internal T ExecuteFunction <T>(DbTableDataReader reader,
DbColumnType valueType,
IEnumerable <int> collection)
{
dynamic oneColumnCollection = collection;
//apply quantifiers here
if (Query.Select.Function != TokenType.COUNT)
{
//get real values
//not transformed, need to
var recordValues = new List <object[]>();
foreach (var offset in collection)
{
recordValues.Add(reader.ReadRecord(offset));
}
//read records return only one column
oneColumnCollection = recordValues.Select(cols => cols[0]).Cast <T>();
}
MethodInfo method =
this.GetType().GetMethod(nameof(ApplyFunction), BindingFlags.Instance | BindingFlags.NonPublic);
MethodInfo genMethod = method.MakeGenericMethod(Type.GetType($"System.{valueType}"));
var result = genMethod.Invoke(this, new object[] { oneColumnCollection, Query.Select.Function });
return((T)result);
}
void StoreKeyIndexedOffsets <T>(DbTableDataReader handler, DbColumn column, io.BinaryWriter writer)
where T : IComparable <T>
{
//write row count
var rows = handler.Rows <T>(column).ToList();
writer.Write(rows.Count);
//write all offsets
foreach (var row in rows)
{
writer.Write(row);
}
}
internal DbQueryExpressionExecuter(DbQueryHandler handler,
DbQuery.ColumnOperand columnOperand, TokenType oper, DbQuery.ConstantOperand constantOperand)
{
if (columnOperand == null || !(Operator = oper).IsComparison() || constantOperand == null ||
(Handler = handler) == null)
{
throw new ArgumentException($"cannot execute comparison expression");
}
//get the table column handler
Column = handler.Database.Index(columnOperand.Column.Hash);
// . handler.WhereColumns[columnOperand.Column.Hash];
//get the constant value to compare
Constant = constantOperand.Evaluate(null);
Reader = Handler.TableReaders.FirstOrDefault(r => r.Table == Column.Table);
if (Reader == null)
{
throw new ArgumentException($"could not resolve data table reader for column: {Column}");
}
}
/// <summary>
///
/// </summary>
/// <param name="forced">true to write it anyways</param>
void SaveKeyIndexedKeyOffsets(bool forced = false)
{
foreach (var table in Tables)
{
var handler = DbTableDataReader.Create(this, table);
foreach (var column in table.Columns.Where(col => col.Key))
{
var path = $"{BinaryPath}\\{column.Hash}.offset";
if (!io.File.Exists(path) || forced)
{
using (var writer = new io.BinaryWriter(io.File.Create(path)))
{
Utils.CallGeneric(
this, nameof(StoreKeyIndexedOffsets), column.TypeEnum,
new object[] { handler, column, writer },
System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance
);
}
}
}
}
}
/// <summary>
///
/// </summary>
/// <param name="db"></param>
/// <param name="query"></param>
public DbQueryHandler(CsvDb db, DbQuery query)
{
if ((Database = db) == null ||
(Query = query) == null)
{
throw new ArgumentException("Cannot create query executer handler");
}
//set index transformers to table columns
SelectIndexColumns = new SelectColumnHandler(query.Select.Columns);
//WhereColumns = new Dictionary<string, DbColumn>();
TableReaders = new List <DbTableDataReader>();
//get table data reader from FROM tables too, in case WHERE has no column
foreach (var table in query.From)
{
if (!TableReaders.Any(t => t.Table.Name == table.Name))
{
TableReaders.Add(DbTableDataReader.Create(db, table.Name, this));
}
}
}
