feat(frontend): output explain result as graphviz dot format

src/frontend/planner_test/tests/testdata/input/explain_dot_format.yaml

@@ -0,0 +1,44 @@
+- name: test dot output format (logical)
+  sql: |
+    CREATE TABLE t (v1 int);
+    explain (logical, format dot) SELECT approx_percentile(0.5) WITHIN GROUP (order by v1) from t;
+  expected_outputs:
+    - explain_output
+- name: test dot output format (batch)
+  sql: |
+    CREATE TABLE t (v1 int);
+    explain (physical, format dot) SELECT approx_percentile(0.5) WITHIN GROUP (order by v1) from t;
+  expected_outputs:
+    - explain_output
+- name: test dot output format (stream)
+  sql: |
+    CREATE TABLE t (v1 int);
+    explain (physical, format dot) create materialized view m1 as SELECT approx_percentile(0.5) WITHIN GROUP (order by v1) from t;
+  expected_outputs:
+    - explain_output
+- name: test long dot output format (stream)
+  sql: |
+    create table t1(a int, b int);
+    create table t2(c int primary key, d int);
+    explain (physical, format dot) create materialized view m1 as SELECT
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col1,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col2,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col3,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col4,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col5,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col6,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col7,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col8,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col9,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col10,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col11,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col12,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col13,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col14,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col15,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col16,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col17,
+    COALESCE((SELECT b FROM t2 WHERE t1.a = t2.c), 0) col18
+    from t1;
+  expected_outputs:
+    - explain_output

src/frontend/src/handler/explain.rs

@@ -232,6 +232,7 @@ async fn do_handle_explain(
                         ExplainFormat::Json => blocks.push(plan.explain_to_json()),
                         ExplainFormat::Xml => blocks.push(plan.explain_to_xml()),
                         ExplainFormat::Yaml => blocks.push(plan.explain_to_yaml()),
+                        ExplainFormat::Dot => blocks.push(plan.explain_to_dot()),
                     }
                 }
             }

src/frontend/src/optimizer/logical_optimization.rs

@@ -700,6 +700,9 @@ impl LogicalOptimizer {
                 ExplainFormat::Yaml => {
                     ctx.store_logical(plan.explain_to_yaml());
                 }
+                ExplainFormat::Dot => {
+                    ctx.store_logical(plan.explain_to_dot());
+                }
             }
         }
 
@@ -819,6 +822,9 @@ impl LogicalOptimizer {
                 ExplainFormat::Yaml => {
                     ctx.store_logical(plan.explain_to_yaml());
                 }
+                ExplainFormat::Dot => {
+                    ctx.store_logical(plan.explain_to_dot());
+                }
             }
         }
 

src/frontend/src/optimizer/plan_node/mod.rs

@@ -27,6 +27,7 @@
 //! - all field should be valued in construction, so the properties' derivation should be finished
 //!   in the `new()` function.
 
+use std::collections::HashMap;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::ops::Deref;
@@ -37,6 +38,8 @@ use dyn_clone::DynClone;
 use fixedbitset::FixedBitSet;
 use itertools::Itertools;
 use paste::paste;
+use petgraph::dot::{Config, Dot};
+use petgraph::graph::{Graph, NodeIndex};
 use pretty_xmlish::{Pretty, PrettyConfig};
 use risingwave_common::catalog::Schema;
 use risingwave_common::util::recursive::{self, Recurse};
@@ -642,6 +645,9 @@ pub trait Explain {
     /// Write explain the whole plan tree.
     fn explain<'a>(&self) -> Pretty<'a>;
 
+    /// Write explain the whole plan tree with node id.
+    fn explain_with_id<'a>(&self) -> Pretty<'a>;
+
     /// Explain the plan node and return a string.
     fn explain_to_string(&self) -> String;
 
@@ -653,6 +659,9 @@ pub trait Explain {
 
     /// Explain the plan node and return a yaml string.
     fn explain_to_yaml(&self) -> String;
+
+    /// Explain the plan node and return a dot format string.
+    fn explain_to_dot(&self) -> String;
 }
 
 impl Explain for PlanRef {
@@ -666,6 +675,21 @@ impl Explain for PlanRef {
         Pretty::Record(node)
     }
 
