public static ProjectedColumns ProjectColumns(Func<Expression, bool> fnCanBeColumn, Expression expression,
IEnumerable<DbColumnDeclaration> existingColumns, DbTableAlias newAlias, IEnumerable<DbTableAlias> existingAliases)
{
ColumnProjector projector = new ColumnProjector(fnCanBeColumn, expression, existingColumns, newAlias, existingAliases);
Expression expr = projector.Visit(expression);
return new ProjectedColumns(expr, projector.columns.AsReadOnly());
}
public static ProjectedColumns ProjectColumns(Func <Expression, bool> fnCanBeColumn, Expression expression,
IEnumerable <DbColumnDeclaration> existingColumns, DbTableAlias newAlias, IEnumerable <DbTableAlias> existingAliases)
{
ColumnProjector projector = new ColumnProjector(fnCanBeColumn, expression, existingColumns, newAlias, existingAliases);
Expression expr = projector.Visit(expression);
return(new ProjectedColumns(expr, projector.columns.AsReadOnly()));
}
protected override Expression VisitProjection(DbProjectionExpression proj)
{
DbSelectExpression save = this.currentSelect;
this.currentSelect = proj.Select;
try
{
if (!this.isTopLevel)
{
if (this.CanJoinOnClient(this.currentSelect))
{
// make a query that combines all the constraints from the outer queries into a single select
DbSelectExpression newOuterSelect = (DbSelectExpression)QueryDuplicator.Duplicate(save);
// remap any references to the outer select to the new alias;
DbSelectExpression newInnerSelect = (DbSelectExpression)ColumnMapper.Map(proj.Select, newOuterSelect.Alias, save.Alias);
// add outer-join test
DbProjectionExpression newInnerProjection = new DbProjectionExpression(newInnerSelect, proj.Projector).AddOuterJoinTest();
newInnerSelect = newInnerProjection.Select;
Expression newProjector = newInnerProjection.Projector;
DbTableAlias newAlias = new DbTableAlias();
var pc = ColumnProjector.ProjectColumns(this.language.CanBeColumn, newProjector, newOuterSelect.Columns, newAlias, newOuterSelect.Alias, newInnerSelect.Alias);
DbJoinExpression join = new DbJoinExpression(DbJoinType.OuterApply, newOuterSelect, newInnerSelect, null);
DbSelectExpression joinedSelect = new DbSelectExpression(newAlias, pc.Columns, join, null, null, null, proj.IsSingleton, null, null);
// apply client-join treatment recursively
this.currentSelect = joinedSelect;
newProjector = this.Visit(pc.Projector);
// compute keys (this only works if join condition was a single column comparison)
List <Expression> outerKeys = new List <Expression>();
List <Expression> innerKeys = new List <Expression>();
if (this.GetEquiJoinKeyExpressions(newInnerSelect.Where, newOuterSelect.Alias, outerKeys, innerKeys))
{
// outerKey needs to refer to the outer-scope's alias
var outerKey = outerKeys.Select(k => ColumnMapper.Map(k, save.Alias, newOuterSelect.Alias));
// innerKey needs to refer to the new alias for the select with the new join
var innerKey = innerKeys.Select(k => ColumnMapper.Map(k, joinedSelect.Alias, ((DbColumnExpression)k).Alias));
DbProjectionExpression newProjection = new DbProjectionExpression(joinedSelect, newProjector, proj.Aggregator);
return(new DbClientJoinExpression(newProjection, outerKey, innerKey));
}
}
}
else
{
this.isTopLevel = false;
}
return(base.VisitProjection(proj));
}
finally
{
this.currentSelect = save;
}
}
protected override Expression VisitJoin(DbJoinExpression join)
{
join = (DbJoinExpression)base.VisitJoin(join);
if (join.Join == DbJoinType.CrossApply || join.Join == DbJoinType.OuterApply)
{
if (join.Right is DbTableExpression)
{
return(new DbJoinExpression(DbJoinType.CrossJoin, join.Left, join.Right, null));
}
else
{
DbSelectExpression select = join.Right as DbSelectExpression;
// Only consider rewriting cross apply if
// 1) right side is a select
// 2) other than in the where clause in the right-side select, no left-side declared aliases are referenced
// 3) and has no behavior that would change semantics if the where clause is removed (like groups, aggregates, take, skip, etc).
// Note: it is best to attempt this after redundant subqueries have been removed.
if (select != null &&
select.Take == null &&
select.Skip == null &&
!AggregateChecker.HasAggregates(select) &&
(select.GroupBy == null || select.GroupBy.Count == 0))
{
DbSelectExpression selectWithoutWhere = select.SetWhere(null);
HashSet <DbTableAlias> referencedAliases = ReferencedAliasGatherer.Gather(selectWithoutWhere);
HashSet <DbTableAlias> declaredAliases = DeclaredAliasGatherer.Gather(join.Left);
referencedAliases.IntersectWith(declaredAliases);
if (referencedAliases.Count == 0)
{
Expression where = select.Where;
select = selectWithoutWhere;
var pc = ColumnProjector.ProjectColumns(this.CanBeColumn, where, select.Columns, select.Alias, DeclaredAliasGatherer.Gather(select.From));
select = select.SetColumns(pc.Columns);
where = pc.Projector;
DbJoinType jt = (where == null) ? DbJoinType.CrossJoin :
(join.Join == DbJoinType.CrossApply ? DbJoinType.InnerJoin : DbJoinType.LeftOuter);
return(new DbJoinExpression(jt, join.Left, select, where));
}
}
}
}
return(join);
}
protected override Expression VisitProjection(DbProjectionExpression proj)
{
if (isTopLevel)
{
isTopLevel = false;
this.currentSelect = proj.Select;
Expression projector = this.Visit(proj.Projector);
if (projector != proj.Projector || this.currentSelect != proj.Select)
{
return(new DbProjectionExpression(this.currentSelect, projector, proj.Aggregator));
}
return(proj);
}
if (proj.IsSingleton && this.CanJoinOnServer(this.currentSelect))
{
DbTableAlias newAlias = new DbTableAlias();
this.currentSelect = this.currentSelect.AddRedundantSelect(newAlias);
// remap any references to the outer select to the new alias;
DbSelectExpression source = (DbSelectExpression)ColumnMapper.Map(proj.Select, newAlias, this.currentSelect.Alias);
// add outer-join test
DbProjectionExpression pex = new DbProjectionExpression(source, proj.Projector).AddOuterJoinTest();
var pc = ColumnProjector.ProjectColumns(this.language.CanBeColumn, pex.Projector, this.currentSelect.Columns,
this.currentSelect.Alias, newAlias, proj.Select.Alias);
DbJoinExpression join = new DbJoinExpression(DbJoinType.OuterApply, this.currentSelect.From, pex.Select, null);
this.currentSelect = new DbSelectExpression(this.currentSelect.Alias, pc.Columns, join, null);
return(this.Visit(pc.Projector));
}
var saveTop = this.isTopLevel;
var saveSelect = this.currentSelect;
this.isTopLevel = true;
this.currentSelect = null;
Expression result = base.VisitProjection(proj);
this.isTopLevel = saveTop;
this.currentSelect = saveSelect;
return(result);
}
private ProjectedColumns ProjectColumns(Expression expression, DbTableAlias newAlias, params DbTableAlias[] existingAliases)
{
return(ColumnProjector.ProjectColumns(this.mapping.Language.CanBeColumn, expression, null, newAlias, existingAliases));
}
