Add new builder iterators, v2

Subcommits:

link iterator next/contains

implement sql_node_iterator next/buildsql

fix optimizers

graph/sql/optimizers.go

@@ -23,141 +23,86 @@ import (
 	"github.com/google/cayley/quad"
 )
 
-func intersect(a *StatementIterator, b *StatementIterator) (*StatementIterator, error) {
-	if a.stType != b.stType {
-		return nil, errors.New("Cannot combine SQL iterators of two different types")
-	}
-	min := a.size
-	if b.size < a.size {
-		min = b.size
-	}
-	var where clause
-	if a.where == nil {
-		if b.where == nil {
-			where = nil
+func intersect(a graph.Iterator, b graph.Iterator) (graph.Iterator, error) {
+	if anew, ok := a.(*SQLNodeIterator); ok {
+		if bnew, ok := b.(*SQLNodeIterator); ok {
+			return intersectNode(anew, bnew)
 		}
-		where = b.where
+	} else if anew, ok := a.(*SQLLinkIterator); ok {
+		if bnew, ok := b.(*SQLLinkIterator); ok {
+			return intersectLink(anew, bnew)
+		}
+
 	} else {
-		if b.where == nil {
-			where = a.where
-		}
-		where = joinClause{a.where, b.where, andClause}
+		return nil, errors.New("Unknown iterator types")
 	}
-	out := &StatementIterator{
-		uid:        iterator.NextUID(),
-		qs:         a.qs,
-		buildWhere: append(a.buildWhere, b.buildWhere...),
-		tags:       append(a.tags, b.tags...),
-		where:      where,
-		stType:     a.stType,
-		size:       min,
-		dir:        a.dir,
-	}
-	out.tagger.CopyFrom(a)
-	out.tagger.CopyFrom(b)
-	if out.stType == node {
-		out.buildWhere = append(out.buildWhere, baseClause{
-			pair:   tableDir{"", a.dir},
-			target: tableDir{b.tableName(), b.dir},
-		})
-	}
-	return out, nil
+	return nil, errors.New("Cannot combine SQL iterators of two different types")
 }
 
-func hasa(a *StatementIterator, d quad.Direction) (*StatementIterator, error) {
-	if a.stType != link {
+func intersectNode(a *SQLNodeIterator, b *SQLNodeIterator) (graph.Iterator, error) {
+	m := &SQLNodeIterator{
+		uid:       iterator.NextUID(),
+		qs:        a.qs,
+		tableName: newTableName(),
+		linkIts:   append(a.linkIts, b.linkIts...),
+		tagdirs:   append(a.tagdirs, b.tagdirs...),
+	}
+	m.Tagger().CopyFrom(a)
+	m.Tagger().CopyFrom(b)
+	return m, nil
+}
+
+func intersectLink(a *SQLLinkIterator, b *SQLLinkIterator) (graph.Iterator, error) {
+	m := &SQLLinkIterator{
+		uid:         iterator.NextUID(),
+		qs:          a.qs,
+		tableName:   newTableName(),
+		nodeIts:     append(a.nodeIts, b.nodeIts...),
+		constraints: append(a.constraints, b.constraints...),
+	}
+	m.Tagger().CopyFrom(a)
+	m.Tagger().CopyFrom(b)
+	return m, nil
+}
+
+func hasa(aIn graph.Iterator, d quad.Direction) (graph.Iterator, error) {
+	a, ok := aIn.(*SQLLinkIterator)
+	if !ok {
 		return nil, errors.New("Can't take the HASA of a link SQL iterator")
 	}
 
