Refactor for readability
Added more documentation, converted logical operations to (hopefully) consistent 'route' metaphor, and moved all AND(iterator, iterator) stanzas out into a single join() function that is more descriptive of what's actually happening
This commit is contained in:
Tyler Gibbons
parent
42aa91b77f
commit
51f5a86232
2 changed files with 116 additions and 85 deletions
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@ -1,4 +1,4 @@
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// Copyright 2014 The Cayley Authors. All rights reserved.
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// Copyright 2015 The Cayley Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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@ -20,58 +20,80 @@ import (
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"github.com/google/cayley/quad"
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)
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// join puts two iterators together by intersecting their result sets with an AND
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// Since we're using an and iterator, it's a good idea to put the smallest result
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// set first so that Next() produces fewer values to check Contains()
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func join(qs graph.QuadStore, itL, itR graph.Iterator) graph.Iterator {
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and := iterator.NewAnd(qs)
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and.AddSubIterator(itL)
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and.AddSubIterator(itR)
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return and
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}
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// isMorphism represents all nodes passed in-- if there are none, this function
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// acts as a passthrough for the previous iterator
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func isMorphism(nodes ...string) morphism {
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return morphism{
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Name: "is",
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Reversal: func() morphism { return isMorphism(nodes...) },
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Apply: func(qs graph.QuadStore, it graph.Iterator) graph.Iterator {
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var sub graph.Iterator
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Apply: func(qs graph.QuadStore, in graph.Iterator) graph.Iterator {
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if len(nodes) == 0 {
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sub = qs.NodesAllIterator()
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} else {
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fixed := qs.FixedIterator()
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for _, n := range nodes {
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fixed.Add(qs.ValueOf(n))
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}
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sub = fixed
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// Acting as a passthrough here is equivalent to
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// building a NodesAllIterator to Next() or Contains()
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// from here as in previous versions
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return in
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}
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and := iterator.NewAnd(qs)
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and.AddSubIterator(sub)
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and.AddSubIterator(it)
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return and
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isNodes := ls.FixedIterator()
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for _, n := range nodes {
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isNodes.Add(qs.ValueOf(n))
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}
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// Anything with fixedIterators will usually have a much
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// smaller result set, so join isNodes first here
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return join(qs, isNodes, in)
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},
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}
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}
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// hasMorphism is
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func hasMorphism(via interface{}, nodes ...string) morphism {
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return morphism{
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Name: "has",
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Reversal: func() morphism { return hasMorphism(via, nodes...) },
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Apply: func(qs graph.QuadStore, it graph.Iterator) graph.Iterator {
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var sub graph.Iterator
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if len(nodes) == 0 {
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sub = qs.NodesAllIterator()
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} else {
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Apply: func(qs graph.QuadStore, in graph.Iterator) graph.Iterator {
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viaIter := buildViaPath(qs, via).
