ElasticSearch

ElasticSearch is considered one of the best open source search engines around.

ElasticSearch is a top of the line product, currently used by companies like StumbleUpon, WordPress, Foursquare, Mozilla, GitHub, Salesforce, Klout, StackOverflow, IGN, Xing, SoundCloud and Sony.

Built on top of Apache Lucene, ElasticSearch takes embeddable search engines to a new level of efficiency and professionalism.

ElasticSearch allows developers to start with one machine and scale to hundreds, working as the simple search engine embedded with a WordPress blog, or as your own Google clone in the cloud.

Deploying the search capabilities of ElasticSearch may be a little difficult for beginners, but if the final performance is what drives you, then it's worth all the effort.

What is new in this release:

• Make PerThreadIDAndVersionLookup per-segment
• TransportNodesAction shouldn't hold on to cluster state
• Add _gce_ network host setting
• Plugin script to set proper plugin bin dir attributes
• Plugin script to set proper plugin config dir attributes

What is new in version 2.1.0:

• Make PerThreadIDAndVersionLookup per-segment
• TransportNodesAction shouldn't hold on to cluster state
• Add _gce_ network host setting
• Plugin script to set proper plugin bin dir attributes
• Plugin script to set proper plugin config dir attributes

What is new in version 1.6.0:

• New features:
• Logging: Add ability to specify a SizeBasedTriggeringPolicy for log configuration
• Mapping: Bring back numeric_resolution
• REST API: Add response filtering with filter_path parameter
• Recovery: Synced flush backport
• Recovery: Move index sealing terminology to synced flush
• Recovery: Seal indices for faster recovery
• Scripting: Add support for fine-grained settings
• Search: Validate API: provide more verbose explanation
• Settings: Add ability to prompt for selected settings on startup
• Settings: bootstrap.mlockall for Windows (VirtualLock)
• Shadow Replicas: Allow shards on shared filesystems to be recovered on any node
• Stats: Add field stats API

What is new in version 1.5.2:

• New features:
• Aggregations: New aggregations feature - "PercentageScore" heuristic for significant_terms
• CAT API: Cat API: show open and closed indices in _cat/indices
• Circuit Breakers: Circuit Breakers: Add NoopCircuitBreaker used in NoneCircuitBreakerService
• Engine: Shadow replicas on shared filesystems
• More Like This: MLT Query: Support for artificial documents
• Query DSL: Add time_zone setting for query_string
• Search: Add format support for date range filter and queries
• Search: Add inner hits to nested and parent/child queries
• Store: Add index.data_path setting
• Term Vectors: Term Vectors/MLT Query: support for different analyzers than default at the field

What is new in version 1.4.4:

• Aggregations: Return the sum of the doc counts of other buckets in terms aggregations.
• Cat API: Show open and closed indices in _cat/indices.
• Circuit Breakers: Allow setting individual breakers to "noop" breakers.
• Circuit Breakers: Add NoopCircuitBreaker used in NoneCircuitBreakerService.
• Upgrade API: Add API to upgrade old Lucene indices to the latest version.

What is new in version 1.3.2:

• Percolator should cache index field data instances
• Query API: Add support for the _name parameter to the simple_query_string query
• Core: Verify for null references that may be returned due to concurrent changes or inconsistent cluster state

What is new in version 1.3.0:

• Created infrastructure for changing easily the significance terms heuristic
• Added the percentiles_rank aggregation
• Deferred aggregations prevent combinatorial explosion
• Added top_hits aggregation
• Added script engine for Lucene expressions
• Added Groovy as a scripting language, add groovy sandboxing
• Allow search templates stored in an index to be retrieved and used at search time
• Allow to run scripts/templates stored in .scripts index

What is new in version 1.2.1:

• Enhancements:
• Networking: Upgrade to Netty 3.9.1
• Cluster: have a dedicated join timeout
• Bug fixes:
• Aggregations: Disable circuit break for aggregations
• Aggregations: The reverse nested aggregator now computes parent documents correctly
• Indexing: Lower translog flush trigger

What is new in version 1.1.1:

• Geo Point Mapping: Allow to parse lat/lon as strings and coerce them.
• Test cluster: Moved wipe* methods, randomIndexTemplate & ensureEstimatedStats to TestCluster.

