public static ITable All(this ITable table, IQueryContext context, Expression expression, Operator op, ITable other)
{
// Check the table only has 1 column
if (other.TableInfo.ColumnCount != 1)
{
throw new ApplicationException("Input table <> 1 columns.");
}
// Handle trivial case of no entries to select from
if (table.RowCount == 0)
{
return(table);
}
var theTable = table as Table;
if (theTable == null)
{
return(table);
}
// If 'table' is empty then we return the complete set. ALL { empty set }
// is always true.
if (other.RowCount == 0)
{
return(table);
}
// Is the lhs expression a constant?
if (expression.IsConstant())
{
// We know lhs is a constant so no point passing arguments,
DataObject value = expression.Evaluate(context);
bool comparedToTrue;
// The various operators
if (op.IsEquivalent(Operator.Greater) ||
op.IsEquivalent(Operator.GreaterOrEqual))
{
// Find the maximum value in the table
DataObject cell = other.GetLastCell(0);
comparedToTrue = CompareCells(value, cell, op);
}
else if (op.IsEquivalent(Operator.Smaller) ||
op.IsEquivalent(Operator.SmallerOrEqual))
{
// Find the minimum value in the table
DataObject cell = other.GetFirstCell(0);
comparedToTrue = CompareCells(value, cell, op);
}
else if (op.IsEquivalent(Operator.Equal))
{
// Only true if rhs is a single value
DataObject cell = other.GetSingleCell(0);
comparedToTrue = (cell != null && CompareCells(value, cell, op));
}
else if (op.IsEquivalent(Operator.NotEqual))
{
// true only if lhs_cell is not found in column.
comparedToTrue = !other.ColumnContainsValue(0, value);
}
else
{
throw new ApplicationException("Don't understand operator '" + op + "' in ALL.");
}
// If matched return this table
if (comparedToTrue)
{
return(table);
}
// No entries matches so return an empty table.
return(table.EmptySelect());
}
Table sourceTable;
int colIndex;
// Is the lhs expression a single variable?
ObjectName expVar = expression.AsVariable();
// NOTE: It'll be less common for this part to be called.
if (expVar == null)
{
// This is a complex expression so make a FunctionTable as our new
// source.
DatabaseQueryContext dbContext = (DatabaseQueryContext)context;
FunctionTable funTable = new FunctionTable((Table)table, new[] { expression }, new [] { "1" }, dbContext);
sourceTable = funTable;
colIndex = 0;
}
else
{
// The expression is an easy to resolve reference in this table.
sourceTable = (Table)table;
colIndex = sourceTable.FindFieldName(expVar);
if (colIndex == -1)
{
throw new ApplicationException("Can't find column '" + expVar + "'.");
}
}
// Check that the first column of 'table' is of a compatible type with
// source table column (lhs_col_index).
// ISSUE: Should we convert to the correct type via a FunctionTable?
DataColumnInfo sourceCol = sourceTable.TableInfo[colIndex];
DataColumnInfo destCol = other.TableInfo[0];
if (!sourceCol.DataType.IsComparable(destCol.DataType))
{
throw new ApplicationException("The type of the sub-query expression " +
sourceCol.DataType + " is incompatible " +
"with the sub-query " + destCol.DataType +
".");
}
// We now have all the information to solve this query.
// We work output as follows:
// For >, >= type ALL we find the highest value in 'table' and
// select from 'source' all the rows that are >, >= than the
// highest value.
// For <, <= type ALL we find the lowest value in 'table' and
// select from 'source' all the rows that are <, <= than the
// lowest value.
// For = type ALL we see if 'table' contains a single value. If it
// does we select all from 'source' that equals the value, otherwise an
// empty table.
// For <> type ALL we use the 'not in' algorithm.
IList <long> selectList;
if (op.IsEquivalent(Operator.Greater) ||
op.IsEquivalent(Operator.GreaterOrEqual))
{
// Select the last from the set (the highest value),
DataObject highestCell = other.GetLastCell(0);
// Select from the source table all rows that are > or >= to the
// highest cell,
selectList = sourceTable.SelectRows(colIndex, op, highestCell).ToList();
}
else if (op.IsEquivalent(Operator.Smaller) ||
op.IsEquivalent(Operator.SmallerOrEqual))
{
// Select the first from the set (the lowest value),
DataObject lowestCell = other.GetFirstCell(0);
// Select from the source table all rows that are < or <= to the
// lowest cell,
selectList = sourceTable.SelectRows(colIndex, op, lowestCell).ToList();
}
else if (op.IsEquivalent(Operator.Equal))
{
// Select the single value from the set (if there is one).
DataObject singleCell = other.GetSingleCell(0);
if (singleCell != null)
{
// Select all from source_table all values that = this cell
selectList = sourceTable.SelectRows(colIndex, op, singleCell).ToList();
}
else
{
// No single value so return empty set (no value in LHS will equal
// a value in RHS).
return(table.EmptySelect());
}
}
else if (op.IsEquivalent(Operator.NotEqual))
{
// Equiv. to NOT IN
selectList = sourceTable.NotIn(other, colIndex, 0).ToList();
}
else
{
throw new ApplicationException("Don't understand operator '" + op + "' in ALL.");
}
// Make into a table to return.
VirtualTable rtable = new VirtualTable(theTable);
rtable.Set((Table)table, selectList);
return(rtable);
}
