public ProjectionExpression(SelectExpression source, Expression projector, LambdaExpression aggregator)
: base(DbExpressionType.Projection, aggregator != null ? aggregator.Body.Type : typeof(IEnumerable<>).MakeGenericType(projector.Type))
{
this.select = source;
this.projector = projector;
this.aggregator = aggregator;
}
protected override Expression VisitSelect(SelectExpression select)
{
IdentifiableAlias newAlias = new IdentifiableAlias();
this.map[select.Alias] = newAlias;
select = (SelectExpression)base.VisitSelect(select);
return new SelectExpression(newAlias, select.Fields, select.From, select.Where, select.OrderBy, select.GroupBy, select.IsDistinct, select.Skip, select.Take, select.IsReverse);
}
protected override Expression VisitSelect(SelectExpression select)
{
Expression saveCurrentFrom = this.currentFrom;
this.currentFrom = this.VisitSource(select.From);
try
{
Expression where = this.Visit(select.Where);
ReadOnlyCollection<OrderExpression> orderBy = this.VisitOrderBy(select.OrderBy);
ReadOnlyCollection<Expression> groupBy = this.VisitExpressionList(select.GroupBy);
Expression skip = this.Visit(select.Skip);
Expression take = this.Visit(select.Take);
ReadOnlyCollection<FieldDeclaration> Fields = this.VisitFieldDeclarations(select.Fields);
if (this.currentFrom != select.From
|| where != select.Where
|| orderBy != select.OrderBy
|| groupBy != select.GroupBy
|| take != select.Take
|| skip != select.Skip
|| Fields != select.Fields
)
{
return new SelectExpression(select.Alias, Fields, this.currentFrom, where, orderBy, groupBy, select.IsDistinct, skip, take, select.IsReverse);
}
return select;
}
finally
{
this.currentFrom = saveCurrentFrom;
}
}
protected DeclarationCommand UpdateDeclaration(DeclarationCommand decl, IEnumerable<VariableDeclaration> variables, SelectExpression source)
{
if (variables != decl.Variables || source != decl.Source)
{
return new DeclarationCommand(variables, source);
}
return decl;
}
protected override Expression VisitSelect(SelectExpression select)
{
// only consider aggregates in these locations
this.Visit(select.Where);
this.VisitOrderBy(select.OrderBy);
this.VisitFieldDeclarations(select.Fields);
return select;
}
public static SelectExpression AddRedundantSelect(this SelectExpression sel, QueryLanguage language, IdentifiableAlias newAlias)
{
var newFields =
from d in sel.Fields
let qt = (d.Expression is FieldExpression) ? ((FieldExpression)d.Expression).QueryType : language.TypeSystem.GetStorageType(d.Expression.Type)
select new FieldDeclaration(d.Name, new FieldExpression(d.Expression.Type, qt, newAlias, d.Name), qt);
var newFrom = new SelectExpression(newAlias, sel.Fields, sel.From, sel.Where, sel.OrderBy, sel.GroupBy, sel.IsDistinct, sel.Skip, sel.Take, sel.IsReverse);
return new SelectExpression(sel.Alias, newFields, newFrom, null, null, null, false, null, null, false);
}
protected override Expression VisitSelect(SelectExpression select)
{
if (this.selectsToRemove.Contains(select))
{
return this.Visit(select.From);
}
else
{
return base.VisitSelect(select);
}
}
internal static bool IsSimpleProjection(SelectExpression select)
{
foreach (FieldDeclaration decl in select.Fields)
{
FieldExpression col = decl.Expression as FieldExpression;
if (col == null || decl.Name != col.Name)
{
return false;
}
}
return true;
}
protected override Expression VisitClientJoin(ClientJoinExpression join)
{
// treat client joins as new top level
var saveTop = this.isTopLevel;
var saveSelect = this.currentSelect;
this.isTopLevel = true;
this.currentSelect = null;
Expression result = base.VisitClientJoin(join);
this.isTopLevel = saveTop;
this.currentSelect = saveSelect;
return result;
}
protected override Expression VisitSelect(SelectExpression select)
{
select = (SelectExpression)base.VisitSelect(select);
// first remove all purely redundant subqueries
List<SelectExpression> redundant = RedundantSubqueryGatherer.Gather(select.From);
if (redundant != null)
{
select = SubqueryRemover.Remove(select, redundant);
}
return select;
}
internal static bool IsNameMapProjection(SelectExpression select)
{
if (select.From is IdentifiableExpression) return false;
SelectExpression fromSelect = select.From as SelectExpression;
if (fromSelect == null || select.Fields.Count != fromSelect.Fields.Count)
return false;
ReadOnlyCollection<FieldDeclaration> fromFields = fromSelect.Fields;
// test that all fields in 'select' are refering to fields in the same position
// in from.
