Make RDBMS cache-size configurable.

Author: stefanseefeld

roundup/backends/rdbms_common.py

@@ -71,9 +71,6 @@
 from sessions_rdbms import Sessions, OneTimeKeys
 from roundup.date import Range
 
-# number of rows to keep in memory
-ROW_CACHE_SIZE = 100
-
 # dummy value meaning "argument not passed"
 _marker = []
 
@@ -108,7 +105,7 @@ class Database(FileStorage, hyperdb.Database, roundupdb.Database):
 
         - some functionality is specific to the actual SQL database, hence
           the sql_* methods that are NotImplemented
-        - we keep a cache of the latest ROW_CACHE_SIZE row fetches.
+        - we keep a cache of the latest N row fetches (where N is configurable).
     """
     def __init__(self, config, journaltag=None):
         """ Open the database and load the schema from it.
@@ -125,6 +122,7 @@ def __init__(self, config, journaltag=None):
 
         # keep a cache of the N most recently retrieved rows of any kind
         # (classname, nodeid) = row
+        self.cache_size = config.RDBMS_CACHE_SIZE
         self.cache = {}
         self.cache_lru = []
         self.stats = {'cache_hits': 0, 'cache_misses': 0, 'get_items': 0,
@@ -1057,7 +1055,7 @@ def getnode(self, classname, nodeid):
         self.cache[key] = node
         # update the LRU
         self.cache_lru.insert(0, key)
-        if len(self.cache_lru) > ROW_CACHE_SIZE:
+        if len(self.cache_lru) > self.cache_size:
             del self.cache[self.cache_lru.pop()]
 
         if __debug__:

roundup/configuration.py

@@ -370,7 +370,7 @@ def _value2str(self, value):
 
 class NullableOption(Option):
 
-    """Option that is set to None if it's string value is one of NULL strings
+    """Option that is set to None if its string value is one of NULL strings
 
     Default nullable strings list contains empty string only.
     There is constructor parameter allowing to specify different nullables.
@@ -592,8 +592,10 @@ def str2value(self, value):
         (NullableOption, 'read_default_group', 'roundup',
             "Name of the group to use in the MySQL defaults file (.my.cnf).\n"
             "Only used in MySQL connections."),
+        (IntegerNumberOption, 'cache_size', '100',
+            "Size of the node cache (in elements)"),
     ), "Settings in this section are used"
-        " by Postgresql and MySQL backends only"
+        " by RDBMS backends only"
     ),
     ("logging", (
         (FilePathOption, "config", "",
@@ -874,7 +876,7 @@ def add_option(self, option):
             _options.append(_name)
         # (section, name) key is used for writing .ini file
         self.options[(_section, _name)] = option
-        # make the option known under all of it's A.K.A.s
+        # make the option known under all of its A.K.A.s
         for _name in option.aliases:
             self.options[_name] = option