fix: terminate backends before dropping databases and close pg-cache pools in codegen

- safeDropDb now catches 'is being accessed by other users' errors,
  terminates backends via pg_terminate_backend, and retries the drop
- PgpmModuleSchemaSource.fetch() now releases pg-cache pool for the
  ephemeral database before calling teardown
- generateMulti() shared PGPM source teardown now releases pg-cache
  pools before dropping ephemeral databases

These changes fix the systemic issue where dropdb fails because
deployPgpm() and getPgPool() cache connections in pg-cache that
are not closed before the database is dropped.

Author: pyramation

graphql/codegen/src/core/generate.ts

@@ -10,6 +10,7 @@ import path from 'node:path';
 import { buildClientSchema, printSchema } from 'graphql';
 
 import { PgpmPackage } from '@pgpmjs/core';
+import { pgCache } from 'pg-cache';
 import { createEphemeralDb, type EphemeralDbResult } from 'pgsql-client';
 import { deployPgpm } from 'pgsql-seed';
 
@@ -840,6 +841,10 @@ export async function generateMulti(
   } finally {
     for (const shared of sharedSources.values()) {
       const keepDb = Object.values(configs).some((c) => c.db?.keepDb);
+      // Release pg-cache pool for this ephemeral database before dropping
+      // deployPgpm() caches connections that must be closed first
+      pgCache.delete(shared.ephemeralDb.config.database);
+      await pgCache.waitForDisposals();
       shared.ephemeralDb.teardown({ keepDb });
     }
   }

graphql/codegen/src/core/introspect/source/pgpm-module.ts

@@ -9,7 +9,7 @@
  */
 import { PgpmPackage } from '@pgpmjs/core';
 import { buildSchema, introspectionFromSchema } from 'graphql';
-import { getPgPool } from 'pg-cache';
+import { getPgPool, pgCache } from 'pg-cache';
 import { createEphemeralDb, type EphemeralDbResult } from 'pgsql-client';
 import { deployPgpm } from 'pgsql-seed';
 
@@ -251,6 +251,11 @@ export class PgpmModuleSchemaSource implements SchemaSource {
 
       return { introspection };
     } finally {
+      // Release pg-cache pool for this ephemeral database before dropping
+      // deployPgpm() and getPgPool() cache connections that must be closed first
+      pgCache.delete(dbConfig.database);
+      await pgCache.waitForDisposals();
+
       // Clean up the ephemeral database
       teardown({ keepDb });
 

postgres/pgsql-client/src/admin.ts

@@ -58,9 +58,22 @@ export class DbAdmin {
     try {
       this.run(`dropdb "${name}"`);
     } catch (err: any) {
-      if (!err.message.includes('does not exist')) {
-        log.warn(`Could not drop database ${name}: ${err.message}`);
+      if (err.message.includes('does not exist')) {
+        return;
       }
+      if (err.message.includes('is being accessed by other users')) {
+        log.warn(`Database ${name} has active sessions, terminating backends and retrying drop...`);
+        try {
+          this.run(
+            `psql -c "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = '${name}' AND pid <> pg_backend_pid();"`
+          );
+          this.run(`dropdb "${name}"`);
+        } catch (retryErr: any) {
+          log.warn(`Could not drop database ${name} after terminating backends: ${retryErr.message}`);
+        }
+        return;
+      }
+      log.warn(`Could not drop database ${name}: ${err.message}`);
     }
   }