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NEWS.txt
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PLEASE READ: MAXIMUM TTL EXPIRATION DATE NOTICE (CASSANDRA-14092)
------------------------------------------------------------------
(General upgrading instructions are available in the next section)
The maximum expiration timestamp that can be represented by the storage engine is
2038-01-19T03:14:06+00:00, which means that inserts with TTL thatl expire after
this date are not currently supported. By default, INSERTS with TTL exceeding the
maximum supported date are rejected, but it's possible to choose a different
expiration overflow policy. See CASSANDRA-14092.txt for more details.
Prior to 3.0.16 (3.0.X) and 3.11.2 (3.11.x) there was no protection against INSERTS
with TTL expiring after the maximum supported date, causing the expiration time
field to overflow and the records to expire immediately. Clusters in the 2.X and
lower series are not subject to this when assertions are enabled. Backed up SSTables
can be potentially recovered and recovery instructions can be found on the
CASSANDRA-14092.txt file.
If you use or plan to use very large TTLS (10 to 20 years), read CASSANDRA-14092.txt
for more information.
GENERAL UPGRADING ADVICE FOR ANY VERSION
========================================
Snapshotting is fast (especially if you have JNA installed) and takes
effectively zero disk space until you start compacting the live data
files again. Thus, best practice is to ALWAYS snapshot before any
upgrade, just in case you need to roll back to the previous version.
(Cassandra version X + 1 will always be able to read data files created
by version X, but the inverse is not necessarily the case.)
When upgrading major versions of Cassandra, you will be unable to
restore snapshots created with the previous major version using the
'sstableloader' tool. You can upgrade the file format of your snapshots
using the provided 'sstableupgrade' tool.
4.1
===
New features
------------
Upgrading
---------
Deprecation
-----------
4.0
===
New features
------------
- The data of the system keyspaces using a local strategy (at the exception of the system.batches,
system.paxos, system.compaction_history, system.prepared_statements and system.repair tables)
is now stored by default in the first data directory, instead of being distributed among all
the data directories. This approach will allow the server to tolerate the failure of the other disks.
To ensure that a disk failure will not bring a node down, it is possible to use the system_data_file_directory
yaml property to store the local system keyspaces data on a directory that provides redundancy.
On node startup the local system keyspaces data will be automatically migrated if needed to the
correct location.
- Nodes will now bootstrap all intra-cluster connections at startup by default and wait
10 seconds for the all but one node in the local data center to be connected and marked
UP in gossip. This prevents nodes from coordinating requests and failing because they
aren't able to connect to the cluster fast enough. block_for_peers_timeout_in_secs in
cassandra.yaml can be used to configure how long to wait (or whether to wait at all)
and block_for_peers_in_remote_dcs can be used to also block on all but one node in
each remote DC as well. See CASSANDRA-14297 and CASSANDRA-13993 for more information.
- *Experimental* support for Transient Replication and Cheap Quorums introduced by CASSANDRA-14404
The intended audience for this functionality is expert users of Cassandra who are prepared
to validate every aspect of the database for their application and deployment practices. Future
releases of Cassandra will make this feature suitable for a wider audience.
- *Experimental* support for Java 11 has been added. JVM options that differ between or are
specific for Java 8 and 11 have been moved from jvm.options into jvm8.options and jvm11.options.
IMPORTANT: Running C* on Java 11 is *experimental* and do it at your own risk.
- LCS now respects the max_threshold parameter when compacting - this was hard coded to 32
before, but now it is possible to do bigger compactions when compacting from L0 to L1.
This also applies to STCS-compactions in L0 - if there are more than 32 sstables in L0
we will compact at most max_threshold sstables in an L0 STCS compaction. See CASSANDRA-14388
for more information.
- There is now an option to automatically upgrade sstables after Cassandra upgrade, enable
either in `cassandra.yaml:automatic_sstable_upgrade` or via JMX during runtime. See
CASSANDRA-14197.
- `nodetool refresh` has been deprecated in favour of `nodetool import` - see CASSANDRA-6719
for details
- An experimental option to compare all merkle trees together has been added - for example, in
a 3 node cluster with 2 replicas identical and 1 out-of-date, with this option enabled, the
out-of-date replica will only stream a single copy from up-to-date replica. Enable it by adding
"-os" to nodetool repair. See CASSANDRA-3200.
- The currentTimestamp, currentDate, currentTime and currentTimeUUID functions have been added.
See CASSANDRA-13132
- Support for arithmetic operations between `timestamp`/`date` and `duration` has been added.
See CASSANDRA-11936
- Support for arithmetic operations on number has been added. See CASSANDRA-11935
- Preview expected streaming required for a repair (nodetool repair --preview), and validate the
consistency of repaired data between nodes (nodetool repair --validate). See CASSANDRA-13257
- Support for selecting Map values and Set elements has been added for SELECT queries. See CASSANDRA-7396
- Change-Data-Capture has been modified to make CommitLogSegments available
immediately upon creation via hard-linking the files. This means that incomplete
segments will be available in cdc_raw rather than fully flushed. See documentation
and CASSANDRA-12148 for more detail.
- The initial build of materialized views can be parallelized. The number of concurrent builder
threads is specified by the property `cassandra.yaml:concurrent_materialized_view_builders`.
This property can be modified at runtime through both JMX and the new `setconcurrentviewbuilders`
and `getconcurrentviewbuilders` nodetool commands. See CASSANDRA-12245 for more details.
- There is now a binary full query log based on Chronicle Queue that can be controlled using
nodetool enablefullquerylog, disablefullquerylog, and resetfullquerylog. The log
contains all queries invoked, approximate time they were invoked, any parameters necessary
to bind wildcard values, and all query options. A human readable version of the log can be
dumped or tailed using the new bin/fqltool utility. The full query log is designed to be safe
to use in production and limits utilization of heap memory and disk space with limits
you can specify when enabling the log.
See nodetool and fqltool help text for more information.
- SSTableDump now supports the -l option to output each partition as it's own json object
See CASSANDRA-13848 for more detail
- Metric for coordinator writes per table has been added. See CASSANDRA-14232
- Nodetool cfstats now has options to sort by various metrics as well as limit results.
- Operators can restrict login user activity to one or more datacenters. See `network_authorizer`
in cassandra.yaml, and the docs for create and alter role statements. CASSANDRA-13985
- Roles altered from login=true to login=false will prevent existing connections from executing any
statements after the cache has been refreshed. CASSANDRA-13985
- Support for audit logging of database activity. If enabled, logs every incoming
CQL command request, Authentication (successful as well as unsuccessful login) to a node.
