/**
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.regionserver;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.NavigableSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hbase.DoNotRetryIOException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.regionserver.HStore.ScanInfo;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
/**
* Scanner scans both the memstore and the HStore. Coalesce KeyValue stream
* into List<KeyValue> for a single row.
*/
@InterfaceAudience.Private
public class StoreScanner extends NonLazyKeyValueScanner
implements KeyValueScanner, InternalScanner, ChangedReadersObserver {
static final Log LOG = LogFactory.getLog(StoreScanner.class);
private HStore store;
private ScanQueryMatcher matcher;
private KeyValueHeap heap;
private boolean cacheBlocks;
private int countPerRow = 0;
private int storeLimit = -1;
private int storeOffset = 0;
private String metricNamePrefix;
// Used to indicate that the scanner has closed (see HBASE-1107)
// Doesnt need to be volatile because it's always accessed via synchronized methods
private boolean closing = false;
private final boolean isGet;
private final boolean explicitColumnQuery;
private final boolean useRowColBloom;
private final Scan scan;
private final NavigableSet<byte[]> columns;
private final long oldestUnexpiredTS;
private final int minVersions;
/** We don't ever expect to change this, the constant is just for clarity. */
static final boolean LAZY_SEEK_ENABLED_BY_DEFAULT = true;
/** Used during unit testing to ensure that lazy seek does save seek ops */
private static boolean lazySeekEnabledGlobally =
LAZY_SEEK_ENABLED_BY_DEFAULT;
// if heap == null and lastTop != null, you need to reseek given the key below
private KeyValue lastTop = null;
/** An internal constructor. */
private StoreScanner(HStore store, boolean cacheBlocks, Scan scan,
final NavigableSet<byte[]> columns, long ttl, int minVersions) {
this.store = store;
this.cacheBlocks = cacheBlocks;
isGet = scan.isGetScan();
int numCol = columns == null ? 0 : columns.size();
explicitColumnQuery = numCol > 0;
this.scan = scan;
this.columns = columns;
oldestUnexpiredTS = EnvironmentEdgeManager.currentTimeMillis() - ttl;
this.minVersions = minVersions;
// We look up row-column Bloom filters for multi-column queries as part of
// the seek operation. However, we also look the row-column Bloom filter
// for multi-row (non-"get") scans because this is not done in
// StoreFile.passesBloomFilter(Scan, SortedSet<byte[]>).
useRowColBloom = numCol > 1 || (!isGet && numCol == 1);
}
/**
* Opens a scanner across memstore, snapshot, and all StoreFiles. Assumes we
* are not in a compaction.
*
* @param store who we scan
* @param scan the spec
* @param columns which columns we are scanning
* @throws IOException
*/
public StoreScanner(HStore store, ScanInfo scanInfo, Scan scan, final NavigableSet<byte[]> columns)
throws IOException {
this(store, scan.getCacheBlocks(), scan, columns, scanInfo.getTtl(),
scanInfo.getMinVersions());
if (columns != null && scan.isRaw()) {
throw new DoNotRetryIOException(
"Cannot specify any column for a raw scan");
}
matcher = new ScanQueryMatcher(scan, scanInfo, columns,
ScanType.USER_SCAN, Long.MAX_VALUE, HConstants.LATEST_TIMESTAMP,
oldestUnexpiredTS);
// Pass columns to try to filter out unnecessary StoreFiles.
List<KeyValueScanner> scanners = getScannersNoCompaction();
// Seek all scanners to the start of the Row (or if the exact matching row
// key does not exist, then to the start of the next matching Row).
// Always check bloom filter to optimize the top row seek for delete
// family marker.
if (explicitColumnQuery && lazySeekEnabledGlobally) {
for (KeyValueScanner scanner : scanners) {
scanner.requestSeek(matcher.getStartKey(), false, true);
}
} else {
for (KeyValueScanner scanner : scanners) {
scanner.seek(matcher.getStartKey());
}
}
// set storeLimit
this.storeLimit = scan.getMaxResultsPerColumnFamily();
// set rowOffset
this.storeOffset = scan.getRowOffsetPerColumnFamily();
// Combine all seeked scanners with a heap
heap = new KeyValueHeap(scanners, store.comparator);
this.store.addChangedReaderObserver(this);
}
/**
* Used for major compactions.<p>
*
* Opens a scanner across specified StoreFiles.
* @param store who we scan
* @param scan the spec
* @param scanners ancillary scanners
* @param smallestReadPoint the readPoint that we should use for tracking
* versions
*/
public StoreScanner(HStore store, ScanInfo scanInfo, Scan scan,
List<? extends KeyValueScanner> scanners, ScanType scanType,
long smallestReadPoint, long earliestPutTs) throws IOException {
this(store, false, scan, null, scanInfo.getTtl(),
scanInfo.getMinVersions());
matcher = new ScanQueryMatcher(scan, scanInfo, null, scanType,
smallestReadPoint, earliestPutTs, oldestUnexpiredTS);
// Filter the list of scanners using Bloom filters, time range, TTL, etc.
scanners = selectScannersFrom(scanners);
// Seek all scanners to the initial key
for(KeyValueScanner scanner : scanners) {
scanner.seek(matcher.getStartKey());
}
// Combine all seeked scanners with a heap
heap = new KeyValueHeap(scanners, store.comparator);
}
/** Constructor for testing. */
StoreScanner(final Scan scan, HStore.ScanInfo scanInfo,
ScanType scanType, final NavigableSet<byte[]> columns,
final List<KeyValueScanner> scanners) throws IOException {
this(scan, scanInfo, scanType, columns, scanners,
HConstants.LATEST_TIMESTAMP);
}
// Constructor for testing.
