PayoutsService getRevenueBreakdown issues N+1 queries without pagination

[RUKAYAT-CODER]

Overview

src/payments/payouts/payouts.service.ts loads all courses for an instructor, then all payments for all course IDs, then all refunds for all payment IDs — three sequential queries that load entire datasets into memory. An instructor with thousands of sales will cause OOM and slow API responses.

Specifications

Features:

• Use a single aggregation query (or at most two) to compute revenue breakdown.
• Support pagination so large result sets are streamed in pages.

Tasks:

• Replace separate find() calls with a TypeORM QueryBuilder that joins Course → Payment → Refund and uses SUM/GROUP BY.
• Accept page and limit parameters and apply OFFSET/LIMIT to the course list.
• Add a database index on payments.courseId and refunds.paymentId if not already present.
• Benchmark before and after with 10k payments.

Impacted Files:

• src/payments/payouts/payouts.service.ts

Acceptance Criteria

• Revenue breakdown for 10k payments returns in under 200ms.
• Memory usage during the call does not scale with dataset size.
• Results are identical to the current output (verified by unit test).

[RemmyAcee]

@RemmyAcee has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I've checked the requirements and am confident I can resolve this efficiently. Happy to take it on.

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[amankoli09]

@amankoli09 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi there, can I work on this issue?

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[GiftedGiftB]

@GiftedGiftB has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I can get this done in less than 30 minutes , just finished one of your task.

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[lekanay2005-coder]

@lekanay2005-coder has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

pls i will like to work on it

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[larryjay007]

@larryjay007 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, i would love to work on this issue.

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