diff --git a/lib/Db/AbstractDriver.php b/lib/Db/AbstractDriver.php
index 45b9476..814159e 100644
--- a/lib/Db/AbstractDriver.php
+++ b/lib/Db/AbstractDriver.php
@@ -78,50 +78,63 @@ abstract class AbstractDriver implements Driver {
     }
 
     public function savepointCreate(bool $lock = false): int {
+        // if no transaction is active and a lock was requested, lock the database using a backend-specific routine
         if ($lock && !$this->transDepth) {
             $this->lock();
             $this->locked = true;
         }
+        // create a savepoint, incrementing the transaction depth
         $this->exec("SAVEPOINT arsse_".(++$this->transDepth));
+        // set the state of the newly created savepoint to pending
         $this->transStatus[$this->transDepth] = self::TR_PEND;
+        // return the depth number
         return $this->transDepth;
     }
 
     public function savepointRelease(int $index = null): bool {
+        // assume the most recent savepoint if none was specified
         $index = $index ?? $this->transDepth;
         if (array_key_exists($index, $this->transStatus)) {
             switch ($this->transStatus[$index]) {
                 case self::TR_PEND:
+                    // release the requested savepoint and set its state to committed
                     $this->exec("RELEASE SAVEPOINT arsse_".$index);
                     $this->transStatus[$index] = self::TR_COMMIT;
+                    // for any later pending savepoints, set their state to implicitly committed
                     $a = $index;
                     while (++$a && $a <= $this->transDepth) {
                         if ($this->transStatus[$a] <= self::TR_PEND) {
                             $this->transStatus[$a] = self::TR_PEND_COMMIT;
                         }
                     }
+                    // return success
                     $out = true;
                     break;
                 case self::TR_PEND_COMMIT:
+                    // set the state to explicitly committed
                     $this->transStatus[$index] = self::TR_COMMIT;
                     $out = true;
                     break;
                 case self::TR_PEND_ROLLBACK:
+                    // set the state to explicitly committed
                     $this->transStatus[$index] = self::TR_COMMIT;
                     $out = false;
                     break;
                 case self::TR_COMMIT:
                 case self::TR_ROLLBACK: //@codeCoverageIgnore
+                    // savepoint has already been released or rolled back; this is an error
                     throw new Exception("savepointStale", ['action' => "commit", 'index' => $index]);
                 default:
                     throw new Exception("savepointStatusUnknown", $this->transStatus[$index]); // @codeCoverageIgnore
             }
             if ($index==$this->transDepth) {
+                // if we've released the topmost savepoint, clean up all prior savepoints which have already been explicitly committed (or rolled back), if any
                 while ($this->transDepth > 0 && $this->transStatus[$this->transDepth] > self::TR_PEND) {
                     array_pop($this->transStatus);
                     $this->transDepth--;
                 }
             }
+            // if no savepoints are pending and the database was locked, unlock it
             if (!$this->transDepth && $this->locked) {
                 $this->unlock();
                 $this->locked = false;
diff --git a/lib/Db/PostgreSQL/Driver.php b/lib/Db/PostgreSQL/Driver.php
index 5e9f637..be8e40e 100644
--- a/lib/Db/PostgreSQL/Driver.php
+++ b/lib/Db/PostgreSQL/Driver.php
@@ -13,6 +13,8 @@ use JKingWeb\Arsse\Db\ExceptionInput;
 use JKingWeb\Arsse\Db\ExceptionTimeout;
 
 class Driver extends \JKingWeb\Arsse\Db\AbstractDriver {
+    protected $transStart = 0;
+
     public function __construct(string $user = null, string $pass = null, string $db = null, string $host = null, int $port = null, string $schema = null, string $service = null) {
         // check to make sure required extension is loaded
         if (!static::requirementsMet()) {
@@ -104,37 +106,44 @@ class Driver extends \JKingWeb\Arsse\Db\AbstractDriver {
     }
 
     public function savepointCreate(bool $lock = false): int {
-        if (!$this->transDepth) {
+        if (!$this->transStart) {
             $this->exec("BEGIN TRANSACTION");
+            $this->transStart = parent::savepointCreate($lock);
+            return $this->transStart;
+        } else {
+            return parent::savepointCreate($lock);
         }
-        return parent::savepointCreate($lock);
     }
 
     public function savepointRelease(int $index = null): bool {
-        $out = parent::savepointUndo($index);
-        if ($out && !$this->transDepth) {
-            $this->exec("COMMIT TRANSACTION");
+        $index = $index ?? $this->transDepth;
+        $out = parent::savepointRelease($index);
+        if ($index == $this->transStart) {
+            $this->exec("COMMIT");
+            $this->transStart = 0;
         }
         return $out;
     }
 
