Struct TreeRenderVisitor 

struct TreeRenderVisitor<'a, 'b> {
    f: &'a mut Formatter<'b>,
    maximum_render_width: usize,
}

This module implements a tree-like art renderer for execution plans, based on DuckDB’s implementation: https://github.com/duckdb/duckdb/blob/main/src/include/duckdb/common/tree_renderer/text_tree_renderer.hpp

The rendered output looks like this:

┌───────────────────────────┐
│    CoalesceBatchesExec    │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│        HashJoinExec       ├──────────────┐
└─────────────┬─────────────┘              │
┌─────────────┴─────────────┐┌─────────────┴─────────────┐
│       DataSourceExec      ││       DataSourceExec      │
└───────────────────────────┘└───────────────────────────┘

The renderer uses a three-layer approach for each node:

1. Top layer: renders the top borders and connections
2. Content layer: renders the node content and vertical connections
3. Bottom layer: renders the bottom borders and connections

Each node is rendered in a box of fixed width (NODE_RENDER_WIDTH).

Fields

f: &'a mut Formatter<'b>

Write to this formatter

maximum_render_width: usize

Maximum total width of the rendered tree

Implementations

impl TreeRenderVisitor<'_, '_>

const LTCORNER: &'static str = "┌"

const RTCORNER: &'static str = "┐"

const LDCORNER: &'static str = "└"

const RDCORNER: &'static str = "┘"

const TMIDDLE: &'static str = "┬"

const LMIDDLE: &'static str = "├"

const DMIDDLE: &'static str = "┴"

const VERTICAL: &'static str = "│"

const HORIZONTAL: &'static str = "─"

const NODE_RENDER_WIDTH: usize = 29usize

const MAX_EXTRA_LINES: usize = 30usize

pub fn visit(&mut self, plan: &dyn ExecutionPlan) -> Result<(), Error>

Main entry point for rendering an execution plan as a tree. The rendering process happens in three stages for each level of the tree:

1. Render top borders and connections
2. Render node content and vertical connections
3. Render bottom borders and connections

fn render_top_layer(&mut self, root: &RenderTree, y: usize) -> Result<(), Error>

Renders the top layer of boxes at the given y-level of the tree. This includes:

• Top corners (┌─┐) for nodes
• Horizontal connections between nodes
• Vertical connections to parent nodes

fn render_box_content( &mut self, root: &RenderTree, y: usize, ) -> Result<(), Error>

Renders the content layer of boxes at the given y-level of the tree. This includes:

• Node names and extra information
• Vertical borders (│) for boxes
• Vertical connections between nodes

fn render_bottom_layer( &mut self, root: &RenderTree, y: usize, ) -> Result<(), Error>

Renders the bottom layer of boxes at the given y-level of the tree. This includes:

• Bottom corners (└─┘) for nodes
• Horizontal connections between nodes
• Vertical connections to child nodes

fn extra_info_separator() -> String

fn remove_padding(s: &str) -> String

pub fn split_up_extra_info( extra_info: &HashMap<String, String>, result: &mut Vec<String>, max_lines: usize, )

fn adjust_text_for_rendering(source: &str, max_render_width: usize) -> String

Adjusts text to fit within the specified width by:

1. Truncating with ellipsis if too long
2. Center-aligning within the available space if shorter

fn should_render_whitespace(root: &RenderTree, x: usize, y: usize) -> bool

Determines if whitespace should be rendered at a given position. This is important for:

1. Maintaining proper spacing between sibling nodes
2. Ensuring correct alignment of connections between parents and children
3. Preserving the tree structure’s visual clarity

fn split_string_buffer(source: &str, result: &mut Vec<String>)

fn can_split_on_this_char(c: char) -> bool