-	out := &StatementIterator{
-		uid:    iterator.NextUID(),
-		qs:     a.qs,
-		stType: node,
-		dir:    d,
-	}
-	where := a.where
-	for _, w := range a.buildWhere {
-		w.pair.table = out.tableName()
-		wherenew := joinClause{where, w, andClause}
-		where = wherenew
-	}
-	out.where = where
-	//out := &StatementIterator{
-	//uid:        iterator.NextUID(),
-	//qs:         a.qs,
-	//stType:     node,
-	//dir:        d,
-	//buildWhere: a.buildWhere,
-	//where:      a.where,
-	//size:       -1,
-	//}
-	for k, v := range a.tagger.Fixed() {
-		out.tagger.AddFixed(k, v)
-	}
-	var tags []tag
-	for _, t := range a.tagger.Tags() {
-		tags = append(tags, tag{
-			pair: tableDir{
-				table: out.tableName(),
-				dir:   quad.Any,
-			},
-			t: t,
-		})
-	}
-	out.tags = append(tags, a.tags...)
-	return out, nil
-}
-
-func linksto(a *StatementIterator, d quad.Direction) (*StatementIterator, error) {
-	if a.stType != node {
-		return nil, errors.New("Can't take the LINKSTO of a node SQL iterator")
-	}
-	out := &StatementIterator{
-		uid:    iterator.NextUID(),
-		qs:     a.qs,
-		stType: link,
-		dir:    d,
-		size:   -1,
-	}
-	where := a.where
-	for _, w := range a.buildWhere {
-		w.pair.table = a.tableName()
-		wherenew := joinClause{where, w, andClause}
-		where = wherenew
-	}
-
-	out.where = where
-	out.buildWhere = []baseClause{
-		baseClause{
-			pair: tableDir{
+	out := &SQLNodeIterator{
+		uid:       iterator.NextUID(),
+		qs:        a.qs,
+		tableName: newTableName(),
+		linkIts: []sqlItDir{
+			sqlItDir{
+				it:  a,
 				dir: d,
 			},
-			target: tableDir{
-				table: a.tableName(),
-				dir:   a.dir,
-			},
 		},
 	}
-	var tags []tag
-	for _, t := range a.tagger.Tags() {
-		tags = append(tags, tag{
-			pair: tableDir{
-				table: a.tableName(),
-				dir:   a.dir,
+	return out, nil
+}
+
+func linksto(aIn graph.Iterator, d quad.Direction) (graph.Iterator, error) {
+	a, ok := aIn.(*SQLNodeIterator)
+	if !ok {
+		return nil, errors.New("Can't take the LINKSTO of a node SQL iterator")
+	}
+
+	out := &SQLLinkIterator{
+		uid:       iterator.NextUID(),
+		qs:        a.qs,
+		tableName: newTableName(),
+		nodeIts: []sqlItDir{
+			sqlItDir{
+				it:  a,
+				dir: d,
 			},
-			t: t,
-		})
+		},
 	}
-	for k, v := range a.tagger.Fixed() {
-		out.tagger.AddFixed(k, v)
-	}
-	for _, t := range a.tags {
-		if t.pair.table == "" {
-			t.pair.table = a.tableName()
-		}
-		tags = append(tags, t)
-	}
-	out.tags = tags
+
 	return out, nil
 }
 
@@ -196,33 +141,34 @@ func (qs *QuadStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bool
 			it.Close()
 			return newIt, true
 		}
-	case sqlBuilderType:
-		newit, err := linksto(primary.(*StatementIterator), it.Direction())
+	case sqlNodeType:
+		//p := primary.(*SQLNodeIterator)
+		newit, err := linksto(primary, it.Direction())
 		if err != nil {
 			glog.Errorln(err)
 			return it, false
 		}
 		newit.Tagger().CopyFrom(it)
 		return newit, true
-	case graph.All:
-		newit := &StatementIterator{
-			uid:    iterator.NextUID(),
-			qs:     qs,
-			stType: link,
-			size:   qs.Size(),
-		}
-		for _, t := range primary.Tagger().Tags() {
-			newit.tags = append(newit.tags, tag{
-				pair: tableDir{"", it.Direction()},
-				t:    t,
-			})
-		}
-		for k, v := range primary.Tagger().Fixed() {
-			newit.tagger.AddFixed(k, v)
-		}
-		newit.tagger.CopyFrom(it)
+		//case graph.All:
+		//newit := &StatementIterator{
+		//uid:    iterator.NextUID(),
+		//qs:     qs,
+		//stType: link,
+		//size:   qs.Size(),
+		//}
+		//for _, t := range primary.Tagger().Tags() {
+		//newit.tags = append(newit.tags, tag{
+		//pair: tableDir{"", it.Direction()},
+		//t:    t,
+		//})
+		//}
+		//for k, v := range primary.Tagger().Fixed() {
+		//newit.tagger.AddFixed(k, v)
+		//}
+		//newit.tagger.CopyFrom(it)
 
