Fix tags table missing PRIMARY KEY causing duplicate tag display

[compscidr]

Summary

Root cause: The tags table on staging was created by an older GORM migration without a PRIMARY KEY:

-- Actual (broken): no constraint, allows duplicates
CREATE TABLE "tags" ("name" varchar(255))

-- Expected: unique names enforced
CREATE TABLE "tags" ("name" varchar(255) PRIMARY KEY)

This allowed duplicate rows (e.g. 14 rows for "android"). GORM's Preload("Tags") JOINs through post_tags → tags, returning all matching tag rows per join entry, so posts displayed duplicated tags.

Staging data: 610 total tag rows, only 545 unique — 65 duplicates.

Fixes

• Add fixTagsTable migration that detects the missing PK, deduplicates with INSERT OR IGNORE INTO tags_new SELECT DISTINCT name FROM tags, and rebuilds with a proper PRIMARY KEY
• Reload UpdatePost response into a fresh Post struct to prevent GORM from appending preloaded tags to the existing slice

Verified against staging DB copy

• Before: post 113 returned 20 tags (3 unique × duplicates)
• After: post 113 returns exactly 3 tags

Test plan

• All existing tests pass
• Verified fix against staging DB copy
• Deploy and confirm tags display correctly on staging

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR improves data integrity and API correctness around tags and post updates by adding a SQLite migration repair for legacy tags schemas and by preventing GORM from accumulating duplicated slice associations in the admin update response.

Changes:

• Add a SQLite-only migration step to rebuild tags with name as a PRIMARY KEY and deduplicate existing rows when the table lacks a PK.
• Update Admin.UpdatePost to reload the updated post into a fresh struct before returning JSON (avoids GORM appending to existing slices).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
tools/migrate.go	Adds fixTagsTable migration helper and invokes it during Migrate() to repair legacy tags schemas missing a primary key.
admin/admin.go	Reloads the updated post into a new struct before computing backlinks and returning the JSON response.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.