[48/50] couch commit: updated refs/heads/windsor-merge to 6e60cbe

[rn...@apache.org]

Make rev tree stemming for interactives optional

Documents with many conflicts and/or tombstones cause significant
performance degradation for couch_db_updater due to the stemming of rev
trees. This commit helps to fix this problem by making rev tree stemming
on interactive updates optional. This change makes it possible for rev
trees to temporarily become longer than revs_limit. When active, the
burden of rev tree stemming will fall on replication and compaction.

BugzID: 30438


Project: http://git-wip-us.apache.org/repos/asf/couchdb-couch/repo
Commit: http://git-wip-us.apache.org/repos/asf/couchdb-couch/commit/34ae188b
Tree: http://git-wip-us.apache.org/repos/asf/couchdb-couch/tree/34ae188b
Diff: http://git-wip-us.apache.org/repos/asf/couchdb-couch/diff/34ae188b

Branch: refs/heads/windsor-merge
Commit: 34ae188b1b3abee893a2360d888e6b93cb48c23e
Parents: 54836e4
Author: Benjamin Bastian <be...@gmail.com>
Authored: Tue Apr 29 13:21:34 2014 -0700
Committer: Robert Newson <rn...@apache.org>
Committed: Thu Aug 7 16:27:58 2014 +0100

----------------------------------------------------------------------
 src/couch_key_tree.erl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
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http://git-wip-us.apache.org/repos/asf/couchdb-couch/blob/34ae188b/src/couch_key_tree.erl
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diff --git a/src/couch_key_tree.erl b/src/couch_key_tree.erl
index 9ad6f7f..57c08a0 100644
--- a/src/couch_key_tree.erl
+++ b/src/couch_key_tree.erl
@@ -76,7 +76,10 @@ stem/2
                 {revtree(), new_leaf | new_branch | internal_node}.
 merge(RevTree, Tree, StemDepth) ->
     {Merged, Result} = merge(RevTree, Tree),
-    {stem(Merged, StemDepth), Result}.
+    case config:get("couchdb", "stem_interactive_updates", "true") of
+        "true" -> {stem(Merged, StemDepth), Result};
+        _ -> {Merged, Result}
+    end.
 
 
 %% @doc Merge a path into a tree.