- Faster streaming of entire SSTables using ZeroCopy APIs. If enabled, Cassandra will use stream
entire SSTables, significantly speeding up transfers. Any streaming related operations will see
corresponding improvement. See CASSANDRA-14556.
- NetworkTopologyStrategy now supports auto-expanding the replication_factor
option into all available datacenters at CREATE or ALTER time. For example,
specifying replication_factor: 3 translates to three replicas in every
datacenter. This auto-expansion will _only add_ datacenters for safety.
See CASSANDRA-14303 for more details.
- Added Python 3 support so cqlsh and cqlshlib is now compatible with Python 2.7 and Python 3.6.
Added --python option to cqlsh so users can specify the path to their chosen Python interpreter.
See CASSANDRA-10190 for details.
- Support for server side DESCRIBE statements has been added. See CASSANDRA-14825
- It is now possible to rate limit snapshot creation/clearing. See CASSANDRA-13019
Upgrading
---------
- DESCRIBE|DESC was moved to server side in Cassandra 4.0. As a consequence DESRIBE|DESC will not work in cqlsh 6.0.0
being connected to earlier major Cassandra versions where DESCRIBE does not exist server side.
- cqlsh shell startup script now prefers 'python3' before 'python' when identifying a runtime.
- As part of the Internode Messaging improvement work in CASSANDRA-15066, matching response verbs for every request
verb were introduced and verbs were renamed. DroppedMessageMetrics pre-4.0 are now available with _REQ suffix. As
part of CASSANDRA-16083, we added DroppedMessageMetrics backward compatibility layer which exposes the metrics with
their old names too. Only the value for verbs READ and RANGE_SLICE will differ from the same metrics in 3.11 as it
does not include anymore the responses dropped, only the requests. After being deprecated in 3.11 PAGED_RANGE was
fully removed in 4.0. ConditionNotMet metric has been moved under scope CASClientWriteRequestMetrtic but as part of
CASSANDRA-16083, backward compatibility layer was added so it can be still exposed under the old 3.11 scope.
- Native protocol v5 is promoted from beta in this release. The wire format has changed
significantly and users should take care to ensure client drivers are upgraded to a version
with support for the final v5 format, if currently connecting over v5-beta. (CASSANDRA-15299, CASSANDRA-14973)
- Cassandra removed support for the OldNetworkTopologyStrategy. Before upgrading you will need to change the
replication strategy for the keyspaces using this strategy to the NetworkTopologyStrategy. (CASSANDRA-13990)
- Sstables for tables using with a frozen UDT written by C* 3.0 appear as corrupted.
Background: The serialization-header in the -Statistics.db sstable component contains the type information
of the table columns. C* 3.0 write incorrect type information for frozen UDTs by omitting the
"frozen" information. Non-frozen UDTs were introduced by CASSANDRA-7423 in C* 3.6. Since then, the missing
"frozen" information leads to deserialization issues that result in CorruptSSTableExceptions, potentially other
exceptions as well.
As a mitigation, the sstable serialization-headers are rewritten to contain the missing "frozen" information for
UDTs once, when an upgrade from C* 3.0 is detected. This migration does not touch snapshots or backups.
The sstablescrub tool now performs a check of the sstable serialization-header against the schema. A mismatch of
the types in the serialization-header and the schema will cause sstablescrub to error out and stop by default.
See the new `-e` option. `-e off` disables the new validation code. `-e fix` or `-e fix-only`, e.g.
`sstablescrub -e fix keyspace table`, will validate the serialization-header, rewrite the non-frozen UDTs
in the serialzation-header to frozen UDTs, if that matches the schema, and continue with scrub.
See `sstablescrub -h`.
(CASSANDRA-15035)
- CASSANDRA-13241 lowered the default chunk_lengh_in_kb for compresesd tables from
64kb to 16kb. For highly compressible data this can have a noticeable impact
on space utilization. You may want to consider manually specifying this value.
- Additional columns have been added to system_distributed.repair_history,
system_traces.sessions and system_traces.events. As a result select queries
against these tables - including queries against tracing tables performed
automatically by the drivers and cqlsh - will fail and generate an error in the log
during upgrade when the cluster is mixed version. On 3.x side this will also lead
to broken internode connections and lost messages.
Cassandra versions 3.0.20 and 3.11.6 pre-add these columns (see CASSANDRA-15385),
so please make sure to upgrade to those versions or higher before upgrading to
4.0 for query tracing to not cause any issues during the upgrade to 4.0.
- Timestamp ties between values resolve differently: if either value has a TTL,
this value always wins. This is to provide consistent reconciliation before
and after the value expires into a tombstone.
- Support for legacy auth tables in the system_auth keyspace (users,
permissions, credentials) and the migration code has been removed. Migration
of these legacy auth tables must have been completed before the upgrade to
4.0 and the legacy tables must have been removed. See the 'Upgrading' section
for version 2.2 for migration instructions.
- Cassandra 4.0 removed support for the deprecated Thrift interface. Amongst
other things, this implies the removal of all yaml options related to thrift
('start_rpc', rpc_port, ...).
- Cassandra 4.0 removed support for any pre-3.0 format. This means you
cannot upgrade from a 2.x version to 4.0 directly, you have to upgrade to
a 3.0.x/3.x version first (and run upgradesstable). In particular, this
mean Cassandra 4.0 cannot load or read pre-3.0 sstables in any way: you
will need to upgrade those sstable in 3.0.x/3.x first.
- Upgrades from 3.0.x or 3.x are supported since 3.0.13 or 3.11.0, previous
versions will causes issues during rolling upgrades (CASSANDRA-13274).
- Cassandra will no longer allow invalid keyspace replication options, such
as invalid datacenter names for NetworkTopologyStrategy. Operators MUST
add new nodes to a datacenter before they can set set ALTER or CREATE
keyspace replication policies using that datacenter. Existing keyspaces
will continue to operate, but CREATE and ALTER will validate that all
datacenters specified exist in the cluster.
- Cassandra 4.0 fixes a problem with incremental repair which caused repaired
data to be inconsistent between nodes. The fix changes the behavior of both
full and incremental repairs. For full repairs, data is no longer marked
repaired. For incremental repairs, anticompaction is run at the beginning
of the repair, instead of at the end. If incremental repair was being used
prior to upgrading, a full repair should be run after upgrading to resolve
any inconsistencies.