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BuildIterator()
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ends := func() graph.Iterator {
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if len(nodes) == 0 {
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return qs.NodesAllIterator()
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}
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fixed := qs.FixedIterator()
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for _, n := range nodes {
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fixed.Add(qs.ValueOf(n))
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}
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sub = fixed
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return fixed
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}()
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trail := iterator.NewLinksTo(qs, viaIter, quad.Predicate)
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dest := iterator.NewLinksTo(qs, ends, graph.Object)
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// If we were given nodes, intersecting with them first will
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// be extremely cheap-- otherwise, it will be the most expensive
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// (requiring iteration over all nodes). We have enough info to
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// make this optimization now since intersections are commutative
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if len(nodes) == 0 { // Where dest involves an All iterator
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route := join(qs, trail, dest)
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has := iterator.NewHasA(qs, route, graph.Subject)
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return join(qs, in, has)
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}
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var viaPath *Path
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if via != nil {
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viaPath = buildViaPath(qs, via)
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} else {
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viaPath = buildViaPath(qs)
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}
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subAnd := iterator.NewAnd(qs)
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subAnd.AddSubIterator(iterator.NewLinksTo(qs, sub, quad.Object))
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subAnd.AddSubIterator(iterator.NewLinksTo(qs, viaPath.BuildIterator(), quad.Predicate))
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hasa := iterator.NewHasA(qs, subAnd, quad.Subject)
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and := iterator.NewAnd(qs)
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and.AddSubIterator(it)
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and.AddSubIterator(hasa)
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return and
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// This looks backwards. That's OK-- see the note above
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route := join(qs, dest, trail)
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has := iterator.NewHasA(qs, route, graph.Subject)
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return join(qs, has, in)
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},
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}
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}
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@ -90,6 +112,7 @@ func tagMorphism(tags ...string) morphism {
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}
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}
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// outMorphism iterates forward one RDF triple or via an entire path
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func outMorphism(via ...interface{}) morphism {
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return morphism{
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Name: "out",
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@ -101,6 +124,7 @@ func outMorphism(via ...interface{}) morphism {
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}
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}
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// inMorphism iterates backwards one RDF triple or via an entire path
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func inMorphism(via ...interface{}) morphism {
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return morphism{
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Name: "in",
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@ -112,43 +136,42 @@ func inMorphism(via ...interface{}) morphism {
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}
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}
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// iteratorMorphism simply tacks the input iterator onto the chain
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func iteratorMorphism(it graph.Iterator) morphism {
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return morphism{
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Name: "iterator",
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Reversal: func() morphism { return iteratorMorphism(it) },
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Apply: func(qs graph.QuadStore, subIt graph.Iterator) graph.Iterator {
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and := iterator.NewAnd(qs)
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and.AddSubIterator(it)
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and.AddSubIterator(subIt)
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return and
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return join(qs, it, subIt)
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},
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}
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}
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// andMorphism sticks a path onto the current iterator chain
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func andMorphism(p *Path) morphism {
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return morphism{
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Name: "and",
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Reversal: func() morphism { return andMorphism(p) },
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Apply: func(qs graph.QuadStore, it graph.Iterator) graph.Iterator {
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subIt := p.BuildIteratorOn(qs)
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and := iterator.NewAnd(qs)
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and.AddSubIterator(it)
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and.AddSubIterator(subIt)
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return and
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Apply: func(qs graph.QuadStore, itL graph.Iterator) graph.Iterator {
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itR := p.BuildIteratorOn(qs)
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return join(qs, itL, itR)
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},
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}
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}
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// orMorphism is the union, vice intersection, of a path and the current iterator
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func orMorphism(p *Path) morphism {
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return morphism{
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Name: "or",
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Reversal: func() morphism { return orMorphism(p) },
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Apply: func(qs graph.QuadStore, it graph.Iterator) graph.Iterator {
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subIt := p.BuildIteratorOn(qs)
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and := iterator.NewOr()
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and.AddSubIterator(it)
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and.AddSubIterator(subIt)
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return and
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Apply: func(qs graph.QuadStore, itL graph.Iterator) graph.Iterator {
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itR := p.BuildIteratorOn(qs)
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or := iterator.NewOr()
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or.AddSubIterator(itL)
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or.AddSubIterator(itR)
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return or
