feat: Improve migration

[Weves]

Description

[Provide a brief description of the changes in this PR]

How Has This Been Tested?

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Summary by cubic

Merge Prompt into Persona and raise prompt size limits to 5,000,000 characters. This simplifies the schema and supports very large prompts.

• Migration

  • Merge Prompt into Persona; drop prompt and persona__prompt tables; remove chat_message.prompt_id.
  • Move prompt data to persona; set defaults for missing values; orphan prompts are discarded.

• Refactors

  • Increase system_prompt/task_prompt limit to 5,000,000 and align models with a PROMPT_LENGTH constant.

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Project	Deployment	Preview	Comments	Updated (UTC)
internal-search	Ready	Preview	Comment	Sep 11, 2025 2:12am

[greptile-apps]

Greptile Summary

This PR improves database migrations by consolidating prompt-related functionality and fixing prompt length limits. The changes include three main components:

1. Model Updates: The models.py file introduces a PROMPT_LENGTH constant set to 5,000,000 characters and updates the Persona model's system_prompt and task_prompt fields to use this new limit, replacing the previous 8,000 character restriction.

2. Schema Consolidation: The existing migration abbfec3a5ac5_merge_prompt_into_persona.py is significantly improved to merge the separate prompt table into the persona table, eliminating complex many-to-many relationships. This migration removes defensive existence checks for a cleaner execution and migrates existing prompt data directly into persona records.

3. Follow-up Migration: A new migration b7ec9b5b505f_adjust_prompt_length.py is added to specifically handle the prompt length adjustment from 8,000 to 5,000,000 characters in the persona table.

These changes align with simplifying the database architecture by removing unnecessary abstraction layers. Previously, personas could have multiple prompts through a junction table, but this complexity was eliminated since personas typically use a single prompt. The massive increase in prompt length (from 8K to 5M characters) enables support for much more detailed system instructions and complex AI prompts. The migrations work together to first consolidate the schema, then adjust the length limits to match the new model definitions.

Confidence score: 1/5

• This PR has critical issues that will cause migration failures and should not be merged without fixes
• Score reflects a serious table name bug in the new migration's downgrade function that references a non-existent table
• Pay close attention to b7ec9b5b505f_adjust_prompt_length.py which has incorrect table references in the downgrade function

_{3 files reviewed, 2 comments}

_{Edit Code Review Bot Settings | Greptile}

[greptile-apps]

logic: Tables may not exist in all environments - could cause migration failures

[cubic-dev-ai]

2 issues found across 3 files

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