public override Expression Visit([NotNull] Expression expression)
{
var currentExpression = expression;
var inExpressionOptimized =
new EqualityPredicateInExpressionOptimizer().Visit(currentExpression);
currentExpression = inExpressionOptimized;
var negationOptimized1 =
new PredicateNegationExpressionOptimizer()
.Visit(currentExpression);
currentExpression = negationOptimized1;
var equalityExpanded =
new EqualityPredicateExpandingVisitor().Visit(currentExpression);
currentExpression = equalityExpanded;
var negationOptimized2 =
new PredicateNegationExpressionOptimizer()
.Visit(currentExpression);
currentExpression = negationOptimized2;
var parameterDectector = new ParameterExpressionDetectingVisitor();
parameterDectector.Visit(currentExpression);
if (!parameterDectector.ContainsParameters
&& !_useRelationalNulls)
{
var optimizedNullExpansionVisitor = new RelationalNullsOptimizedExpandingVisitor();
var relationalNullsExpandedOptimized = optimizedNullExpansionVisitor.Visit(currentExpression);
if (optimizedNullExpansionVisitor.OptimizedExpansionPossible)
{
currentExpression = relationalNullsExpandedOptimized;
}
else
{
currentExpression = new RelationalNullsExpandingVisitor()
.Visit(currentExpression);
}
}
if (_useRelationalNulls)
{
currentExpression = new NotNullableExpression(currentExpression);
}
var negationOptimized3 =
new PredicateNegationExpressionOptimizer()
.Visit(currentExpression);
currentExpression = negationOptimized3;
return currentExpression;
}
Expression Db2ApplyNullSemantics(Expression expression)
{
RelationalNullsOptimizedExpandingVisitor relationalNullsOptimizedExpandingVisitor = new RelationalNullsOptimizedExpandingVisitor();
Expression result = (relationalNullsOptimizedExpandingVisitor).Visit(expression);
if (!relationalNullsOptimizedExpandingVisitor.IsOptimalExpansion)
{
return(_relationalNullsExpandingVisitor.Visit(expression));
}
return(result);
}
private Expression ApplyNullSemantics(Expression expression)
{
var newExpression
= new NullComparisonTransformingVisitor(_parametersValues)
.Visit(expression);
var relationalNullsOptimizedExpandingVisitor = new RelationalNullsOptimizedExpandingVisitor();
var optimizedExpression = relationalNullsOptimizedExpandingVisitor.Visit(newExpression);
newExpression
= relationalNullsOptimizedExpandingVisitor.IsOptimalExpansion
? optimizedExpression
: new RelationalNullsExpandingVisitor().Visit(newExpression);
newExpression = new PredicateNegationExpressionOptimizer().Visit(newExpression);
newExpression = new ReducingExpressionVisitor().Visit(newExpression);
return(newExpression);
}
public virtual Expression VisitSelect(SelectExpression selectExpression)
{
Check.NotNull(selectExpression, nameof(selectExpression));
IDisposable subQueryIndent = null;
if (selectExpression.Alias != null)
{
_sql.AppendLine("(");
subQueryIndent = _sql.Indent();
}
_sql.Append("SELECT ");
if (selectExpression.IsDistinct)
{
_sql.Append("DISTINCT ");
}
GenerateTop(selectExpression);
var projectionAdded = false;
if (selectExpression.IsProjectStar)
{
_sql.Append(_sqlGenerator.DelimitIdentifier(selectExpression.Tables.Single().Alias))
.Append(".*");
projectionAdded = true;
}
if (selectExpression.Projection.Any())
{
if (selectExpression.IsProjectStar)
{
_sql.Append(", ");
}
VisitJoin(selectExpression.Projection);
projectionAdded = true;
}
if (!projectionAdded)
{
_sql.Append("1");
}
if (selectExpression.Tables.Any())
{
_sql.AppendLine()
.Append("FROM ");
VisitJoin(selectExpression.Tables, sql => sql.AppendLine());
}
if (selectExpression.Predicate != null)
{
_sql.AppendLine()
.Append("WHERE ");
var constantExpression = selectExpression.Predicate as ConstantExpression;
if (constantExpression != null)
{
_sql.Append((bool)constantExpression.Value ? "1 = 1" : "1 = 0");
}
else
{
var predicate
= new NullComparisonTransformingVisitor(_parameterValues)
.Visit(selectExpression.Predicate);
// we have to optimize out comparisons to null-valued parameters before we can expand null semantics
if (_parameterValues.Count > 0)
{
var optimizedNullExpansionVisitor = new RelationalNullsOptimizedExpandingVisitor();
var relationalNullsExpandedOptimized = optimizedNullExpansionVisitor.Visit(predicate);
if (optimizedNullExpansionVisitor.OptimizedExpansionPossible)
{
predicate = relationalNullsExpandedOptimized;
}
else
{
predicate = new RelationalNullsExpandingVisitor()
.Visit(predicate);
}
}
predicate = new ReducingExpressionVisitor().Visit(predicate);
Visit(predicate);
if (selectExpression.Predicate is ParameterExpression ||
selectExpression.Predicate.IsAliasWithColumnExpression() ||
selectExpression.Predicate is SelectExpression)
{
_sql.Append(" = ");
_sql.Append(TrueLiteral);
}
}
}
if (selectExpression.OrderBy.Any())
{
_sql.AppendLine();
GenerateOrderBy(selectExpression.OrderBy);
}
GenerateLimitOffset(selectExpression);
if (subQueryIndent != null)
{
subQueryIndent.Dispose();
_sql.AppendLine()
.Append(")");
if (selectExpression.Alias.Length > 0)
{
_sql.Append(" AS ")
.Append(_sqlGenerator.DelimitIdentifier(selectExpression.Alias));
}
}
return(selectExpression);
}
