Fix PQ file path canonicalization and migrate legacy PQ files

[tae898]

Problem
PQ files could be written/read using shortened base paths, leaving legacy PQ artifacts in non-canonical locations and risking missing PQ data on load. Issue (#3161)

Changes

• Use the mutable component file path as the canonical PQ base for both create and load paths.
• Add a migration helper that detects legacy PQ paths, creates parent directories if needed, moves the PQ file to the canonical location, and logs success/failure LSMVectorIndex.java.
• Import required file I/O utilities for the migration LSMVectorIndex.java.

Testing

• Tested and now it correctly locates the path.

[gemini-code-assist]

Summary of Changes

Hello @tae898, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical issue where Product Quantization (PQ) files could be stored or accessed using non-canonical, shortened file paths, potentially leading to data loss or incorrect loading. The changes introduce a robust system to enforce canonical paths for all PQ file operations and include an automatic migration utility to relocate any existing legacy PQ files to their correct, canonical locations, ensuring data integrity and consistent behavior.

Highlights

• Canonical PQ File Paths: Ensured that Product Quantization (PQ) files are consistently created and loaded using their canonical file paths, preventing issues arising from shortened or inconsistent base paths.
• Legacy PQ File Migration: Implemented a migration mechanism that automatically detects and moves existing legacy PQ files from their old, non-canonical locations to the new, canonical paths upon index loading. This includes creating necessary parent directories.
• Improved Data Robustness: Enhanced the system's ability to correctly locate and load PQ data, reducing the risk of missing data due to previous path inconsistencies.

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[gemini-code-assist]

Code Review

This pull request introduces a fix for Product Quantization (PQ) file path canonicalization and adds a migration path for legacy PQ files. The changes ensure that PQ files are consistently read from and written to a canonical path derived from the mutable component file path. A new private method, createPQFileWithFallback, handles the logic for finding and migrating legacy PQ files to their new canonical location. The implementation is solid, but I have a few suggestions to improve robustness and clarity in the new migration logic.

[gemini-code-assist]

The current logic for deriving the legacy base path using primaryBasePath.indexOf('.') is fragile. It can fail if the database path itself contains a dot (e.g., /path/to/db.v1/). A more robust approach would be to find the dot within the filename part of the path, after the last file separator.

Suggested change

	final int dot = primaryBasePath.indexOf('.');
	if (dot > 0) {
	legacyBasePath = primaryBasePath.substring(0, dot);
	}
	final int lastSeparator = primaryBasePath.lastIndexOf(File.separator);
	final int dot = primaryBasePath.indexOf('.', lastSeparator > -1 ? lastSeparator + 1 : 0);
	if (dot > -1) {
	legacyBasePath = primaryBasePath.substring(0, dot);
	}

[gemini-code-assist]

The code checks if the canonical PQ file exists with !pq.exists() before attempting to move the legacy file. Therefore, using StandardCopyOption.REPLACE_EXISTING is redundant and could mask a potential race condition. Removing it would allow Files.move to fail with a FileAlreadyExistsException if the file is created concurrently, which would provide a clearer signal of an underlying issue.

Suggested change

	Files.move(legacyPQ.getFilePath(), pq.getFilePath(), StandardCopyOption.REPLACE_EXISTING);
	Files.move(legacyPQ.getFilePath(), pq.getFilePath());

[gemini-code-assist]

Catching the generic Exception is too broad and can hide RuntimeExceptions that might indicate bugs. It's better practice to catch more specific exceptions related to file operations, such as IOException and SecurityException, to make the error handling more precise and intentional.

Suggested change

	} catch (final Exception e) {
	} catch (final IOException | SecurityException e) {

[tae898]

@lvca

could you take a look at this? thanks!