⚡ Bolt: [performance improvement] optimize D1 query generation memory allocations

[bashandbone]

💡 What: Used String::with_capacity and std::fmt::Write instead of standard format! and intermediate Vec bindings.
🎯 Why: Cloudflare D1 query construction via build_upsert_stmt and build_delete_stmt had overhead from unnecessary intermediate memory allocations for loops string formatting operations.
📊 Impact: Expected to reduce memory overhead and latency during Cloudflare D1 edge database target mutations.
🔬 Measurement: Verify via executing target tests with cargo test -p thread-flow --test d1_target_tests --test d1_minimal_tests --test d1_cache_integration to confirm standard D1 functional parity.

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PR created automatically by Jules for task 1083225261666678753 started by @bashandbone

Summary by Sourcery

Optimize Cloudflare D1 upsert and delete SQL generation to reduce memory allocations and improve performance.

Enhancements:

• Replace intermediate vector-based SQL construction with preallocated String builders for D1 upsert statements.
• Streamline DELETE statement generation by building SQL directly into a preallocated String while collecting parameters.

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[sourcery-ai]

Reviewer's Guide

Refactors D1 upsert and delete SQL construction to build query strings directly into preallocated Strings using std::fmt::Write, avoiding intermediate Vec allocations and format!/join overhead while preserving existing behavior and parameters ordering.

Flow diagram for optimized D1 delete SQL construction

flowchart TD
    A[Start build_delete_stmt] --> B[Init params Vec::with_capacity]
    B --> C[Init sql String::with_capacity and write DELETE FROM table_name WHERE]
    C --> D[Loop key_fields_schema]
    D -->|key_part present| E[Append column = ? to sql with AND]
    E --> F[Push key_part_to_json to params]
    D -->|no key_part| D
    F --> D
    D --> G[Return sql and params]

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File-Level Changes

Change	Details	Files
Optimize D1 upsert statement construction by streaming SQL into a preallocated String and collecting parameters in a single pass.	Replaced intermediate vectors for columns, placeholders, and update clauses with direct writes into a String using std::fmt::Write Preallocated the SQL buffer with String::with_capacity(256) and the params vector with combined key/value schema length Inlined comma handling for column lists, value placeholders, and update clauses using counters to track when to insert separators Preserved existing parameter push order for keys and values while changing the string-building strategy	crates/flow/src/targets/d1.rs
Optimize D1 delete statement construction by building the WHERE clause directly into a preallocated String.	Replaced vector of WHERE clauses and final format!/join with direct writes into a String using std::fmt::Write Preallocated the SQL buffer with String::with_capacity(128) and the params vector with key schema length Used a boolean flag to manage AND separator insertion while iterating key fields Preserved behavior and parameter ordering while avoiding intermediate allocations	crates/flow/src/targets/d1.rs

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[Copilot]

Pull request overview

Refactors build_upsert_stmt and build_delete_stmt in the D1 target to construct SQL strings directly via String::with_capacity + std::fmt::Write instead of building intermediate Vec<String>s and using format! + join. Behavior is preserved: the same columns/placeholders/update clauses and parameter ordering are produced.

Changes:

• Rewrote build_upsert_stmt to incrementally write columns, placeholders, and ON CONFLICT DO UPDATE SET clauses into a single pre-sized String, pre-sizing the params Vec.
• Rewrote build_delete_stmt similarly, joining WHERE clauses with AND via inline writes.
• No changes to public signatures or semantics.

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[sourcery-ai]

Hey - I've left some high level feedback:

• In both build_upsert_stmt and build_delete_stmt, the write! results are silently discarded (let _ = ...); since these functions already return a Result, consider propagating or at least asserting on the fmt::Result to avoid masking future formatting errors.
• In build_upsert_stmt, you now iterate over values.fields twice (once for columns/placeholders and once for update clauses); you could fold the update-clause construction into the first loop to avoid duplication and keep the column and update logic tightly coupled.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In both `build_upsert_stmt` and `build_delete_stmt`, the `write!` results are silently discarded (`let _ = ...`); since these functions already return a `Result`, consider propagating or at least asserting on the `fmt::Result` to avoid masking future formatting errors.
- In `build_upsert_stmt`, you now iterate over `values.fields` twice (once for columns/placeholders and once for update clauses); you could fold the update-clause construction into the first loop to avoid duplication and keep the column and update logic tightly coupled.

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