// For implementation of Alter Table.
public void AlterData(ColInfo newcols, int[] map)
{
// For each record, read the old data, copy the columns, write the new data.
// Each column in the new table will either be new, in which case it gets a default value,
// or is copied from an old column. The types do not have to match exactly, but need to have the same base type.
// Map holds the old colId for eaach new column ( or -1 if it is a new column ).
// Doesn't currently check for overflow.
long [] oldRow = new long[Cols.Count];
long [] newRow = new long[newcols.Count];
// Initialise newRow to default values.
for (int i = 0; i < newRow.Length; i += 1)
{
newRow[i] = DTI.Default(newcols.Types[i]).L;
}
int newRowSize = CalcRowSize(newcols);
byte [] blank = new byte[newRowSize];
RB = new byte[newRowSize];
// So that old data is not over-written before it has been converted, if new row size is bigger, use descending order.
bool desc = newRowSize > RowSize;
long id = desc ? RowCount - 1 : 0; // Note : zero based, whereas actual id values are 1-based.
long n = RowCount;
while (n > 0)
{
DF.Position = id * RowSize;
bool ok = AlterRead(Cols.Types, oldRow);
for (int i = 0; i < newRow.Length; i += 1)
{
int m = map[i];
if (m >= 0)
{
newRow[i] = oldRow[m];
}
}
DF.Position = id * newRowSize;
if (ok)
{
AlterWrite(newcols.Types, newRow, newRowSize);
}
else
{
DF.Write(blank, 0, blank.Length);
}
n -= 1;
id = desc ? id - 1 : id + 1;
}
if (!desc)
{
DF.SetLength(RowCount * newRowSize);
}
Dirty = true;
RowSize = newRowSize;
Cols = newcols;
}
public Inserter(Table t, int[] colIx, int idCol, TableExpression te)
{
T = t; ColIx = colIx; IdCol = idCol; TE = te;
DataType [] types = t.CI.Type;
Row = new Value[types.Length];
// Initialise row to default values.
for (int i = 0; i < types.Length; i += 1)
{
Row[i] = DTI.Default(types[i]);
}
}
public Inserter(Table t, int[] colIx, int idCol, TableExpression te)
{
T = t; ColIx = colIx; IdCol = idCol; TE = te;
DataType [] types = t.Cols.Types;
Row = new Value[types.Length];
// The line below is not required as Writer.SaveRecord handles any nulls, but this may be safer.
for (int i = 0; i < types.Length; i += 1)
{
Row[i] = DTI.Default(types[i]);
}
}
