// We assume plan is with normalized shape:
// LogicFilter
// LogicJoin
// ...
// There shall be only 1 join filter on top.
// Subqueries is not considered here.
//
internal static JoinGraph ExtractJoinGraph(LogicNode plan,
out LogicNode filterNodeParent, out int index, out LogicFilter filterNode)
{
// find the join filter
var parents = new List <LogicNode>();
var indexes = new List <int>();
var filters = new List <LogicFilter>();
plan.FindNodeTypeMatch <LogicFilter>(parents, indexes, filters);
var joinfilters = filters.Where(x => x.child_() is LogicJoin).ToList();
Debug.Assert(joinfilters.Count <= 1);
if (joinfilters.Count == 1)
{
JoinGraph graph = null;
var joinfilter = joinfilters[0];
var topjoin = joinfilter.child_() as LogicJoin;
// vertices are non-join nodes. We don't do any cross boundary optimization
// (say pull aggregation up thus we have bigger join space etc), which is
// the job of upper layer.
//
var vertices = new List <LogicNode>();
topjoin.VisitEach(x =>
{
if (!(x is LogicJoin))
{
vertices.Add(x as LogicNode);
}
});
graph = new JoinGraph(vertices, joinfilters[0].filter_.FilterToAndList());
index = indexes[0];
filterNodeParent = parents[0];
filterNode = joinfilter;
Debug.Assert(filterNodeParent is null || filterNodeParent.children_[index] == filterNode);
return(graph);
}
// there is no join or we can't handle this query
filterNodeParent = null;
index = -1;
filterNode = null;
return(null);
}
LogicNode FilterPushDown(LogicNode plan, bool pushJoinFilter)
{
// locate the all filters ingoring any within FromQuery as it will
// be optimized by subquery optimization and this will cause double
// predicate push down (e.g., a1>1 && a1>1)
//
var parents = new List <LogicNode>();
var indexes = new List <int>();
var filters = new List <LogicFilter>();
var cntFilter = plan.FindNodeTypeMatch(parents,
indexes, filters, skipParentType: typeof(LogicFromQuery));
for (int i = 0; i < cntFilter; i++)
{
var parent = parents[i];
var filter = filters[i];
var index = indexes[i];
Debug.Assert(!(parent is LogicFromQuery));
if (filter?.filter_ != null && filter?.movable_ is true)
{
List <Expr> andlist = new List <Expr>();
var filterexpr = filter.filter_;
// if it is a constant true filer, remove it. If a false filter, we leave
// it there - shall we try hard to stop query early? Nope, it is no deserved
// to poke around for this corner case.
//
var isConst = filterexpr.FilterIsConst(out bool trueOrFalse);
if (isConst)
{
if (!trueOrFalse)
{
andlist.Add(LiteralExpr.MakeLiteral("false", new BoolType()));
}
else
{
Debug.Assert(andlist.Count == 0);
}
}
else
{
// filter push down
andlist = filterexpr.FilterToAndList();
andlist.RemoveAll(e =>
{
var isConst = e.FilterIsConst(out bool trueOrFalse);
if (isConst)
{
Debug.Assert(trueOrFalse);
return(true);
}
return(pushdownFilter(plan, e, pushJoinFilter));
});
}
// stich the new plan
if (andlist.Count == 0)
{
if (parent is null)
{
// take it out from the tree
plan = plan.child_();
}
else
{
parent.children_[index] = filter.child_();
}
}
else
{
filter.filter_ = andlist.AndListToExpr();
}
}
}
return(plan);
}