     public function savepointUndo(int $index = null): bool {
+        $index = $index ?? $this->transDepth;
         $out = parent::savepointUndo($index);
-        if ($out && !$this->transDepth) {
-            $this->exec("ROLLBACK TRANSACTION");
+        if ($index == $this->transStart) {
+            $this->exec("ROLLBACK");
+            $this->transStart = 0;
         }
         return $out;
     }
 
     protected function lock(): bool {
-        if ($this->schemaVersion()) {
+        if ($this->query("SELECT count(*) from information_schema.tables where table_schema = current_schema() and table_name = 'arsse_meta'")->getValue()) {
             $this->exec("LOCK TABLE arsse_meta IN EXCLUSIVE MODE NOWAIT");
         }
         return true;
     }
 
     protected function unlock(bool $rollback = false): bool {
-        $this->exec((!$rollback) ? "COMMIT" : "ROLLBACK");
+        // do nothing; transaction is committed or rolled back later
         return true;
     }
 
diff --git a/tests/cases/Db/BaseDriver.php b/tests/cases/Db/BaseDriver.php
index e918fa9..87f2d17 100644
--- a/tests/cases/Db/BaseDriver.php
+++ b/tests/cases/Db/BaseDriver.php
@@ -375,7 +375,7 @@ abstract class BaseDriver extends \JKingWeb\Arsse\Test\AbstractTest {
         // so the effect is usually the same
         $this->drv->savepointCreate(true);
         $this->assertException();
-        $this->exec(str_replace("#", "3", $this->setVersion));
+        $this->exec($this->lock);
     }
 
     public function testUnlockTheDatabase() {
diff --git a/tests/cases/Db/PostgreSQL/TestDriver.php b/tests/cases/Db/PostgreSQL/TestDriver.php
index 63e73c6..ae4c4b2 100644
--- a/tests/cases/Db/PostgreSQL/TestDriver.php
+++ b/tests/cases/Db/PostgreSQL/TestDriver.php
@@ -13,6 +13,14 @@ namespace JKingWeb\Arsse\TestCase\Db\PostgreSQL;
 class TestDriver extends \JKingWeb\Arsse\TestCase\Db\BaseDriver {
     protected static $implementation = "PDO PostgreSQL";
     protected $create = "CREATE TABLE arsse_test(id bigserial primary key)";
-    protected $lock = ["BEGIN", "LOCK TABLE arsse_test IN EXCLUSIVE MODE NOWAIT"];
+    protected $lock = ["BEGIN", "LOCK TABLE arsse_meta IN EXCLUSIVE MODE NOWAIT"];
     protected $setVersion = "UPDATE arsse_meta set value = '#' where key = 'schema_version'";
+
+    public function tearDown() {
+        try {
+            $this->drv->exec("ROLLBACK");
+        } catch (\Throwable $e) {
+        }
+        parent::tearDown();
+    }
 }
diff --git a/tests/lib/DatabaseInformation.php b/tests/lib/DatabaseInformation.php
index 0ec4d1d..01cc444 100644
--- a/tests/lib/DatabaseInformation.php
+++ b/tests/lib/DatabaseInformation.php
@@ -197,9 +197,13 @@ class DatabaseInformation {
                     }
                 },
                 'razeFunction' => function($db, array $afterStatements = []) use ($pgObjectList) {
+                    // rollback any pending transaction
+                    try {
+                        $db->exec("ROLLBACK");
+                    } catch(\Throwable $e) {
+                    }
                     foreach ($pgObjectList($db) as $obj) {
                         $db->exec("DROP {$obj['type']} IF EXISTS {$obj['name']} cascade");
-                        
                     }
                     foreach ($afterStatements as $st) {
                         $db->exec($st);
diff --git a/tests/phpunit.xml b/tests/phpunit.xml
index 343f381..06b3d6a 100644
--- a/tests/phpunit.xml
+++ b/tests/phpunit.xml
@@ -60,7 +60,7 @@
 
         <file>cases/Db/PostgreSQL/TestStatement.php</file>
         <file>cases/Db/PostgreSQL/TestCreation.php</file>
-    <!--<file>cases/Db/PostgreSQL/TestDriver.php</file>-->
+        <file>cases/Db/PostgreSQL/TestDriver.php</file>
     <!--<file>cases/Db/PostgreSQL/TestUpdate.php</file>-->
     </testsuite>
     <testsuite name="Database functions">