for (int i = 0, n = select.Fields.Count; i < n; i++)
{
FieldExpression col = select.Fields[i].Expression as FieldExpression;
if (col == null || !(col.Name == fromFields[i].Name))
return false;
}
return true;
}
protected override Expression VisitSelect(SelectExpression select)
{
select = (SelectExpression)base.VisitSelect(select);
if (lookup.Contains(select.Alias))
{
List<FieldDeclaration> aggFields = new List<FieldDeclaration>(select.Fields);
foreach (AggregateSubqueryExpression ae in lookup[select.Alias])
{
string name = "agg" + aggFields.Count;
var colType = this.language.TypeSystem.GetStorageType(ae.Type);
FieldDeclaration cd = new FieldDeclaration(name, ae.AggregateInGroupSelect, colType);
this.map.Add(ae, new FieldExpression(ae.Type, colType, ae.GroupByAlias, name));
aggFields.Add(cd);
}
return new SelectExpression(select.Alias, aggFields, select.From, select.Where, select.OrderBy, select.GroupBy, select.IsDistinct, select.Skip, select.Take, select.IsReverse);
}
return select;
}
protected override Expression VisitSelect(SelectExpression select)
{
var saveWhere = this.currentWhere;
try
{
this.currentWhere = select.Where;
var result = (SelectExpression)base.VisitSelect(select);
if (this.currentWhere != result.Where)
{
return result.SetWhere(this.currentWhere);
}
return result;
}
finally
{
this.currentWhere = saveWhere;
}
}
protected override Expression VisitSelect(SelectExpression select)
{
select = (SelectExpression)base.VisitSelect(select);
// look for redundant field declarations
List<FieldDeclaration> cols = select.Fields.OrderBy(c => c.Name).ToList();
BitArray removed = new BitArray(select.Fields.Count);
bool anyRemoved = false;
for (int i = 0, n = cols.Count; i < n - 1; i++)
{
FieldDeclaration ci = cols[i];
FieldExpression cix = ci.Expression as FieldExpression;
StorageType qt = cix != null ? cix.QueryType : ci.QueryType;
FieldExpression cxi = new FieldExpression(ci.Expression.Type, qt, select.Alias, ci.Name);
for (int j = i + 1; j < n; j++)
{
if (!removed.Get(j))
{
FieldDeclaration cj = cols[j];
if (SameExpression(ci.Expression, cj.Expression))
{
// any reference to 'j' should now just be a reference to 'i'
FieldExpression cxj = new FieldExpression(cj.Expression.Type, qt, select.Alias, cj.Name);
this.map.Add(cxj, cxi);
removed.Set(j, true);
anyRemoved = true;
}
}
}
}
if (anyRemoved)
{
List<FieldDeclaration> newDecls = new List<FieldDeclaration>();
for (int i = 0, n = cols.Count; i < n; i++)
{
if (!removed.Get(i))
{
newDecls.Add(cols[i]);
}
}
select = select.SetFields(newDecls);
}
return select;
}
protected override Expression VisitProjection(ProjectionExpression 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 ProjectionExpression(this.currentSelect, projector, proj.Aggregator);
}
return proj;
}
if (proj.IsSingleton && this.CanJoinOnServer(this.currentSelect))
{
IdentifiableAlias newAlias = new IdentifiableAlias();
this.currentSelect = this.currentSelect.AddRedundantSelect(this.language, newAlias);
// remap any references to the outer select to the new alias;
SelectExpression source = (SelectExpression)FieldMapper.Map(proj.Select, newAlias, this.currentSelect.Alias);
// add outer-join test
ProjectionExpression pex = this.language.AddOuterJoinTest(new ProjectionExpression(source, proj.Projector));
var pc = FieldProjector.ProjectFields(this.language, pex.Projector, this.currentSelect.Fields, this.currentSelect.Alias, newAlias, proj.Select.Alias);
JoinExpression join = new JoinExpression(JoinType.OuterApply, this.currentSelect.From, pex.Select, null);
this.currentSelect = new SelectExpression(this.currentSelect.Alias, pc.Fields, 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;
}
protected override Expression VisitSelect(SelectExpression select)
{
var from = this.VisitSource(select.From);
var where = this.Visit(select.Where);
var orderBy = this.VisitOrderBy(select.OrderBy);
var groupBy = this.VisitExpressionList(select.GroupBy);