-		return newit, true
+		//return newit, true
 	}
 	return it, false
 }
@@ -230,18 +176,18 @@ func (qs *QuadStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bool
 func (qs *QuadStore) optimizeAnd(it *iterator.And) (graph.Iterator, bool) {
 	subs := it.SubIterators()
 	var unusedIts []graph.Iterator
-	var newit *StatementIterator
+	var newit graph.Iterator
 	newit = nil
 	changed := false
 	var err error
 
 	for _, it := range subs {
-		if it.Type() == sqlBuilderType {
+		if it.Type() == sqlLinkType || it.Type() == sqlNodeType {
 			if newit == nil {
-				newit = it.(*StatementIterator)
+				newit = it
 			} else {
 				changed = true
-				newit, err = intersect(newit, it.(*StatementIterator))
+				newit, err = intersect(newit, it)
 				if err != nil {
 					glog.Error(err)
 					return it, false
@@ -256,7 +202,7 @@ func (qs *QuadStore) optimizeAnd(it *iterator.And) (graph.Iterator, bool) {
 		return it, false
 	}
 	if len(unusedIts) == 0 {
-		newit.tagger.CopyFrom(it)
+		newit.Tagger().CopyFrom(it)
 		return newit, true
 	}
 	newAnd := iterator.NewAnd(qs)
@@ -274,8 +220,8 @@ func (qs *QuadStore) optimizeHasA(it *iterator.HasA) (graph.Iterator, bool) {
 		return it, false
 	}
 	primary := subs[0]
-	if primary.Type() == sqlBuilderType {
-		newit, err := hasa(primary.(*StatementIterator), it.Direction())
+	if primary.Type() == sqlLinkType {
+		newit, err := hasa(primary, it.Direction())
 		if err != nil {
 			glog.Errorln(err)
 			return it, false

graph/sql/optimizers_test.go

@@ -23,41 +23,43 @@ import (
 )
 
 func TestBuildIntersect(t *testing.T) {
-	a := NewStatementIterator(nil, quad.Subject, "Foo")
-	b := NewStatementIterator(nil, quad.Predicate, "is_equivalent_to")
+	a := NewSQLLinkIterator(nil, quad.Subject, "Foo")
+	b := NewSQLLinkIterator(nil, quad.Predicate, "is_equivalent_to")
 	it, err := intersect(a, b)
+	i := it.(*SQLLinkIterator)
 	if err != nil {
 		t.Error(err)
 	}
-	s, v := it.buildQuery(false, nil)
+	s, v := i.buildSQL(true, nil)
 	fmt.Println(s, v)
 }
 
 func TestBuildHasa(t *testing.T) {
-	a := NewStatementIterator(nil, quad.Subject, "Foo")
+	a := NewSQLLinkIterator(nil, quad.Subject, "Foo")
 	a.tagger.Add("foo")
-	b := NewStatementIterator(nil, quad.Predicate, "is_equivalent_to")
+	b := NewSQLLinkIterator(nil, quad.Predicate, "is_equivalent_to")
 	it1, err := intersect(a, b)
 	if err != nil {
 		t.Error(err)
 	}
 	it2, err := hasa(it1, quad.Object)
+	i2 := it2.(*SQLNodeIterator)
 	if err != nil {
 		t.Error(err)
 	}
-	s, v := it2.buildQuery(false, nil)
+	s, v := i2.buildSQL(true, nil)
 	fmt.Println(s, v)
 }
 
 func TestBuildLinksTo(t *testing.T) {
-	a := NewStatementIterator(nil, quad.Subject, "Foo")
-	b := NewStatementIterator(nil, quad.Predicate, "is_equivalent_to")
+	a := NewSQLLinkIterator(nil, quad.Subject, "Foo")
+	b := NewSQLLinkIterator(nil, quad.Predicate, "is_equivalent_to")
 	it1, err := intersect(a, b)
 	if err != nil {
 		t.Error(err)
 	}
 	it2, err := hasa(it1, quad.Object)
-	it2.tagger.Add("foo")
+	it2.Tagger().Add("foo")
 	if err != nil {
 		t.Error(err)
 	}
@@ -65,7 +67,8 @@ func TestBuildLinksTo(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	s, v := it3.buildQuery(false, nil)
+	i3 := it3.(*SQLLinkIterator)
+	s, v := i3.buildSQL(true, nil)
 	fmt.Println(s, v)
 }
 
