Source Code for Module gavo.rsc.metatable

 1  """ 
 2  Handling table metadata in the dc.(table|column)meta tables. 
 3   
 4  This has been a mediocre plan, and it's almost unused these days except 
 5  to locate RDs for tables.  Hence, we should tear this entire thing down 
 6  and have the table->RD mapping stowed somewhere else. 
 7   
 8  Or at least give up on the extra connection and have the clients use 
 9  base.getTableDefForTable(connection, tableName) directly. 
10  """ 
11   
12  #c Copyright 2008-2019, the GAVO project 
13  #c 
14  #c This program is free software, covered by the GNU GPL.  See the 
15  #c COPYING file in the source distribution. 
16   
17   
18  import functools 
19   
20  from gavo import base 
21   
22   
23   
24 -def _retryProtect(m): 
25          """decorates m such that any function call is retried after self.reset 
26          is called. 
27          """ 
28          def f(self, *args, **kwargs): 
29                  try: 
30                          return m(self, *args, **kwargs) 
31                  except: 
32                          self.reset() 
33                          return m(self, *args, **kwargs) 
34   
35          return functools.update_wrapper(f, m) 
36   
37   
38 -class MetaTableHandler(object): 
39          """an interface to DaCHS meta tables. 
40   
41          This used to be a fairly complex interface to all sorts for DC-related 
42          metadata.  These day, the only thing it does is figure out where 
43          table definitions reside and which are available for ADQL.  This thing  
44          has been a bad idea all around. 
45   
46          Though you can construct MetaTableHandlers of your own, you should 
47          use base.caches.getMTH(None) when reading. 
48          """ 
49 -        def __init__(self): 
50                  self.rd = base.caches.getRD("__system__/dc_tables") 
51                  self._createObjects() 
52   
53 -        def _createObjects(self): 
54                  self.readerConnection = base.getDBConnection( 
55                          "trustedquery", autocommitted=True) 
56   
57 -        def close(self): 
58                  try: 
59                          self.readerConnection.close() 
60                  except base.InterfaceError: 
61                          # connection already closed 
62                          pass 
63   
64 -        def reset(self): 
65                  self.close() 
66                  self._createObjects() 
67   
68          @_retryProtect 
69 -        def getTableDefForTable(self, tableName): 
70                  """returns a TableDef for tableName. 
71   
72                  As it is not a priori clear which RD a given table lives in, 
73                  this goes through dc.tablemeta to figure this out.  The 
74                  object comes from the actual RD, though, so this might very well 
75                  trigger database action and RD loading. 
76                  """ 
77                  return base.getTableDefForTable( 
78                          self.readerConnection, 
79                          tableName) 
80   
81          @_retryProtect 
82 -        def getTAPTables(self): 
83                  """returns a list of all names of tables accessible through TAP in 
84                  this data center. 
85                  """ 
86                  return [r["tablename"] for r in 
87                          self.readerConnection.queryToDicts( 
88                                  "select tablename from dc.tablemeta where adql")] 
89   
90   
91 -def _getMetaTable(ignored): 
92          return MetaTableHandler() 
93   
94  base.caches.makeCache("getMTH", _getMetaTable) 
95