Module org.apache.jena.arq
Package org.apache.jena.system

Class TxnCounter

java.lang.Object
org.apache.jena.system.TxnCounter
All Implemented Interfaces:
Transactional
public class TxnCounter extends Object implements Transactional
A MR+SW transactional Counter

  • Nested Class Summary

    Nested classes/interfaces inherited from interface org.apache.jena.sparql.core.Transactional

    Transactional.Promote

  • Constructor Summary

    Constructors
    Constructor
    Description
    TxnCounter(long x)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    abort()
    Abort a transaction - finish the transaction and undo any changes (if a "write" transaction)
    void
    begin(ReadWrite readWrite)
    Start either a READ or WRITE transaction.
    void
    begin(TxnType txnType)
    Start a transaction.
    READ or WRITE transactions start in that state and do not change for the lifetime of the transaction.
    void
    commit()
    Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
    void
    dec()
    Decrement the value inside a write transaction
    void
    end()
    Finish the transaction - if a write transaction and commit() has not been called, then abort
    long
    get()
    Return the current value.
    void
    inc()
    Increment the value inside a write transaction
    boolean
    isInTransaction()
    Say whether inside a transaction.
    boolean
    promote(Transactional.Promote promoteMode)
    Attempt to promote a transaction from "read" mode to "write" and the transaction.
    long
    read()
    Return the current value in a transaction.
    long
    set(long x)
    Set the value inside a write transaction, return the old value
    ReadWrite
    transactionMode()
    Return the current mode of the transaction - "read" or "write".
    TxnType
    transactionType()
    Return the transaction type used in begin(TxnType).
    long
    value()
    Read the current global state (that is, the last committed value) outside a transaction.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface org.apache.jena.sparql.core.Transactional

    begin, calc, calculate, calculateRead, calculateWrite, exec, execute, executeRead, executeWrite, promote

  • Constructor Details

    • TxnCounter

      public TxnCounter(long x)

  • Method Details

    • begin

      public void begin(ReadWrite readWrite)
      Description copied from interface: Transactional
      Start either a READ or WRITE transaction.
      Specified by:
      begin in interface Transactional

    • begin

      public void begin(TxnType txnType)
      Description copied from interface: Transactional
      Start a transaction.
      READ or WRITE transactions start in that state and do not change for the lifetime of the transaction.
      • WRITE: this guarantees a WRITE will complete if commit() is called. The same as begin(ReadWrite.WRITE).
      • READ: the transaction can not promote to WRITE,ensuring read-only access to the data. The same as begin(ReadWrite.READ).
      • READ_PROMOTE: the transaction will go from "read" to "write" if an update is attempted and if the dataset has not been changed by another write transaction. See also Transactional.promote().
      • READ_COMMITTED_PROMOTE: Use this with care. The promotion will succeed but changes from other transactions become visible.
      Read committed: at the point transaction attempts promotion from "read" to "write", the system checks if the dataset has change since the transaction started (called begin). If READ_PROMOTE, the dataset must not have changed; if READ_COMMITTED_PROMOTE any intermediate changes are visible but the application can not assume any data it has read in the transaction is the same as it was at the point the transaction started.

      This operation is optional and some implementations may throw a JenaTransactionException exception for some or all TxnType values.

      See Transactional.begin(ReadWrite) for a form that is required of implementations.

      Specified by:
      begin in interface Transactional

    • promote

      public boolean promote(Transactional.Promote promoteMode)
      Description copied from interface: Transactional
      Attempt to promote a transaction from "read" mode to "write" and the transaction. This method allows the form of promotion to be specified. The transaction must not have been started with READ, which is read-only.

      An argument of READ_PROMOTE treats the promotion as if the transaction was started with READ_PROMOTE (any other writer commiting since the transaction started blocks promotion) and READ_COMMITTED_PROMOTE treats the promotion as if the transaction was started with READ_COMMITTED_PROMOTE (intemediate writer commits become visible).

      Returns "true" if the transaction is in write mode after the call. The method always succeeds of the transaction is already "write".

      This method returns true if a READ_PROMOTE or READ_COMMITTED_PROMOTE is promoted.

      This method returns false if a READ_PROMOTE can't be promoted - the transaction is still valid and in "read" mode.

      This method throws an exception if there is an attempt to promote a READ transaction.

      Specified by:
      promote in interface Transactional

    • commit

      public void commit()
      Description copied from interface: Transactional
      Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
      Specified by:
      commit in interface Transactional

    • abort

      public void abort()
      Description copied from interface: Transactional
      Abort a transaction - finish the transaction and undo any changes (if a "write" transaction)
      Specified by:
      abort in interface Transactional

    • isInTransaction

      public boolean isInTransaction()
      Description copied from interface: Transactional
      Say whether inside a transaction.
      Specified by:
      isInTransaction in interface Transactional

    • transactionMode

      public ReadWrite transactionMode()
      Description copied from interface: Transactional
      Return the current mode of the transaction - "read" or "write". If the caller is not in a transaction, this method returns null.
      Specified by:
      transactionMode in interface Transactional

    • transactionType

      public TxnType transactionType()
      Description copied from interface: Transactional
      Return the transaction type used in begin(TxnType). If the caller is not in a transaction, this method returns null.
      Specified by:
      transactionType in interface Transactional

    • end

      public void end()
      Description copied from interface: Transactional
      Finish the transaction - if a write transaction and commit() has not been called, then abort
      Specified by:
      end in interface Transactional

    • inc

      public void inc()
      Increment the value inside a write transaction

    • dec

      public void dec()
      Decrement the value inside a write transaction

    • set

      public long set(long x)
      Set the value inside a write transaction, return the old value

    • read

      public long read()
      Return the current value in a transaction. Must be inside a transaction.
      See Also:

    • get

      public long get()
      Return the current value. If inside a transaction, return the transaction view of the value. If not in a transaction return the state value (effectively a read transaction, optimized by the fact that reading the TransInteger state is atomic).

    • value

      public long value()
      Read the current global state (that is, the last committed value) outside a transaction.