@@ -77,8 +80,8 @@ func TestInterestingQuery(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	a := NewStatementIterator(db.(*QuadStore), quad.Object, "Humphrey Bogart")
-	b := NewStatementIterator(db.(*QuadStore), quad.Predicate, "name")
+	a := NewSQLLinkIterator(db.(*QuadStore), quad.Object, "Humphrey Bogart")
+	b := NewSQLLinkIterator(db.(*QuadStore), quad.Predicate, "name")
 	it1, err := intersect(a, b)
 	if err != nil {
 		t.Error(err)
@@ -92,7 +95,7 @@ func TestInterestingQuery(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	b = NewStatementIterator(db.(*QuadStore), quad.Predicate, "/film/performance/actor")
+	b = NewSQLLinkIterator(db.(*QuadStore), quad.Predicate, "/film/performance/actor")
 	it4, err := intersect(it3, b)
 	if err != nil {
 		t.Error(err)
@@ -105,7 +108,7 @@ func TestInterestingQuery(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	b = NewStatementIterator(db.(*QuadStore), quad.Predicate, "/film/film/starring")
+	b = NewSQLLinkIterator(db.(*QuadStore), quad.Predicate, "/film/film/starring")
 	it7, err := intersect(it6, b)
 	if err != nil {
 		t.Error(err)
@@ -114,13 +117,14 @@ func TestInterestingQuery(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	s, v := it8.buildQuery(false, nil)
-	it8.Tagger().Add("id")
+	finalIt := it8.(*SQLNodeIterator)
+	s, v := finalIt.buildSQL(true, nil)
+	finalIt.Tagger().Add("id")
 	fmt.Println(s, v)
-	for graph.Next(it8) {
-		fmt.Println(it8.Result())
+	for graph.Next(finalIt) {
+		fmt.Println(finalIt.Result())
 		out := make(map[string]graph.Value)
-		it8.TagResults(out)
+		finalIt.TagResults(out)
 		for k, v := range out {
 			fmt.Printf("%s: %v\n", k, v.(string))
 		}

graph/sql/quadstore.go

@@ -200,7 +200,7 @@ func (qs *QuadStore) Quad(val graph.Value) quad.Quad {
 }
 
 func (qs *QuadStore) QuadIterator(d quad.Direction, val graph.Value) graph.Iterator {
-	return NewStatementIterator(qs, d, val.(string))
+	return NewSQLLinkIterator(qs, d, val.(string))
 }
 
 func (qs *QuadStore) NodesAllIterator() graph.Iterator {

graph/sql/sql_link_iterator_test.go

@@ -0,0 +1,87 @@
+// Copyright 2015 The Cayley Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sql
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/cayley/graph"
+	"github.com/google/cayley/graph/iterator"
+	"github.com/google/cayley/quad"
+)
+
+func TestSQLLink(t *testing.T) {
+	it := NewSQLLinkIterator(nil, quad.Object, "cool")
+	s, v := it.buildSQL(true, nil)
+	fmt.Println(s, v)
+}
+
+func TestSQLLinkIteration(t *testing.T) {
+	if *dbpath == "" {
+		t.SkipNow()
+	}
+	db, err := newQuadStore(*dbpath, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	it := NewSQLLinkIterator(db.(*QuadStore), quad.Object, "Humphrey Bogart")
+	for graph.Next(it) {
+		fmt.Println(it.Result())
+	}
+	it = NewSQLLinkIterator(db.(*QuadStore), quad.Subject, "/en/casablanca_1942")
+	s, v := it.buildSQL(true, nil)
+	fmt.Println(s, v)
+	c := 0
+	for graph.Next(it) {
+		fmt.Println(it.Result())
+		c += 1
+	}
+	if c != 18 {
+		t.Errorf("Not enough results, got %d expected 18", c)
+	}
+}
+
+func TestSQLNodeIteration(t *testing.T) {
+	if *dbpath == "" {
+		t.SkipNow()
+	}
+	db, err := newQuadStore(*dbpath, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	link := NewSQLLinkIterator(db.(*QuadStore), quad.Object, "/en/humphrey_bogart")
+	it := &SQLNodeIterator{
+		uid:       iterator.NextUID(),
+		qs:        db.(*QuadStore),
+		tableName: newTableName(),
+		linkIts: []sqlItDir{
+			sqlItDir{it: link,
+				dir: quad.Subject,
+			},
+		},
+	}
+	s, v := it.buildSQL(true, nil)
+	fmt.Println(s, v)
+	c := 0
+	for graph.Next(it) {
+		fmt.Println(it.Result())
+		c += 1
+	}
+	if c != 56 {
+		t.Errorf("Not enough results, got %d expected 56", c)
+	}
+
+}

