public IndexCollation(SqlType type, CollationColumn[] columns, string function)
{
if (columns.Length == 0)
throw new ArgumentException("Cannot create an empty collation.", "columns");
if (columns.Length > 1) {
if (!(type is SqlCompositeType))
throw new ArgumentException("Composite indexes must be represented by composite-type");
SqlCompositeType ctype = (SqlCompositeType) type;
if (ctype.PartCount != columns.Length)
throw new ArgumentException("Composite type size different to the number of columns given", "columns");
}
// Can't contain identical columns
for (int i = 0; i < columns.Length; ++i) {
for (int n = 0; n < columns.Length; ++n) {
if (i != n && columns[i].ColumnName.Equals(columns[n].ColumnName))
throw new ArgumentException("Repeat column '" + columns[i] +"' name");
}
}
this.type = type;
this.function = function;
this.columns = (CollationColumn[]) columns.Clone();
}
public IndexCollation(SqlType type, CollationColumn[] columns)
: this(type, columns, null)
{
}
public IndexCollation(SqlType type, CollationColumn column)
: this(type, new CollationColumn[] { column }, null)
{
}
public IndexCollation Reverse()
{
CollationColumn[] reverseColumns = new CollationColumn[columns.Length];
for (int i = 0; i < columns.Length; i++)
reverseColumns[i] = new CollationColumn(columns[i].ColumnName, !columns[i].Ascending);
return new IndexCollation(type, reverseColumns, function);
}
private IndexCollation DecodeCollation(SystemTable table)
{
string[] columnNames = index.ColumnNames;
// Each column is encoded as '(+|-)[column name]' representing ascending
// or descending order of the column.
int sz = columnNames.Length;
CollationColumn[] sortColumns = new CollationColumn[sz];
SqlType[] columnTypes = new SqlType[sz];
// For each column in the index,
for (int i = 0; i < sz; ++i) {
string columnName = columnNames[i];
bool ascending = index.ColumnOrder[i];
columnTypes[i] = table.Columns[columnName].Type;
// Fail if the column is a type we can't index
if (columnTypes[i].IsBinary)
//TODO: check better...
return null;
sortColumns[i] = new CollationColumn(columnName, ascending);
}
// No columns, so return null
if (sz == 0)
return null;
if (sz == 1)
// Create the collation
return new IndexCollation(columnTypes[0], sortColumns[0]);
SqlCompositeType compositeType = new SqlCompositeType(columnTypes);
return new IndexCollation(compositeType, sortColumns);
}