Expression expr = expressions.get(0);
expr = expr.getNonAliasExpression();
if (expr instanceof ExpressionColumn) {
Column column = ((ExpressionColumn) expr).getColumn();
int selectivity = column.getSelectivity();
Index columnIndex = topTableFilter.getTable().getIndexForColumn(column, true);
if (columnIndex != null && selectivity != Constants.SELECTIVITY_DEFAULT && selectivity < 20) {
// the first column must be ascending
boolean ascending = columnIndex.getIndexColumns()[0].sortType == SortOrder.ASCENDING;
Index current = topTableFilter.getIndex();
// if another index is faster
if (columnIndex.canFindNext() && ascending &&
(current == null || current.getIndexType().isScan() || columnIndex == current)) {
IndexType type = columnIndex.getIndexType();
// hash indexes don't work, and unique single column indexes don't work
if (!type.isHash() && (!type.isUnique() || columnIndex.getColumns().length > 1)) {
topTableFilter.setIndex(columnIndex);
isDistinctQuery = true;
}
}
}
}
}
if (sort != null && !isQuickAggregateQuery && !isGroupQuery) {
Index index = getSortIndex();
if (index != null) {
Index current = topTableFilter.getIndex();
if (current.getIndexType().isScan() || current == index) {
topTableFilter.setIndex(index);
if (!topTableFilter.hasInComparisons()) {
// in(select ...) and in(1,2,3) my return the key in another order
sortUsingIndex = true;
}
} else if (index.getIndexColumns().length >= current.getIndexColumns().length) {
IndexColumn[] sortColumns = index.getIndexColumns();
IndexColumn[] currentColumns = current.getIndexColumns();
boolean swapIndex = false;
for (int i = 0; i < currentColumns.length; i++) {
if (sortColumns[i].column != currentColumns[i].column) {
swapIndex = false;
break;
}
if (sortColumns[i].sortType != currentColumns[i].sortType) {
swapIndex = true;
}
}
if (swapIndex) {
topTableFilter.setIndex(index);
sortUsingIndex = true;
}
}
}
}
if (!isQuickAggregateQuery && isGroupQuery && getGroupByExpressionCount() > 0) {
Index index = getGroupSortedIndex();
Index current = topTableFilter.getIndex();
if (index != null && (current.getIndexType().isScan() || current == index)) {
topTableFilter.setIndex(index);
isGroupSortedQuery = true;
}
}
expressionArray = new Expression[expressions.size()];