var skip = this.Visit(select.Skip);
var take = this.Visit(select.Take);
var fields = this.VisitFieldDeclarations(select.Fields);
select = this.UpdateSelect(select, from, where, orderBy, groupBy, skip, take, select.IsDistinct, select.IsReverse, fields);
// first remove all purely redundant subqueries
List<SelectExpression> redundant = ORedundantSubqueryGatherer.Gather(select.From);
if (redundant != null)
{
select = OSubqueryRemover.Remove(select, redundant);
}
return select;
}
protected override Expression VisitSelect(SelectExpression select)
{
if (!_visited)
{
_visited = true;
if (select.Take == null)
{
Expression take = Visit(Expression.Constant(Policy.Limit));
select = new SelectExpression(
select.Alias,
select.Fields,
select.From,
select.Where,
select.OrderBy,
select.GroupBy,
select.IsDistinct,
select.Skip,
take,
select.IsReverse);
}
}
return select;
}
protected InExpression UpdateIn(InExpression @in, Expression expression, SelectExpression select, IEnumerable<Expression> values)
{
if (expression != @in.Expression || select != @in.Select || values != @in.Values)
{
if (select != null)
{
return new InExpression(expression, select);
}
else
{
return new InExpression(expression, values);
}
}
return @in;
}
protected ExistsExpression UpdateExists(ExistsExpression exists, SelectExpression select)
{
if (select != exists.Select)
{
return new ExistsExpression(select);
}
return exists;
}
protected ProjectionExpression UpdateProjection(ProjectionExpression proj, SelectExpression select, Expression projector, LambdaExpression aggregator)
{
if (select != proj.Select || projector != proj.Projector || aggregator != proj.Aggregator)
{
return new ProjectionExpression(select, projector, aggregator);
}
return proj;
}
protected SelectExpression UpdateSelect(
SelectExpression select,
Expression from, Expression where,
IEnumerable<OrderExpression> orderBy, IEnumerable<Expression> groupBy,
Expression skip, Expression take,
bool isDistinct, bool isReverse,
IEnumerable<FieldDeclaration> fields
)
{
if (from != select.From
|| where != select.Where
|| orderBy != select.OrderBy
|| groupBy != select.GroupBy
|| take != select.Take
|| skip != select.Skip
|| isDistinct != select.IsDistinct
|| fields != select.Fields
|| isReverse != select.IsReverse
)
{
return new SelectExpression(select.Alias, fields, from, where, orderBy, groupBy, isDistinct, skip, take, isReverse);
}
return select;
}
internal static bool IsInitialProjection(SelectExpression select)
{
return select.From is IdentifiableExpression;
}
protected ScalarExpression UpdateScalar(ScalarExpression scalar, SelectExpression select)
{
if (select != scalar.Select)
{
return new ScalarExpression(scalar.Type, select);
}
return scalar;
}
private static bool IsRedudantSubquery(SelectExpression select)
{
return (IsSimpleProjection(select) || IsNameMapProjection(select))
&& !select.IsDistinct
&& !select.IsReverse
&& select.Take == null
&& select.Skip == null
&& select.Where == null
&& (select.OrderBy == null || select.OrderBy.Count == 0)
&& (select.GroupBy == null || select.GroupBy.Count == 0);
}
protected virtual Expression VisitSelect(SelectExpression select)
{
var from = this.VisitSource(select.From);
var where = this.Visit(select.Where);
var orderBy = this.VisitOrderBy(select.OrderBy);
var groupBy = this.VisitExpressionList(select.GroupBy);
var skip = this.Visit(select.Skip);
var take = this.Visit(select.Take);
var fields = this.VisitFieldDeclarations(select.Fields);
return this.UpdateSelect(select, from, where, orderBy, groupBy, skip, take, select.IsDistinct, select.IsReverse, fields);
}
protected override Expression VisitSelect(SelectExpression select)
{
bool wasTopLevel = isTopLevel;
isTopLevel = false;
select = (SelectExpression)base.VisitSelect(select);
// next attempt to merge subqueries that would have been removed by the above
// logic except for the existence of a where clause
