[GitHub] jena pull request: JENA-1085: Common pattern for transaction lifec...

[ajs6f <gi...@git.apache.org>]

Github user ajs6f commented on a diff in the pull request:

    https://github.com/apache/jena/pull/108#discussion_r47445013
  
    --- Diff: jena-arq/src/main/java/org/apache/jena/sparql/core/mem/DatasetGraphInMemory.java ---
    @@ -55,21 +51,15 @@
     
         private final DatasetPrefixStorage prefixes = new DatasetPrefixStorageInMemory();
     
    +    /** This lock imposes the multiple-reader and single-writer policy of transactions */
         private final Lock writeLock = new LockMRPlusSW();
     
    -    private Lock writeLock() {
    -        return writeLock;
    -    }
    -
    -    private final ReentrantReadWriteLock commitLock = new ReentrantReadWriteLock(true);
    -
         /**
    -     * Commits must be atomic, and because a thread that is committing alters the various indexes one after another, we
    -     * lock out {@link #begin(ReadWrite)} while {@link #commit()} is executing.
    +     * Transaction lifecycle operations must be atomi, especially begin and commit where
    --- End diff --
    
    This comment is a bit confusing. How about:
    ```
    We have a lock for committing because transaction lifecycle operations must be atomic, especially {@link Transactional#begin} and {@link Transactional#commit}, for which the global state of the (possibly multiple) indexes may be read or written one after another.
    ```


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