- Config option index_interval has been removed (it was deprecated since 2.0)
- Deprecated repair JMX APIs are removed.
- The version of snappy-java has been upgraded to 1.1.2.6
- the miniumum value for internode message timeouts is 10ms. Previously, any
positive value was allowed. See cassandra.yaml entries like
read_request_timeout_in_ms for more details.
- Cassandra 4.0 allows a single port to be used for both secure and insecure
connections between cassandra nodes (CASSANDRA-10404). See the yaml for
specific property changes, and see the security doc for full details.
- Due to the parallelization of the initial build of materialized views,
the per token range view building status is stored in the new table
`system.view_builds_in_progress`. The old table `system.views_builds_in_progress`
is no longer used and can be removed. See CASSANDRA-12245 for more details.
- Config option commitlog_sync_batch_window_in_ms has been deprecated as it's
documentation has been incorrect and the setting itself near useless.
Batch mode remains a valid commit log mode, however.
- There is a new commit log mode, group, which is similar to batch mode
but blocks for up to a configurable number of milliseconds between disk flushes.
- nodetool clearsnapshot now required the --all flag to remove all snapshots.
Previous behavior would delete all snapshots by default.
- Nodes are now identified by a combination of IP, and storage port.
Existing JMX APIs, nodetool, and system tables continue to work
and accept/return just an IP, but there is a new
version of each that works with the full unambiguous identifier.
You should prefer these over the deprecated ambiguous versions that only
work with an IP. This was done to support multiple instances per IP.
Additionally we are moving to only using a single port for encrypted and
unencrypted traffic and if you want multiple instances per IP you must
first switch encrypted traffic to the storage port and not a separate
encrypted port. If you want to use multiple instances per IP
with SSL you will need to use StartTLS on storage_port and set
outgoing_encrypted_port_source to gossip outbound connections
know what port to connect to for each instance. Before changing
storage port or native port at nodes you must first upgrade the entire cluster
and clients to 4.0 so they can handle the port not being consistent across
the cluster.
- Names of AWS regions/availability zones have been cleaned up to more correctly
match the Amazon names. There is now a new option in conf/cassandra-rackdc.properties
that lets users enable the correct names for new clusters, or use the legacy
names for existing clusters. See conf/cassandra-rackdc.properties for details.
- Background repair has been removed. dclocal_read_repair_chance and
read_repair_chance table options have been removed and are now rejected.
See CASSANDRA-13910 for details.
- Internode TCP connections that do not ack segments for 30s will now
be automatically detected and closed via the Linux TCP_USER_TIMEOUT
socket option. This should be exceedingly rare, but AWS networks (and
other stateful firewalls) apparently suffer from this issue. You can
tune the timeouts on TCP connection and segment ack via the
`cassandra.yaml:internode_tcp_connect_timeout_in_ms` and
`cassandra.yaml:internode_tcp_user_timeout_in_ms` options respectively.
See CASSANDRA-14358 for details.
- repair_session_space_in_mb setting has been added to cassandra.yaml to allow operators to reduce
merkle tree size if repair is creating too much heap pressure. The repair_session_max_tree_depth
setting added in 3.0.19 and 3.11.5 is deprecated in favor of this setting. See CASSANDRA-14096
- The flags 'enable_materialized_views' and 'enable_sasi_indexes' in cassandra.yaml
have been set as false by default. Operators should modify them to allow the
creation of new views and SASI indexes, the existing ones will continue working.
See CASSANDRA-14866 for details.
- CASSANDRA-15216 - The flag 'cross_node_timeout' has been set as true by default.
This change is done under the assumption that users have setup NTP on
their clusters or otherwise synchronize their clocks, and that clocks are
mostly in sync, since this is a requirement for general correctness of
last write wins.
- CASSANDRA-15257 removed the joda time dependency. Any time formats
passed will now need to conform to java.time.format.DateTimeFormatter.
Most notably, days and months must be two digits, and years exceeding
four digits need to be prefixed with a plus or minus sign.
- cqlsh now returns a non-zero code in case of errors. This is a backward incompatible change so it may
break existing scripts that rely on the current behavior. See CASSANDRA-15623 for more details.
- Updated the default compaction_throughput_mb_per_sec to to 64. The original
default (16) was meant for spinning disk volumes. See CASSANDRA-14902 for details.
- Custom compaction strategies must now handle getting sstables added/removed notifications for
sstables already added/removed - see CASSANDRA-14103 for details.
- Support for JNA with glibc 2.6 and earlier has been removed. Centos 5, Debian 4, and Ubuntu 7.10 operating systems
must be first upgraded. See CASSANDRA-16212 for more.
- In cassandra.yaml, when using vnodes num_tokens must be defined if initial_token is defined.
If it is not defined, or not equal to the numbers of tokens defined in initial_tokens,
the node will not start. See CASSANDRA-14477 for details.
- CASSANDRA-13701 To give a better out of the box experience, the default 'num_tokens'
value has been changed from 256 to 16 for reasons described in
https://cassandra.apache.org/doc/latest/getting_started/production.html#tokens
'allocate_tokens_for_local_replication_factor' is also uncommented and set to 3.
Please note when upgrading that if the 'num_tokens' value is different than what you have
configured, the upgraded node will refuse to start. Also note that if a new node joining
the cluster has a different value for 'num_tokens' than the rest of the datacenter,
the new node will be responsible for a different amount of data than the rest of the datacenter.
Deprecation
-----------
- The JMX MBean org.apache.cassandra.metrics:type=Streaming,name=ActiveOutboundStreams has been
deprecated and will be removed in a subsequent major version. This metric was not updated since several version
already.
- The JMX MBean org.apache.cassandra.db:type=BlacklistedDirectories has been
deprecated in favor of org.apache.cassandra.db:type=DisallowedDirectories
and will be removed in a subsequent major version.
- cqlsh support of 2.7 is deprecated and will warn when running with Python 2.7.
ALTER ... DROP COMPACT STORAGE
------------------------------
- Following a discussion regarding concerns about the safety of the 'ALTER ... DROP COMPACT STORAGE' statement,
the C* development community does not recommend its use in production and considers it experimental
(see https://www.mail-archive.com/[email protected]/msg16789.html).
- An 'enable_drop_compact_storage' flag has been added to cassandra.yaml to allow operators to prevent its use.
