From 6d8f4f9f0d357beceb4a112e0ba9e3c1f314b8bb Mon Sep 17 00:00:00 2001
From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Sat, 21 Jul 2018 18:32:02 +0100
Subject: [PATCH] Close named cursor if exist, even if we didn't run execute

Close #746
---
 NEWS                  |  7 +++++++
 psycopg/cursor_type.c | 47 ++++++++++++++++++++++++++++++++++---------
 tests/test_cursor.py  | 13 ++++++++++++
 3 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/NEWS b/NEWS
index 54237b84..e0c4da57 100644
--- a/NEWS
+++ b/NEWS
@@ -21,6 +21,13 @@ Other changes:
   install``.
 
 
+What's new in psycopg 2.7.6
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Close named cursors if exist, even if `~cursor.execute()` wasn't called
+  (:ticket:`#746`).
+
+
 What's new in psycopg 2.7.5
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/psycopg/cursor_type.c b/psycopg/cursor_type.c
index d73bc3a4..14647a45 100644
--- a/psycopg/cursor_type.c
+++ b/psycopg/cursor_type.c
@@ -49,21 +49,22 @@
 static PyObject *
 psyco_curs_close(cursorObject *self)
 {
+    PyObject *rv = NULL;
+    char *lname = NULL;
+
     EXC_IF_ASYNC_IN_PROGRESS(self, close);
 
     if (self->closed) {
+        rv = Py_None;
+        Py_INCREF(rv);
         goto exit;
     }
 
     if (self->qname != NULL) {
-        char buffer[128];
+        const int bufsize = 255;
+        char buffer[bufsize + 1];
         PGTransactionStatusType status;
 
-        if (!self->query) {
-            Dprintf("skipping named cursor close because unused");
-            goto close;
-        }
-
         if (self->conn) {
             status = PQtransactionStatus(self->conn->pgconn);
         }
@@ -77,17 +78,45 @@ psyco_curs_close(cursorObject *self)
             goto close;
         }
 
+        /* We should close a server-side cursor only if exists, or we get an
+         * error (#716). If we execute()d the cursor should exist alright, but
+         * if we didn't there is still the expectation that the cursor is
+         * closed (#746).
+         *
+         * So if we didn't execute() check for the cursor existence before
+         * closing it (the view exists since PG 8.2 according to docs).
+         */
+        if (!self->query && self->conn->server_version >= 80200) {
+            if (!(lname = psycopg_escape_string(
+                    self->conn, self->name, -1, NULL, NULL))) {
+                goto exit;
+            }
+            PyOS_snprintf(buffer, bufsize,
+                "SELECT 1 FROM pg_catalog.pg_cursors where name = %s",
+                lname);
+            if (pq_execute(self, buffer, 0, 0, 1) == -1) { goto exit; }
+
+            if (self->rowcount == 0) {
+                Dprintf("skipping named cursor close because not existing");
+                goto close;
+            }
+        }
+
         EXC_IF_NO_MARK(self);
-        PyOS_snprintf(buffer, 127, "CLOSE %s", self->qname);
-        if (pq_execute(self, buffer, 0, 0, 1) == -1) return NULL;
+        PyOS_snprintf(buffer, bufsize, "CLOSE %s", self->qname);
+        if (pq_execute(self, buffer, 0, 0, 1) == -1) { goto exit; }
     }
 
 close:
     self->closed = 1;
     Dprintf("psyco_curs_close: cursor at %p closed", self);
 
+    rv = Py_None;
+    Py_INCREF(rv);
+
 exit:
-    Py_RETURN_NONE;
+    PyMem_Free(lname);
+    return rv;
 }
 
 
diff --git a/tests/test_cursor.py b/tests/test_cursor.py
index b48fe7fc..b0a37890 100755
--- a/tests/test_cursor.py
+++ b/tests/test_cursor.py
@@ -441,6 +441,19 @@ class CursorTests(ConnectingTestCase):
         cur = self.conn.cursor('test')
         cur.close()
 
+    @skip_before_postgres(8, 2)
+    def test_stolen_named_cursor_close(self):
+        cur1 = self.conn.cursor()
+        cur1.execute("DECLARE test CURSOR WITHOUT HOLD "
+            " FOR SELECT generate_series(1,7)")
+        cur2 = self.conn.cursor('test')
+        cur2.close()
+
+        cur1.execute("DECLARE test CURSOR WITHOUT HOLD "
+            " FOR SELECT generate_series(1,7)")
+        cur2 = self.conn.cursor('test')
+        cur2.close()
+
     @skip_before_postgres(8, 0)
     def test_scroll(self):
         cur = self.conn.cursor()