⚡ Bolt: [performance improvement] Reduce O(E) allocation churn in graph construction

[bashandbone]

💡 What

Replaced expensive .entry().or_insert() and .entry().or_default() uses in crates/flow/src/incremental/graph.rs with .contains_key() and .get_mut() checks to eliminate redundant PathBuf string clones.

🎯 Why

During graph construction (ensure_node and add_edge), entry(key.clone()) unconditionally allocates and clones strings even if the key is already present in the HashMap. In large codebases with heavily connected dependency graphs, this results in significant O(E) memory churn.

📊 Impact

Changes allocations from O(E) to O(V). It greatly reduces memory allocation pressure and improves speed during full-graph dependency updates and analysis cycles.

🔬 Measurement

Run cargo bench -p thread-flow --bench graph_bench or profile the application graph builder. Graph insertion times should be tangibly lower and jemalloc should report significantly reduced allocation volume inside DependencyGraph::add_edge.

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PR created automatically by Jules for task 8275981448862509516 started by @bashandbone

Summary by Sourcery

Optimize graph construction performance and simplify rule-engine helper signatures.

Enhancements:

• Reduce allocation churn in dependency graph edge and node insertion by avoiding unnecessary HashMap entry cloning.
• Simplify rule-engine constraint and transform variable-check helpers by removing redundant lifetime annotations in their function signatures.

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[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Optimizes dependency graph construction to avoid unnecessary hash map entry allocations and minorly simplifies lifetimes on rule-engine helpers, reducing allocation churn and improving performance during graph building.

Flow diagram for optimized add_edge adjacency updates

flowchart TD
    A["add_edge(edge)"] --> B["compute idx for new edge"]
    B --> C["ensure_node(edge.from)"]
    C --> D["ensure_node(edge.to)"]

    D --> E{"forward_adj has key edge.from?"}
    E --> F["get_mut(&edge.from).push(idx)"]:::fast
    E --> G["insert(edge.from.clone(), vec![idx])"]:::alloc

    F --> H{"reverse_adj has key edge.to?"}
    G --> H

    H --> I["get_mut(&edge.to).push(idx)"]:::fast
    H --> J["insert(edge.to.clone(), vec![idx])"]:::alloc

    I --> K["edges.push(edge)"]
    J --> K

    classDef fast fill:#bbf,stroke:#333,stroke-width:1px
    classDef alloc fill:#fdd,stroke:#333,stroke-width:1px

Loading

File-Level Changes

Change	Details	Files
Optimize adjacency list updates in DependencyGraph::add_edge to avoid unconditional key cloning and allocation.	Replace HashMap::entry(...).or_default() pattern with get_mut() + insert() branching for forward_adj Apply same pattern to reverse_adj to reuse existing vectors when present and only clone edge keys when inserting new ones	crates/flow/src/incremental/graph.rs
Avoid redundant allocation during node creation in DependencyGraph::ensure_node by checking for key existence before inserting.	Replace HashMap::entry(...).or_insert_with(...) with contains_key() + insert() to prevent cloning file paths when nodes already exist	crates/flow/src/incremental/graph.rs
Simplify function signatures in rule-engine variable checking helpers by removing unnecessary lifetimes and using direct references.	Remove explicit lifetime parameter from check_var_in_constraints and accept &RapidMap instead of a lifetime-annotated reference Remove explicit lifetime parameter from check_var_in_transform and accept &Option instead of a lifetime-annotated reference	crates/rule-engine/src/check_var.rs

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[Copilot]

Pull request overview

This PR targets allocation/performance hot paths by avoiding unconditional PathBuf cloning during dependency graph construction, and includes a small Rust signature cleanup in the rule engine.

Changes:

• Reworked DependencyGraph::add_edge adjacency updates to clone PathBufs only on first insertion into adjacency maps.
• Reworked DependencyGraph::ensure_node to avoid allocating a PathBuf when the node already exists.
• Removed unnecessary explicit lifetimes from internal helper functions in check_var.rs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/rule-engine/src/check_var.rs	Simplifies internal helper signatures by removing unused lifetime parameters.
crates/flow/src/incremental/graph.rs	Reduces allocation churn by avoiding unconditional key cloning when populating nodes and adjacency maps.

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