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},
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}
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}
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@ -163,17 +186,17 @@ func followMorphism(p *Path) morphism {
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}
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}
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// exceptMorphism removes all results on p.(*Path) from the current iterators
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func exceptMorphism(p *Path) morphism {
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return morphism{
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Name: "except",
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Reversal: func() morphism { return exceptMorphism(p) },
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Apply: func(qs graph.QuadStore, base graph.Iterator) graph.Iterator {
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subIt := p.BuildIteratorOn(qs)
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notIt := iterator.NewNot(subIt, qs.NodesAllIterator())
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and := iterator.NewAnd(qs)
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and.AddSubIterator(base)
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and.AddSubIterator(notIt)
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return and
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in := p.BuildIteratorOn(qs)
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allNodes := qs.NodesAllIterator()
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notIn := iterator.NewNot(in, allNodes)
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return join(qs, base, notIn)
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},
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}
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}
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@ -200,40 +223,44 @@ func saveReverseMorphism(via interface{}, tag string) morphism {
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}
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}
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func buildSave(qs graph.QuadStore, via interface{}, tag string, it graph.Iterator, reverse bool) graph.Iterator {
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all := qs.NodesAllIterator()
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func buildSave(
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qs graph.QuadStore, via interface{},
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tag string, from graph.Iterator, reverse bool,
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) graph.Iterator {
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allNodes := qs.NodesAllIterator()
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all.Tagger().Add(tag)
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node, allDir := quad.Subject, quad.Object
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var viaPath *Path
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if via != nil {
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viaPath = buildViaPath(qs, via)
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} else {
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viaPath = buildViaPath(qs)
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}
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start, goal := graph.Subject, graph.Object
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if reverse {
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node, allDir = allDir, node
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start, goal = goal, start
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}
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lto := iterator.NewLinksTo(qs, all, allDir)
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subAnd := iterator.NewAnd(qs)
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subAnd.AddSubIterator(iterator.NewLinksTo(qs, viaPath.BuildIterator(), quad.Predicate))
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subAnd.AddSubIterator(lto)
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hasa := iterator.NewHasA(qs, subAnd, node)
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and := iterator.NewAnd(qs)
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and.AddSubIterator(hasa)
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and.AddSubIterator(it)
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return and
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viaIter := buildViaPath(qs, via).
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BuildIterator()
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dest := iterator.NewLinksTo(qs, allNodes, goal)
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trail := iterator.NewLinksTo(qs, viaIter, graph.Predicate)
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route := join(qs, trail, dest)
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save := iterator.NewHasA(qs, route, start)
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return join(qs, from, save)
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}
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func inOutIterator(viaPath *Path, it graph.Iterator, reverse bool) graph.Iterator {
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in, out := quad.Subject, quad.Object
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if reverse {
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in, out = out, in
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func inOutIterator(viaPath *Path, from graph.Iterator, inIterator bool) graph.Iterator {
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start, goal := quad.Subject, quad.Object
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if inIterator {
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start, goal = goal, start
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}
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lto := iterator.NewLinksTo(viaPath.qs, it, in)
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and := iterator.NewAnd(viaPath.qs)
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and.AddSubIterator(iterator.NewLinksTo(viaPath.qs, viaPath.BuildIterator(), quad.Predicate))
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and.AddSubIterator(lto)
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return iterator.NewHasA(viaPath.qs, and, out)
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viaIter := viaPath.BuildIterator()
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source := iterator.NewLinksTo(viaPath.qs, from, start)
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trail := iterator.NewLinksTo(viaPath.qs, viaIter, graph.Predicate)
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route := join(viaPath.qs, source, trail)
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return iterator.NewHasA(viaPath.qs, route, goal)
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}
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func buildViaPath(qs graph.QuadStore, via ...interface{}) *Path {
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@ -1,4 +1,4 @@
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// Copyright 2014 The Cayley Authors. All rights reserved.
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// Copyright 2015 The Cayley Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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@ -140,11 +140,15 @@ func (p *Path) Except(path *Path) *Path {
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return p
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}
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// Follow allows you to stitch two paths together. The resulting path will start
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// from where the first path left off and continue iterating down the path given
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func (p *Path) Follow(path *Path) *Path {
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p.stack = append(p.stack, followMorphism(path))
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return p
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}
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// FollowReverse is the same as follow, except it will iterate backwards up the
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// path given as argument
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func (p *Path) FollowReverse(path *Path) *Path {
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p.stack = append(p.stack, followMorphism(path.Reverse()))
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return p
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