Example usage for java.util.concurrent ConcurrentSkipListMap floorEntry

Introduction

In this page you can find the example usage for java.util.concurrent ConcurrentSkipListMap floorEntry.

Prototype

public Map.Entry<K, V> floorEntry(K key) 

Source Link

Document

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.

Usage

From source file:org.apache.hadoop.hbase.client.MetaCache.java

/**
 * Search the cache for a location that fits our table and row key.
 * Return null if no suitable region is located.
 *
 *
 * @param tableName//from  w  ww .j a  v  a 2 s  . c  om
 * @param row
 * @return Null or region location found in cache.
 */
public RegionLocations getCachedLocation(final TableName tableName, final byte[] row) {
    ConcurrentSkipListMap<byte[], RegionLocations> tableLocations = getTableLocations(tableName);

    Entry<byte[], RegionLocations> e = tableLocations.floorEntry(row);
    if (e == null) {
        return null;
    }
    RegionLocations possibleRegion = e.getValue();

    // make sure that the end key is greater than the row we're looking
    // for, otherwise the row actually belongs in the next region, not
    // this one. the exception case is when the endkey is
    // HConstants.EMPTY_END_ROW, signifying that the region we're
    // checking is actually the last region in the table.
    byte[] endKey = possibleRegion.getRegionLocation().getRegionInfo().getEndKey();
    // Here we do direct Bytes.compareTo and not doing CellComparator/MetaCellComparator path.
    // MetaCellComparator is for comparing against data in META table which need special handling.
    // Not doing that is ok for this case because
    // 1. We are getting the Region location for the given row in non META tables only. The compare
    // checks the given row is within the end key of the found region. So META regions are not
    // coming in here.
    // 2. Even if META region comes in, its end key will be empty byte[] and so Bytes.equals(endKey,
    // HConstants.EMPTY_END_ROW) check itself will pass.
    if (Bytes.equals(endKey, HConstants.EMPTY_END_ROW)
            || Bytes.compareTo(endKey, 0, endKey.length, row, 0, row.length) > 0) {
        return possibleRegion;
    }

    // Passed all the way through, so we got nothing - complete cache miss
    return null;
}

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