From f6b116abdcc92986d0a51b4a7e9f362fa95c5213 Mon Sep 17 00:00:00 2001
From: Christoph Kempen <christoph@downsized.nl>
Date: Thu, 27 Aug 2026 13:07:24 +0200
Subject: [PATCH] Tolerate deallocation of statements the server has already
 dropped

---
 src/Internal/PgSqlHandle.php     | 12 +++++++-
 src/Internal/PqHandle.php        |  9 +++++-
 test/StatementDeallocateTest.php | 51 ++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100644 test/StatementDeallocateTest.php

diff --git a/src/Internal/PgSqlHandle.php b/src/Internal/PgSqlHandle.php
index 022a09a..797be27 100644
--- a/src/Internal/PgSqlHandle.php
+++ b/src/Internal/PgSqlHandle.php
@@ -413,7 +413,17 @@ public function statementDeallocate(string $name): void
                 return; // Statement already deallocated.
             }
 
-            $this->query(\sprintf("DEALLOCATE %s", $name));
+            try {
+                // Send the DEALLOCATE without building a result object: an error result
+                // must not be processed through createResult(), whose fatal-error drain
+                // would consume results belonging to an operation dispatched after this
+                // one and leave that operation awaiting a response forever.
+                $this->send(\pg_send_query(...), \sprintf("DEALLOCATE %s", $name));
+            } catch (\Throwable) {
+                // Ignore failures: the server may have already dropped the statement,
+                // e.g. via the DISCARD ALL issued when the pool resets connections.
+            }
+
             unset($this->statements[$name]);
         });
         $storage->future->ignore();
diff --git a/src/Internal/PqHandle.php b/src/Internal/PqHandle.php
index a71f5bb..f46512d 100644
--- a/src/Internal/PqHandle.php
+++ b/src/Internal/PqHandle.php
@@ -338,9 +338,16 @@ public function statementDeallocate(string $name): void
                 return; // Statement already deallocated.
             }
 
-            $this->send(null, $statement->deallocateAsync(...));
+            try {
+                $this->send(null, $statement->deallocateAsync(...));
+            } catch (\Throwable) {
+                // Ignore failures: the server may have already dropped the statement,
+                // e.g. via the DISCARD ALL issued when the pool resets connections.
+            }
+
             unset($this->statements[$name]);
         });
+        $storage->future->ignore();
     }
 
     #[\Override]
diff --git a/test/StatementDeallocateTest.php b/test/StatementDeallocateTest.php
new file mode 100644
index 0000000..5c186cf
--- /dev/null
+++ b/test/StatementDeallocateTest.php
@@ -0,0 +1,51 @@
+<?php declare(strict_types=1);
+
+namespace Amp\Postgres\Test;
+
+use Amp\PHPUnit\AsyncTestCase;
+use Amp\Postgres\PostgresConfig;
+use Amp\Postgres\PostgresConnectionPool;
+use Revolt\EventLoop;
+
+/**
+ * @requires extension pgsql
+ */
+class StatementDeallocateTest extends AsyncTestCase
+{
+    public function testDeallocateRacingConnectionResetDoesNotBreakSubsequentOperations(): void
+    {
+        if (EventLoop::getDriver()->getHandle() instanceof \EvLoop) {
+            $this->markTestSkipped("ext-pgsql is not compatible with pecl-ev");
+        }
+
+        $this->setTimeout(5);
+
+        $pool = new PostgresConnectionPool(
+            PostgresConfig::fromString('host=localhost user=postgres password=postgres'),
+            1,
+        );
+
+        try {
+            $statement = $pool->prepare('SELECT 1 AS value');
+            $result = $statement->execute();
+            \iterator_to_array($result);
+
+            // Dropping the statement and result queues a DEALLOCATE for the prepared
+            // statement, while the pool's DISCARD ALL reset on the next checkout drops
+            // it server-side. The failing DEALLOCATE must not consume responses that
+            // belong to operations dispatched after it.
+            unset($result, $statement);
+
+            for ($i = 1; $i <= 3; ++$i) {
+                $rows = \iterator_to_array($pool->query(\sprintf('SELECT %d AS value', $i)));
+                self::assertSame($i, $rows[0]['value']);
+            }
+
+            $statement = $pool->prepare('SELECT 2 AS value');
+            $rows = \iterator_to_array($statement->execute());
+            self::assertSame(2, $rows[0]['value']);
+        } finally {
+            $pool->close();
+        }
+    }
+}