perf: optimizing db WorkflowAppLog index

[horochx]

Summary

Currently, the primary slow queries in our database are originating from the get_paginate_workflow_app_logs method of the WorkflowAppService. I've noticed that there might be room for optimization in the index of the WorkflowAppLog table.

Consequently, I have added the most frequently used fields, created_at and workflow_run_id, to the index.

Close #14752

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Checklist

Important

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• This change requires a documentation update, included: Dify Document
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• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

Hello, please open an issue and link it in the description.

[horochx]

Hello, please open an issue and link it in the description.

I've created issue #14752 and attached the relevant SQL statements.

I was wondering if adding a partial index on WorkflowRun.status=failed might further optimize query performance. However, I wasn't certain whether this use case was generally applicable or just specific to my situation, so I didn't pursue it further.

[bowenliang123]

Reasonable to add field to the existed index workflow_app_log_app_idx and introduce new index with workflow_run_id for joining.

And please make sure all the DDL operations are applied by running flask db migrate to generation all the necessary changes in db migrations.

[horochx]

Reasonable to add field to the existed index workflow_app_log_app_idx and introduce new index with workflow_run_id for joining.

And please make sure all the DDL operations are applied by running flask db migrate to generation all the necessary changes in db migrations.

Thank you for your suggestion. The reason I haven't run flask db migrate yet is because when I tested it, I noticed there are still some pending model migrations in the main branch. I'm unsure if this is the intended behavior within Dify's development workflow, so I've left it as is for now 😂.

[laipz8200]

Can you provide a performance testing process for large-scale datasets? I would like to understand how significant the impact of this improvement can be. Thank you.