IGNITE-9624: MVCC: improved JavaDocs for CacheAtomicityMode.TRANSACTIONAL_SNAPSHOT. This closes #4777.
Project: http://git-wip-us.apache.org/repos/asf/ignite/repo Commit: http://git-wip-us.apache.org/repos/asf/ignite/commit/3ab35336 Tree: http://git-wip-us.apache.org/repos/asf/ignite/tree/3ab35336 Diff: http://git-wip-us.apache.org/repos/asf/ignite/diff/3ab35336 Branch: refs/heads/ignite-gg-14206 Commit: 3ab353367a1f89b29c32ad267b045084a26653dd Parents: 5e220f9 Author: ipavlukhin <vololo...@gmail.com> Authored: Thu Sep 27 14:14:57 2018 +0300 Committer: devozerov <voze...@gridgain.com> Committed: Thu Sep 27 14:14:57 2018 +0300 ---------------------------------------------------------------------- .../apache/ignite/cache/CacheAtomicityMode.java | 42 ++++++++++---------- 1 file changed, 20 insertions(+), 22 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/ignite/blob/3ab35336/modules/core/src/main/java/org/apache/ignite/cache/CacheAtomicityMode.java ---------------------------------------------------------------------- diff --git a/modules/core/src/main/java/org/apache/ignite/cache/CacheAtomicityMode.java b/modules/core/src/main/java/org/apache/ignite/cache/CacheAtomicityMode.java index 1584286..43c561c 100644 --- a/modules/core/src/main/java/org/apache/ignite/cache/CacheAtomicityMode.java +++ b/modules/core/src/main/java/org/apache/ignite/cache/CacheAtomicityMode.java @@ -33,12 +33,12 @@ import org.jetbrains.annotations.Nullable; */ public enum CacheAtomicityMode { /** - * Specified fully {@code ACID}-compliant transactional cache behavior for key-value API. See - * {@link Transaction} for more information about transactions. + * Enables fully {@code ACID}-compliant transactional cache behavior for the key-value API. * <p> - * <b>Note:</b> this mode guaranties transactional behavior <b>only for key-value API</b> operations. - * For ACID SQL transactions use {@code CacheAtomicityMode.TRANSACTIONAL_SNAPSHOT} mode. - * </p> + * <b>Note!</b> In this mode, transactional consistency is guaranteed for key-value API operations only. + * To enable ACID capabilities for SQL transactions, use the {@code TRANSACTIONAL_SNAPSHOT} mode. + * <p> + * See {@link Transaction} for more information about transactions. */ TRANSACTIONAL, @@ -95,26 +95,24 @@ public enum CacheAtomicityMode { ATOMIC, /** - * Specified fully {@code ACID}-compliant transactional cache behavior not only for key-value API, - * but also for SQL transactions. + * Specifies fully {@code ACID}-compliant transactional cache behavior for both key-value API and SQL transactions. + * <p> + * This atomicity mode enables multiversion concurrency control (MVCC) for the cache. In MVCC-enabled caches, + * when a transaction updates a row, it creates a new version of that row instead of overwriting it. + * Other users continue to see the old version of the row until the transaction is committed. + * In this way, readers and writers do not conflict with each other and always work with a consistent dataset. + * The old version of data is cleaned up when it's no longer accessed by anyone. * <p> - * This cache atomicity mode is implemented within multiversion concurrency control (MVCC) where database can - * contain multiple versions of each row to allow readers do not collide with writers. - * Each update in this mode generates a new version of a row and don't remove a previous one. - * Old versions are cleaned only when they are not visible to anyone. - * </p> + * With this mode enabled, one node is elected as an MVCC coordinator. This node tracks all in-flight transactions + * and queries executed in the cluster. Each transaction or query executed over the cache with + * {@code TRANSACTIONAL_SNAPSHOT} mode works with a current snapshot of data generated for this transaction or query + * by the coordinator. This snapshot ensures that the transaction works with a consistent database state + * during its execution period. * <p> - * There is one node in cluster is elected as MVCC coordinator. This node tracks all in-flight transactions and - * queries in the cluster. - * Each transaction or query over the cache with {@code TRANSACTIONAL_SNAPSHOT} mode obtains current - * database snapshot from the coordinator. This snapshot allows transactions and queries to skip invisible - * updates made by concurrent transactions to always observe the same consistent database state. - * </p> + * Note! This atomicity mode is not compatible with the other modes within the same transaction. + * If a transaction is executed over multiple caches, all caches must have the same mode, + * either {@code TRANSACTIONAL_SNAPSHOT} or {@code TRANSACTIONAL} * <p> - * <b>Note!</b> This atomicity mode is not interoperable with the other atomicity modes in the same transaction. - * Caches participated in transaction should either be all {@code TRANSACTIONAL} or all - * {@code TRANSACTIONAL_SNAPSHOT}, but not the mixed ones. - * </p> * See {@link Transaction} for more information about transactions. */ TRANSACTIONAL_SNAPSHOT;
