/// <summary>
/// For CASE statements which represent boolean values:
///
/// CASE XXX
/// WHEN AAA THEN true ===> (XXX==AAA) || (XXX==BBB)
/// WHEN BBB THEN true
/// ELSE false
/// etc.
/// END
///
/// Also,
///
/// CASE XXX
/// WHEN AAA THEN false ===> (XXX!=AAA) && (XXX!=BBB)
/// WHEN BBB THEN false
/// ELSE true
/// etc.
/// END
///
/// The reduce to a conjunction or disjunction of equality or inequality.
/// The possibility of NULL in XXX is taken into account.
/// </summary>
private SqlExpression TryToWriteAsSimpleBooleanExpression(Type caseType, SqlExpression discriminator, List <SqlWhen> newWhens, bool allValuesLiteral)
{
SqlExpression rewrite = null;
if (caseType == typeof(bool) && allValuesLiteral)
{
bool?holdsNull = SqlExpressionNullability.CanBeNull(discriminator);
// The discriminator can't hold a NULL.
// In this case, we don't need the special fallback that CASE-ELSE gives.
// We can just construct a boolean operation.
bool?whenValue = null;
for (int i = 0; i < newWhens.Count; ++i)
{
SqlValue lit = (SqlValue)newWhens[i].Value; // Must be SqlValue because of allValuesLiteral.
bool value = (bool)lit.Value; // Must be bool because of caseType==typeof(bool).
if (newWhens[i].Match != null)
{ // Skip the ELSE
if (value)
{
rewrite = _sql.OrAccumulate(rewrite, _sql.Binary(SqlNodeType.EQ, discriminator, newWhens[i].Match));
}
else
{
rewrite = _sql.AndAccumulate(rewrite, _sql.Binary(SqlNodeType.NE, discriminator, newWhens[i].Match));
}
}
else
{
whenValue = value;
}
}
// If it could possibly hold null values.
if (holdsNull != false && whenValue != null)
{
if (whenValue == true)
{
rewrite = _sql.OrAccumulate(rewrite, _sql.Unary(SqlNodeType.IsNull, discriminator, discriminator.SourceExpression));
}
else
{
rewrite = _sql.AndAccumulate(rewrite, _sql.Unary(SqlNodeType.IsNotNull, discriminator, discriminator.SourceExpression));
}
}
}
return(rewrite);
}
internal override SqlExpression VisitBinaryOperator(SqlBinary bo)
{
base.VisitBinaryOperator(bo);
if (bo.NodeType.IsComparisonOperator() &&
bo.Left.ClrType != typeof(bool) && bo.Right.ClrType != typeof(bool))
{
// Strip unnecessary CONVERT calls.
if (bo.Left.NodeType == SqlNodeType.Convert)
{
var conv = (SqlUnary)bo.Left;
if (CanDbConvert(conv.Operand.ClrType, bo.Right.ClrType) &&
conv.Operand.SqlType.ComparePrecedenceTo(bo.Right.SqlType) != 1)
{
return(VisitBinaryOperator(new SqlBinary(bo.NodeType, bo.ClrType, bo.SqlType, conv.Operand, bo.Right)));
}
}
if (bo.Right.NodeType == SqlNodeType.Convert)
{
var conv = (SqlUnary)bo.Right;
if (CanDbConvert(conv.Operand.ClrType, bo.Left.ClrType) &&
conv.Operand.SqlType.ComparePrecedenceTo(bo.Left.SqlType) != 1)
{
return(VisitBinaryOperator(new SqlBinary(bo.NodeType, bo.ClrType, bo.SqlType, bo.Left, conv.Operand)));
}
}
}
if (bo.Right != null && bo.NodeType != SqlNodeType.Concat)
{
SqlExpression left = bo.Left;
SqlExpression right = bo.Right;
this.CoerceBinaryArgs(ref left, ref right);
if (bo.Left != left || bo.Right != right)
{
bo = sql.Binary(bo.NodeType, left, right);
}
bo.SetSqlType(typeProvider.PredictTypeForBinary(bo.NodeType, left.SqlType, right.SqlType));
}
if (bo.NodeType.IsComparisonOperator())
{
// When comparing a unicode value against a non-unicode column,
// we want retype the parameter as non-unicode.
Func <SqlExpression, SqlExpression, bool> needsRetype =
(expr, val) => (val.NodeType == SqlNodeType.Value || val.NodeType == SqlNodeType.ClientParameter) &&
!(expr.NodeType == SqlNodeType.Value || expr.NodeType == SqlNodeType.ClientParameter) &&
val.SqlType.IsUnicodeType && !expr.SqlType.IsUnicodeType;
SqlSimpleTypeExpression valueToRetype = null;
if (needsRetype(bo.Left, bo.Right))
{
valueToRetype = (SqlSimpleTypeExpression)bo.Right;
}
else if (needsRetype(bo.Right, bo.Left))
{
valueToRetype = (SqlSimpleTypeExpression)bo.Left;
}
if (valueToRetype != null)
{
valueToRetype.SetSqlType(valueToRetype.SqlType.GetNonUnicodeEquivalent());
}
}
return(bo);
}
private SqlBinary MakeCompareTo(SqlExpression left, SqlExpression right, SqlNodeType op, int iValue)
{
if (iValue == 0)
{
return(sql.Binary(op, left, right));
}
if (op == SqlNodeType.EQ || op == SqlNodeType.EQ2V)
{
switch (iValue)
{
case -1:
return(sql.Binary(SqlNodeType.LT, left, right));
case 1:
return(sql.Binary(SqlNodeType.GT, left, right));
}
}
return(null);
}
