What's new for release 3.6

doc/release/3.5.0.rst

@@ -113,19 +113,19 @@ if the ``fail_if`` expression evaluates to ``true``.
 [CE] Faster large (500+) clusters reload
 ----------------------------------------
 
-The new patch processes an instance's configuration only when it is explicitly accessed,
-such as through a ``config:get(<...>, {instance = <...>})`` call. This significantly speeds up startup and
-configuration reloads, especially for large clusters.
+The new release processes an instance's configuration only when it is explicitly accessed,
+such as through a ``config:get(<...>, {instance = <...>})`` call.
+This significantly speeds up startup and configuration reloads, especially for large clusters.
 
 .. _3-5-quorum-synchronous-replication:
 
-[EE] Support of the quorum synchronous replication setup in three availability zones
-------------------------------------------------------------------------------------
+[EE] Support for quorum synchronous replication setup in three availability zones
+---------------------------------------------------------------------------------
 
-A new patchset makes the ``replication.failover = supervised`` mode supports the quorum synchronous 
+This release makes the ``replication.failover = supervised`` mode support quorum synchronous
 replication setup in three availability zones.
 
-The patchset includes several preliminary patches, which make the ``appoint_commit`` logic more safe
+This release includes several preliminary patches, which make the ``appoint_commit`` logic more safe
 in regards to various possible situations, and the main patch, which adds the ``box.ctl.promote()`` call to
 ``appoint_commit`` if the ``failover.replicasets.<replicaset_name>.synchro_mode`` is set to ``true``.
 
@@ -137,7 +137,7 @@ in regards to various possible situations, and the main patch, which adds the ``
 When applying centralized configuration updates, Tarantool supervised failover coordinator no longer performs RW
 switch within the replicaset if there are dead instances.
 
-A new patch introduces a smarter configuration update process for the Tarantool supervised failover
+This release introduces a smarter configuration update process for the Tarantool supervised failover
 coordinator. Previously, any change would trigger a full restart of all services, causing unnecessary downtime.
 Now, the system intelligently differentiates between option types: most settings can be applied dynamically without
 any restart. A restart will only occur if you modify critical core parameters, specifically any options under
@@ -155,7 +155,7 @@ It is now possible to define a field with the ``decimal32/64/128/256`` type (fix
   (``MP_DECIMAL``) in all engines (MemTX, Vinyl, MemCS, Quiver (if applicable)).
 * The internal representation of fixed point decimal values remains the same as the exisitng decimal
   type (decNumber) in all engines except MemCS and Quiver.
-* It is now possible to batch insert and scan fixed point decimal values in the Arrow format 
+* It is now possible to batch insert and scan fixed point decimal values in the Apache Arrow format
   in MemCS and Quiver engines.
 
 .. _3-5-memcs-brin-indexes:
@@ -180,8 +180,8 @@ improvements of 2.5x for 10% filled columns and 11x for 1% filled columns.
 
 .. _3-5-memcs-index-batch-insertion:
 
-Secondary index batch insertion performance is improved in MemCS
-----------------------------------------------------------------
+[EE] Secondary index batch insertion performance is improved in MemCS
+---------------------------------------------------------------------
 
 This release introduces a new ``next_row`` method that significantly accelerates batch insertion and secondary
 index building. The method replaces the old tuple-based iterator, using a column mask to process only necessary
@@ -190,8 +190,8 @@ index insertion has improved by over 550%, with rates jumping from ~10k to 62k r
 
 .. _3-5-memcs-storage-string-scanning:
 
-Storage format and string scanning performance improvements in MemCS
---------------------------------------------------------------------
+[EE] Storage format and string scanning performance improvements in MemCS
+-------------------------------------------------------------------------
 
 This release combines a new optimized storage format for short strings with a powerful Arrow view layout to
 deliver huge performance improvements for string scanning.
@@ -205,9 +205,9 @@ Storage format updates:
 * The ``memcs_column_data_size()`` API function has been split into ``memcs_column_int_data_size()``
   and ``memcs_column_ext_data_size()`` to account for the new dual storage format.
 
-Scan performance for 3 different sets of strings (the lengths are randomly distributed in the range 1-12, 1-100, 1-1000)
-and 2 different modes, ``notouch`` and ``touch``. In the ``notouch`` mode strings are only scanned as a batch, without
-accessing them; in the ``touch`` mode, strings are scanned and the first external character is checked:
+We ran scan performance tests for 3 different sets of strings (the lengths were randomly distributed in the ranges 1-12, 1-100, 1-1000)
+and 2 different modes, ``notouch`` and ``touch``. In the ``notouch`` mode strings were only scanned as a batch, without
+accessing them; in the ``touch`` mode, strings were scanned and the first external character was checked:
 
 * Strings 1-12 chars: Up to 4.8x faster in the ``notouch`` mode, and 3.2x faster in the ``touch`` mode.
 * Strings 1-100 chars: Up to 3.1x faster in the ``notouch`` mode, and 1.8x faster in the ``touch`` mode.

