elasticsearch/elasticsearch — pull request #5780 by s1monw (2014-04-11 16:23:04+00:00)
Title: Ensure pending merges are updated on segment flushes

Due to the default of `async_merge` to `true` we never run
the merge policy on a segment flush which prevented the
pending merges from being updated and that caused actual
pending merges not to contribute to the merge decision.

This commit sets the `async_merge` to `false` by default to enforce
updateing the pending merges. The setting is actually misleading
since we take care of this on a different level (the merge scheduler)
since 1.1.
This commit also adds an additional check when to run a refresh
since soely relying on the dirty flag might leave merges un-refreshed
which can cause search slowdowns and higher memory consumption.

Closes #5779