fix(migrations): actually drop _customer_location_uc (list == set no-op)

[mikebridge]

SUMMARY

Migration df3d7e2eb9a4 (2024) intended to drop the legacy 3-column unique constraint _customer_location_uc (database_id, schema, table_name) from tables, but passed a list to generic_find_uq_constraint_name, whose body compares columns == set(uq["column_names"]). list == set is always False in Python, so the constraint was never found and never dropped — a silent no-op.

Consequences on databases migrated through it:

• The NULL-leaky 3-column constraint (no catalog leg) is still present, while schemas built from model metadata (create_all, e.g. CI) carry the model's intended 4-column constraint (database_id, catalog, schema, table_name) instead — so CI cannot reproduce production failure shapes.
• A row keeps occupying (database_id, schema, table_name) across catalogs: creating the same table under a different catalog passes every catalog-aware app-level check and then hits an opaque IntegrityError only on migrated databases.

Two-part fix:

1. generic_find_uq_constraint_name now coerces its columns argument to a set (parameter widened to Collection[str]), removing the foot-gun for all callers. Existing set-passing callers are unaffected.
2. A take-2 migration (16755d4ca4ae) re-attempts the drop with exact set matching. It is a harmless no-op where the constraint is already absent, and the model's 4-column constraint can never match a 3-column set comparison, so it is not at risk. Downgrade restores the legacy constraint best-effort (rows written after the drop may legitimately collide across catalogs), mirroring the tolerant try/except posture of the constraint's original creator.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A — schema-only change.

TESTING INSTRUCTIONS

1. pytest tests/unit_tests/utils/test_core.py -k generic_find_uq — 3 tests: the list-argument regression pin (fails against the pre-fix helper), the set-argument happy path, and the exact-match guarantee (a 3-column lookup never matches the model's 4-column constraint).
2. Migration verified on SQLite and PostgreSQL: fresh full-chain superset db upgrade (clean), then superset db downgrade (constraint recreated: _customer_location_uc (database_id, schema, table_name)), then superset db upgrade (constraint dropped), with uq_tables_uuid untouched throughout. On a database that still carries the legacy constraint, the upgrade drops it; on one that never had it, the lookup finds nothing and the migration no-ops.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided: single ALTER TABLE ... DROP CONSTRAINT on tables (or a no-op lookup); sub-second on PostgreSQL/MySQL, table-rebuild via batch mode on SQLite. No data movement, no downtime expected.
• Introduces new feature or API
• Removes existing feature or API

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.44%. Comparing base (7d2b184) to head (01ee065).

Files with missing lines	Patch %	Lines
superset/utils/core.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #42642      +/-   ##
==========================================
- Coverage   65.44%   65.44%   -0.01%     
==========================================
  Files        2810     2810              
  Lines      159362   159363       +1     
  Branches    36372    36372              
==========================================
- Hits       104301   104298       -3     
- Misses      53019    53022       +3     
- Partials     2042     2043       +1     

Flag	Coverage Δ
hive	38.09% <33.33%> (-0.01%)	⬇️
mysql	57.82% <33.33%> (-0.01%)	⬇️
postgres	57.86% <33.33%> (-0.01%)	⬇️
presto	39.98% <33.33%> (-0.01%)	⬇️
python	59.25% <33.33%> (-0.01%)	⬇️
sqlite	57.49% <33.33%> (-0.01%)	⬇️
unit	100.00% <ø> (ø)

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