Add concurrent role creation test demonstrating race condition (intentionally fails on main)

[pyramation]

Add concurrent role creation test (reproduces unique_violation bug)

Summary

This PR adds a comprehensive test suite that intentionally demonstrates the race condition in concurrent PostgreSQL role creation on the main branch. The test should FAIL on main and PASS on the fix branches (PR #325 and PR #326).

Key Changes:

• New test file: packages/pgsql-test/__tests__/postgres-test.concurrent-roles.test.ts
• Four test cases covering different concurrency scenarios
• Performance benchmarks measuring latency at concurrency levels 2, 4, and 8

The Bug Being Demonstrated:
When multiple processes attempt to create the same PostgreSQL role simultaneously, the current code only catches duplicate_object exceptions. However, under concurrency, the actual error is unique_violation (error code 23505) when both sessions race to insert into pg_authid and hit the pg_authid_rolname_index unique constraint.

Test Cases:

1. Concurrent role creation - Reproduces the bug (should FAIL on main)
2. Performance benchmarks - Measures latency with both exceptions caught (informational)
3. Concurrent GRANT operations - Tests role membership grants under concurrency
4. High concurrency stress test - Tests 10 roles × 3 concurrent attempts each with retries

Review & Testing Checklist for Human

CRITICAL - This PR is expected to FAIL on main branch:

• Verify the first test case (should handle concurrent role creation without errors) actually FAILS on main with a unique_violation error
• Run the performance benchmark test and note the latency results for comparison with fix PRs
• Cherry-pick or merge this test onto PR Fix concurrent role creation race condition #325 branch and verify it PASSES
• Cherry-pick or merge this test onto PR Fix concurrent role creation with exception handling only (no advisory locks) #326 branch and verify it PASSES
• Review the test for potential flakiness - concurrent tests can be timing-dependent

Test Plan:

# On main branch (should fail):
cd packages/pgsql-test
pnpm test postgres-test.concurrent-roles.test.ts

# Expected: First test fails with unique_violation error
# Expected: Performance benchmark completes and prints latency stats

# On PR #325 or #326 branches (should pass):
git checkout devin/1763429451-fix-concurrent-role-creation  # or PR #326 branch
cd packages/pgsql-test
pnpm test postgres-test.concurrent-roles.test.ts

# Expected: All tests pass

Notes

Related PRs:

• PR Fix concurrent role creation race condition #325: Fix with advisory locks + pre-checks + both exceptions
• PR Fix concurrent role creation with exception handling only (no advisory locks) #326: Fix with pre-checks + both exceptions (no locks)

Why this test is valuable:

• Provides reproducible demonstration of the concurrency bug
• Establishes performance baseline for comparing lock vs no-lock approaches
• Can be used for regression testing to ensure the fix works

Potential Issues:

• Test may be flaky due to timing - concurrent operations might not always race
• If test infrastructure doesn't support high concurrency, the bug might not reproduce consistently
• Database cleanup could fail if tests are interrupted

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Session Info:

• Devin Session: https://app.devin.ai/sessions/2c33cab4511f4a7897e29001895487df
• Requested by: Dan Lynch (pyramation@gmail.com) / @pyramation

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[devin-ai-integration]

Related PRs

This PR demonstrates the concurrent role creation race condition that is fixed by:

• PR Fix concurrent role creation race condition #325 (with advisory locks): Fix concurrent role creation race condition #325
• PR Fix concurrent role creation with exception handling only (no advisory locks) #326 (no locks, exceptions only): Fix concurrent role creation with exception handling only (no advisory locks) #326

Note: This test is expected to FAIL on the main branch to demonstrate the bug. It should PASS when applied to either PR #325 or PR #326.

Performance Comparison

The test includes performance benchmarks at concurrency levels 2, 4, and 8 to measure the performance impact of the lock-based vs exceptions-only approaches.

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Link to Devin run: https://app.devin.ai/sessions/2c33cab4511f4a7897e29001895487df
Requested by: Dan Lynch (pyramation@gmail.com) / @pyramation