Overview

Sort rows by inserting them in sorted order into a memory buffer, then into on-disk files, and performing a multi-way merge sort on the resulting files.

Behavior

The rows of the input stream are written into a memory pool (40MB as a default). When (if) the memory pool is filled, the pool is written to disk, then emptied and rows are written again to the memory pool. When the final row is written to the disk files are merged in an n-way merge sort. The default is 16 way sort. When all of the temp files are merged into one file, the rows are read from the file in sorted order. If the initial input stream does not produce enough data to overflow the memory pool, no disk files will be produced.

Performance

The MergeJoinSorter generates IO dependent upon the size of the input stream. If the input stream generates less than the memory pool size (40MB default), there is no IO generated. If the input stream generates more than the memory pool size, but less than 16x the pool size, it should generate two read and two writes for each row. One write to, one read from into the initial temporary file, one write to, one read from the final sorted temporary file. For each 16x larger the input set gets it adds one more write to/read from temporary file cycle.

Memory Requirements

The MergeJoinSorter allocates a single memory buffer for each instance to perform an initial sort, defaulting to 40MB in size.

                               API.Ordering ordering,
                               API.SortOption sortOption,
                               InOutTap loadTap)
    {
        //return new PersistitSorter(context, bindings, input, rowType, ordering, sortOption, loadTap);
        return new MergeJoinSorter(context, bindings, input, rowType, ordering, sortOption, loadTap);
    }


    @Override
    public Sorter createSorter(QueryContext context, QueryBindings bindings,
            Cursor input, RowType rowType, Ordering ordering,
            SortOption sortOption, InOutTap loadTap) {
        return new MergeJoinSorter(context, bindings, input, rowType, ordering, sortOption, loadTap);
    }

                               RowCursor input,
                               RowType rowType,
                               API.Ordering ordering,
                               API.SortOption sortOption,
                               InOutTap loadTap) {
        return new MergeJoinSorter(context, bindings, input, rowType, ordering, sortOption, loadTap);
    }

Examples of com.foundationdb.qp.storeadapter.indexcursor.MergeJoinSorter

Overview

Behavior

Performance

Memory Requirements

Related Classes of com.foundationdb.qp.storeadapter.indexcursor.MergeJoinSorter