com.datastax.driver.core.PagingState Java Examples

protected void setPageState(Query query, List<Select> selects) {
    if (query.nolimit()) {
        return;
    }
    for (Select select : selects) {
        long total = query.total();
        String page = query.page();
        if (page == null) {
            // Set limit
            select.limit((int) total);
        } else {
            select.setFetchSize((int) total);
            // It's the first time if page is empty
            if (!page.isEmpty()) {
                byte[] position = PageState.fromString(page).position();
                try {
                    select.setPagingState(PagingState.fromBytes(position));
                } catch (PagingStateException e) {
                    throw new BackendException(e);
                }
            }
        }
    }
}
 

@Override
protected PageState pageState() {
    PagingState page = this.results.getExecutionInfo().getPagingState();
    if (page == null || this.results.isExhausted()) {
        return new PageState(PageState.EMPTY_BYTES, 0, (int) this.count());
    }
    byte[] position = page.toBytes();
    return new PageState(position, 0, (int) this.count());
}
 

/**
 * Reduces the fetch size and retries the query.  Returns true if the query succeeded, false if the root cause
 * of the exception does not indicate a frame size issue, if the frame size cannot be adjusted down any further,
 * or if the retried query fails for an unrelated reason.
 */
private boolean reduceFetchSize(Throwable reason) {
    if (!isAdaptiveException(reason) || --_remainingAdaptations == 0) {
        return false;
    }

    ExecutionInfo executionInfo = _delegate.getExecutionInfo();
    Statement statement = executionInfo.getStatement();
    PagingState pagingState = executionInfo.getPagingState();
    int fetchSize = statement.getFetchSize();

    while (fetchSize > MIN_FETCH_SIZE) {
        fetchSize = Math.max(fetchSize / 2, MIN_FETCH_SIZE);
        _log.debug("Retrying query at next page with fetch size {} due to {}", fetchSize, reason.getMessage());
        statement.setFetchSize(fetchSize);
        statement.setPagingState(pagingState);
        try {
            _delegate = _session.execute(statement);
            return true;
        } catch (Throwable t) {
            // Exit the adaptation loop if the exception isn't one where adapting further may help
            if (!isAdaptiveException(t) || --_remainingAdaptations == 0) {
                return false;
            }
        }
    }

    return false;
}
 

@Override
public Result<AuditLog> getAuditLogs( UUID messageId ) {

    Statement query = QueryBuilder.select().all().from(TABLE_AUDIT_LOG)
        .where( QueryBuilder.eq( COLUMN_MESSAGE_ID, messageId ) );

    ResultSet rs = cassandraClient.getApplicationSession().execute( query );

    final List<AuditLog> auditLogs = rs.all().stream().map( row ->
        new AuditLog(
            AuditLog.Action.valueOf( row.getString( COLUMN_ACTION )),
            AuditLog.Status.valueOf( row.getString( COLUMN_STATUS )),
            row.getString( COLUMN_QUEUE_NAME ),
            row.getString( COLUMN_REGION ),
            row.getUUID( COLUMN_MESSAGE_ID ),
            row.getUUID( COLUMN_QUEUE_MESSAGE_ID ),
            row.getLong( COLUMN_TRANSFER_TIME ) )
    ).collect( Collectors.toList() );

    return new Result<AuditLog>() {

        @Override
        public PagingState getPagingState() {
            return null; // no paging
        }

        @Override
        public List<AuditLog> getEntities() {
            return auditLogs;
        }
    };

}
 

@Override
public Result<TransferLog> getAllTransferLogs(PagingState pagingState, int fetchSize ) {

    Statement query = QueryBuilder.select().all().from(TABLE_TRANSFER_LOG);

    query.setFetchSize( fetchSize );
    if ( pagingState != null ) {
        query.setPagingState( pagingState );
    }

    ResultSet rs = cassandraClient.getApplicationSession().execute( query );
    final PagingState newPagingState = rs.getExecutionInfo().getPagingState();

    final List<TransferLog> transferLogs = new ArrayList<>();
    int numReturned = rs.getAvailableWithoutFetching();
    for ( int i=0; i<numReturned; i++ ) {
        Row row = rs.one();
        TransferLog tlog = new TransferLog(
                row.getString( COLUMN_QUEUE_NAME ),
                row.getString( COLUMN_SOURCE_REGION ),
                row.getString( COLUMN_DEST_REGION ),
                row.getUUID( COLUMN_MESSAGE_ID ),
                row.getLong( COLUMN_TRANSFER_TIME ));
        transferLogs.add( tlog );
    }

    return new Result<TransferLog>() {

        @Override
        public PagingState getPagingState() {
            return newPagingState;
        }

        @Override
        public List<TransferLog> getEntities() {
            return transferLogs;
        }
    };
}
 

@Test
public void recordTransferLog() throws Exception {

    TransferLogSerialization logSerialization = getInjector().getInstance( TransferLogSerialization.class );

    CassandraClient cassandraClient = getInjector().getInstance( CassandraClientImpl.class );

    String queueName = "tlst_queue_" + RandomStringUtils.randomAlphanumeric( 15 );
    String source = RandomStringUtils.randomAlphanumeric( 15 );
    String dest = RandomStringUtils.randomAlphanumeric( 15 );

    int numLogs = 100;

    for ( int i=0; i<numLogs; i++ ) {
        logSerialization.recordTransferLog( queueName, source, dest, UUIDGen.getTimeUUID());
    }

    int count = 0;
    int fetchCount = 0;
    PagingState pagingState = null;
    while ( true ) {

        Result<TransferLog> all = logSerialization.getAllTransferLogs( pagingState, 10 );

        // we only want entities for our queue
        List<TransferLog> logs = all.getEntities().stream()
            .filter( log -> log.getQueueName().equals( queueName ) ).collect( Collectors.toList() );

        count += logs.size();
        fetchCount++;
        if ( all.getPagingState() == null ) {
            break;
        }
        pagingState = all.getPagingState();
    }

    Assert.assertEquals( numLogs, count );
}
 

private List<TransferLog> getTransferLogs(TransferLogSerialization logSerialization) {
    PagingState pagingState = null;
    List<TransferLog> allLogs = new ArrayList<>();
    while ( true ) {
        Result<TransferLog> result = logSerialization.getAllTransferLogs( pagingState, 100 );
        allLogs.addAll( result.getEntities() );
        if ( result.getPagingState() == null ) {
            break;
        }
        pagingState = result.getPagingState();
    }
    return allLogs;
}
 

/**
 * Get all transfer logs (for testing purposes)
 *
 * @param pagingState Paging state (or null if none)
 * @param fetchSize Number of rows to be fetched per page (or -1 for default)
 */
Result<TransferLog> getAllTransferLogs(PagingState pagingState, int fetchSize);
 

PagingState getPagingState();