Lower & evaluate Graph Match Modes (#575)

Author: jpschorr

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Added lowering and evaluation of graph `MATCH` label negation, conjunction, and disjunction
 - Added lowering and evaluation of graph `MATCH` `WHERE` clauses
+- Added lowering and evaluation of graph `MATCH` modes (i.e., `WALK`, `TRAIL`, `ACYCLIC`, `SIMPLE`)
 
 ### Removed
 

partiql-ast/src/ast/graph.rs

@@ -24,7 +24,7 @@ pub struct GraphMatch {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct GraphPattern {
     #[visit(skip)]
-    pub mode: Option<GraphMatchMode>,
+    pub match_mode: Option<GraphMatchMode>,
     pub patterns: Vec<AstNode<GraphPathPattern>>,
     #[visit(skip)]
     pub keep: Option<GraphPathPrefix>,
@@ -34,7 +34,9 @@ pub struct GraphPattern {
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum GraphMatchMode {
+    /// Edges are not allowed to bind to more than one edge variable in a path
     DifferentEdges,
+    /// No restrictions on binding of edges or vertices
     RepeatableElements,
 }
 
@@ -89,8 +91,9 @@ pub enum GraphTableExport {
 }
 
 /// The direction of an edge
+///
 /// | Orientation               | Edge pattern | Abbreviation |
-/// |---------------------------+--------------+--------------|
+/// |---------------------------|--------------|--------------|
 /// | Pointing left             | <−[ spec ]−  | <−           |
 /// | Undirected                | ~[ spec ]~   | ~            |
 /// | Pointing right            | −[ spec ]−>  | −>           |
@@ -118,20 +121,17 @@ pub struct GraphMatchQuantifier {
     pub upper: Option<NonZeroU32>,
 }
 
-/// A path mode
-/// | Keyword        | Description
-/// |----------------+--------------
-/// | WALK           |
-/// | TRAIL          | No repeated edges.
-/// | ACYCLIC        | No repeated nodes.
-/// | SIMPLE         | No repeated nodes, except that the first and last nodes may be the same.
-
+/// Filters paths. Options other than `Walk` ensure a finite number of matches.
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum GraphPathMode {
+    /// No filtering of edges/nodes.
     Walk,
+    /// No repeated edges.
     Trail,
+    /// No repeated nodes.
     Acyclic,
+    /// No repeated nodes, except that the first and last nodes may be the same.
     Simple,
 }
 

partiql-ast/src/pretty/graph.rs

@@ -184,14 +184,14 @@ impl PrettyDoc for GraphPattern {
         A: Clone,
     {
         let GraphPattern {
-            mode,
+            match_mode,
             patterns,
             keep,
             where_clause,
         } = &self;
         let patterns = pretty_list(patterns, PRETTY_INDENT_MINOR_NEST, arena).group();
         let parts = [
-            mode.as_ref().map(|inner| inner.pretty_doc(arena)),
+            match_mode.as_ref().map(|inner| inner.pretty_doc(arena)),
             Some(patterns),
             keep.as_ref().map(|keep| {
                 arena.intersperse([arena.text("KEEP"), keep.pretty_doc(arena)], arena.space())

partiql-eval/src/eval/expr/graph_match.rs

@@ -49,7 +49,7 @@ impl BindEvalExpr for EvalGraphMatch {
 mod tests {
     use crate::eval::expr::{BindEvalExpr, EvalGlobalVarRef, EvalGraphMatch};
     use crate::eval::graph::plan::{
-        BindSpec, DirectionFilter, EdgeFilter, LabelFilter, NodeFilter, NodeMatch,
+        BindSpec, DirectionFilter, EdgeFilter, LabelFilter, NodeFilter, NodeMatch, PathMode,
         PathPatternMatch, TripleFilter, TripleStepFilter, TripleStepMatch, ValueFilter,
     };
     use crate::eval::graph::string_graph::StringGraphTypes;
@@ -202,6 +202,7 @@ mod tests {
             binders,
             spec,
             filter: ValueFilter::Always,
+            path_mode: PathMode::Walk,
         };
 
         test_graph(matcher.into(), "<<  >>")
@@ -230,6 +231,7 @@ mod tests {
             binders,
             spec,
             filter: ValueFilter::Always,
+            path_mode: PathMode::Walk,
         };
 
         test_graph(matcher.into(), "<<  >>")
@@ -256,6 +258,7 @@ mod tests {
             binders,
             spec,
             filter: ValueFilter::Always,
+            path_mode: PathMode::Walk,
         };
 
         test_graph(matcher.into(), "<< {'x': 2, 'z': 1.2, 'y': 1} >>")
@@ -284,6 +287,7 @@ mod tests {
             binders,
             spec,
             filter: ValueFilter::Always,
+            path_mode: PathMode::Walk,
         };
 
         test_graph(matcher.into(), "<< {  }, {  } >>")
@@ -312,6 +316,7 @@ mod tests {
             binders,
             spec,
             filter: ValueFilter::Always,
+            path_mode: PathMode::Walk,
         };
 