+    /// Write explain the whole plan tree with node id.
+    fn explain_with_id<'a>(&self) -> Pretty<'a> {
+        let node_id = self.id();
+        let mut node = self.distill();
+        // NOTE(kwannoel): Can lead to poor performance if plan is very large,
+        // but we want to show the id first.
+        node.fields
+            .insert(0, ("id".into(), Pretty::display(&node_id.0)));
+        let inputs = self.inputs();
+        for input in inputs.iter().peekable() {
+            node.children.push(input.explain_with_id());
+        }
+        Pretty::Record(node)
+    }
+
     /// Explain the plan node and return a string.
     fn explain_to_string(&self) -> String {
         let plan = reorganize_elements_id(self.clone());
@@ -680,22 +704,74 @@ impl Explain for PlanRef {
     fn explain_to_json(&self) -> String {
         let plan = reorganize_elements_id(self.clone());
         let explain_ir = plan.explain();
-        serde_json::to_string_pretty(&PrettySerde(explain_ir))
+        serde_json::to_string_pretty(&PrettySerde(explain_ir, true))
             .expect("failed to serialize plan to json")
     }
 
     /// Explain the plan node and return a xml string.
     fn explain_to_xml(&self) -> String {
         let plan = reorganize_elements_id(self.clone());
         let explain_ir = plan.explain();
-        quick_xml::se::to_string(&PrettySerde(explain_ir)).expect("failed to serialize plan to xml")
+        quick_xml::se::to_string(&PrettySerde(explain_ir, true))
+            .expect("failed to serialize plan to xml")
     }
 
     /// Explain the plan node and return a yaml string.
     fn explain_to_yaml(&self) -> String {
         let plan = reorganize_elements_id(self.clone());
         let explain_ir = plan.explain();
-        serde_yaml::to_string(&PrettySerde(explain_ir)).expect("failed to serialize plan to yaml")
+        serde_yaml::to_string(&PrettySerde(explain_ir, true))
+            .expect("failed to serialize plan to yaml")
+    }
+
+    /// Explain the plan node and return a dot format string.
+    fn explain_to_dot(&self) -> String {
+        let plan = reorganize_elements_id(self.clone());
+        let explain_ir = plan.explain_with_id();
+        let mut graph = Graph::<String, String>::new();
+        let mut nodes = HashMap::new();
+        build_graph_from_pretty(&explain_ir, &mut graph, &mut nodes, None);
+        let dot = Dot::with_config(&graph, &[Config::EdgeNoLabel]);
+        dot.to_string()
+    }
+}
+
+fn build_graph_from_pretty(
+    pretty: &Pretty<'_>,
+    graph: &mut Graph<String, String>,
+    nodes: &mut HashMap<String, NodeIndex>,
+    parent_label: Option<&str>,
+) {
+    if let Pretty::Record(r) = pretty {
+        let mut label = String::new();
+        label.push_str(&r.name);
+        for (k, v) in &r.fields {
+            label.push('\n');
+            label.push_str(k);
+            label.push_str(": ");
+            label.push_str(
+                &serde_json::to_string(&PrettySerde(v.clone(), false))
+                    .expect("failed to serialize plan to dot"),
+            );
+        }
+        // output alignment.
+        if !r.fields.is_empty() {
+            label.push('\n');
+        }
+
+        let current_node = *nodes
+            .entry(label.clone())
+            .or_insert_with(|| graph.add_node(label.clone()));
+
+        if let Some(parent_label) = parent_label {
+            if let Some(&parent_node) = nodes.get(parent_label) {
+                graph.add_edge(parent_node, current_node, "contains".to_string());
+            }
+        }
+
+        for child in &r.children {
+            build_graph_from_pretty(child, graph, nodes, Some(&label));
+        }
     }
 }
 

src/frontend/src/utils/pretty_serde.rs

@@ -28,7 +28,9 @@ use pretty_xmlish::Pretty;
 use serde::ser::{SerializeSeq, SerializeStruct};
 use serde::{Serialize, Serializer};
 
