/// <summary>
/// Returns an operation between two SELECT clauses (UNION, UNION ALL, etc.)
/// </summary>
/// <param name="selectOperator"></param>
/// <param name="selectA"></param>
/// <param name="selectB"></param>
/// <returns></returns>
public virtual SqlStatement GetLiteral(SelectOperatorType selectOperator, SqlStatement selectA, SqlStatement selectB)
{
switch (selectOperator)
{
case SelectOperatorType.Union:
return GetLiteralUnion(selectA, selectB);
case SelectOperatorType.UnionAll:
return GetLiteralUnionAll(selectA, selectB);
case SelectOperatorType.Intersection:
return GetLiteralIntersect(selectA, selectB);
case SelectOperatorType.Exception:
return GetLiteralExcept(selectA, selectB);
default:
throw new ArgumentOutOfRangeException(selectOperator.ToString());
}
}
protected virtual Expression AnalyzeSelectOperation(SelectOperatorType operatorType, IList<Expression> parameters, TranslationContext context)
{
// a special case: if we have several SELECT expressions linked together,
// we maximize the load to the database, since the result must use the same parameters
// types and count.
//context.QueryContext.MaximumDatabaseLoad = true; // all select expression goes to SQL tier
var subQuery = parameters[1];
if (subQuery != null) {
// Handle second select first
TranslationContext newContext = context.NewSisterSelect();
Expression tableExpression = AnalyzeSubQuery(subQuery, newContext);
BuildSelect(tableExpression, newContext);
// add the second select select to the chain
if (newContext.CurrentSelect.NextSelectExpression != null) {
var typedTable = tableExpression as TableExpression;
var dbTable = typedTable == null ? null : typedTable.TableInfo;
var operand0 = new SubSelectExpression(newContext.CurrentSelect, tableExpression.Type, "source", dbTable);
newContext.NewParentSelect();
newContext.CurrentSelect.Tables.Add(operand0);
}
SelectExpression selectToModify = context.CurrentSelect;
while (selectToModify.NextSelectExpression != null)
selectToModify = selectToModify.NextSelectExpression;
selectToModify.NextSelectExpression = newContext.CurrentSelect;
selectToModify.NextSelectExpressionOperator = operatorType;
Expression firstSelection = Analyze(parameters[0], context);
BuildSelect(firstSelection, context);
return firstSelection;
}
return Analyze(parameters[0], context);
}
