Upgrade Notes:

• Upgrading from 0.18 requires issuing a full flush of all the indices in the cluster (curl host:9200/_flush) before shutting down the cluster, with no indexing operations happening after the flush.
• The local gateway state structure has changed, a backup of the state files is created when upgrading, they can then be used to downgrade back to 0.18. Don’t downgrade without using them.

New features:

• API: Multi Search (#1722)
• Date Mapping: Support “date math” when searching (#1708)

Enhancements:

• Indices query should accept alias names (#1698)
• Return 503 for search against a node which is not yet ready (#1713)
• Failed shards allocation can “poison” allocation and might cause not allocating other shards (#1717)
• Analysis: Add trim token filter that trims whitespaces (#1693)
• Index Templates: Allow to place them under config/templates (#1703)
• Local Gateway: Delete dangling indices after a (configurable) timeout, and not immediately (#1718)
• Search: Allow to execute search with no parameters (#1696)

Bug fixes:

• Retrieving byte type stored field fails (#1702)
• StackOverflowError when accessing NodeIndicesStats.refresh() (#1706)
• top_children query returns no results when child field has the same name as a nested field as a nested field in the parent mapping (#1709)
• Search: When using _all for types, field name/type resolution might fail (#1704)