From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Sun, 27 Mar 2022 17:18:17 +0000 (+0200)
Subject: feat: add 'Pipeline.is_supported()'
X-Git-Tag: 3.1~146^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=86ec0eabcee0bde299435888c5976dbe9dde7151;p=thirdparty%2Fpsycopg.git

feat: add 'Pipeline.is_supported()'

This makes easier to write conditional code depending on whether we
support pipeline mode or not.
---

diff --git a/psycopg/psycopg/_pipeline.py b/psycopg/psycopg/_pipeline.py
index 429b2c75d..8a7456910 100644
--- a/psycopg/psycopg/_pipeline.py
+++ b/psycopg/psycopg/_pipeline.py
@@ -43,6 +43,7 @@ class BasePipeline:
 
     command_queue: Deque[PipelineCommand]
     result_queue: Deque[PendingResult]
+    _is_supported: Optional[bool] = None
 
     def __init__(self, conn: "BaseConnection[Any]") -> None:
         self._conn = conn
@@ -59,6 +60,16 @@ class BasePipeline:
         self.command_queue.append(self.pgconn.pipeline_sync)
         self.result_queue.append(None)
 
+    @staticmethod
+    def is_supported() -> bool:
+        """Return `True` if the psycopg libpq wrapper suports pipeline mode."""
+        if BasePipeline._is_supported is None:
+            # Support only depends on the libpq functions available in the pq
+            # wrapper, not on the database version.
+            pq_version = pq.__build_version__ or pq.version()
+            BasePipeline._is_supported = pq_version >= 140000
+        return BasePipeline._is_supported
+
     def _enter(self) -> None:
         self.pgconn.enter_pipeline_mode()
 
diff --git a/tests/pq/test_pq.py b/tests/pq/test_pq.py
index e859a122a..41e4b72a1 100644
--- a/tests/pq/test_pq.py
+++ b/tests/pq/test_pq.py
@@ -1,3 +1,4 @@
+import psycopg
 from psycopg import pq
 
 
@@ -14,3 +15,12 @@ def test_build_version():
         assert pq.__build_version__ and pq.__build_version__ >= 70400
     else:
         assert False, f"unexpected libpq implementation: {pq.__impl__}"
+
+
+def test_pipeline_supported():
+    # Note: This test is here because pipeline tests are skipped on libpq < 14
+    if pq.__impl__ == "python":
+        assert psycopg.Pipeline.is_supported() == (pq.version() >= 140000)
+    else:
+        assert pq.__build_version__ is not None
+        assert psycopg.Pipeline.is_supported() == (pq.__build_version__ >= 140000)