Documentation
¶
Overview ¶
Package query provides a fluent, type-safe programmatic API for expressing MATCH-style pattern queries against a labelled property graph snapshot.
The API is intentionally minimal in v1: it covers the high-value "MATCH (n:Label1) WHERE n.prop = v RETURN n" pattern and its single-hop extension "(:Label1)-[]->(:Label2)". Multi-hop chains compose via repeated Pattern.Out / [Pattern.Filter] calls; the engine transparently uses the lpg.Graph's NodeIndex (Roaring bitmaps) when a WithLabel predicate seeds the pattern.
A future iteration will plug in graph/index.Manager so the planner can choose between hash, btree, and full-scan plans based on cardinality estimates.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Engine ¶
type Engine[N comparable, W any] struct { // contains filtered or unexported fields }
Engine bundles an lpg.Graph with its CSR snapshot for read-only query execution. The CSR is used for adjacency traversal; the LPG is used for label / property lookups.
func (*Engine[N, W]) Match ¶
Match opens a new MATCH expression seeded with every node in the graph.
Example ¶
ExampleEngine_Match expresses "MATCH (n:Person) RETURN n" with the fluent pattern API. The label predicate seeds the working set from the graph's label index; Cardinality reports its size and Collect returns the matching user keys (order unspecified, sorted here).
package main
import (
"fmt"
"sort"
"github.com/FlavioCFOliveira/GoGraph/graph/adjlist"
"github.com/FlavioCFOliveira/GoGraph/graph/csr"
"github.com/FlavioCFOliveira/GoGraph/graph/lpg"
"github.com/FlavioCFOliveira/GoGraph/graph/query"
)
// buildSocialGraph returns a tiny labelled property graph and its CSR
// snapshot: two :Person nodes (alice, bob) who both BOUGHT a :Product
// (widget).
func buildSocialGraph() (*lpg.Graph[string, int], *csr.CSR[int]) {
g := lpg.New[string, int](adjlist.Config{Directed: true})
for _, p := range []string{"alice", "bob"} {
_ = g.AddNode(p)
_ = g.SetNodeLabel(p, "Person")
_ = g.SetNodeProperty(p, "name", lpg.StringValue(p))
}
_ = g.AddNode("widget")
_ = g.SetNodeLabel("widget", "Product")
_ = g.AddEdge("alice", "widget", 0)
_ = g.AddEdge("bob", "widget", 0)
return g, csr.BuildFromAdjList(g.AdjList())
}
func main() {
g, snap := buildSocialGraph()
eng := query.New(g, snap)
people := eng.Match().Vertex(query.WithLabel[string, int]("Person"))
keys := people.Collect()
sort.Strings(keys)
fmt.Println("count:", people.Cardinality())
fmt.Println("people:", keys)
}
Output: count: 2 people: [alice bob]
type Pattern ¶
type Pattern[N comparable, W any] struct { // contains filtered or unexported fields }
Pattern is a single MATCH expression under construction.
func (*Pattern[N, W]) Cardinality ¶
Cardinality returns the size of the current working set.
func (*Pattern[N, W]) Collect ¶
func (p *Pattern[N, W]) Collect() []N
Collect returns the user-facing N values in the working set.
func (*Pattern[N, W]) Out ¶
Out expands the working set to the out-neighbours of every node in it.
Example ¶
ExamplePattern_Out follows out-edges one hop — "MATCH (:Person)-[]->(p) RETURN p" — collapsing both buyers onto the single product they bought.
package main
import (
"fmt"
"github.com/FlavioCFOliveira/GoGraph/graph/adjlist"
"github.com/FlavioCFOliveira/GoGraph/graph/csr"
"github.com/FlavioCFOliveira/GoGraph/graph/lpg"
"github.com/FlavioCFOliveira/GoGraph/graph/query"
)
// buildSocialGraph returns a tiny labelled property graph and its CSR
// snapshot: two :Person nodes (alice, bob) who both BOUGHT a :Product
// (widget).
func buildSocialGraph() (*lpg.Graph[string, int], *csr.CSR[int]) {
g := lpg.New[string, int](adjlist.Config{Directed: true})
for _, p := range []string{"alice", "bob"} {
_ = g.AddNode(p)
_ = g.SetNodeLabel(p, "Person")
_ = g.SetNodeProperty(p, "name", lpg.StringValue(p))
}
_ = g.AddNode("widget")
_ = g.SetNodeLabel("widget", "Product")
_ = g.AddEdge("alice", "widget", 0)
_ = g.AddEdge("bob", "widget", 0)
return g, csr.BuildFromAdjList(g.AdjList())
}
func main() {
g, snap := buildSocialGraph()
eng := query.New(g, snap)
bought := eng.Match().
Vertex(query.WithLabel[string, int]("Person")).
Out()
fmt.Println("count:", bought.Cardinality())
fmt.Println("products:", bought.Collect())
}
Output: count: 1 products: [widget]
type Predicate ¶
Predicate is the type-safe interface a Vertex constraint implements. Implementations may consult the lpg.Graph freely; returning true keeps the NodeID in the working set.
func WithLabel ¶
func WithLabel[N comparable, W any](name string) Predicate[N, W]
WithLabel returns a Predicate selecting nodes carrying the given label.
func WithProperty ¶
func WithProperty[N comparable, W any](key string, expected lpg.PropertyValue) Predicate[N, W]
WithProperty returns a Predicate selecting nodes whose named property matches the given expected value (kind and value-equality both required).
Example ¶
ExampleWithProperty filters a pattern by an exact property match — "MATCH (n) WHERE n.name = 'alice' RETURN n".
package main
import (
"fmt"
"github.com/FlavioCFOliveira/GoGraph/graph/adjlist"
"github.com/FlavioCFOliveira/GoGraph/graph/csr"
"github.com/FlavioCFOliveira/GoGraph/graph/lpg"
"github.com/FlavioCFOliveira/GoGraph/graph/query"
)
// buildSocialGraph returns a tiny labelled property graph and its CSR
// snapshot: two :Person nodes (alice, bob) who both BOUGHT a :Product
// (widget).
func buildSocialGraph() (*lpg.Graph[string, int], *csr.CSR[int]) {
g := lpg.New[string, int](adjlist.Config{Directed: true})
for _, p := range []string{"alice", "bob"} {
_ = g.AddNode(p)
_ = g.SetNodeLabel(p, "Person")
_ = g.SetNodeProperty(p, "name", lpg.StringValue(p))
}
_ = g.AddNode("widget")
_ = g.SetNodeLabel("widget", "Product")
_ = g.AddEdge("alice", "widget", 0)
_ = g.AddEdge("bob", "widget", 0)
return g, csr.BuildFromAdjList(g.AdjList())
}
func main() {
g, snap := buildSocialGraph()
eng := query.New(g, snap)
match := eng.Match().Vertex(
query.WithProperty[string, int]("name", lpg.StringValue("alice")),
)
fmt.Println("count:", match.Cardinality())
fmt.Println("keys:", match.Collect())
}
Output: count: 1 keys: [alice]
Source Files