# TableStats.java

    /*
    ** Module   : TableStats.java
    ** Abstract : Table CRUD operations statistics holder
    **
    ** Copyright (c) 2013-2022, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --------------------------------------Description----------------------------------------
    ** 001 IAS 20200819 Created initial version.
    ** 002 ECF 20220630 Code cleanup.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.persist.meta;

    import java.util.concurrent.atomic.*;
    import java.util.concurrent.locks.*;

    /**
     * Table CRUD operations statistics holder
     */
    public class TableStats
    {
       /** Statistics guard */
       private final ReentrantReadWriteLock guard = new ReentrantReadWriteLock();

       /** Database CRUD operations statistics version */
       private final AtomicLong statisticsVersion;

       /** Number of creates */
       private final AtomicLong create = new AtomicLong(0);

       /** Number of retrieves */
       private final AtomicLong retrieve = new AtomicLong(0);

       /** Number of updates */
       private final AtomicLong update = new AtomicLong(0);

       /** Number of deletes */
       private final AtomicLong delete = new AtomicLong(0);

       /** Table statistics version */
       private final AtomicLong version = new AtomicLong(0);

       /** Table statistics version last persisted */
       private final AtomicLong persisted = new AtomicLong(-1);

       /**
        * Constructor.
        *
        * @param   statisticsVersion
        *          database CRUD operations statistics
        */
       public TableStats(AtomicLong statisticsVersion)
       {
          super();
          this.statisticsVersion = statisticsVersion;
       }

       /**
        * Register create
        */
       public void create()
       {
          guard.readLock().lock();
          try
          {
             create.incrementAndGet();
             version.incrementAndGet();
          }
          finally
          {
             guard.readLock().unlock();
          }
          statisticsVersion.incrementAndGet();
       }

       /**
        * Register retrieve
        */
       public void retrieve()
       {
          guard.readLock().lock();
          try
          {
             retrieve.incrementAndGet();
             version.incrementAndGet();
          }
          finally
          {
             guard.readLock().unlock();
          }
          statisticsVersion.incrementAndGet();
       }

       /**
        * Register update
        */
       public void update()
       {
          guard.readLock().lock();
          try
          {
             update.incrementAndGet();
             version.incrementAndGet();
          }
          finally
          {
             guard.readLock().unlock();
          }
          statisticsVersion.incrementAndGet();
       }

       /**
        * Register delete
        */
       public void delete()
       {
          guard.readLock().lock();
          try
          {
             delete.incrementAndGet();
             version.incrementAndGet();
          }
          finally
          {
             guard.readLock().unlock();
          }
          statisticsVersion.incrementAndGet();
       }

       /**
        * Get table statistics version
        *
        * @return  table statistics version
        */
       public long version()
       {
          return version.get();
       }

       /**
        * Get table statistics version last persisted
        *
        * @return  table statistics version last persisted
        */
       public long persisted()
       {
          return persisted.get();
       }

       /**
        * Set table statistics version last persisted
        *
        * @param   version
        *          table statistics version last persisted
        */
       public void persisted(long version)
       {
          persisted.set(version);
       }

       /**
        * Get table statistics snapshot
        *
        * @return  long[5] array. First four entries contain CRUD operation counters, the last one holds
        *          table statistics version.
        */
       public Snapshot getStat()
       {
          guard.writeLock().lock();
          try
          {
             return new Snapshot(create.get(),
                                 retrieve.get(),
                                 update.get(),
                                 delete.get(),
                                 version.get(),
                                 persisted.get());
          }
          finally
          {
             guard.writeLock().unlock();
          }
       }

       /**
        * Table statistics snapshot
        */
       public static class Snapshot
       {
          /** Number of creates */
          public final long create;

          /** Number of retrieves */
          public final long retrieve;

          /** Number of updates */
          public final long update;

          /** Number of deletes */
          public final long delete;

          /** Table statistics version */
          public final long version;

          /** Table statistics version last persisted */
          public final long persisted;

          /**
           * Constructor
           * @param   create
           *          Number of creates
           * @param   retrieve
           *          Number of retrieves
           * @param   update
           *          Number of updates
           * @param   delete
           *          Number of deletes
           * @param   version
           *          Table statistics version
           * @param   persisted
           *          Table statistics version last persisted
           */
          public Snapshot(long create, long retrieve, long update, long delete, long version, long persisted)
          {
             super();
             this.create = create;
             this.retrieve = retrieve;
             this.update = update;
             this.delete = delete;
             this.version = version;
             this.persisted = persisted;
          }
       }
    }