graph/sql/sql_node_iterator.go

@@ -0,0 +1,435 @@
+// Copyright 2015 The Cayley Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sql
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+
+	"github.com/barakmich/glog"
+	"github.com/google/cayley/graph"
+	"github.com/google/cayley/graph/iterator"
+	"github.com/google/cayley/quad"
+)
+
+var sqlNodeType graph.Type
+
+func init() {
+	sqlNodeType = graph.RegisterIterator("sqlnode")
+}
+
+type SQLNodeIterator struct {
+	uid       uint64
+	qs        *QuadStore
+	tagger    graph.Tagger
+	tableName string
+	err       error
+
+	cursor  *sql.Rows
+	linkIts []sqlItDir
+	size    int64
+	tagdirs []tagDir
+
+	result      map[string]string
+	resultIndex int
+	resultList  [][]string
+	resultNext  [][]string
+	cols        []string
+}
+
+func (n *SQLNodeIterator) sqlClone() sqlIterator {
+	return n.Clone().(*SQLNodeIterator)
+}
+
+func (n *SQLNodeIterator) Clone() graph.Iterator {
+	m := &SQLNodeIterator{
+		uid:       iterator.NextUID(),
+		qs:        n.qs,
+		size:      n.size,
+		tableName: n.tableName,
+	}
+	for _, i := range n.linkIts {
+		m.linkIts = append(m.linkIts, sqlItDir{
+			dir: i.dir,
+			it:  i.it.sqlClone(),
+		})
+	}
+	copy(n.tagdirs, m.tagdirs)
+	m.tagger.CopyFrom(n)
+	return m
+}
+
+func (n *SQLNodeIterator) UID() uint64 {
+	return n.uid
+}
+
+func (n *SQLNodeIterator) Reset() {
+	n.err = nil
+	n.Close()
+}
+
+func (n *SQLNodeIterator) Err() error {
+	return n.err
+}
+
+func (n *SQLNodeIterator) Close() error {
+	if n.cursor != nil {
+		err := n.cursor.Close()
+		if err != nil {
+			return err
+		}
+		n.cursor = nil
+	}
+	return nil
+}
+
+func (n *SQLNodeIterator) Tagger() *graph.Tagger {
+	return &n.tagger
+}
+
+func (n *SQLNodeIterator) Result() graph.Value {
+	return n.result["__execd"]
+}
+
+func (n *SQLNodeIterator) TagResults(dst map[string]graph.Value) {
+	for tag, value := range n.result {
+		if tag == "__execd" {
+			for _, tag := range n.tagger.Tags() {
+				dst[tag] = value
+			}
+			continue
+		}
+		dst[tag] = value
+	}
+
+	for tag, value := range n.tagger.Fixed() {
+		dst[tag] = value
+	}
+}
+
+func (n *SQLNodeIterator) Type() graph.Type {
+	return sqlNodeType
+}
+
+func (n *SQLNodeIterator) SubIterators() []graph.Iterator {
+	// TODO(barakmich): SQL Subiterators shouldn't count? If it makes sense,
+	// there's no reason not to expose them though.
+	return nil
+}
+
+func (n *SQLNodeIterator) Sorted() bool                     { return false }
+func (n *SQLNodeIterator) Optimize() (graph.Iterator, bool) { return n, false }
+
+func (n *SQLNodeIterator) Size() (int64, bool) {
+	return n.qs.Size() / int64(len(n.linkIts)+1), true
+}
+
+func (n *SQLNodeIterator) Describe() graph.Description {
+	size, _ := n.Size()
+	return graph.Description{
+		UID:  n.UID(),
+		Name: fmt.Sprintf("SQL_NODE_QUERY: %#v", n),
+		Type: n.Type(),
+		Size: size,
+	}
+}
+
+func (n *SQLNodeIterator) Stats() graph.IteratorStats {
+	size, _ := n.Size()
+	return graph.IteratorStats{
+		ContainsCost: 1,
+		NextCost:     5,
+		Size:         size,
+	}
+}
+