doc/release/3.6.0.rst

@@ -0,0 +1,116 @@
+Tarantool 3.6
+=============
+
+Release date:  2025-12-12
+
+Releases on GitHub: :tarantool-release:`3.6.0`
+
+The 3.6 release of Tarantool adds the following main product features and improvements
+for the Community and Enterprise editions:
+
+*   **Community Edition (CE)**
+
+    *   Memtx: significantly faster snapshot recovery.
+    *   New privileges: ``grant`` and ``metagrant``.
+
+*   **Enterprise Edition (EE)**
+
+    *   Failover coordinator: synchronous replication for 2 DC topology.
+    *   MemCS: multiple improvements.
+
+.. _3-6-faster-snapshot-recovery-ce:
+
+[CE] Memtx: significantly faster snapshot recovery
+--------------------------------------------------
+
+This release speeds up memtx snapshot recovery by up to 70% by offloading MsgPack decoding
+to a separate thread. Space and transactional triggers (``space.on_replace``, ``space.before_replace``)
+are now deprecated during recovery.
+
+.. _3-6-grant-metagrant-privileges-ce:
+
+[CE] New privileges: ``grant`` and ``metagrant``
+------------------------------------------------
+
+This release introduces new privileges, ``grant`` and ``metagrant``. They allow Tarantool users
+to create new users with a complete range of privileges, like the builtin ``admin`` user does.
+
+The ``grant`` privilege allows granting any privilege, except ``grant`` and ``metagrant``, on an object, object class or universe.
+The ``metagrant`` privilege allows granting ``grant`` and ``metagrant`` privileges.
+
+Both ``grant`` and ``metagrant`` are only grantable on the universe and
+allow granting privileges only to other users, not to the current user.
+
+.. _3-6-sync-replication-2-dc-ee:
+
+[EE] Failover coordinator: synchronous replication for 2 DC topology
+--------------------------------------------------------------------
+
+In previous releases, the failover coordinator supported synchronous replication
+for topologies with data storages located in 3 and more data centers.
+With N instances within a replica set, the minimal quorum size could be ``N/2 + 1``.
+Topologies with 2 data centers were not supported because the quorum size could not be
+dynamically decreased if connection to the second data center was lost.
+For example, in a minimal replica set of 2 instances the default quorum size is 2
+(calculated as 2/2 + 1 = 2).
+If one of the instances fails, no new transactions can be committed, because it is
+impossible to get an ack from the second instance.
+So, new transactions are lost.
+
+Now, for *supervised failover*, Tarantool supports synchronous replication for topologies
+with data storages located in 2 data centers.
+The failover coordinator automatically decreases the quorum size if connection
+to the second data center is lost, and restores the cluster's operability within
+the available data center.
+When connection to the second data center is up again, the failover coordinator
+automatically restores the normal quorum size.
+So, no transactions are lost.
+
+However, there are some limitations.
+An important thing is that while data storages can be deployed in just 2 DCs,
+we need yet another DC (a so-called "quorum DC") for an extra configuration storage
+(based on etcd or Tarantool). So, the effective topology (also known as "2,5 DC topology")
+implies 3 DCs all in all: two DCs with a complete set of components
+(data storages, routers, configuration storages) + one DC with configuration storage.
+
+Here are the cases when a topology with data storages deployed in 2 DCs may fail.
+
+**Case #1:** "interrupted data enrichment after DC failure"
+
+a. DC #1 goes down, while DC #2 is up. The failover coordinator decreases the quorum size
+   to 1. The cluster keeps serving the clients.
+b. DC #1 goes up and starts obtaining missed data from DC #2. The quorum size is still 1.
+c. The data enrichment process for DC #1 is still in progress, but DC #2 goes down now.
+   In this case, the cluster becomes unavailable.
+
+**Case #2:** "no multiple quorum decrease"
+
+a. DC #1 (2 instances) goes down, while DC #2 (2 instances) is up.
+b. One of the 2 instances in DC #2 goes down.
+   In this case, the cluster becomes unavailable as well.
+
+**Case #3:** Both DCs go down -- the ultimate case when the cluster becomes unavailable.
+
+In other cases, the cluster will keep working.
+
+.. _3-6-memcs-improvements:
+
+[EE] MemCS: multiple improvements
+---------------------------------
+
+This release brings multiple minor enhancements to the MemCS engine, most of them
+focusing on indexes and performance.
+
+MemCS now supports:
+
+* Aggregates over decimal fields,
+* Inserting into the middle of MemCS primary index with aggregates,
+* Specifying per-column layout in space format and secondary index definitions,
+* ``index:quantile()``,
+* Bloom aggregates,
+* Statistics of index aggregates and scanner,
+* Index aggregates exported to their Lua objects,
+* Some C API improvements related to inserting and scanning data in the Apache Arrow format.
+
+Furthermore, the performance of MemCS skip index writes is increased. Now this index
+doesn't reallocate blocks if they are not used by any read view.

doc/release/index.rst

@@ -63,8 +63,14 @@ For information about earlier versions, see :doc:`eos_versions`.
             -   End of support
             -   Versions
 
-        *   -   :doc:`3.5 </release/3.5.0>`
+        *   -   :doc:`3.6 </release/3.6.0>`
+            -   **December 12, 2025**
+            -   **Not planned yet**
             -   **Not planned yet**
+            -   | :tarantool-release:`3.6.0`
+
+        *   -   :doc:`3.5 </release/3.5.0>`
+            -   **August 27, 2025**
             -   **Not planned yet**
             -   **Not planned yet**
             -   | :tarantool-release:`3.5.0`
@@ -93,6 +99,7 @@ For information about earlier versions, see :doc:`eos_versions`.
     :maxdepth: 1
 
     policy
+    3.6.0
     3.5.0
     3.4.0
     3.3.0