private SqlJoin GetLeftOuterWithUnreferencedSingletonOnLeft(SqlSource source)
{
SqlAlias alias = source as SqlAlias;
if (alias != null)
{
SqlSelect select = alias.Node as SqlSelect;
if (select != null &&
select.Where == null &&
select.Top == null &&
select.GroupBy.Count == 0 &&
select.OrderBy.Count == 0)
{
return(this.GetLeftOuterWithUnreferencedSingletonOnLeft(select.From));
}
}
SqlJoin join = source as SqlJoin;
if (join == null || join.JoinType != SqlJoinType.LeftOuter)
{
return(null);
}
if (!this.IsSingletonSelect(join.Left))
{
return(null);
}
HashSet <SqlAlias> p = SqlGatherProducedAliases.Gather(join.Left);
HashSet <SqlAlias> c = SqlGatherConsumedAliases.Gather(join.Right);
if (p.Overlaps(c))
{
return(null);
}
return(join);
}
internal override SqlSource VisitJoin(SqlJoin join)
{
if (join.JoinType == SqlJoinType.CrossApply)
{
// Look down the left side to see what table aliases are produced.
HashSet <SqlAlias> p = SqlGatherProducedAliases.Gather(join.Left);
// Look down the right side to see what table aliases are consumed.
HashSet <SqlAlias> c = SqlGatherConsumedAliases.Gather(join.Right);
// Look at each consumed alias and see if they are mentioned in produced.
if (p.Overlaps(c))
{
Annotations.Add(join, new CompatibilityAnnotation(Strings.SourceExpressionAnnotation(join.SourceExpression), _providerModesWithIncompatibilities));
// Can't reduce because this consumed alias is produced on the left.
return(base.VisitJoin(join));
}
// Can turn this into a CROSS JOIN
join.JoinType = SqlJoinType.Cross;
return(VisitJoin(join));
}
return(base.VisitJoin(join));
}
internal override SqlSource VisitSource(SqlSource source)
{
source = base.VisitSource(source);
SqlJoin join = source as SqlJoin;
if (join != null)
{
if (join.JoinType == SqlJoinType.OuterApply)
{
// Reduce outer-apply into left-outer-join
HashSet <SqlAlias> leftProducedAliases = SqlGatherProducedAliases.Gather(join.Left);
HashSet <SqlExpression> liftedExpressions = new HashSet <SqlExpression>();
if (SqlPredicateLifter.CanLift(join.Right, leftProducedAliases, liftedExpressions) &&
SqlSelectionLifter.CanLift(join.Right, leftProducedAliases, liftedExpressions) &&
!SqlAliasDependencyChecker.IsDependent(join.Right, leftProducedAliases, liftedExpressions))
{
SqlExpression liftedPredicate = SqlPredicateLifter.Lift(join.Right, leftProducedAliases);
List <List <SqlColumn> > liftedSelections = SqlSelectionLifter.Lift(join.Right, leftProducedAliases, liftedExpressions);
join.JoinType = SqlJoinType.LeftOuter;
join.Condition = liftedPredicate;
if (liftedSelections != null)
{
foreach (List <SqlColumn> selection in liftedSelections)
{
source = this.PushSourceDown(source, selection);
}
}
}
else
{
#warning [FB] REFACTOR: SQL SERVER SPECIFIC: MOVE TO A CTOR PROVIDED SET OF INCOMPATIBLE MODES.
this.AnnotateSqlIncompatibility(join, SqlServerProviderMode.Sql2000);
}
}
else if (join.JoinType == SqlJoinType.CrossApply)
{
// reduce cross apply with special nested left-outer-join's into a single left-outer-join
//
// SELECT x.*, y.*
// FROM X
// CROSS APPLY (
// SELECT y.*
// FROM (
// SELECT ?
// )
// LEFT OUTER JOIN (
// SELECT y.* FROM Y
// ) AS y
//
// ==>
//
// SELECT x.*, y.*
// FROM X
// LEFT OUTER JOIN (
// SELECT y.* FROM Y
// )
SqlJoin leftOuter = this.GetLeftOuterWithUnreferencedSingletonOnLeft(join.Right);
if (leftOuter != null)
{
HashSet <SqlAlias> leftProducedAliases = SqlGatherProducedAliases.Gather(join.Left);
HashSet <SqlExpression> liftedExpressions = new HashSet <SqlExpression>();
if (SqlPredicateLifter.CanLift(leftOuter.Right, leftProducedAliases, liftedExpressions) &&
SqlSelectionLifter.CanLift(leftOuter.Right, leftProducedAliases, liftedExpressions) &&
!SqlAliasDependencyChecker.IsDependent(leftOuter.Right, leftProducedAliases, liftedExpressions)
)
{
SqlExpression liftedPredicate = SqlPredicateLifter.Lift(leftOuter.Right, leftProducedAliases);
List <List <SqlColumn> > liftedSelections = SqlSelectionLifter.Lift(leftOuter.Right, leftProducedAliases, liftedExpressions);
// add intermediate selections
this.GetSelectionsBeforeJoin(join.Right, liftedSelections);
// push down all selections
foreach (List <SqlColumn> selection in liftedSelections.Where(s => s.Count > 0))
{
source = this.PushSourceDown(source, selection);
}
join.JoinType = SqlJoinType.LeftOuter;
join.Condition = this.factory.AndAccumulate(leftOuter.Condition, liftedPredicate);
join.Right = leftOuter.Right;
}
else
{
#warning [FB] REFACTOR: SQL SERVER SPECIFIC: MOVE TO A CTOR PROVIDED SET OF INCOMPATIBLE MODES.
this.AnnotateSqlIncompatibility(join, SqlServerProviderMode.Sql2000);
}
}
}
// re-balance join tree of left-outer-joins to expose LOJ w/ leftside unreferenced
while (join.JoinType == SqlJoinType.LeftOuter)
{
// look for buried left-outer-joined-with-unreferenced singleton
SqlJoin leftLeftOuter = this.GetLeftOuterWithUnreferencedSingletonOnLeft(join.Left);
if (leftLeftOuter == null)
{
break;
}
List <List <SqlColumn> > liftedSelections = new List <List <SqlColumn> >();
// add intermediate selections
this.GetSelectionsBeforeJoin(join.Left, liftedSelections);
// push down all selections
foreach (List <SqlColumn> selection in liftedSelections)
{
source = this.PushSourceDown(source, selection);
}
// bubble this one up on-top of this 'join'.
SqlSource jRight = join.Right;
SqlExpression jCondition = join.Condition;
join.Left = leftLeftOuter.Left;
join.Right = leftLeftOuter;
join.Condition = leftLeftOuter.Condition;
leftLeftOuter.Left = leftLeftOuter.Right;
leftLeftOuter.Right = jRight;
leftLeftOuter.Condition = jCondition;
}
}
return(source);
}