+func (n *SQLNodeIterator) NextPath() bool {
+	n.resultIndex += 1
+	if n.resultIndex >= len(n.resultList) {
+		return false
+	}
+	n.buildResult(n.resultIndex)
+	return true
+}
+
+func (n *SQLNodeIterator) buildResult(i int) {
+	container := n.resultList[i]
+	n.result = make(map[string]string)
+	for i, c := range n.cols {
+		n.result[c] = container[i]
+	}
+}
+
+func (n *SQLNodeIterator) getTables() []string {
+	var out []string
+	for _, i := range n.linkIts {
+		out = append(out, i.it.getTables()...)
+	}
+	if len(out) == 0 {
+		out = append(out, n.tableName)
+	}
+	return out
+}
+
+func (n *SQLNodeIterator) tableID() tagDir {
+	if len(n.linkIts) == 0 {
+		return tagDir{
+			table: n.tableName,
+			dir:   quad.Any,
+		}
+	}
+	return tagDir{
+		table: n.linkIts[0].it.tableID().table,
+		dir:   n.linkIts[0].dir,
+	}
+}
+
+func (n *SQLNodeIterator) getTags() []tagDir {
+	myTag := n.tableID()
+	var out []tagDir
+	for _, tag := range n.tagger.Tags() {
+		out = append(out, tagDir{
+			dir:   myTag.dir,
+			table: myTag.table,
+			tag:   tag,
+		})
+	}
+	for _, tag := range n.tagdirs {
+		out = append(out, tagDir{
+			dir:   tag.dir,
+			table: myTag.table,
+			tag:   tag.tag,
+		})
+
+	}
+	for _, i := range n.linkIts {
+		out = append(out, i.it.getTags()...)
+	}
+	return out
+}
+
+func (n *SQLNodeIterator) height() int {
+	v := 0
+	for _, i := range n.linkIts {
+		if i.it.height() > v {
+			v = i.it.height()
+		}
+	}
+	return v + 1
+}
+
+func (n *SQLNodeIterator) buildWhere() (string, []string) {
+	var q []string
+	var vals []string
+	if len(n.linkIts) > 1 {
+		baseTable := n.linkIts[0].it.tableID().table
+		baseDir := n.linkIts[0].dir
+		for _, i := range n.linkIts[1:] {
+			table := i.it.tableID().table
+			dir := i.dir
+			q = append(q, fmt.Sprintf("%s.%s = %s.%s", baseTable, baseDir, table, dir))
+		}
+	}
+	for _, i := range n.linkIts {
+		s, v := i.it.buildWhere()
+		q = append(q, s)
+		vals = append(vals, v...)
+	}
+	query := strings.Join(q, " AND ")
+	return query, vals
+}
+
+func (n *SQLNodeIterator) buildSQL(next bool, val graph.Value) (string, []string) {
+	topData := n.tableID()
+	query := "SELECT "
+	var t []string
+	t = append(t, fmt.Sprintf("%s.%s as __execd", topData.table, topData.dir))
+	for _, v := range n.getTags() {
+		t = append(t, fmt.Sprintf("%s.%s as %s", v.table, v.dir, v.tag))
+	}
+	query += strings.Join(t, ", ")
+	query += " FROM "
+	t = []string{}
+	for _, k := range n.getTables() {
+		t = append(t, fmt.Sprintf("quads as %s", k))
+	}
+	query += strings.Join(t, ", ")
+	query += " WHERE "
+	constraint, values := n.buildWhere()
+
+	if !next {
+		v := val.(string)
+		if constraint != "" {
+			constraint += " AND "
+		}
+		constraint += fmt.Sprintf("%s.%s = ?", topData.table, topData.dir)
+		values = append(values, v)
+	}
+	query += constraint
+	query += ";"
+
+	glog.V(2).Infoln(query)
+
+	if glog.V(4) {
+		dstr := query
+		for i := 1; i <= len(values); i++ {
+			dstr = strings.Replace(dstr, "?", fmt.Sprintf("'%s'", values[i-1]), 1)
+		}
+		glog.V(4).Infoln(dstr)
+	}
+	return query, values
+}
+