StoreScanner(final Scan scan, HStore.ScanInfo scanInfo,
ScanType scanType, final NavigableSet<byte[]> columns,
final List<KeyValueScanner> scanners, long earliestPutTs)
throws IOException {
this(null, scan.getCacheBlocks(), scan, columns, scanInfo.getTtl(),
scanInfo.getMinVersions());
this.matcher = new ScanQueryMatcher(scan, scanInfo, columns, scanType,
Long.MAX_VALUE, earliestPutTs, oldestUnexpiredTS);
// Seek all scanners to the initial key
for (KeyValueScanner scanner : scanners) {
scanner.seek(matcher.getStartKey());
}
heap = new KeyValueHeap(scanners, scanInfo.getComparator());
}
/**
* Get a filtered list of scanners. Assumes we are not in a compaction.
* @return list of scanners to seek
*/
private List<KeyValueScanner> getScannersNoCompaction() throws IOException {
final boolean isCompaction = false;
return selectScannersFrom(store.getScanners(cacheBlocks, isGet,
isCompaction, matcher));
}
/**
* Filters the given list of scanners using Bloom filter, time range, and
* TTL.
*/
private List<KeyValueScanner> selectScannersFrom(
final List<? extends KeyValueScanner> allScanners) {
boolean memOnly;
boolean filesOnly;
if (scan instanceof InternalScan) {
InternalScan iscan = (InternalScan)scan;
memOnly = iscan.isCheckOnlyMemStore();
filesOnly = iscan.isCheckOnlyStoreFiles();
} else {
memOnly = false;
filesOnly = false;
}
List<KeyValueScanner> scanners =
new ArrayList<KeyValueScanner>(allScanners.size());
// We can only exclude store files based on TTL if minVersions is set to 0.
// Otherwise, we might have to return KVs that have technically expired.
long expiredTimestampCutoff = minVersions == 0 ? oldestUnexpiredTS :
Long.MIN_VALUE;
// include only those scan files which pass all filters
for (KeyValueScanner kvs : allScanners) {
boolean isFile = kvs.isFileScanner();
if ((!isFile && filesOnly) || (isFile && memOnly)) {
continue;
}
if (kvs.shouldUseScanner(scan, columns, expiredTimestampCutoff)) {
scanners.add(kvs);
}
}
return scanners;
}
@Override
public synchronized KeyValue peek() {
if (this.heap == null) {
return this.lastTop;
}
return this.heap.peek();
}
@Override
public KeyValue next() {
// throw runtime exception perhaps?
throw new RuntimeException("Never call StoreScanner.next()");
}
@Override
public synchronized void close() {
if (this.closing) return;
this.closing = true;
// under test, we dont have a this.store
if (this.store != null)
this.store.deleteChangedReaderObserver(this);
if (this.heap != null)
this.heap.close();
this.heap = null; // CLOSED!
this.lastTop = null; // If both are null, we are closed.
}
@Override
public synchronized boolean seek(KeyValue key) throws IOException {
if (this.heap == null) {
List<KeyValueScanner> scanners = getScannersNoCompaction();
heap = new KeyValueHeap(scanners, store.comparator);
}
return this.heap.seek(key);
}
/**
* Get the next row of values from this Store.
* @param outResult
* @param limit
* @return true if there are more rows, false if scanner is done
*/
@Override
public synchronized boolean next(List<KeyValue> outResult, int limit) throws IOException {
return next(outResult, limit, null);
}
/**
* Get the next row of values from this Store.
* @param outResult
* @param limit
* @return true if there are more rows, false if scanner is done
*/
@Override
public synchronized boolean next(List<KeyValue> outResult, int limit,
String metric) throws IOException {
if (checkReseek()) {
return true;
}
// if the heap was left null, then the scanners had previously run out anyways, close and
// return.
if (this.heap == null) {
close();
return false;
}
KeyValue peeked = this.heap.peek();
if (peeked == null) {
close();
return false;
}
// only call setRow if the row changes; avoids confusing the query matcher
// if scanning intra-row
if ((matcher.row == null) || !peeked.matchingRow(matcher.row)) {
this.countPerRow = 0;
matcher.setRow(peeked.getRow());
}
KeyValue kv;
KeyValue prevKV = null;
// Only do a sanity-check if store and comparator are available.
