internal override SqlExpression VisitSimpleCase(SqlSimpleCase c) {
c.Expression = this.VisitExpression(c.Expression);
for (int i = 0, n = c.Whens.Count; i < n; i++) {
// Don't walk down the match side. This can't be a column.
c.Whens[i].Value = this.VisitExpression(c.Whens[i].Value);
}
return c;
}
internal bool AreCaseWhenValuesConstant(SqlSimpleCase sc)
{
foreach(SqlWhen when in sc.Whens)
{
if(when.Value.NodeType != SqlNodeType.Value)
{
return false;
}
}
return true;
}
/// <summary>
/// Helper for VisitBinaryOperator. Builds the new case with distributed valueds.
/// </summary>
private SqlExpression DistributeOperatorIntoCase(SqlNodeType nt, SqlSimpleCase sc, SqlExpression expr)
{
if(nt != SqlNodeType.EQ && nt != SqlNodeType.NE && nt != SqlNodeType.EQ2V && nt != SqlNodeType.NE2V)
throw Error.ArgumentOutOfRange("nt");
object val = Eval(expr);
List<SqlExpression> values = new List<SqlExpression>();
List<SqlExpression> matches = new List<SqlExpression>();
foreach(SqlWhen when in sc.Whens)
{
matches.Add(when.Match);
object whenVal = Eval(when.Value);
bool eq = when.Value.SqlType.AreValuesEqual(whenVal, val);
values.Add(_sql.ValueFromObject((nt == SqlNodeType.EQ || nt == SqlNodeType.EQ2V) == eq, false, sc.SourceExpression));
}
return this.VisitExpression(_sql.Case(typeof(bool), sc.Expression, matches, values, sc.SourceExpression));
}
internal virtual SqlExpression VisitSimpleCase(SqlSimpleCase c) {
c.Expression = this.VisitExpression(c.Expression);
for (int i = 0, n = c.Whens.Count; i < n; i++) {
SqlWhen when = c.Whens[i];
when.Match = this.VisitExpression(when.Match);
when.Value = this.VisitExpression(when.Value);
}
return c;
}
internal override SqlExpression VisitSimpleCase(SqlSimpleCase c)
{
_depth++;
this.NewLine();
_commandStringBuilder.Append("(CASE");
_depth++;
if(c.Expression != null)
{
_commandStringBuilder.Append(" ");
this.Visit(c.Expression);
}
for(int i = 0, n = c.Whens.Count; i < n; i++)
{
SqlWhen when = c.Whens[i];
if(i == n - 1 && when.Match == null)
{
this.NewLine();
_commandStringBuilder.Append("ELSE ");
this.Visit(when.Value);
}
else
{
this.NewLine();
_commandStringBuilder.Append("WHEN ");
this.Visit(when.Match);
_commandStringBuilder.Append(" THEN ");
this.Visit(when.Value);
}
}
_depth--;
this.NewLine();
_commandStringBuilder.Append(" END)");
_depth--;
return c;
}
internal override SqlExpression VisitSimpleCase(SqlSimpleCase c)
{
SqlExpression expr = this.VisitExpression(c.Expression);
SqlWhen[] whens = new SqlWhen[c.Whens.Count];
for(int i = 0, n = whens.Length; i < n; i++)
{
SqlWhen when = c.Whens[i];
whens[i] = new SqlWhen(this.VisitExpression(when.Match), this.VisitExpression(when.Value));
}
return new SqlSimpleCase(c.ClrType, expr, whens, c.SourceExpression);
}
internal override SqlExpression VisitSimpleCase(SqlSimpleCase c)
{
c.Expression = this.VisitExpression(c.Expression);
int compareWhen = 0;
// Find the ELSE if it exists.
for(int i = 0, n = c.Whens.Count; i < n; i++)
{
if(c.Whens[i].Match == null)
{
compareWhen = i;
break;
}
}
c.Whens[compareWhen].Match = VisitExpression(c.Whens[compareWhen].Match);
c.Whens[compareWhen].Value = VisitExpression(c.Whens[compareWhen].Value);
// Compare each other when value to the compare when
List<SqlWhen> newWhens = new List<SqlWhen>();
bool allValuesLiteral = true;
for(int i = 0, n = c.Whens.Count; i < n; i++)
{
if(compareWhen != i)
{
SqlWhen when = c.Whens[i];
when.Match = this.VisitExpression(when.Match);
when.Value = this.VisitExpression(when.Value);
if(!SqlComparer.AreEqual(c.Whens[compareWhen].Value, when.Value))
{
newWhens.Add(when);
}
allValuesLiteral = allValuesLiteral && when.Value.NodeType == SqlNodeType.Value;
}
}
newWhens.Add(c.Whens[compareWhen]);
// Did everything reduce to a single CASE?
SqlExpression rewrite = TryToConsolidateAllValueExpressions(newWhens.Count, c.Whens[compareWhen].Value);
if(rewrite != null)
return rewrite;
// Can it be a conjuction (or disjunction) of clauses?
rewrite = TryToWriteAsSimpleBooleanExpression(c.ClrType, c.Expression, newWhens, allValuesLiteral);
if(rewrite != null)
return rewrite;
// Can any WHEN clauses be reduced to fall into the ELSE clause?
rewrite = TryToWriteAsReducedCase(c.ClrType, c.Expression, newWhens, c.Whens[compareWhen].Match, c.Whens.Count);
if(rewrite != null)
return rewrite;
return c;
}
internal override SqlExpression VisitSimpleCase(SqlSimpleCase c)
{
base.VisitSimpleCase(c);
// determine the best common type for all the when values
ProviderType type = c.Whens[0].Value.SqlType;
for(int i = 1; i < c.Whens.Count; i++)
{
ProviderType whenType = c.Whens[i].Value.SqlType;
type = typeProvider.GetBestType(type, whenType);
}
// coerce each one
foreach(SqlWhen when in c.Whens.Where(w => w.Value.SqlType != type && !w.Value.SqlType.IsRuntimeOnlyType))
{
when.Value = sql.UnaryConvert(when.Value.ClrType, type, when.Value, when.Value.SourceExpression);
}
return c;
}
private static SqlExpression UnwrapTrivialCaseExpression(SqlSimpleCase sc)
{
if(sc.Whens.Count != 1)
{
return sc;
}
if(!SqlComparer.AreEqual(sc.Expression, sc.Whens[0].Match))
{
return sc;
}
SqlExpression result = sc.Whens[0].Value;
if(result.NodeType == SqlNodeType.SimpleCase)
{
return UnwrapTrivialCaseExpression((SqlSimpleCase)result);
}
return result;
}
internal override SqlExpression VisitSimpleCase(SqlSimpleCase c)
{
bool saveCanJoin = this.canJoin;
this.canJoin = false;
try
{
return base.VisitSimpleCase(c);
}
finally
{
this.canJoin = saveCanJoin;
}
}