Materialized Views
-------------------
- Following a discussion regarding concerns about the design and safety of Materialized Views, the C* development
community no longer recommends them for production use, and considers them experimental. Warnings messages will
now be logged when they are created. (See https://www.mail-archive.com/[email protected]/msg11511.html)
- An 'enable_materialized_views' flag has been added to cassandra.yaml to allow operators to prevent creation of
views
- CREATE MATERIALIZED VIEW syntax has become stricter. Partition key columns are no longer implicitly considered
to be NOT NULL, and no base primary key columns get automatically included in view definition. You have to
specify them explicitly now.
Windows Support Removed
-----------------------
- Due to the lack of maintenance and testing, Windows support is removed from this version onward. The developers
who use Windows 10 still can run Apache Cassandra locally using WSL2 (Windows Subsystem for Linux version 2),
Docker for Windows, or virtualization platform like Hyper-V and VirtualBox.
3.11.10
======
Upgrading
---------
- This release fix a correctness issue with SERIAL reads, and LWT writes that do not apply.
Unfortunately, this fix has a performance impact on read performance at the SERIAL or
LOCAL_SERIAL consistency levels. For heavy users of such SERIAL reads, the performance
impact may be noticeable and may also result in an increased of timeouts. For that
reason, a opt-in system property has been added to disable the fix:
-Dcassandra.unsafe.disable-serial-reads-linearizability=true
Use this flag at your own risk as it revert SERIAL reads to the incorrect behavior of
previous versions. See CASSANDRA-12126 for details.
- SASI's `max_compaction_flush_memory_in_mb` setting was previously getting interpreted in bytes. From 3.11.8
it is correctly interpreted in megabytes, but prior to 3.11.10 previous configurations of this setting will
lead to nodes OOM during compaction. From 3.11.10 previous configurations will be detected as incorrect,
logged, and the setting reverted to the default value of 1GB. It is up to the user to correct the setting
after an upgrade, via dropping and recreating the index. See CASSANDRA-16071 for details.
3.11.6
======
Upgrading
---------
- Sstables for tables using with a frozen UDT written by C* 3.0 appear as corrupted.
Background: The serialization-header in the -Statistics.db sstable component contains the type information
of the table columns. C* 3.0 write incorrect type information for frozen UDTs by omitting the
"frozen" information. Non-frozen UDTs were introduced by CASSANDRA-7423 in C* 3.6. Since then, the missing
"frozen" information leads to deserialization issues that result in CorruptSSTableExceptions, potentially other
exceptions as well.
As a mitigation, the sstable serialization-headers are rewritten to contain the missing "frozen" information for
UDTs once, when an upgrade from C* 3.0 is detected. This migration does not touch snapshots or backups.
The sstablescrub tool now performs a check of the sstable serialization-header against the schema. A mismatch of
the types in the serialization-header and the schema will cause sstablescrub to error out and stop by default.
See the new `-e` option. `-e off` disables the new validation code. `-e fix` or `-e fix-only`, e.g.
`sstablescrub -e fix keyspace table`, will validate the serialization-header, rewrite the non-frozen UDTs
in the serialzation-header to frozen UDTs, if that matches the schema, and continue with scrub.
See `sstablescrub -h`.
(CASSANDRA-15035)
- repair_session_max_tree_depth setting has been added to cassandra.yaml to allow operators to reduce
merkle tree size if repair is creating too much heap pressure. See CASSANDRA-14096 for details.
3.11.5
======
Experimental features
---------------------
- An 'enable_sasi_indexes' flag, true by default, has been added to cassandra.yaml to allow operators to prevent
the creation of new SASI indexes, which are considered experimental and are not recommended for production use.
(See https://www.mail-archive.com/[email protected]/msg13582.html)
- The flags 'enable_sasi_indexes' and 'enable_materialized_views' have been grouped under an experimental features
section in cassandra.yaml.
3.11.4
======
Upgrading
---------
- The order of static columns in SELECT * has been fixed to match that of 2.0 and 2.1 - they are now sorted
alphabetically again, by their name, just like regular columns are. If you use prepared statements and
SELECT * queries, and have both simple and collection static columns in those tables, and are upgrading from an
earlier 3.0 version, then you might be affected by this change. Please see CASSANDRA-14638 for details.
3.11.3
=====
Upgrading
---------
- Materialized view users upgrading from 3.0.15 (3.0.X series) or 3.11.1 (3.11.X series) and later that have performed range movements (join, decommission, move, etc),
should run repair on the base tables, and subsequently on the views to ensure data affected by CASSANDRA-14251 is correctly propagated to all replicas.
- Changes to bloom_filter_fp_chance will no longer take effect on existing sstables when the node is restarted. Only
compactions/upgradesstables regenerates bloom filters and Summaries sstable components. See CASSANDRA-11163
3.11.2
======
Upgrading
---------
- See MAXIMUM TTL EXPIRATION DATE NOTICE above.
- Cassandra is now relying on the JVM options to properly shutdown on OutOfMemoryError. By default it will
rely on the OnOutOfMemoryError option as the ExitOnOutOfMemoryError and CrashOnOutOfMemoryError options
are not supported by the older 1.7 and 1.8 JVMs. A warning will be logged at startup if none of those JVM
options are used. See CASSANDRA-13006 for more details
- Cassandra is not logging anymore by default an Heap histogram on OutOfMemoryError. To enable that behavior
set the 'cassandra.printHeapHistogramOnOutOfMemoryError' System property to 'true'. See CASSANDRA-13006
for more details.
3.11.1
======
Upgrading
---------
- Creating Materialized View with filtering on non-primary-key base column
(added in CASSANDRA-10368) is disabled, because the liveness of view row
is depending on multiple filtered base non-key columns and base non-key
column used in view primary-key. This semantic cannot be supported without
storage format change, see CASSANDRA-13826. For append-only use case, you
may still use this feature with a startup flag: "-Dcassandra.mv.allow_filtering_nonkey_columns_unsafe=true"
Compact Storage (only when upgrading from 3.X or any version lower than 3.0.15)
---------------
- Starting version 4.0, Thrift is no longer supported.
Starting version 5.0, COMPACT STORAGE will no longer be supported.
'ALTER ... DROP COMPACT STORAGE' statement makes Compact Tables CQL-compatible,
exposing internal structure of Thrift/Compact Tables. You can find more details
on exposed internal structure under:
http://cassandra.apache.org/doc/latest/cql/appendices.html#appendix-c-dropping-compact-storage
For uninterrupted cluster upgrades, drivers now support 'NO_COMPACT' startup option.
Supplying this flag will have same effect as 'DROP COMPACT STORAGE', but only for the
current connection.
