public override ExpressionNode VisitNullIfExpression(NullIfExpression expression)
{
// First visit all expressions
base.VisitNullIfExpression(expression);
// Since a NULLIF expression can be expressed using a CASE expression we convert
// them to simplify the evaluation and optimization engine.
//
// NULLIF(expression1, expression1) is equivalent to this CASE expression:
//
// CASE
// WHEN expression1 = expression2 THEN NULL
// ELSE expression1
// END
CaseExpression caseExpression = new CaseExpression();
caseExpression.WhenExpressions = new ExpressionNode[1];
caseExpression.ThenExpressions = new ExpressionNode[1];
caseExpression.WhenExpressions[0] = new BinaryExpression(BinaryOperator.Equal, expression.LeftExpression, expression.RightExpression);
caseExpression.ThenExpressions[0] = LiteralExpression.FromNull();
caseExpression.ElseExpression = expression.LeftExpression;
return(VisitExpression(caseExpression));
}
private ExpressionNode ParsePrimaryExpression()
{
switch (_token.Id)
{
case TokenId.NULL:
NextToken();
return(LiteralExpression.FromNull());
case TokenId.TRUE:
case TokenId.FALSE:
return(ParseBooleanLiteral());
case TokenId.Date:
return(ParseDateLiteral());
case TokenId.Number:
return(ParseNumberLiteral());
case TokenId.String:
return(LiteralExpression.FromString(ParseString()));
case TokenId.EXISTS:
{
ExistsSubselect result = new ExistsSubselect();
NextToken();
Match(TokenId.LeftParentheses);
result.Query = ParseQuery();
Match(TokenId.RightParentheses);
return(result);
}
case TokenId.ParameterMarker:
{
_rangeRecorder.Begin();
NextToken();
Identifier name = ParseIdentifier();
SourceRange nameSourceRange = _rangeRecorder.End();
ParameterExpression result = new ParameterExpression();
result.Name = name;
result.NameSourceRange = nameSourceRange;
return(result);
}
case TokenId.CAST:
{
NextToken();
CastExpression castExpression = new CastExpression();
Match(TokenId.LeftParentheses);
castExpression.Expression = ParseExpression();
Match(TokenId.AS);
castExpression.TypeReference = ParseTypeReference();
Match(TokenId.RightParentheses);
return(castExpression);
}
case TokenId.CASE:
{
NextToken();
CaseExpression caseExpression = new CaseExpression();
if (_token.Id != TokenId.WHEN && _token.Id != TokenId.ELSE && _token.Id != TokenId.END)
{
caseExpression.InputExpression = ParseExpression();
}
List <ExpressionNode> whenExpressionList = new List <ExpressionNode>();
List <ExpressionNode> expressionList = new List <ExpressionNode>();
if (_token.Id != TokenId.WHEN)
{
Match(TokenId.WHEN);
}
else
{
while (_token.Id == TokenId.WHEN)
{
NextToken();
whenExpressionList.Add(ParseExpression());
Match(TokenId.THEN);
expressionList.Add(ParseExpression());
}
}
caseExpression.WhenExpressions = whenExpressionList.ToArray();
caseExpression.ThenExpressions = expressionList.ToArray();
if (_token.Id == TokenId.ELSE)
{
NextToken();
caseExpression.ElseExpression = ParseExpression();
}
Match(TokenId.END);
return(caseExpression);
}
case TokenId.COALESCE:
{
NextToken();
CoalesceExpression coalesceExpression = new CoalesceExpression();
coalesceExpression.Expressions = ParseExpressionList();
return(coalesceExpression);
}
case TokenId.NULLIF:
{
NextToken();
NullIfExpression nullIfExpression = new NullIfExpression();
Match(TokenId.LeftParentheses);
nullIfExpression.LeftExpression = ParseExpression();
Match(TokenId.Comma);
nullIfExpression.RightExpression = ParseExpression();
Match(TokenId.RightParentheses);
return(nullIfExpression);
}
case TokenId.Identifier:
{
_rangeRecorder.Begin();
Identifier name = ParseIdentifier();
SourceRange nameSourceRange = _rangeRecorder.End();
if (_token.Id != TokenId.LeftParentheses)
{
NameExpression result = new NameExpression();
result.Name = name;
result.NameSourceRange = nameSourceRange;
return(result);
}
else
{
bool hasAsteriskModifier;
ExpressionNode[] args;
if (_lookahead.Id != TokenId.Multiply)
{
hasAsteriskModifier = false;
args = ParseExpressionList();
}
else
{
NextToken();
NextToken();
Match(TokenId.RightParentheses);
hasAsteriskModifier = true;
args = new ExpressionNode[0];
}
FunctionInvocationExpression result = new FunctionInvocationExpression();
result.Name = name;
result.NameSourceRange = nameSourceRange;
result.Arguments = args;
result.HasAsteriskModifier = hasAsteriskModifier;
return(result);
}
}
case TokenId.LeftParentheses:
{
NextToken();
ExpressionNode expr;
if (_token.Id != TokenId.SELECT)
{
expr = ParseExpression();
}
else
{
SingleRowSubselect singleRowSubselect = new SingleRowSubselect();
singleRowSubselect.Query = ParseQuery();
expr = singleRowSubselect;
}
Match(TokenId.RightParentheses);
return(expr);
}
default:
{
_errorReporter.SimpleExpressionExpected(_token.Range, _token.Text);
return(LiteralExpression.FromNull());
}
}
}