+func (n *SQLNodeIterator) Next() bool {
+	var err error
+	graph.NextLogIn(n)
+	if n.cursor == nil {
+		err = n.makeCursor(true, nil)
+		n.cols, err = n.cursor.Columns()
+		if err != nil {
+			glog.Errorf("Couldn't get columns")
+			n.err = err
+			n.cursor.Close()
+			return false
+		}
+		// iterate the first one
+		if !n.cursor.Next() {
+			glog.V(4).Infoln("sql: No next")
+			err := n.cursor.Err()
+			if err != nil {
+				glog.Errorf("Cursor error in SQL: %v", err)
+				n.err = err
+			}
+			n.cursor.Close()
+			return false
+		}
+		s, err := scan(n.cursor, len(n.cols))
+		if err != nil {
+			n.err = err
+			n.cursor.Close()
+			return false
+		}
+		n.resultNext = append(n.resultNext, s)
+	}
+	if n.resultList != nil && n.resultNext == nil {
+		// We're on something and there's no next
+		return false
+	}
+	n.resultList = n.resultNext
+	n.resultNext = nil
+	n.resultIndex = 0
+	for {
+		if !n.cursor.Next() {
+			glog.V(4).Infoln("sql: No next")
+			err := n.cursor.Err()
+			if err != nil {
+				glog.Errorf("Cursor error in SQL: %v", err)
+				n.err = err
+			}
+			n.cursor.Close()
+			break
+		}
+		s, err := scan(n.cursor, len(n.cols))
+		if err != nil {
+			n.err = err
+			n.cursor.Close()
+			return false
+		}
+		if n.resultList[0][0] != s[0] {
+			n.resultNext = append(n.resultNext, s)
+			break
+		} else {
+			n.resultList = append(n.resultList, s)
+		}
+
+	}
+	if len(n.resultList) == 0 {
+		return graph.NextLogOut(n, nil, false)
+	}
+	n.buildResult(0)
+	return graph.NextLogOut(n, n.Result(), true)
+}
+
+func (n *SQLNodeIterator) makeCursor(next bool, value graph.Value) error {
+	if n.cursor != nil {
+		n.cursor.Close()
+	}
+	var q string
+	var values []string
+	q, values = n.buildSQL(next, value)
+	q = convertToPostgres(q, values)
+	ivalues := make([]interface{}, 0, len(values))
+	for _, v := range values {
+		ivalues = append(ivalues, v)
+	}
+	cursor, err := n.qs.db.Query(q, ivalues...)
+	if err != nil {
+		glog.Errorf("Couldn't get cursor from SQL database: %v", err)
+		cursor = nil
+		return err
+	}
+	n.cursor = cursor
+	return nil
+}
+
+func (n *SQLNodeIterator) Contains(v graph.Value) bool {
+	var err error
+	//if it.preFilter(v) {
+	//return false
+	//}
+	err = n.makeCursor(false, v)
+	if err != nil {
+		glog.Errorf("Couldn't make query: %v", err)
+		n.err = err
+		n.cursor.Close()
+		return false
+	}
+	n.cols, err = n.cursor.Columns()
+	if err != nil {
+		glog.Errorf("Couldn't get columns")
+		n.err = err
+		n.cursor.Close()
+		return false
+	}
+	n.resultList = nil
+	for {
+		if !n.cursor.Next() {
+			glog.V(4).Infoln("sql: No next")
+			err := n.cursor.Err()
+			if err != nil {
+				glog.Errorf("Cursor error in SQL: %v", err)
+				n.err = err
+			}
+			n.cursor.Close()
+			break
+		}
+		s, err := scan(n.cursor, len(n.cols))
+		if err != nil {
+			n.err = err
+			n.cursor.Close()
+			return false
+		}
+		n.resultList = append(n.resultList, s)
+	}
+	n.cursor.Close()
+	n.cursor = nil
+	if len(n.resultList) != 0 {
+		n.resultIndex = 0
+		n.buildResult(0)
+		return true
+	}
+	return false
+}