In order to upgrade, clients supporting a non-compact schema view can be rolled out
gradually. When all the clients are updated 'ALTER ... DROP COMPACT STORAGE' can be
executed. After dropping compact storage, ’NO_COMPACT' option will have no effect
after that.
Materialized Views
-------------------
Materialized Views (only when upgrading from any version lower than 3.0.15 (3.0 series) or 3.11.1 (3.X series))
---------------------------------------------------------------------------------------
- Cassandra will no longer allow dropping columns on tables with Materialized Views.
- A change was made in the way the Materialized View timestamp is computed, which
may cause an old deletion to a base column which is view primary key (PK) column
to not be reflected in the view when repairing the base table post-upgrade. This
condition is only possible when a column deletion to an MV primary key (PK) column
not present in the base table PK (via UPDATE base SET view_pk_col = null or DELETE
view_pk_col FROM base) is missed before the upgrade and received by repair after the upgrade.
If such column deletions are done on a view PK column which is not a base PK, it's advisable
to run repair on the base table of all nodes prior to the upgrade. Alternatively it's possible
to fix potential inconsistencies by running repair on the views after upgrade or drop and
re-create the views. See CASSANDRA-11500 for more details.
- Removal of columns not selected in the Materialized View (via UPDATE base SET unselected_column
= null or DELETE unselected_column FROM base) may not be properly reflected in the view in some
situations so we advise against doing deletions on base columns not selected in views
until this is fixed on CASSANDRA-13826.
3.11.0
======
Upgrading
---------
- Creating Materialized View with filtering on non-primary-key base column
(added in CASSANDRA-10368) is disabled, because the liveness of view row
is depending on multiple filtered base non-key columns and base non-key
column used in view primary-key. This semantic cannot be supported without
storage format change, see CASSANDRA-13826. For append-only use case, you
may still use this feature with a startup flag: "-Dcassandra.mv.allow_filtering_nonkey_columns_unsafe=true"
- The NativeAccessMBean isAvailable method will only return true if the
native library has been successfully linked. Previously it was returning
true if JNA could be found but was not taking into account link failures.
- Primary ranges in the system.size_estimates table are now based on the keyspace
replication settings and adjacent ranges are no longer merged (CASSANDRA-9639).
- In 2.1, the default for otc_coalescing_strategy was 'DISABLED'.
In 2.2 and 3.0, it was changed to 'TIMEHORIZON', but that value was shown
to be a performance regression. The default for 3.11.0 and newer has
been reverted to 'DISABLED'. Users upgrading from Cassandra 2.2 or 3.0 should
be aware that the default has changed.
- The StorageHook interface has been modified to allow to retrieve read information from
SSTableReader (CASSANDRA-13120).
3.10
====
New features
------------
- New `DurationType` (cql duration). See CASSANDRA-11873
- Runtime modification of concurrent_compactors is now available via nodetool
- Support for the assignment operators +=/-= has been added for update queries.
- An Index implementation may now provide a task which runs prior to joining
the ring. See CASSANDRA-12039
- Filtering on partition key columns is now also supported for queries without
secondary indexes.
- A slow query log has been added: slow queries will be logged at DEBUG level.
For more details refer to CASSANDRA-12403 and slow_query_log_timeout_in_ms
in cassandra.yaml.
- Support for GROUP BY queries has been added.
- A new compaction-stress tool has been added to test the throughput of compaction
for any cassandra-stress user schema. see compaction-stress help for how to use.
- Compaction can now take into account overlapping tables that don't take part
in the compaction to look for deleted or overwritten data in the compacted tables.
Then such data is found, it can be safely discarded, which in turn should enable
the removal of tombstones over that data.
The behavior can be engaged in two ways:
- as a "nodetool garbagecollect -g CELL/ROW" operation, which applies
single-table compaction on all sstables to discard deleted data in one step.
- as a "provide_overlapping_tombstones:CELL/ROW/NONE" compaction strategy flag,
which uses overlapping tables as a source of deletions/overwrites during all
compactions.
The argument specifies the granularity at which deleted data is to be found:
- If ROW is specified, only whole deleted rows (or sets of rows) will be
discarded.
- If CELL is specified, any columns whose value is overwritten or deleted
will also be discarded.
- NONE (default) specifies the old behavior, overlapping tables are not used to
decide when to discard data.
Which option to use depends on your workload, both ROW and CELL increase the
disk load on compaction (especially with the size-tiered compaction strategy),
with CELL being more resource-intensive. Both should lead to better read
performance if deleting rows (resp. overwriting or deleting cells) is common.
- Prepared statements are now persisted in the table prepared_statements in
the system keyspace. Upon startup, this table is used to preload all
previously prepared statements - i.e. in many cases clients do not need to
re-prepare statements against restarted nodes.
- cqlsh can now connect to older Cassandra versions by downgrading the native
protocol version. Please note that this is currently not part of our release
testing and, as a consequence, it is not guaranteed to work in all cases.
See CASSANDRA-12150 for more details.
- Snapshots that are automatically taken before a table is dropped or truncated
will have a "dropped" or "truncated" prefix on their snapshot tag name.
- Metrics are exposed for successful and failed authentication attempts.
These can be located using the object names org.apache.cassandra.metrics:type=Client,name=AuthSuccess
and org.apache.cassandra.metrics:type=Client,name=AuthFailure respectively.
- Add support to "unset" JSON fields in prepared statements by specifying DEFAULT UNSET.
See CASSANDRA-11424 for details
- Allow TTL with null value on insert and update. It will be treated as equivalent to inserting a 0.
- Removed outboundBindAny configuration property. See CASSANDRA-12673 for details.
Upgrading
---------
- Support for alter types of already defined tables and of UDTs fields has been disabled.
If it is necessary to return a different type, please use casting instead. See
CASSANDRA-12443 for more details.
- Specifying the default_time_to_live option when creating or altering a
materialized view was erroneously accepted (and ignored). It is now
properly rejected.
- Only Java and JavaScript are now supported UDF languages.
The sandbox in 3.0 already prevented the use of script languages except Java
and JavaScript.
- Compaction now correctly drops sstables out of CompactionTask when there
isn't enough disk space to perform the full compaction. This should reduce
pending compaction tasks on systems with little remaining disk space.
