Share FreeSpaceIndex in single-file mode and make insert-side FSI updates rollback-safe

[Copilot]

• Inspect the review thread referenced in the new PR comment
• Update FreeSpaceIndex.EnterGate() to use fully synchronous gate acquisition
• Run targeted build/tests for the FreeSpaceIndex change
• Reply to the new PR comment with the fixing commit hash
• Run final validation for the updated change

[mrdevrobot]

Please review comments there is a missing else statement that will break the compilation

[Copilot]

Please review comments there is a missing else statement that will break the compilation

I reviewed the referenced FreeSpaceIndex.cs block and rebuilt BLite.Core for both target frameworks; the current branch compiles cleanly. I only see the ambiguous block already discussed on the line comment, so if there’s another exact snippet you want changed, point me to it and I’ll patch it.

[Copilot]

Pull request overview

This PR updates free-space tracking so that (1) FreeSpaceIndex instances are shared across collections/sessions in single-file (embedded) mode, and (2) insert-side FreeSpaceIndex updates are made rollback-safe via per-transaction snapshots and rollback/commit hooks.

Changes:

• Introduces FreeSpaceIndexProvider to supply a shared FSI in single-file mode and per-collection FSIs in multi-file mode.
• Adds per-transaction snapshot/rollback/commit handling to FreeSpaceIndex, and wires snapshotting into insert/allocation paths in DocumentCollection and DynamicCollection.
• Adds regression tests covering FSI sharing and rollback behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/BLite.Tests/FreeSpaceIndexTests.cs	Adds unit tests validating snapshot + rollback behavior in FreeSpaceIndex.
tests/BLite.Tests/DocumentCollectionTests.cs	Adds regression tests for shared FSI behavior and rollback-safe inserts.
src/BLite.Core/Storage/StorageEngine.cs	Exposes UsesSeparateCollectionFiles to let higher layers choose FSI sharing strategy.
src/BLite.Core/DynamicCollection.cs	Allows injecting an FSI and snapshots FSI changes for rollback/commit around insert/allocation.
src/BLite.Core/DocumentDbContext.cs	Creates and reuses FreeSpaceIndexProvider; passes FSIs into collections/sessions.
src/BLite.Core/Collections/FreeSpaceIndexProvider.cs	New provider that shares an FSI in single-file mode (and serializes access).
src/BLite.Core/Collections/FreeSpaceIndex.cs	Adds transaction snapshots and optional serialized access for shared use.
src/BLite.Core/Collections/DocumentCollection.cs	Allows injecting an FSI and snapshots FSI changes for rollback/commit across write paths.
src/BLite.Core/BLiteSession.cs	Plumbs FreeSpaceIndexProvider into session-created dynamic collections.
src/BLite.Core/BLiteEngine.cs	Owns FreeSpaceIndexProvider and shares it with sessions/collections.

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[mrdevrobot]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied the review-thread change in a95514c: FreeSpaceIndex.EnterGate() now uses synchronous SemaphoreSlim.Wait() instead of blocking on WaitAsync(...).GetResult(). Targeted build plus the FreeSpaceIndex test slice are passing on this commit.