
}
break;
case RIGHT:
// use a leafward bias, but no more leafward than the leafdmost table
int leafMostDepth = leafMostTable().getDepth();
for (ListIterator<Column> reverseCols =
equivalentColumns.listIterator(equivalentColumns.size());
reverseCols.hasPrevious(); ) {
Column equivalentColumn = reverseCols.previous();
int equivalentColumnDepth = equivalentColumn.getTable().getDepth();
if (undeclaredHKeyColumn == null && equivalentColumnDepth <= leafMostDepth) {
undeclaredHKeyColumn = equivalentColumn;
}
}
break;
}
if (undeclaredHKeyColumn == null) {
undeclaredHKeyColumn = hKeyColumn.column();
}
return undeclaredHKeyColumn;
}
private int substituteHKeyColumnPosition(HKeyColumn hKeyColumn) {
int substituteHKeyColumnPosition = -1;
// Given an hkey row, we need to construct an hkey for some table, either a table covered by the
// index
// or some ancestor table. hKeyColumn is an hkey column of that table. If we're here, then
// hKeyColumn.column() cannot be obtained from the index row itself, so the question is: which
// of the
// hKeyColumn's equivalent columns should be used.
// - If the hkey column is above the root: Use the rootmost equivalent column of the hkey
// columns in the index
// row.
// - Otherwise the hkey column belongs to a table covered by the index.
// - For a left join index, use the nearest rootward equivalent column.
// - For a right join index, use the nearest leafward equivalent column.
List<Column> equivalentColumns = hKeyColumn.equivalentColumns(); // sorted by depth, root first
Integer targetTableDepth = hKeyColumn.column().getTable().getDepth();
if (targetTableDepth < rootMostTable().getDepth()) {
for (int i = 0; substituteHKeyColumnPosition == -1 && i < equivalentColumns.size(); i++) {
Column equivalentColumn = equivalentColumns.get(i);
substituteHKeyColumnPosition = positionOf(equivalentColumn);
}
} else {
switch (getJoinType()) {
case LEFT:
for (int i = 0; i < equivalentColumns.size(); i++) {
Column equivalentColumn = equivalentColumns.get(i);
int equivalentColumnPosition = positionOf(equivalentColumn);
if (equivalentColumnPosition != -1 && depth(equivalentColumn) < targetTableDepth) {
substituteHKeyColumnPosition = equivalentColumnPosition;
}
}
break;
case RIGHT:
for (int i = equivalentColumns.size() - 1; i >= 0; i--) {
Column equivalentColumn = equivalentColumns.get(i);
int equivalentColumnPosition = positionOf(equivalentColumn);
if (equivalentColumnPosition != -1 && depth(equivalentColumn) > targetTableDepth) {
substituteHKeyColumnPosition = equivalentColumnPosition;
}
}
break;
}
}
assert substituteHKeyColumnPosition != -1 : hKeyColumn;
return substituteHKeyColumnPosition;
}