Struct RewriteRule 

pub struct RewriteRule {
    pub pattern: SqliteGraph,
    pub replacement: SqliteGraph,
    pub interface: Vec<(usize, usize)>,
}

A rewrite rule for DPO-style graph transformation.

A rewrite rule specifies how to transform a graph by replacing matched pattern subgraphs with replacement subgraphs.

Interface Nodes

The interface field maps pattern node indices to replacement node indices. These nodes are preserved during the rewrite and serve as connection points between the deleted pattern and inserted replacement.

For example, to replace A -> B -> C with A -> D -> C:

• Pattern nodes: [A, B, C] at indices [0, 1, 2]
• Replacement nodes: [A’, D, C’] at indices [0, 1, 2]
• Interface: [(0, 0), (2, 2)] means A and C are preserved

Example

use sqlitegraph::{algo::RewriteRule, SqliteGraph};

// Replace chain A->B->C with A->D (simplify through B)
let rule = RewriteRule {
    pattern: pattern_graph,     // A -> B -> C
    replacement: replacement_graph,  // A' -> D
    interface: vec![(0, 0), (2, 0)],  // A->A', C->D (merge C into D)
};

Fields

pattern: SqliteGraph

Pattern graph to search for in the target graph.

replacement: SqliteGraph

Replacement graph to insert in place of matched patterns.

interface: Vec<(usize, usize)>

Interface mapping: (pattern_node_index, replacement_node_index).

Interface nodes are preserved during the rewrite and serve as connection points between pattern and replacement. Each pair maps a node index in the pattern to a node index in the replacement.

Implementations

impl RewriteRule

pub fn interface_size(&self) -> usize

Returns the number of interface nodes.