Save and Load Index from Disk

[OmarMGaber]

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Description

Add support to save the current in-memory index to disk and reload it automatically when the engine starts. This avoids rebuilding the index every time the system restarts.

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Why

• Currently, the index exists only in memory and is lost on terminating.
• Re-indexing on every startup is totaly inefficient, especially for large datasets.

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What to Add

• A function to serialize and save the index to disk (e.g., using Go’s encoding/gob).
• A function to load the index from disk on startup if exists.
• Automatically call load/save during startup/shutdown of the engine.

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Example

//                    load/save index path
engine := engine.NewEngine(......, "index.gob")
err := engine.SaveIndex()
err := engine.LoadIndex()

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