fix: block UPDATE of the partition column on a tiered view (#20)

[vyruss]

An UPDATE that changes the partition column (ts) could move a row across the hot/cold cutoff; the in-place rewrite left it in its old tier where the view's tier predicate then hid it, silently losing the row (#20). Block such updates with a clear error for now; relocating the row across tiers is a separate follow-up.

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ℹ️ Recent review info

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Run ID: 49d93844-6758-4d9f-80d8-6070ce82ba44

📥 Commits

Reviewing files that changed from the base of the PR and between 88cfdb2 and 111cd8e.

⛔ Files ignored due to path filters (1)

• extension/coldfront/test/expected/update_partition_key_blocked.out is excluded by !**/*.out

📒 Files selected for processing (5)

• .gitignore
• docs/architecture_tiered.md
• extension/coldfront/Makefile
• extension/coldfront/src/coldfront.c
• extension/coldfront/test/sql/update_partition_key_blocked.sql

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📝 Walkthrough

Walkthrough

A new guard function cf_reject_partition_col_update() is introduced in coldfront.c and hooked into cf_dispatch_emit(). It scans a query's targetList and raises FEATURE_NOT_SUPPORTED when an UPDATE on a tiered view attempts to assign the partition column, regardless of coldfront.allow_mixed_writes. A full SQL regression test, Makefile entry, and architecture documentation update accompany the change.

Changes

Partition column UPDATE rejection

Layer / File(s)	Summary
cf_reject_partition_col_update() implementation and dispatch hook extension/coldfront/src/coldfront.c	Adds cf_reject_partition_col_update() which iterates the query targetList and raises FEATURE_NOT_SUPPORTED for any non-junk assignment targeting the partition column. Calls this function from cf_dispatch_emit() before tier classification begins.
Regression test, Makefile, docs, and .gitignore extension/coldfront/test/sql/update_partition_key_blocked.sql, extension/coldfront/Makefile, docs/architecture_tiered.md, .gitignore	Adds a 60-line SQL test validating blocked (hot→cold, cold→hot, constant, per-row, tier-deterministic WHERE) and allowed (non-partition-column) UPDATE cases under both allow_mixed_writes modes. Registers the test in REGRESS, extends architecture docs with the SET-clause restriction and delete+reinsert workflow, and excludes CROSS_TIER_MOVE_DESIGN.md from version control.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title accurately describes the main change: blocking UPDATE operations on the partition column of a tiered view, which directly addresses issue #20.
Description check	✅ Passed	The description clearly explains the problem (silent row loss when partition column is updated), the solution (blocking such updates), and references issue #20, all of which align with the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/issue-20-block-partition-key-update

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🟢 Metrics 5 complexity · 0 duplication

Metric	Results
Complexity	5
Duplication	0

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