Expression Db2ApplyOptimizations(Expression expression, bool searchCondition, bool joinCondition = false)
{
var expression2 = (new NullComparisonTransformingVisitor_DB2(ParameterValues)).Visit(expression);
var binaryExpression = (expression2 is BinaryExpression) ? (expression2 as BinaryExpression) : null;
if (_relationalNullsExpandingVisitor == null)
{
_relationalNullsExpandingVisitor = new RelationalNullsExpandingVisitor();
}
if (_predicateReductionExpressionOptimizer == null)
{
_predicateReductionExpressionOptimizer = new PredicateReductionExpressionOptimizer();
}
if (_predicateNegationExpressionOptimizer == null)
{
_predicateNegationExpressionOptimizer = new PredicateNegationExpressionOptimizer();
}
if (_reducingExpressionVisitor == null)
{
_reducingExpressionVisitor = new ReducingExpressionVisitor();
}
if (_booleanExpressionTranslatingVisitor == null)
{
_booleanExpressionTranslatingVisitor = new BooleanExpressionTranslatingVisitor_DB2();
}
expression2 = ((!joinCondition || binaryExpression == null || binaryExpression.NodeType != ExpressionType.Equal) ? Db2ApplyNullSemantics(expression2) : Expression.MakeBinary(binaryExpression.NodeType, Db2ApplyNullSemantics(binaryExpression.Left), Db2ApplyNullSemantics(binaryExpression.Right)));
expression2 = _predicateReductionExpressionOptimizer.Visit(expression2);
expression2 = _predicateNegationExpressionOptimizer.Visit(expression2);
expression2 = _reducingExpressionVisitor.Visit(expression2);
if (binaryExpression == null || (expression.NodeType != ExpressionType.Or && expression.NodeType != ExpressionType.And))
{
expression2 = _booleanExpressionTranslatingVisitor.Translate(expression2, searchCondition);
}
return(expression2);
}
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);
}