What is new in version 1.1.0:

• Aggregations:
• New cardinality aggregation
• New percentiles aggregation
• New significant terms aggregation
• Allow geo_hash agg to return all hashes
• Allow terms agg to return all terms
• Add script support to value_count aggregations
• Query API:
• Added cross_fields type to multi_match query
• Add fuzzy/slop support to simple_query_string query
• Use mustache based templates to prerender search requests
• Added support for multiple sequential rescores
• Search Template API:
• Added dedicated /_search/template endpoint
• cat API:
• Added _cat/plugins endpoint
• Added _cat/segments endpoint

What is new in version 1.0.0:

• New features:
• Allow to change transport.publish_port setting to support systems as OpenShift, where public communication ports may be different than internal ones.
• Enhancements:
• Cluster state: Add local flag support to all read operations that are usually executed on the master node.
• REST API: Unify RestRequest.paramAsBoolean() and RestRequest.paramAsBooleanOptional.
• REST API: The RestRequest class now uses the same logic for all methods, which try to read boolean values from parameters.
• REST cluster pending tasks API: Support master_timeout parameter.
• Create Index API: Remove omit_term_freq_and_positions option for index creation.
• Field data: Allow to configure circuit breaker with a percentage (based on the total heap).
• Mapping: Custom _all fields are now possible by specifying additional fields in the mapping, the data should be copied to, thus their name copy_to fields.
• Lucene internals: Use patched version of ReferenceManager to prevent infinite loop in ReferenceManager#accquire().
• Lucene internals: Prevent possibly undefined behaviour in SearchContext due to the initial state of a DocSetIterato.
• Allocation: Add explanations for all AllocationDeciders.
• Bug fixes:
• Testing: Add tracking of pages to MockPageCacheRecycler.
• Plugins: Upgrading analysis plugins failed.
• Allocation: Trying to allocate a shard on a non-data node caused a NullPointerException.
• Hot Threads API: Failed to detect hot threads due to not-alive threads not returning needed data.
• Filter: Ensure to never cache a filter that wraps a parent/child filter.
• Scroll API: Scrolling with has_child filter returns correct hits on further request.
• Start: Logging of immediate startup exceptions to files or standard output was reversed.
• Packaging RPMs: Add correct timeout to shutdown with KILL signal to prevent unwanted hard shutdowns.
• Rivers: Make sure rivers get started when index templates are configured.

What is new in version 0.90.5:

• New:
• Running ElasticSearch as a service on Windows.

What is new in version 0.90.2:

• Added a minimum_should_match parameter when Common query has only high frequent terms.
• Change Version methods to be more readable.

What is new in version 0.90.0:

• PolygonBuilder does not support holes.
• Expose field level field data statistics.
• Allow FieldData loading to be filtered.

What is new in version 0.20.5:

• Upgrade Notes:
• Upgrading from 0.19 requires a full cluster restart.
• Breaking Changes:
• Shared Gateway has been deprecated.
• Snappy compression has been deprecated.
• Plugins Installer: Allow to download plugins from download.elasticsearch.org.

What is new in version 0.20.4:

• Upgrading from 0.19 requires a full cluster restart.

What is new in version 0.20.2:

• Shared Gateway has been deprecated.
• Snappy compression has been deprecated.

What is new in version 0.19.9:

• Explain API.
• Multi match query.
• Cluster Nodes hot_threads API.

What is new in version 0.19.6:

• 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.

What is new in version 0.19.3:

• Upgraded to Lucene 3.6.

What is new in version 0.19.2:

• 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.

What is new in version 0.19.0:

• msearch should accept a leading \n.
• Date Histogram Facet: Add pre_zone_adjust_large_interval.
• Flush: Add a specific thread pool for flush operations (scheduled and API).
• Translog Flush: When disabling flush and enabling it again, scheduled flush stops executing.

What is new in version 0.19.0.RC3:

• New features:
• API: Multi Search.
• Date Mapping: Support "date math" when searching.
• Enhancements:
• Indices query should accept alias names.
• Return 503 for search against a node which is not yet ready.
• Failed shards allocation can "poison" allocation and might cause not allocating other shards.

What is new in version 0.19.0.RC1:

• Index shard search slow log (query and fetch).
• Upgrade to Lucene 3.5.
• Support Multicast discovery for external clients.
• Set an index / indices to read only, or make the cluster read only.
• Add query validation feature.
• Add thread_pool to nodes info and nodes stats APIs.
• Add generic execution of APIs to Client (and indices/cluster) and allow for plugins to register custom APIs.
• Local Gateway: Store specific index metadata under dedicated index locations.
• Plugins: Allow for plugins to implement onModule method that will be automatically injected with the relevant module type.
• Search: Support partial fields that can returns partial view of the _source.
• Update API: Allow to update a document based on a script.