postgres_fdw: Make postgres_fdw.application_name support more escape sequences.

Commit 6e0cb3dec1 allowed postgres_fdw.application_name to include
escape sequences %a (application name), %d (database name), %u (user name)
and %p (pid). In addition to them, this commit makes it support
the escape sequences for session ID (%c) and cluster name (%C).
These are helpful to investigate where each remote transactions came from.

Author: Fujii Masao
Reviewed-by: Ryohei Takahashi, Kyotaro Horiguchi
Discussion: https://postgr.es/m/1041dc9a-c976-049f-9f14-e7d94c29c4b2@oss.nttdata.com

1 files changed, 20 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index b2e02caefe4..057342083c6 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -10910,6 +10910,26 @@ SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
  t
 (1 row)
 
+-- Test %c (session ID) and %C (cluster name) escape sequences.
+SET postgres_fdw.application_name TO 'fdw_%C%c';
+SELECT 1 FROM ft6 LIMIT 1;
+ ?column? 
+----------
+        1
+(1 row)
+
+SELECT pg_terminate_backend(pid, 180000) FROM pg_stat_activity
+  WHERE application_name =
+    substring('fdw_' || current_setting('cluster_name') ||
+      to_hex(trunc(EXTRACT(EPOCH FROM (SELECT backend_start FROM
+      pg_stat_get_activity(pg_backend_pid()))))::integer) || '.' ||
+      to_hex(pg_backend_pid())
+      for current_setting('max_identifier_length')::int);
+ pg_terminate_backend 
+----------------------
+ t
+(1 row)
+
 --Clean up
 RESET postgres_fdw.application_name;
 RESET debug_discard_caches;