while (CanMergeWithFrom(select, wasTopLevel))
{
SelectExpression fromSelect = GetLeftMostSelect(select.From);
// remove the redundant subquery
select = SubqueryRemover.Remove(select, fromSelect);
// merge where expressions
Expression where = select.Where;
if (fromSelect.Where != null)
{
if (where != null)
{
where = fromSelect.Where.And(where);
}
else
{
where = fromSelect.Where;
}
}
var orderBy = select.OrderBy != null && select.OrderBy.Count > 0 ? select.OrderBy : fromSelect.OrderBy;
var groupBy = select.GroupBy != null && select.GroupBy.Count > 0 ? select.GroupBy : fromSelect.GroupBy;
Expression skip = select.Skip != null ? select.Skip : fromSelect.Skip;
Expression take = select.Take != null ? select.Take : fromSelect.Take;
bool isDistinct = select.IsDistinct | fromSelect.IsDistinct;
if (where != select.Where
|| orderBy != select.OrderBy
|| groupBy != select.GroupBy
|| isDistinct != select.IsDistinct
|| skip != select.Skip
|| take != select.Take)
{
select = new SelectExpression(select.Alias, select.Fields, select.From, where, orderBy, groupBy, isDistinct, skip, take, select.IsReverse);
}
}
return select;
}
public ScalarExpression(Type type, SelectExpression select)
: base(DbExpressionType.Scalar, type, select)
{
}
private static bool CanMergeWithFrom(SelectExpression select, bool isTopLevel)
{
SelectExpression fromSelect = GetLeftMostSelect(select.From);
if (fromSelect == null)
return false;
if (!IsFieldProjection(fromSelect))
return false;
bool selHasNameMapProjection = IsNameMapProjection(select);
bool selHasOrderBy = select.OrderBy != null && select.OrderBy.Count > 0;
bool selHasGroupBy = select.GroupBy != null && select.GroupBy.Count > 0;
bool selHasAggregates = AggregateChecker.HasAggregates(select);
bool selHasJoin = select.From is JoinExpression;
bool frmHasOrderBy = fromSelect.OrderBy != null && fromSelect.OrderBy.Count > 0;
bool frmHasGroupBy = fromSelect.GroupBy != null && fromSelect.GroupBy.Count > 0;
bool frmHasAggregates = AggregateChecker.HasAggregates(fromSelect);
// both cannot have orderby
if (selHasOrderBy && frmHasOrderBy)
return false;
// both cannot have groupby
if (selHasGroupBy && frmHasGroupBy)
return false;
// these are distinct operations
if (select.IsReverse || fromSelect.IsReverse)
return false;
// cannot move forward order-by if outer has group-by
if (frmHasOrderBy && (selHasGroupBy || selHasAggregates || select.IsDistinct))
return false;
// cannot move forward group-by if outer has where clause
if (frmHasGroupBy /*&& (select.Where != null)*/) // need to assert projection is the same in order to move group-by forward
return false;
// cannot move forward a take if outer has take or skip or distinct
if (fromSelect.Take != null && (select.Take != null || select.Skip != null || select.IsDistinct || selHasAggregates || selHasGroupBy || selHasJoin))
return false;
// cannot move forward a skip if outer has skip or distinct
if (fromSelect.Skip != null && (select.Skip != null || select.IsDistinct || selHasAggregates || selHasGroupBy || selHasJoin))
return false;
// cannot move forward a distinct if outer has take, skip, groupby or a different projection
if (fromSelect.IsDistinct && (select.Take != null || select.Skip != null || !selHasNameMapProjection || selHasGroupBy || selHasAggregates || (selHasOrderBy && !isTopLevel) || selHasJoin))
return false;
if (frmHasAggregates && (select.Take != null || select.Skip != null || select.IsDistinct || selHasAggregates || selHasGroupBy || selHasJoin))
return false;
return true;
}
public ExistsExpression(SelectExpression select)
: base(DbExpressionType.Exists, typeof(bool), select)
{
}
private static bool IsFieldProjection(SelectExpression select)
{
for (int i = 0, n = select.Fields.Count; i < n; i++)
{
var cd = select.Fields[i];
if (cd.Expression.NodeType != (ExpressionType)DbExpressionType.Field &&
cd.Expression.NodeType != ExpressionType.Constant)
return false;
}
return true;
}
