Summary

Fixes#28896

This PR fixes issue#28896 where$connect() succeeds even when PostgreSQL is stopped when using@prisma/adapter-pg. The root cause was thatpg.Pool uses lazy connection initialization, so creating a pool doesn't actually establish a database connection until the first query is executed.

Problem

Before this fix:

constadapter=newPrismaPgAdapterFactory(config)awaitprisma.$connect()// ✅ Succeeds even when PostgreSQL is offlineawaitprisma.user.findMany()// ❌ Fails here with connection error

Expected behavior:

constadapter=newPrismaPgAdapterFactory(config)awaitprisma.$connect()// ❌ Should fail immediately if database is unreachable

Root Cause

ThePrismaPgAdapterFactory.connect() method only instantiatednew pg.Pool(config) without validating the connection. Sincepg.Pool uses lazy connection initialization, no actual connection attempt occurred until the first query execution, causing$connect() to succeed even when the database was offline.

Solution

Added avalidateConnection() private method that executesSELECT 1 during theconnect() phase to validate the database is reachable:

privateasyncvalidateConnection(pool:pg.Pool):Promise<void>{consttag='[js::validateConnection]'try{// SELECT 1 is the lightest query (best for connection validation)awaitpool.query('SELECT 1')debug(`${tag} Connection validated successfully`)}catch(e){debug(`${tag} Connection failed: %O`,e)throwe}}

This method is called inconnect() before returning the adapter, ensuring that any connection errors are surfaced immediately during$connect() rather than being deferred to the first query.

Changes Made

packages/adapter-pg/src/pg.ts:

• AddedvalidateConnection() private method (lines 318-329)
• CallvalidateConnection() inconnect() before returning adapter (line 284)

packages/adapter-pg/src/__tests__/pg.test.ts:

• AddedgetTestConfig() helper to parse PostgreSQL connection URI from environment
• Refactored existing tests to use real PostgreSQL from Docker instead of mocks
• Added two regression tests for issue$connect() always succeeds in Prisma v7 using @prisma/adapter-pg even when DB is unreachable #28896:
  1. Test with unreachable database using reserved IP (192.0.2.1)
  2. Test with external pool that fails connection validation

Testing

Regression Tests:

it('should throw an error when database is unreachable during connect',async()=>{constconfig:pg.PoolConfig={user:'test',password:'test',database:'test',host:'192.0.2.1',// TEST-NET-1 - reserved for documentation, guaranteed to be unreachableport:54321,connectionTimeoutMillis:100,}constfactory=newPrismaPgAdapterFactory(config)awaitexpect(factory.connect()).rejects.toThrow()})it('should throw an error when database connection fails with external pool',async()=>{constmockPool=newpg.Pool({...})mockPool.query=vi.fn().mockRejectedValue(newError('Connection refused'))constfactory=newPrismaPgAdapterFactory(mockPool)awaitexpect(factory.connect()).rejects.toThrow('Connection refused')awaitmockPool.end()})

Test Requirements:

• Tests require Docker PostgreSQL to be running (postgres://prisma:prisma@localhost:5432/tests)
• Matches Prisma's CI/CD testing pattern
• Uses real database connections instead of mocks for integration testing

Behavior Changes

After this fix:

constadapter=newPrismaPgAdapterFactory(config)awaitprisma.$connect()// ❌ Now fails immediately if PostgreSQL is unreachable

This is the correct behavior and matches user expectations for connection validation.

Related Work

• Similar validation pattern exists in@prisma/adapter-mariadb which usesSELECT VERSION() for capability detection
• @prisma/adapter-neon has similar connection error handling tests

Breaking Changes

None. This is a bug fix that makes the behavior match documented expectations.

Additional Notes

The ECONNREFUSED error when Docker PostgreSQL is not running is expected and acceptable behavior - it confirms that the connection validation is working correctly and surfacing errors immediately during$connect() as intended.

Summary by CodeRabbit

• New Features

  • Added stronger connection validation and error handling during adapter initialization to ensure the database is reachable.

• Tests

  • Enhanced tests for connection failure scenarios, covering unreachable databases and simulated pool connection errors.

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