75 lines
2.3 KiB
Plaintext
75 lines
2.3 KiB
Plaintext
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;; Postgresql C library interface, example program 2, using the xedit
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;; lisp interface
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;; Test of the asynchronous notification interface
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;;
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;; Start this program, then from psql in another window do
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;; NOTIFY TBL2;
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;;
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;; Or, if you want to get fancy, try this:
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;; Populate a database with the following:
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;;
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;; CREATE TABLE TBL1 (i int4);
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;;
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;; CREATE TABLE TBL2 (i int4);
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;;
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;; CREATE RULE r1 AS ON INSERT TO TBL1 DO
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;; (INSERT INTO TBL2 values (new.i); NOTIFY TBL2);
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;;
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;; and do
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;;
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;; INSERT INTO TBL1 values (10);
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(require "psql")
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(defun exit-nicely (conn)
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(pq-finish conn)
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(quit 1)
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)
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;; begin, by setting the parameters for a backend connection if the
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;; parameters are null, then the system will try to use reasonable
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;; defaults by looking up environment variables or, failing that,
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;; using hardwired constants
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(setq pghost nil) ; host name of the backend server
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(setq pgport nil) ; port of the backend server
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(setq pgoptions nil) ; special options to start up the backend server
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(setq pgtty nil) ; debugging tty for the backend server
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(setq pgdbname "test") ; change this to the name of your test database
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;; XXX Note: getenv not yet implemented in the
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; lisp interpreter
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;; make a connection to the database
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(setq conn (pq-setdb pghost pgport pgoptions pgtty pgdbname))
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;; check to see that the backend connection was successfully made
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(when (= (pq-status conn) pg-connection-bad)
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(format t "Connection to database '~A' failed.~%" pgdbname)
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(format t "~A" (pq-error-message conn))
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(exit-nicely conn))
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(setq res (pq-exec conn "LISTEN TBL2"))
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(when (= (pq-status conn) pg-connection-bad)
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(format t "LISTEN command failed~%")
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(format t "~A" (pq-error-message conn))
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(exit-nicely conn))
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;; Should PQclear PGresult whenever it is no longer needed to avoid memory leaks
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(pq-clear res)
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(loop
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;; wait a little bit between checks; waiting with select()
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;; would be more efficient.
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;; XXX Note: sleep not yet implemented in the lisp interpreter
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;; collect any asynchronous backend messages
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(pq-consume-input conn)
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;; check for asynchronous notify messages
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(when (setq notifies (pq-notifies conn))
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(format t "ASYNC NOTIFY of '~A' from backend pid '~D' received~%"
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(pg-notify-relname notifies) (pg-notify-be-pid notifies))
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)
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)
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(pq-finish conn)
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