How would you import a large CSV or external dataset with EF Core without exhausting memory or creating duplicates?

Design a large EF Core import with change tracker control

Explains batching, tracking control, idempotency, validation, and operational safety for large EF Core imports.

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TL;DR

I would process the file in batches instead of loading everything into memory. Each row needs validation, normalization, and a stable identity such as an external id or natural key. EF Core can save batches with bounded SaveChanges calls, then clear the change tracker or use a fresh context per batch to avoid memory growth. The import needs a status record so users can see progress and failures.

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Batching, SaveChanges strategy, change tracker behavior, validation, idempotent keys, transactions, and progress.

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Imports are a strong real-world test because they combine database constraints, EF Core memory behavior, validation, progress, and retry safety.
I would process the file in batches instead of loading everything into memory. Each row needs validation, normalization, and a stable identity such as an external id or natural key. EF Core can save batches with bounded SaveChanges calls, then clear the change tracker or use a fresh context per batch to avoid memory growth. The import needs a status record so users can see progress and failures.
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I would make the import idempotent. Re-running the same file after a failure must not create duplicates, so I would use unique constraints and upsert-like logic where appropriate. I would decide the transaction boundary carefully: one transaction for the whole file can be too large, while one per row is slow and hard to recover. Batch-level transactions with checkpoints often give a better balance. Failed rows need clear reporting without losing the whole import unnecessarily.

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Details

Loading the entire file and all entities into one DbContext.
No stable key for detecting duplicate rows.
One huge transaction that locks too much for too long.
No progress, failure report, or retry strategy.

How would you import a large CSV or external dataset with EF Core without exhausting memory or creating duplicates?

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How would you import a large CSV or external dataset with EF Core without exhausting memory or creating duplicates?

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