void reclaim()

in mavibot/src/main/java/org/apache/directory/mavibot/btree/PageReclaimer.java [64:184]
82 lines of code
16 McCabe index (conditional complexity)

    /* no qualifier */ void reclaim()
    {
        //System.out.println( "reclaiming pages" );
        try
        {
            if ( running )
            {
                return;
            }
            
            running = true;
            
            Set<String> managed = rm.getManagedTrees();

            for ( String name : managed )
            {
                PersistedBTree tree = ( PersistedBTree ) rm.getManagedTree( name );

                long latestRev = tree.getRevision();
                
                Set<Long> inUseRevisions = new TreeSet<Long>();
                
                // the tree might have been removed
                if ( tree != null )
                {
                    Iterator<ReadTransaction> txnItr = tree.getReadTransactions().iterator();
                    while ( txnItr.hasNext() )
                    {
                        inUseRevisions.add( txnItr.next().getRevision() );
                    }
                }

                List<RevisionOffset> copiedRevisions = getRevisions( name );

                // the revision last removed from copiedPage BTree
                long lastRemovedRev = -1;

                List<Long> freeList = new ArrayList<Long>();
                
                for ( RevisionOffset ro : copiedRevisions )
                {
                    long rv = ro.getRevision();
                    if ( inUseRevisions.contains( rv ) )
                    {
                        //System.out.println( "Revision " + rv + " of BTree " + name + " is in use, not reclaiming pages" );
                        break;
                    }

                    long[] offsets = ro.getOffsets();

                    //System.out.println( "Reclaiming " + Arrays.toString( offsets ) + "( " + offsets.length + " ) pages of the revision " + rv + " of BTree " + name );

                    for( long l : offsets )
                    {
                        freeList.add( l );
                    }

                    RevisionName key = new RevisionName( rv, name );
                    
                    //System.out.println( "delete cpb key " + key );
                    rm.copiedPageBtree.delete( key );
                    lastRemovedRev = rv;
                }

                // no new txn is needed for the operations on BoB
                // and also no need to traverse BoB if the tree is a sub-btree
                if ( ( lastRemovedRev != -1 ) && !tree.isAllowDuplicates() )
                {
                    // we SHOULD NOT delete the latest revision from BoB
                    NameRevision nr = new NameRevision( name, latestRev );
                    TupleCursor<NameRevision, Long> cursor = rm.btreeOfBtrees.browseFrom( nr );
                    
                    List<Long> btreeHeaderOffsets = new ArrayList<Long>();
                    
                    while ( cursor.hasPrev() )
                    {
                        Tuple<NameRevision, Long> t = cursor.prev();
                        //System.out.println( "deleting BoB rev " + t.getKey()  + " latest rev " + latestRev );
                        rm.btreeOfBtrees.delete( t.getKey() );
                        btreeHeaderOffsets.add( t.value );
                    }

                    cursor.close();
                    
                    for( Long l : btreeHeaderOffsets )
                    {
                        // the offset may have already been present while
                        // clearing CPB so skip it here, otherwise it will result in OOM
                        // due to the attempt to free and already freed page
                        if(freeList.contains( l ))
                        {
                            //System.out.println( "bob duplicate offset " + l );
                            continue;
                        }

                        freeList.add( l );
                    }
                }
                
                for( Long offset : freeList )
                {
                    PageIO[] pageIos = rm.readPageIOs( offset, -1L );
                    
                    for ( PageIO pageIo : pageIos )
                    {
                        rm.free( pageIo );
                    }
                }

            }

            running = false;
        }
        catch ( Exception e )
        {
        	running = false;
        	rm.rollback();
        	LOG.warn( "Errors while reclaiming", e );
        	throw new RuntimeException( e );
        }
    }