Examples with PagingState com.datastax.driver.core.PagingState used on opensource projects

Example 1 with PagingState

use of com.datastax.driver.core.PagingState in project emodb by bazaarvoice.

the class AdaptiveResultSet method reduceFetchSize.

/**
 * 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;
}

Example 2 with PagingState

use of com.datastax.driver.core.PagingState in project incubator-hugegraph by apache.

the class CassandraEntryIterator method pageState.

@Override
protected PageState pageState() {
    byte[] position;
    int offset = 0;
    int count = (int) this.count();
    assert this.fetched() == count;
    int extra = this.availableLocal();
    List<ExecutionInfo> infos = this.results.getAllExecutionInfo();
    if (extra > 0 && infos.size() >= 2) {
        /*
             * Go back to the previous page if there are still available
             * results fetched to local memory but not consumed, and set page
             * offset with consumed amount of results.
             *
             * Safely, we should get the remaining size of the current page by:
             *  `Whitebox.getInternalState(results, "currentPage").size()`
             * instead of
             *  `results.getAvailableWithoutFetching()`
             */
        ExecutionInfo previous = infos.get(infos.size() - 2);
        PagingState page = previous.getPagingState();
        position = page.toBytes();
        offset = this.fetchdPageSize - extra;
    } else {
        PagingState page = this.results.getExecutionInfo().getPagingState();
        if (page == null || this.expected > 0L) {
            // Call isExhausted() will lead to try to fetch the next page
            E.checkState(this.results.isExhausted(), "Unexpected paging state with expected=%s, " + "ensure consume all the fetched results before " + "calling pageState()", this.expected);
            position = PageState.EMPTY_BYTES;
        } else {
            /*
                 * Exist page position which used to fetch the next page.
                 * Maybe it happens to the last page (that's the position is
                 * at the end of results and next page is empty)
                 */
            position = page.toBytes();
        }
    }
    return new PageState(position, offset, count);
}