Tablestore:Split data for parallel scans

Prerequisites

Install the Tablestore SDK for Java and initialize the client.

Description

Tablestore logically divides a table into splits of the specified approximate size on the server. Each split includes its primary key range (lowerBound / upperBound) and a location hint for the machine that hosts the split (location). Pass these primary key ranges to RangeRowQueryCriteria, then process the splits in parallel by reading data by range or reading data with an iterator.

public ComputeSplitsBySizeResponse computeSplitsBySize(ComputeSplitsBySizeRequest request) throws TableStoreException, ClientException

The following example divides the split_demo table into splits of approximately 200 MB and prints the location and primary key range of each split.

String tableName = "split_demo";

// Divide the full data of the table into splits of approximately 200 MB (2 * 100 MB).
ComputeSplitsBySizeRequest request =
        new ComputeSplitsBySizeRequest(tableName, 2);

ComputeSplitsBySizeResponse response = client.computeSplitsBySize(request);

System.out.println("PrimaryKeySchema: " + response.getPrimaryKeySchema());
List<Split> splits = response.getSplits();
System.out.println("Splits size: " + splits.size());

Iterator<Split> iterator = splits.iterator();
while (iterator.hasNext()) {
    Split split = iterator.next();
    // The primary key ranges returned by getLowerBound() and getUpperBound() can be passed directly
    // to RangeRowQueryCriteria for parallel reads with getRange or createRangeIterator.
    System.out.println("Location: " + split.getLocation());
    System.out.println("LowerBound: " + split.getLowerBound().jsonize());
    System.out.println("UpperBound: " + split.getUpperBound().jsonize());
}

Parameters

Response