         test_graph(
@@ -340,6 +345,7 @@ mod tests {
             binders,
             spec,
             filter: Default::default(),
+            path_mode: PathMode::Walk,
         };
 
         let binders = (
@@ -359,6 +365,7 @@ mod tests {
             binders,
             spec,
             filter: Default::default(),
+            path_mode: PathMode::Walk,
         };
 
         let pattern_match = PathPatternMatch::Concat(
@@ -367,6 +374,7 @@ mod tests {
                 PathPatternMatch::Match(matcher2),
             ],
             Default::default(),
+            PathMode::Walk,
         );
 
         test_graph(
@@ -397,6 +405,7 @@ mod tests {
             binders,
             spec,
             filter: Default::default(),
+            path_mode: PathMode::Walk,
         };
 
         let binders = (
@@ -416,6 +425,7 @@ mod tests {
             binders,
             spec,
             filter: Default::default(),
+            path_mode: PathMode::Walk,
         };
 
         let pattern_match = PathPatternMatch::Concat(
@@ -424,6 +434,7 @@ mod tests {
                 PathPatternMatch::Match(matcher2),
             ],
             Default::default(),
+            PathMode::Walk,
         );
         test_graph(
             pattern_match,

partiql-eval/src/eval/graph/engine.rs

@@ -1,5 +1,5 @@
 use crate::eval::graph::plan::{
-    BindSpec, DirectionFilter, GraphPlanConvert, NodeFilter, NodeMatch, TripleFilter,
+    BindSpec, DirectionFilter, GraphPlanConvert, NodeFilter, NodeMatch, PathMode, TripleFilter,
     TripleStepFilter, TripleStepMatch, ValueFilter,
 };
 use crate::eval::graph::result::{PathPatternNodes, Triple};
@@ -50,6 +50,7 @@ pub trait TripleScan<GT: GraphTypes> {
         &self,
         binders: &(BindSpec<GT>, BindSpec<GT>, BindSpec<GT>),
         spec: &TripleFilter<GT>,
+        allow_repeated_nodes: bool,
         filter: &ValueFilter,
         ctx: &dyn EvalContext,
     ) -> impl Iterator<Item = Triple<GT>>;
@@ -58,6 +59,7 @@ pub trait TripleScan<GT: GraphTypes> {
         &self,
         binders: &(BindSpec<GT>, BindSpec<GT>, BindSpec<GT>),
         spec: &TripleFilter<GT>,
+        allow_repeated_nodes: bool,
         filter: &ValueFilter,
         ctx: &dyn EvalContext,
     ) -> impl Iterator<Item = Triple<GT>>;
@@ -66,6 +68,7 @@ pub trait TripleScan<GT: GraphTypes> {
         &self,
         binders: &(BindSpec<GT>, BindSpec<GT>, BindSpec<GT>),
         spec: &TripleFilter<GT>,
+        allow_repeated_nodes: bool,
         filter: &ValueFilter,
         ctx: &dyn EvalContext,
     ) -> impl Iterator<Item = Triple<GT>>;
@@ -74,6 +77,7 @@ pub trait TripleScan<GT: GraphTypes> {
         &self,
         binders: &(BindSpec<GT>, BindSpec<GT>, BindSpec<GT>),
         spec: &TripleFilter<GT>,
+        allow_repeated_nodes: bool,
         filter: &ValueFilter,
         ctx: &dyn EvalContext,
     ) -> impl Iterator<Item = Triple<GT>>;
@@ -95,6 +99,7 @@ where
             binders,
             spec: TripleStepFilter { dir, triple },
             filter,
+            path_mode,
         } = spec;
         let (to_from, undirected, from_to) = match dir {
             DirectionFilter::L => (true, false, false),
@@ -106,19 +111,38 @@ where
             DirectionFilter::LUR => (true, true, true),
         };
 
+        let allow_repeated_nodes = !matches!(path_mode, PathMode::Acyclic);
         let mut result = vec![];
         if undirected {
-            result.extend(self.scan_undirected(binders, triple, filter, ctx));
+            result.extend(self.scan_undirected(binders, triple, allow_repeated_nodes, filter, ctx));
         }
         match (from_to, to_from) {
             (true, true) => {
-                result.extend(self.scan_directed_both(binders, triple, filter, ctx));
+                result.extend(self.scan_directed_both(
+                    binders,
+                    triple,
+                    allow_repeated_nodes,
+                    filter,
+                    ctx,
+                ));
             }
             (true, false) => {
-                result.extend(self.scan_directed_from_to(binders, triple, filter, ctx));
+                result.extend(self.scan_directed_from_to(
+                    binders,
+                    triple,
+                    allow_repeated_nodes,
+                    filter,
+                    ctx,
+                ));
             }
             (false, true) => {
-                result.extend(self.scan_directed_to_from(binders, triple, filter, ctx));
+                result.extend(self.scan_directed_to_from(
+                    binders,
+                    triple,
+                    allow_repeated_nodes,
+                    filter,
+                    ctx,
+                ));
             }
             (false, false) => {}
         }