Implement databases <section> latest|oldest, to only list latest or o…

…ldest existing database

pg_staging.1.txt

@@ -155,7 +155,7 @@ postsql <dbname> [<YYYYMMDD>]::
 
 ===  listings ===
 
-databases [<dbname>]::
+databases [<dbname>] [oldest|latest]::
 
 	Show the list of database sections parsed into the .ini file.  When
 	given a +<dbname>+ show the list of known databases from +pgbouncer+.
@@ -183,9 +183,10 @@ show <dbname> [<YYYYMMDD>] <setting>::
 
 === pgbouncer ===
 
-pgbouncer <dbname>::
+pgbouncer <dbname> [oldest|latest]::
 
-	 Show +pgbouncer+ database listing for given dbname.
+	 Show +pgbouncer+ database listing for given dbname.  When given
+	 +oldest+ or +latest+, only display this one database line.
 
 pause <dbname> [<YYYMMDD>]::
 

pgstaging/commands.py

@@ -417,7 +417,7 @@ def list_databases(conffile, args):
         for section in config.sections():
             print section
 
-    elif len(args) == 1:
+    elif len(args) in (1, 2):
         list_pgbouncer_databases(conffile, args)
 
     else:
@@ -529,14 +529,23 @@ def show_all_dbsizes(conffile, args):
 
 def list_pgbouncer_databases(conffile, args):
     """ list configured pgbouncer databases """
-    usage = "pgbouncer <dbname>"
-    if len(args) != 1:
+    usage = "pgbouncer <dbname> [oldest|latest]"
+    if len(args) not in (1, 2) or \
+       (len(args) == 2 and args[1] not in ('oldest', 'latest')):
         raise WrongNumberOfArgumentsException, usage
 
+    target = None
     dbname = args[0]
     staging = parse_config(conffile, dbname)
+
+    if len(args) == 2 and args[1] == 'oldest':
+        target = staging.get_oldest_dbname()
+    elif len(args) == 2 and args[1] == 'latest':
+        target = staging.get_latest_dbname()
+
     for name, database, host, port in staging.pgbouncer_databases():
-        print "%25s %25s %s:%s" % (name, database, host, port)
+        if target is None or name == target:
+            print "%25s %25s %s:%s" % (name, database, host, port)
 
 def pause_pgbouncer_database(conffile, args):
     """ pause <dbname> [date] (when no date given, not expanded to today) """

pgstaging/staging.py

@@ -167,6 +167,10 @@ def parse_backup_file_date(self, filename):
         """ extract date from foo_db.2011-03-11.dump """
         return self.parse_date(filename.split(".")[1])
 
+    def parse_dbname_date(self, dbname):
+        """ extract date from allopass_db_20100209 """
+        return self.parse_date(dbname.split("_")[-1])
+
     def get_latest_backup(self):
         """ return the latest backup date available """
         b = None
@@ -638,16 +642,44 @@ def drop(self, dbname = None):
         # and remove it from pgbouncer configuration
         self.pgbouncer_del_database(dbname)
 
-    def purge(self):
-        """ keep only self.keep_bases databases """
-        from options import TERSE, VERBOSE
-
+    def pgbouncer_dbnames(self):
+        """return sorted list of databases available in pgbouncer and
+        matching self.dbname
+        """
         dlist = [d[1].strip('"')
                  for d in self.pgbouncer_databases()
                  if d[0].strip('"') != self.dbname \
                  and d[1].strip('"').startswith(self.dbname)]
         dlist.sort()
 
+        return dlist
+
+    def get_latest_dbname(self):
+        """ return the oldest available (through pgbouncer) """
+        latest = None
+        for dbname in self.pgbouncer_dbnames():
+            d = self.parse_dbname_date(dbname)
+            if latest is None or d > latest[0]:
+                latest = d, dbname
+
+        return latest[1]
+
+    def get_oldest_dbname(self):
+        """ return the oldest available (through pgbouncer) """
+        oldest = None
+        for dbname in self.pgbouncer_dbnames():
+            d = self.parse_dbname_date(dbname)
+            if oldest is None or d < oldest[0]:
+                oldest = d, dbname
+
+        return oldest[1]
+
+    def purge(self):
+        """ keep only self.keep_bases databases """
+        from options import TERSE, VERBOSE
+
+        dlist = self.pgbouncer_dbnames()
+
         if len(dlist) <= self.keep_bases:
             if not TERSE:
                 print "cleandb: we keep %d databases and have only %d" %\