From a155a23e88c446294ea9787e10ab7c04095501a1 Mon Sep 17 00:00:00 2001
From: Zac Medico <zmedico@gentoo.org>
Date: Thu, 28 Dec 2006 13:07:03 +0000
Subject: Use a pickle to cache vdb metadata.  This greatly improves the
 performance for loading the vdb when the buffer cache is cold.

svn path=/main/trunk/; revision=5402
---
 pym/portage.py | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

(limited to 'pym')

diff --git a/pym/portage.py b/pym/portage.py
index 9d2526f21..d7dc3b561 100644
--- a/pym/portage.py
+++ b/pym/portage.py
@@ -4706,6 +4706,12 @@ class vardbapi(dbapi):
 		if vartree is None:
 			vartree = globals()["db"][root]["vartree"]
 		self.vartree = vartree
+		self._aux_cache_keys = set(["SLOT", "COUNTER", "PROVIDE", "USE",
+			"IUSE", "DEPEND", "RDEPEND", "PDEPEND"])
+		self._aux_cache = None
+		self._aux_cache_version = "1"
+		self._aux_cache_filename = os.path.join(self.root,
+			CACHE_PATH.lstrip(os.path.sep), "vdb_metadata.pickle")
 
 	def cpv_exists(self,mykey):
 		"Tells us whether an actual ebuild exists on disk (no masking)"
@@ -4969,7 +4975,96 @@ class vardbapi(dbapi):
 	def findname(self, mycpv):
 		return self.root+VDB_PATH+"/"+str(mycpv)+"/"+mycpv.split("/")[1]+".ebuild"
 
+	def flush_cache(self):
+		"""If the current user has permission and the internal aux_get cache has
+		been updated, save it to disk and mark it unmodified.  This is called
+		by emerge after it has loaded the full vdb for use in dependency
+		calculations.  Currently, the cache is only written if the user has
+		superuser privileges (since that's required to obtain a lock), but all
+		users have read access and benefit from faster metadata lookups (as
+		long as at least part of the cache is still valid)."""
+		if self._aux_cache is not None and \
+			self._aux_cache["modified"] and \
+			secpass >= 2:
+			valid_nodes = set(self.cpv_all())
+			for cpv in self._aux_cache["packages"].keys():
+				if cpv not in valid_nodes:
+					del self._aux_cache["packages"][cpv]
+			del self._aux_cache["modified"]
+			try:
+				f = atomic_ofstream(self._aux_cache_filename)
+				cPickle.dump(self._aux_cache, f, -1)
+				f.close()
+				portage_util.apply_secpass_permissions(
+					self._aux_cache_filename, gid=portage_gid, mode=0644)
+			except (IOError, OSError), e:
+				pass
+			self._aux_cache["modified"] = False
+
 	def aux_get(self, mycpv, wants):
+		"""This automatically caches selected keys that are frequently needed
+		by emerge for dependency calculations.  The cached metadata is
+		considered valid if the mtime of the package directory has not changed
+		since the data was cached.  The cache is stored in a pickled dict
+		object with the following format:
+
+		{version:"1", "packages":{cpv1:(mtime,{k1,v1, k2,v2, ...}), cpv2...}}
+
+		If an error occurs while loading the cache pickle or the version is
+		unrecognized, the cache will simple be recreated from scratch (it is
+		completely disposable).
+		"""
+		if not self._aux_cache_keys.intersection(wants):
+			return self._aux_get(mycpv, wants)
+		if self._aux_cache is None:
+			try:
+				f = open(self._aux_cache_filename)
+				mypickle = cPickle.Unpickler(f)
+				mypickle.find_global = None
+				self._aux_cache = mypickle.load()
+				f.close()
+				del f
+			except (IOError, OSError, EOFError, cPickle.UnpicklingError):
+				pass
+			if not self._aux_cache or \
+				not isinstance(self._aux_cache, dict) or \
+				self._aux_cache.get("version") != self._aux_cache_version:
+				self._aux_cache = {"version":self._aux_cache_version}
+				self._aux_cache["packages"] = {}
+			self._aux_cache["modified"] = False
+		mydir = os.path.join(self.root, VDB_PATH, mycpv)
+		mydir_stat = None
+		try:
+			mydir_stat = os.stat(mydir)
+		except OSError, e:
+			if e.errno != errno.ENOENT:
+				raise
+			raise KeyError(mycpv)
+		mydir_mtime = long(mydir_stat.st_mtime)
+		pkg_data = self._aux_cache["packages"].get(mycpv)
+		mydata = {}
+		cache_valid = False
+		if pkg_data:
+			cache_mtime, metadata = pkg_data
+			cache_valid = cache_mtime == mydir_mtime
+		if cache_valid:
+			mydata.update(metadata)
+			pull_me = set(wants).difference(self._aux_cache_keys)
+		else:
+			pull_me = self._aux_cache_keys.union(wants)
+		if pull_me:
+			# pull any needed data and cache it
+			aux_keys = list(pull_me)
+			mydata.update(izip(aux_keys, self._aux_get(mycpv, aux_keys)))
+			if not cache_valid:
+				cache_data = {}
+				for aux_key in self._aux_cache_keys:
+					cache_data[aux_key] = mydata[aux_key]
+				self._aux_cache["packages"][mycpv] = (mydir_mtime, cache_data)
+				self._aux_cache["modified"] = True
+		return [mydata[x] for x in wants]
+
+	def _aux_get(self, mycpv, wants):
 		mydir = os.path.join(self.root, VDB_PATH, mycpv)
 		if not os.path.isdir(mydir):
 			raise KeyError(mycpv)
-- 
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