Struct PgJsonVisitor 

pub struct PgJsonVisitor<'a, 'b> {
    f: &'a mut Formatter<'b>,
    objects: HashMap<u32, Value>,
    next_id: u32,
    with_schema: bool,
    parent_ids: Vec<u32>,
}

Formats plans to display as postgresql plan json format.

There are already many existing visualizer for this format, for example dalibo. Unfortunately, there is no formal spec for this format, but it is widely used in the PostgreSQL community.

Here is an example of the format:

[
    {
        "Plan": {
            "Node Type": "Sort",
            "Output": [
                "question_1.id",
                "question_1.title",
                "question_1.text",
                "question_1.file",
                "question_1.type",
                "question_1.source",
                "question_1.exam_id"
            ],
            "Sort Key": [
                "question_1.id"
            ],
            "Plans": [
                {
                    "Node Type": "Seq Scan",
                    "Parent Relationship": "Left",
                    "Relation Name": "question",
                    "Schema": "public",
                    "Alias": "question_1",
                    "Output": [
                       "question_1.id",
                        "question_1.title",
                       "question_1.text",
                        "question_1.file",
                        "question_1.type",
                        "question_1.source",
                        "question_1.exam_id"
                    ],
                    "Filter": "(question_1.exam_id = 1)"
                }
            ]
        }
    }
]

Fields

f: &'a mut Formatter<'b>

objects: HashMap<u32, Value>

A mapping from plan node id to the plan node json representation.

next_id: u32

with_schema: bool

If true, includes summarized schema information

parent_ids: Vec<u32>

Holds the ids (as generated from graphviz_builder of all parent nodes

Implementations

impl<'a, 'b> PgJsonVisitor<'a, 'b>

pub fn new(f: &'a mut Formatter<'b>) -> Self

pub fn with_schema(&mut self, with_schema: bool)

Sets a flag which controls if the output schema is displayed

fn to_json_value(node: &LogicalPlan) -> Value

Converts a logical plan node to a json object.

Trait Implementations

impl<'n> TreeNodeVisitor<'n> for PgJsonVisitor<'_, '_>

type Node = LogicalPlan

The node type which is visitable.

fn f_down(&mut self, node: &'n LogicalPlan) -> Result<TreeNodeRecursion>

Invoked while traversing down the tree, before any children are visited. Default implementation continues the recursion.

fn f_up(&mut self, _node: &Self::Node) -> Result<TreeNodeRecursion>

Invoked while traversing up the tree after children are visited. Default implementation continues the recursion.