[jira] [Created] (IGNITE-18733) Mechanism to synchronize database schema changes between nodes

["Sergey Chugunov (Jira)" <ji...@apache.org>]

Sergey Chugunov created IGNITE-18733:
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             Summary: Mechanism to synchronize database schema changes between nodes
                 Key: IGNITE-18733
                 URL: https://issues.apache.org/jira/browse/IGNITE-18733
             Project: Ignite
          Issue Type: Epic
          Components: persistence
            Reporter: Sergey Chugunov


Usability of Apache Ignite as a distributed database to a large extent depends on a solid support of dynamic schema changes.
DDL operations like adding of deleting columns of a table or (more importantly) adding or dropping indexes require proper syncronization between nodes and integration with a number of other components.

Regardless of implementation details synchronization mechanism:
 * should allow (most) user operations and schema change operations to execute concurrently;
 * should allow access to the data despite of the version of its schema;
 * should shorten periods of time when certain types of operations are suspended or work ineffectively (e.g. because of rebuilding of an index).

Schema synchronization needs integration with the following components (the list may not be exhaustive):
 * SQL engine - provide information about start and stop of operations, notify about [un]availability of certain indexes;
 * TX engine - e.g. if a transaction is started concurrently with DDL operations;
 * GC for MV storages - garbage collector needs to be aware of schema changes.



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