ecn-robots: refactored pgdb to use only one psql process per object.

pgdb.py

@@ -2,12 +2,13 @@ r'''Python interface to PostgreSQL for managing database nodes.
 '''
 
 from subprocess import Popen, PIPE
-
+import time
 class Db(object):
     
     def __init__(self,name):
         self._name = name
-    
+        self._p = Popen('/usr/bin/psql -Aqt -U postgres', stdin=PIPE, stdout=PIPE, stderr=PIPE, shell=True)
+
     def _run(self, command,args=[]):
         execfn = [command] + list(args)
 	try:
@@ -19,8 +20,15 @@ class Db(object):
 
     def _runsql(self, sql, db='postgres'):
 	given_sql = sql
-        out,error = self._run('/usr/bin/psql', ['-Aqt','-U','postgres','-d', db, '-c', given_sql])
-        return out.strip()
+        sql = sql +'\echo this is the end' +'\n'
+        self._p.stdout.flush()
+        self._p.stdin.write(str(sql))
+	out = ""
+	out  = self._p.stdout.readline()
+	while out.find("this is the end") == -1:
+	    out = out +self._p.stdout.readline()
+        lout = out.replace('this is the end','')
+	return lout.strip()
     
     def _get_owner(self):
         sql = "SELECT pg_get_userbyid(datdba) FROM pg_database WHERE datname ='"+self._name+"';"
@@ -43,10 +51,9 @@ class Db(object):
     @property
     def info(self):
         information = {'size':'', 'encoding':'', 'collation':'','ctype':''}
-        information['size'] = self._runsql("SELECT pg_size_pretty(pg_database_size('"+self._name+"'));").strip()
+        information['size'] = self._runsql("SELECT pg_size_pretty(pg_database_size('"+self._name+"'));")
         information['encoding'], information['collation'], \
-	    information['ctype'] = self._runsql("""SELECT pg_encoding_to_char(encoding), 
-                datcollate, datctype FROM pg_database WHERE datname='"""+self._name+"';").split('|')
+	    information['ctype'] = self._runsql("SELECT pg_encoding_to_char(encoding), datcollate, datctype FROM pg_database WHERE datname='"+self._name+"';").split('|')
         return information
 
     @property
@@ -103,16 +110,18 @@ class Db(object):
 
     def dblist(self):
         sql = "SELECT datname FROM pg_database WHERE datname NOT IN ('template0', 'template1', 'postgres');"
-	dblist = self._runsql(sql)
-	return dblist
+	dbl = self._runsql(sql)
+	return dbl
 
     def usrlist(self):
         sql = "SELECT rolname FROM pg_authid WHERE rolcanlogin=true;"
-	usrlist = self._runsql(sql)
-	return usrlist
+	usrl = self._runsql(sql)
+	return usrl
 
 def _test():
     test = Db(u'postgres')
+    print    test.dblist()
+    print    test.usrlist()
     print test.info['encoding'], test.info['collation'], test.info['ctype']
     #print test.owner
     #print test.connections