-pub struct PrettySerde<'a>(pub Pretty<'a>);
+// Second anymous field is include_children.
+// If true the children information will be serialized.
+pub struct PrettySerde<'a>(pub Pretty<'a>, pub bool);
 
 impl Serialize for PrettySerde<'_> {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -46,31 +48,33 @@ impl Serialize for PrettySerde<'_> {
                     &node
                         .fields
                         .iter()
-                        .map(|(k, v)| (k.as_ref(), PrettySerde(v.clone())))
+                        .map(|(k, v)| (k.as_ref(), PrettySerde(v.clone(), self.1)))
                         .collect::<BTreeMap<_, _>>(),
                 )?;
-                state.serialize_field(
-                    "children",
-                    &node
-                        .children
-                        .iter()
-                        .map(|c| PrettySerde(c.clone()))
-                        .collect::<Vec<_>>(),
-                )?;
+                if self.1 {
+                    state.serialize_field(
+                        "children",
+                        &node
+                            .children
+                            .iter()
+                            .map(|c| PrettySerde(c.clone(), self.1))
+                            .collect::<Vec<_>>(),
+                    )?;
+                }
                 state.end()
             }
 
             Pretty::Array(elements) => {
                 let mut seq = serializer.serialize_seq(Some(elements.len()))?;
                 for element in elements {
-                    seq.serialize_element(&PrettySerde((*element).clone()))?;
+                    seq.serialize_element(&PrettySerde((*element).clone(), self.1))?;
                 }
                 seq.end()
             }
 
             Pretty::Linearized(inner, size) => {
                 let mut state = serializer.serialize_struct("Linearized", 2)?;
-                state.serialize_field("inner", &PrettySerde((**inner).clone()))?;
+                state.serialize_field("inner", &PrettySerde((**inner).clone(), self.1))?;
                 state.serialize_field("size", size)?;
                 state.end()
             }
@@ -94,7 +98,7 @@ mod tests {
     #[test]
     fn test_pretty_serde() {
         let pretty = Pretty::childless_record("root", vec![("a", Pretty::Text("1".into()))]);
-        let pretty_serde = PrettySerde(pretty);
+        let pretty_serde = PrettySerde(pretty, true);
         let serialized = serde_json::to_string(&pretty_serde).unwrap();
         check(
             serialized,

src/sqlparser/src/ast/mod.rs

@@ -1141,6 +1141,7 @@ pub enum ExplainFormat {
     Json,
     Xml,
     Yaml,
+    Dot,
 }
 
 impl fmt::Display for ExplainFormat {
@@ -1150,6 +1151,7 @@ impl fmt::Display for ExplainFormat {
             ExplainFormat::Json => f.write_str("JSON"),
             ExplainFormat::Xml => f.write_str("XML"),
             ExplainFormat::Yaml => f.write_str("YAML"),
+            ExplainFormat::Dot => f.write_str("DOT"),
         }
     }
 }

src/sqlparser/src/keywords.rs

@@ -202,6 +202,7 @@ define_keywords!(
     DISTRIBUTED,
     DISTSQL,
     DO,
+    DOT,
     DOUBLE,
     DROP,
     DYNAMIC,

src/sqlparser/src/parser.rs

@@ -4039,11 +4039,13 @@ impl Parser<'_> {
                             Keyword::JSON,
                             Keyword::XML,
                             Keyword::YAML,
+                            Keyword::DOT,
                         ])? {
                             Keyword::TEXT => ExplainFormat::Text,
                             Keyword::JSON => ExplainFormat::Json,
                             Keyword::XML => ExplainFormat::Xml,
                             Keyword::YAML => ExplainFormat::Yaml,
+                            Keyword::DOT => ExplainFormat::Dot,
                             _ => unreachable!("{}", keyword),
                         }
                     }