- Request timeouts in cassandra.yaml (read_request_timeout_in_ms, etc) now apply to the
"full" request time on the coordinator. Previously, they only covered the time from
when the coordinator sent a message to a replica until the time that the replica
responded. Additionally, the previous behavior was to reset the timeout when performing
a read repair, making a second read to fix a short read, and when subranges were read
as part of a range scan or secondary index query. In 3.10 and higher, the timeout
is no longer reset for these "subqueries". The entire request must complete within
the specified timeout. As a consequence, your timeouts may need to be adjusted
to account for this. See CASSANDRA-12256 for more details.
- Logs written to stdout are now consistent with logs written to files.
Time is now local (it was UTC on the console and local in files). Date, thread, file
and line info where added to stdout. (see CASSANDRA-12004)
- The 'clientutil' jar, which has been somewhat broken on the 3.x branch, is not longer provided.
The features provided by that jar are provided by any good java driver and we advise relying on drivers rather on
that jar, but if you need that jar for backward compatiblity until you do so, you should use the version provided
on previous Cassandra branch, like the 3.0 branch (by design, the functionality provided by that jar are stable
accross versions so using the 3.0 jar for a client connecting to 3.x should work without issues).
- (Tools development) DatabaseDescriptor no longer implicitly startups components/services like
commit log replay. This may break existing 3rd party tools and clients. In order to startup
a standalone tool or client application, use the DatabaseDescriptor.toolInitialization() or
DatabaseDescriptor.clientInitialization() methods. Tool initialization sets up partitioner,
snitch, encryption context. Client initialization just applies the configuration but does not
setup anything. Instead of using Config.setClientMode() or Config.isClientMode(), which are
deprecated now, use one of the appropiate new methods in DatabaseDescriptor.
- Application layer keep-alives were added to the streaming protocol to prevent idle incoming connections from
timing out and failing the stream session (CASSANDRA-11839). This effectively deprecates the streaming_socket_timeout_in_ms
property in favor of streaming_keep_alive_period_in_secs. See cassandra.yaml for more details about this property.
- Duration litterals support the ISO 8601 format. By consequence, identifiers matching that format
(e.g P2Y or P1MT6H) will not be supported anymore (CASSANDRA-11873).
3.8
===
New features
------------
- Shared pool threads are now named according to the stage they are executing
tasks for. Thread names mentioned in traced queries change accordingly.
- A new option has been added to cassandra-stress "-rate fixed={number}/s"
that forces a scheduled rate of operations/sec over time. Using this, stress can
accurately account for coordinated ommission from the stress process.
- The cassandra-stress "-rate limit=" option has been renamed to "-rate throttle="
- hdr histograms have been added to stress runs, it's output can be saved to disk using:
"-log hdrfile=" option. This histogram includes response/service/wait times when used with the
fixed or throttle rate options. The histogram file can be plotted on
http://hdrhistogram.github.io/HdrHistogram/plotFiles.html
- TimeWindowCompactionStrategy has been added. This has proven to be a better approach
to time series compaction and new tables should use this instead of DTCS. See
CASSANDRA-9666 for details.
- Change-Data-Capture is now available. See cassandra.yaml and for cdc-specific flags and
a brief explanation of on-disk locations for archived data in CommitLog form. This can
be enabled via ALTER TABLE ... WITH cdc=true.
Upon flush, CommitLogSegments containing data for CDC-enabled tables are moved to
the data/cdc_raw directory until removed by the user and writes to CDC-enabled tables
will be rejected with a WriteTimeoutException once cdc_total_space_in_mb is reached
between unflushed CommitLogSegments and cdc_raw.
NOTE: CDC is disabled by default in the .yaml file. Do not enable CDC on a mixed-version
cluster as it will lead to exceptions which can interrupt traffic. Once all nodes
have been upgraded to 3.8 it is safe to enable this feature and restart the cluster.
Upgrading
---------
- The ReversedType behaviour has been corrected for clustering columns of
BYTES type containing empty value. Scrub should be run on the existing
SSTables containing a descending clustering column of BYTES type to correct
their ordering. See CASSANDRA-12127 for more details.
- Ec2MultiRegionSnitch will no longer automatically set broadcast_rpc_address
to the public instance IP if this property is defined on cassandra.yaml.
- The name "json" and "distinct" are not valid anymore a user-defined function
names (they are still valid as column name however). In the unlikely case where
you had defined functions with such names, you will need to recreate
those under a different name, change your code to use the new names and
drop the old versions, and this _before_ upgrade (see CASSANDRA-10783 for more
details).
Deprecation
-----------
- DateTieredCompactionStrategy has been deprecated - new tables should use
TimeWindowCompactionStrategy. Note that migrating an existing DTCS-table to TWCS might
cause increased compaction load for a while after the migration so make sure you run
tests before migrating. Read CASSANDRA-9666 for background on this.
3.7
===
Upgrading
---------
- A maximum size for SSTables values has been introduced, to prevent out of memory
exceptions when reading corrupt SSTables. This maximum size can be set via
max_value_size_in_mb in cassandra.yaml. The default is 256MB, which matches the default
value of native_transport_max_frame_size_in_mb. SSTables will be considered corrupt if
they contain values whose size exceeds this limit. See CASSANDRA-9530 for more details.
3.6
=====
New features
------------
- JMX connections can now use the same auth mechanisms as CQL clients. New options
in cassandra-env.(sh|ps1) enable JMX authentication and authorization to be delegated
to the IAuthenticator and IAuthorizer configured in cassandra.yaml. The default settings
still only expose JMX locally, and use the JVM's own security mechanisms when remote
connections are permitted. For more details on how to enable the new options, see the
comments in cassandra-env.sh. A new class of IResource, JMXResource, is provided for
the purposes of GRANT/REVOKE via CQL. See CASSANDRA-10091 for more details.
Also, directly setting JMX remote port via the com.sun.management.jmxremote.port system
property at startup is deprecated. See CASSANDRA-11725 for more details.
- JSON timestamps are now in UTC and contain the timezone information, see CASSANDRA-11137 for more details.
- Collision checks are performed when joining the token ring, regardless of whether
the node should bootstrap. Additionally, replace_address can legitimately be used
without bootstrapping to help with recovery of nodes with partially failed disks.
See CASSANDRA-10134 for more details.
- Key cache will only hold indexed entries up to the size configured by
column_index_cache_size_in_kb in cassandra.yaml in memory. Larger indexed entries
will never go into memory. See CASSANDRA-11206 for more details.
- For tables having a default_time_to_live specifying a TTL of 0 will remove the TTL
from the inserted or updated values.
- Startup is now aborted if corrupted transaction log files are found. The details
of the affected log files are now logged, allowing the operator to decide how
to resolve the situation.
