From 0b87eb8e0c8e2dd4a426005dce53dfdd57282475 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Thu, 21 Jul 2022 17:13:44 +0100 Subject: Make DictionaryCache have better expiry properties (#13292) --- synapse/util/caches/treecache.py | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'synapse/util/caches/treecache.py') diff --git a/synapse/util/caches/treecache.py b/synapse/util/caches/treecache.py index e78305f787..c1b8ec0c73 100644 --- a/synapse/util/caches/treecache.py +++ b/synapse/util/caches/treecache.py @@ -64,6 +64,15 @@ class TreeCache: self.size += 1 def get(self, key, default=None): + """When `key` is a full key, fetches the value for the given key (if + any). + + If `key` is only a partial key (i.e. a truncated tuple) then returns a + `TreeCacheNode`, which can be passed to the `iterate_tree_cache_*` + functions to iterate over all entries in the cache with keys that start + with the given partial key. + """ + node = self.root for k in key[:-1]: node = node.get(k, None) @@ -139,3 +148,32 @@ def iterate_tree_cache_entry(d): yield from iterate_tree_cache_entry(value_d) else: yield d + + +def iterate_tree_cache_items(key, value): + """Helper function to iterate over the leaves of a tree, i.e. a dict of that + can contain dicts. + + The provided key is a tuple that will get prepended to the returned keys. + + Example: + + cache = TreeCache() + cache[(1, 1)] = "a" + cache[(1, 2)] = "b" + cache[(2, 1)] = "c" + + tree_node = cache.get((1,)) + + items = iterate_tree_cache_items((1,), tree_node) + assert list(items) == [((1, 1), "a"), ((1, 2), "b")] + + Returns: + A generator yielding key/value pairs. + """ + if isinstance(value, TreeCacheNode): + for sub_key, sub_value in value.items(): + yield from iterate_tree_cache_items((*key, sub_key), sub_value) + else: + # we've reached a leaf of the tree. + yield key, value -- cgit 1.4.1