Attached is a patch that adds Postmodern support for asynchronous
notifications, as documented here:
http://www.postgresql.org/docs/current/static/sql-listen.html
http://www.postgresql.org/docs/current/static/sql-notify.html
http://www.postgresql.org/docs/current/static/sql-unlisten.html
and
http://www.postgresql.org/docs/current/interactive/protocol-message-formats.html
(under "NotificationResponse")
It updates MESSAGE-CASE to watch for async notifications and, by
default, issue a warning that looks very similar to what the psql client
displays for async notifications:
WARNING:
Asynchornous notification "lisp" received from server process with
PID 22063.
It also adds a blocking function, WAIT-FOR-NOTIFICATION, that adds a
handler-bind around the warning and returns the notification data when a
notification is received.
The patch isn't complete, though -- I wasn't sure how best to integrate
the new public function, condition, and condition accessors into the
documentation. How should I proceed?
Zach
diff --git a/cl-postgres/package.lisp b/cl-postgres/package.lisp
index 43468dc..71cae30 100644
--- a/cl-postgres/package.lisp
+++ b/cl-postgres/package.lisp
@@ -16,6 +16,7 @@
#:reopen-database
#:database-open-p
#:close-database
+ #:wait-for-notification
#:exec-query
#:prepare-query
#:exec-prepared
@@ -29,6 +30,9 @@
#:log-query
#:vector-row-reader
#:alist-row-reader
+ #:postgresql-notification
+ #:postgresql-notification-pid
+ #:postgresql-notification-condition
#:postgresql-warning
#:ignore-row-reader
#:*sql-readtable*
diff --git a/cl-postgres/protocol.lisp b/cl-postgres/protocol.lisp
index a047732..4cc169b 100644
--- a/cl-postgres/protocol.lisp
+++ b/cl-postgres/protocol.lisp
@@ -36,6 +36,9 @@ Cases for error and warning messages are always added."
(type (unsigned-byte 32) ,size-name)
(ignorable ,size-name))
(case ,char-name
+ (#.(char-code #\A)
+ (get-notification ,socket-name)
+ (,iter-name))
(#.(char-code #\E) (get-error ,socket-name))
(#.(char-code #\S) ;; ParameterStatus: read and continue
(update-parameter ,socket-name)
@@ -72,6 +75,25 @@ and put them in an alist."
:until (zerop type)
:collect (cons (code-char type) (read-str socket))))
+(define-condition postgresql-notification (simple-warning)
+ ((pid :initarg :pid :accessor postgresql-notification-pid)
+ (condition :initarg :condition :accessor
postgresql-notification-condition)))
+
+(defun get-notification (socket)
+ "Read an asynchronous notification message from the socket and
+signal a condition for it."
+ (let ((pid (read-int4 socket))
+ (condition (read-str socket))
+ (additional-info (read-str socket)))
+ ;; Per the documentation, the additional-info string is always empty.
+ (declare (ignore additional-info))
+ (warn 'postgresql-notification
+ :pid pid
+ :condition condition
+ :format-control "Asynchornous notification ~s received from ~
+ server process with PID ~D."
+ :format-arguments (list condition pid))))
+
(defun get-error (socket)
"Read an error message from the socket and raise the corresponding
database-error condition."
diff --git a/cl-postgres/public.lisp b/cl-postgres/public.lisp
index dbdfcde..a3b0b9d 100644
--- a/cl-postgres/public.lisp
+++ b/cl-postgres/public.lisp
@@ -169,6 +169,17 @@ offering a :reconnect restart."
(,body-name)))))
(,body-name)))))
+(defun wait-for-notification (connection)
+ "Perform a blocking wait for asynchronous notification. Return the
+condition string and notifying pid as multiple values."
+ (block nil
+ (with-reconnect-restart connection
+ (handler-bind ((postgresql-notification
+ (lambda (c)
+ (return (values (postgresql-notification-condition c)
+ (postgresql-notification-pid c))))))
+ (message-case (connection-socket connection))))))
+
(defun exec-query (connection query &optional (row-reader 'ignore-row-reader))
"Execute a query string and apply the given row-reader to the
result."
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