- Filtering expressions are made more pluggable and can be added programatically via
a QueryHandler implementation. See CASSANDRA-11295 for more details.
3.4
===
New features
------------
- Internal authentication now supports caching of encrypted credentials.
Reference cassandra.yaml:credentials_validity_in_ms
- Remote configuration of auth caches via JMX can be disabled using the
the system property cassandra.disable_auth_caches_remote_configuration
- sstabledump tool is added to be 3.0 version of former sstable2json. The tool only
supports v3.0+ SSTables. See tool's help for more detail.
Upgrading
---------
- Nothing specific to 3.4 but please see previous versions upgrading section,
especially if you are upgrading from 2.2.
Deprecation
-----------
- The mbean interfaces org.apache.cassandra.auth.PermissionsCacheMBean and
org.apache.cassandra.auth.RolesCacheMBean are deprecated in favor of
org.apache.cassandra.auth.AuthCacheMBean. This generalized interface is
common across all caches in the auth subsystem. The specific mbean interfaces
for each individual cache will be removed in a subsequent major version.
3.2
===
New features
------------
- We now make sure that a token does not exist in several data directories. This
means that we run one compaction strategy per data_file_directory and we use
one thread per directory to flush. Use nodetool relocatesstables to make sure your
tokens are in the correct place, or just wait and compaction will handle it. See
CASSANDRA-6696 for more details.
- bound maximum in-flight commit log replay mutation bytes to 64 megabytes
tunable via cassandra.commitlog_max_outstanding_replay_bytes
- Support for type casting has been added to the selection clause.
- Hinted handoff now supports compression. Reference cassandra.yaml:hints_compression.
Note: hints compression is currently disabled by default.
Upgrading
---------
- The compression ratio metrics computation has been modified to be more accurate.
- Running Cassandra as root is prevented by default.
- JVM options are moved from cassandra-env.(sh|ps1) to jvm.options file
Deprecation
-----------
- The Thrift API is deprecated and will be removed in Cassandra 4.0.
3.1
=====
Upgrading
---------
- The return value of SelectStatement::getLimit as been changed from DataLimits
to int.
- Custom index implementation should be aware that the method Indexer::indexes()
has been removed as its contract was misleading and all custom implementation
should have almost surely returned true inconditionally for that method.
- GC logging is now enabled by default (you can disable it in the jvm.options
file if you prefer).
3.0
===
New features
------------
- EACH_QUORUM is now a supported consistency level for read requests.
- Support for IN restrictions on any partition key component or clustering key
as well as support for EQ and IN multicolumn restrictions has been added to
UPDATE and DELETE statement.
- Support for single-column and multi-colum slice restrictions (>, >=, <= and <)
has been added to DELETE statements
- nodetool rebuild_index accepts the index argument without
the redundant table name
- Materialized Views, which allow for server-side denormalization, is now
available. Materialized views provide an alternative to secondary indexes
for non-primary key queries, and perform much better for indexing high
cardinality columns.
See http://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views
- Hinted handoff has been completely rewritten. Hints are now stored in flat
files, with less overhead for storage and more efficient dispatch.
See CASSANDRA-6230 for full details.
- Option to not purge unrepaired tombstones. To avoid users having data resurrected
if repair has not been run within gc_grace_seconds, an option has been added to
only allow tombstones from repaired sstables to be purged. To enable, set the
compaction option 'only_purge_repaired_tombstones':true but keep in mind that if
you do not run repair for a long time, you will keep all tombstones around which
can cause other problems.
- Enabled warning on GC taking longer than 1000ms. See
cassandra.yaml:gc_warn_threshold_in_ms
Upgrading
---------
- Clients must use the native protocol version 3 when upgrading from 2.2.X as
the native protocol version 4 is not compatible between 2.2.X and 3.Y. See
https://www.mail-archive.com/[email protected]/msg45381.html for details.
- A new argument of type InetAdress has been added to IAuthenticator::newSaslNegotiator,
representing the IP address of the client attempting authentication. It will be a breaking
change for any custom implementations.
- token-generator tool has been removed.
- Upgrade to 3.0 is supported from Cassandra 2.1 versions greater or equal to 2.1.9,
or Cassandra 2.2 versions greater or equal to 2.2.2. Upgrade from Cassandra 2.0 and
older versions is not supported.
- The 'memtable_allocation_type: offheap_objects' option has been removed. It should
be re-introduced in a future release and you can follow CASSANDRA-9472 to know more.
- Configuration parameter memory_allocator in cassandra.yaml has been removed.
- The native protocol versions 1 and 2 are not supported anymore.
- Max mutation size is now configurable via max_mutation_size_in_kb setting in
cassandra.yaml; the default is half the size commitlog_segment_size_in_mb * 1024.
- 3.0 requires Java 8u40 or later.
- Garbage collection options were moved from cassandra-env to jvm.options file.
- New transaction log files have been introduced to replace the compactions_in_progress
system table, temporary file markers (tmp and tmplink) and sstable ancerstors.
Therefore, compaction metadata no longer contains ancestors. Transaction log files
list sstable descriptors involved in compactions and other operations such as flushing
and streaming. Use the sstableutil tool to list any sstable files currently involved
in operations not yet completed, which previously would have been marked as temporary.
A transaction log file contains one sstable per line, with the prefix "add:" or "remove:".
They also contain a special line "commit", only inserted at the end when the transaction
is committed. On startup we use these files to cleanup any partial transactions that were
in progress when the process exited. If the commit line is found, we keep new sstables
(those with the "add" prefix) and delete the old sstables (those with the "remove" prefix),
vice-versa if the commit line is missing. Should you lose or delete these log files,
both old and new sstable files will be kept as live files, which will result in duplicated
sstables. These files are protected by incremental checksums so you should not manually
edit them. When restoring a full backup or moving sstable files, you should clean-up
any left over transactions and their temporary files first. You can use this command:
===> sstableutil -c ks table
See CASSANDRA-7066 for full details.
- New write stages have been added for batchlog and materialized view mutations
you can set their size in cassandra.yaml
- User defined functions are now executed in a sandbox.
To use UDFs and UDAs, you have to enable them in cassandra.yaml.
- New SSTable version 'la' with improved bloom-filter false-positive handling
compared to previous version 'ka' used in 2.2 and 2.1. Running sstableupgrade
is not necessary but recommended.
- Before upgrading to 3.0, make sure that your cluster is in complete agreement
(schema versions outputted by `nodetool describecluster` are all the same).
