fix: bound component operation concurrency and pre-allocate future buffers

[Copilot]

The previous try_join_all approach launched all delete/upsert futures simultaneously — unbounded concurrency that can saturate a DB connection pool at scale, with no protection against partial application on error.

Changes

• Bounded concurrency: replaced try_join_all with buffer_unordered(COMPONENT_CONCURRENCY_LIMIT) + try_collect, capping simultaneous in-flight DB/network ops at 16
• Named constant: COMPONENT_CONCURRENCY_LIMIT: usize = 16 with doc comment — visible and tunable relative to connection pool size
• Pre-allocated buffers: Vec::with_capacity sized from upfront sum of all change counts, eliminating incremental reallocations

// Before — unbounded, all futures in flight at once
futures::future::try_join_all(delete_futures).await?;

// After — at most COMPONENT_CONCURRENCY_LIMIT concurrent ops
futures::stream::iter(delete_futures)
    .buffer_unordered(COMPONENT_CONCURRENCY_LIMIT)
    .try_collect::<Vec<_>>()
    .await?;

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	recoco-docs	8ee551b	Commit Preview URL Branch Preview URL	Mar 13 2026, 03:36 AM

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[Copilot]

Pull request overview

This PR bounds concurrency for component delete/upsert operations and reduces allocation churn when applying many component changes.

Changes:

• Replace unbounded try_join_all with buffer_unordered(COMPONENT_CONCURRENCY_LIMIT) to cap in-flight operations.
• Introduce COMPONENT_CONCURRENCY_LIMIT constant (16) with documentation.
• Pre-allocate the futures vectors using upfront totals to avoid repeated reallocations.

Comments suppressed due to low confidence (1)

crates/recoco-core/src/setup/components.rs:1

• buffer_unordered bounds execution, but this still eagerly allocates and builds a Vec containing all delete/upsert futures up front, and then try_collect::<Vec<_>>() allocates a second Vec of results that is immediately discarded. For large change sets, this can be a significant memory spike and delays starting IO until the vectors are fully built. Consider switching to a lazy stream + try_for_each_concurrent(COMPONENT_CONCURRENCY_LIMIT, ...) (and ideally avoid the intermediate Vec entirely by streaming over keys/states directly) so work starts immediately and no result vector is allocated.

// Recoco is a Rust-only fork of CocoIndex, by [CocoIndex](https://CocoIndex)

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