/// <summary>
/// Enumerates the terms of an expression tree that are specific to a table.
/// </summary>
/// <param name="node"></param>
/// <param name="table"></param>
/// <returns></returns>
/// <remarks>The expression must be in CNF</remarks>
private static IEnumerable<LogicalExpressions.Expression> EnumerateCnfTermsSpecificToTable(LogicalExpressions.Expression node, TableReference table)
{
foreach (var term in EnumerateCnfTerms(node))
{
if (term is LogicalExpressions.OperatorOr)
{
// A term is only specific to a table if it contains predicates
// only specific to the particular table
var specifictotable = true;
foreach (var exp in EnumerateCnfTermPredicates(term))
{
if (!GetCnfLiteralPredicate(exp).IsSpecificToTable(table))
{
specifictotable = false;
break;
}
}
if (specifictotable)
{
yield return term;
}
}
else
{
if (GetCnfLiteralPredicate(term).IsSpecificToTable(table))
{
yield return term;
}
}
}
}
/// <summary>
/// Returns a search condition predicate associated with a CNF literal
/// </summary>
/// <param name="term"></param>
/// <returns></returns>
private static Predicate GetCnfLiteralPredicate(LogicalExpressions.Expression term)
{
if (term is LogicalExpressions.OperatorNot)
{
return ((LogicalExpressions.Predicate)((LogicalExpressions.OperatorNot)term).Operand).Value;
}
else if (term is LogicalExpressions.Predicate)
{
return ((LogicalExpressions.Predicate)term).Value;
}
else
{
throw new InvalidOperationException();
}
}
/// <summary>
/// Enumerates terms of an expression tree of a search condition.
/// </summary>
/// <param name="node"></param>
/// <returns></returns>
/// <remarks>The expression tree must be in CNF</remarks>
private static IEnumerable<LogicalExpressions.Expression> EnumerateCnfTerms(LogicalExpressions.Expression node)
{
if (node == null)
{
throw new ArgumentNullException("node");
}
if (node is LogicalExpressions.OperatorAnd)
{
// The CNF has multiple terms
foreach (var exp in ((LogicalExpressions.OperatorAnd)node).EnumerateTerms())
{
yield return exp;
}
}
else if (node is LogicalExpressions.OperatorOr ||
node is LogicalExpressions.OperatorNot ||
node is LogicalExpressions.Predicate)
{
// The CNF has only one term
yield return node;
}
else
{
throw new InvalidOperationException();
}
}