- Schema metadata is now stored in the new `system_schema` keyspace, and
legacy `system.schema_*` tables are now gone; see CASSANDRA-6717 for details.
- Pig's support has been removed.
- Hadoop BulkOutputFormat and BulkRecordWriter have been removed; use
CqlBulkOutputFormat and CqlBulkRecordWriter instead.
- Hadoop ColumnFamilyInputFormat and ColumnFamilyOutputFormat have been removed;
use CqlInputFormat and CqlOutputFormat instead.
- Hadoop ColumnFamilyRecordReader and ColumnFamilyRecordWriter have been removed;
use CqlRecordReader and CqlRecordWriter instead.
- hinted_handoff_enabled in cassandra.yaml no longer supports a list of data centers.
To specify a list of excluded data centers when hinted_handoff_enabled is set to true,
use hinted_handoff_disabled_datacenters, see CASSANDRA-9035 for details.
- The `sstable_compression` and `chunk_length_kb` compression options have been deprecated.
The new options are `class` and `chunk_length_in_kb`. Disabling compression should now
be done by setting the new option `enabled` to `false`.
- The compression option `crc_check_chance` became a top-level table option, but is currently
enforced only against tables with enabled compression.
- Only map syntax is now allowed for caching options. ALL/NONE/KEYS_ONLY/ROWS_ONLY syntax
has been deprecated since 2.1.0 and is being removed in 3.0.0.
- The 'index_interval' option for 'CREATE TABLE' statements, which has been deprecated
since 2.1 and replaced with the 'min_index_interval' and 'max_index_interval' options,
has now been removed.
- The 'replicate_on_write' and 'populate_io_cache_on_flush' options for 'CREATE TABLE' statements,
which have been deprecated since 2.1, have also been removed.
- Batchlog entries are now stored in a new table - system.batches.
The old one has been deprecated.
- JMX methods set/getCompactionStrategyClass have been removed, use
set/getCompactionParameters or set/getCompactionParametersJson instead.
- SizeTieredCompactionStrategy parameter cold_reads_to_omit has been removed.
- The secondary index API has been comprehensively reworked. This will be a breaking
change for any custom index implementations, which should now look to implement
the new org.apache.cassandra.index.Index interface. New syntax has been added to create
and query row-based indexes, which are not explicitly linked to a single column in the
base table.
2.2.4
=====
Deprecation
-----------
- Pig support has been deprecated, and will be removed in 3.0.
Please see CASSANDRA-10542 for more details.
- Configuration parameter memory_allocator in cassandra.yaml has been deprecated
and will be removed in 3.0.0. As mentioned below for 2.2.0, jemalloc is
automatically preloaded on Unix platforms.
Operations
----------
- Switching data center or racks is no longer an allowed operation on a node
which has data. Instead, the node will need to be decommissioned and
rebootstrapped. If moving from the SimpleSnitch, make sure that the data
center and rack containing all current nodes is named "datacenter1" and
"rack1". To override this behaviour use -Dcassandra.ignore_rack=true and/or
-Dcassandra.ignore_dc=true.
- Reloading the configuration file of GossipingPropertyFileSnitch has been disabled.
Upgrading
---------
- The default for the inter-DC stream throughput setting
(inter_dc_stream_throughput_outbound_megabits_per_sec in cassandra.yaml) is
the same than the one for intra-DC one (200Mbps) instead of being unlimited.
Having it unlimited was never intended and was a bug.
New features
------------
- Time windows in DTCS are now limited to 1 day by default to be able to
handle bootstrap and repair in a better way. To get the old behaviour,
increase max_window_size_seconds.
- DTCS option max_sstable_age_days is now deprecated and defaults to 1000 days.
- Native protocol server now allows both SSL and non-SSL connections on
the same port.
2.2.3
=====
Upgrading
---------
- Nothing specific to this release, but please see 2.2 if you are upgrading
from a previous version.
2.2.2
=====
Changed Defaults
----------------
- commitlog_total_space_in_mb will use the smaller of 8192, and 1/4
of the total space of the commitlog volume. (Before: always used
8192)
- The following INFO logs were reduced to DEBUG level and will now show
on debug.log instead of system.log:
- Memtable flushing actions
- Commit log replayed files
- Compacted sstables
- SStable opening (SSTableReader)
New features
------------
- Custom QueryHandlers can retrieve the column specifications for the bound
variables from QueryOptions by using the hasColumnSpecifications()
and getColumnSpecifications() methods.
- A new default assynchronous log appender debug.log was created in addition
to the system.log appender in order to provide more detailed log debugging.
In order to disable debug logging, you must comment-out the ASYNCDEBUGLOG
appender on conf/logback.xml. See CASSANDRA-10241 for more information.
2.2.1
=====
New features
------------
- COUNT(*) and COUNT(1) can be selected with other columns or functions
2.2
===
Upgrading
---------
- The authentication & authorization subsystems have been redesigned to
support role based access control (RBAC), resulting in a change to the
schema of the system_auth keyspace. See below for more detail.
For systems already using the internal auth implementations, the process
for converting existing data during a rolling upgrade is straightforward.
As each node is restarted, it will attempt to convert any data in the
legacy tables into the new schema. Until enough nodes to satisfy the
replication strategy for the system_auth keyspace are upgraded and so have
the new schema, this conversion will fail with the failure being reported
in the system log.
During the upgrade, Cassandra's internal auth classes will continue to use
the legacy tables, so clients experience no disruption. Issuing DCL
statements during an upgrade is not supported.
Once all nodes are upgraded, an operator with superuser privileges should
drop the legacy tables, system_auth.users, system_auth.credentials and
system_auth.permissions. Doing so will prompt Cassandra to switch over to
the new tables without requiring any further intervention.
While the legacy tables are present a restarted node will re-run the data
conversion and report the outcome so that operators can verify that it is
safe to drop them.
New features
------------
- The LIMIT clause applies now only to the number of rows returned to the user,
not to the number of row queried. By consequence, queries using aggregates will not
be impacted by the LIMIT clause anymore.
- Very large batches will now be rejected (defaults to 50kb). This
can be customized by modifying batch_size_fail_threshold_in_kb.
- Selecting columns,scalar functions, UDT fields, writetime or ttl together
with aggregated is now possible. The value returned for the columns,
scalar functions, UDT fields, writetime and ttl will be the ones for
the first row matching the query.
- Windows is now a supported platform. Powershell execution for startup scripts
is highly recommended and can be enabled via an administrator command-prompt
with: 'powershell set-executionpolicy unrestricted'