KeyValue.KVComparator comparator =
store != null ? store.getComparator() : null;
long cumulativeMetric = 0;
int count = 0;
try {
LOOP: while((kv = this.heap.peek()) != null) {
// Check that the heap gives us KVs in an increasing order.
assert prevKV == null || comparator == null || comparator.compare(prevKV, kv) <= 0 :
"Key " + prevKV + " followed by a " + "smaller key " + kv + " in cf " + store;
prevKV = kv;
ScanQueryMatcher.MatchCode qcode = matcher.match(kv);
switch(qcode) {
case INCLUDE:
case INCLUDE_AND_SEEK_NEXT_ROW:
case INCLUDE_AND_SEEK_NEXT_COL:
Filter f = matcher.getFilter();
if (f != null) {
kv = f.transform(kv);
}
this.countPerRow++;
if (storeLimit > -1 &&
this.countPerRow > (storeLimit + storeOffset)) {
// do what SEEK_NEXT_ROW does.
if (!matcher.moreRowsMayExistAfter(kv)) {
return false;
}
reseek(matcher.getKeyForNextRow(kv));
break LOOP;
}
// add to results only if we have skipped #storeOffset kvs
// also update metric accordingly
if (this.countPerRow > storeOffset) {
if (metric != null) {
cumulativeMetric += kv.getLength();
}
outResult.add(kv);
count++;
}
if (qcode == ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_ROW) {
if (!matcher.moreRowsMayExistAfter(kv)) {
return false;
}
reseek(matcher.getKeyForNextRow(kv));
} else if (qcode == ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_COL) {
reseek(matcher.getKeyForNextColumn(kv));
} else {
this.heap.next();
}
if (limit > 0 && (count == limit)) {
break LOOP;
}
continue;
case DONE:
return true;
case DONE_SCAN:
close();
return false;
case SEEK_NEXT_ROW:
// This is just a relatively simple end of scan fix, to short-cut end
// us if there is an endKey in the scan.
if (!matcher.moreRowsMayExistAfter(kv)) {
return false;
}
reseek(matcher.getKeyForNextRow(kv));
break;
case SEEK_NEXT_COL:
reseek(matcher.getKeyForNextColumn(kv));
break;
case SKIP:
this.heap.next();
break;
case SEEK_NEXT_USING_HINT:
KeyValue nextKV = matcher.getNextKeyHint(kv);
if (nextKV != null) {
reseek(nextKV);
} else {
heap.next();
}
break;
default:
throw new RuntimeException("UNEXPECTED");
}
}
} finally {
if (cumulativeMetric > 0 && metric != null) {
}
}
if (count > 0) {
return true;
}
// No more keys
close();
return false;
}
@Override
public synchronized boolean next(List<KeyValue> outResult) throws IOException {
return next(outResult, -1, null);
}
@Override
public synchronized boolean next(List<KeyValue> outResult, String metric)
throws IOException {
return next(outResult, -1, metric);
}
// Implementation of ChangedReadersObserver
@Override
public synchronized void updateReaders() throws IOException {
if (this.closing) return;
// All public synchronized API calls will call 'checkReseek' which will cause
// the scanner stack to reseek if this.heap==null && this.lastTop != null.
// But if two calls to updateReaders() happen without a 'next' or 'peek' then we
// will end up calling this.peek() which would cause a reseek in the middle of a updateReaders
// which is NOT what we want, not to mention could cause an NPE. So we early out here.
if (this.heap == null) return;
// this could be null.
this.lastTop = this.peek();
//DebugPrint.println("SS updateReaders, topKey = " + lastTop);
// close scanners to old obsolete Store files
this.heap.close(); // bubble thru and close all scanners.
this.heap = null; // the re-seeks could be slow (access HDFS) free up memory ASAP
// Let the next() call handle re-creating and seeking
}
/**
* @return true if top of heap has changed (and KeyValueHeap has to try the
* next KV)
* @throws IOException
*/
private boolean checkReseek() throws IOException {
if (this.heap == null && this.lastTop != null) {
resetScannerStack(this.lastTop);
if (this.heap.peek() == null
|| store.comparator.compareRows(this.lastTop, this.heap.peek()) != 0) {
LOG.debug("Storescanner.peek() is changed where before = "
+ this.lastTop.toString() + ",and after = " + this.heap.peek());
this.lastTop = null;
return true;
}
this.lastTop = null; // gone!
}
// else dont need to reseek
return false;
}
private void resetScannerStack(KeyValue lastTopKey) throws IOException {
if (heap != null) {
throw new RuntimeException("StoreScanner.reseek run on an existing heap!");
}
/* When we have the scan object, should we not pass it to getScanners()
* to get a limited set of scanners? We did so in the constructor and we
* could have done it now by storing the scan object from the constructor */
List<KeyValueScanner> scanners = getScannersNoCompaction();
for(KeyValueScanner scanner : scanners) {
scanner.seek(lastTopKey);
}
// Combine all seeked scanners with a heap
heap = new KeyValueHeap(scanners, store.comparator);
// Reset the state of the Query Matcher and set to top row.
// Only reset and call setRow if the row changes; avoids confusing the
// query matcher if scanning intra-row.
KeyValue kv = heap.peek();
if (kv == null) {
kv = lastTopKey;
}
if ((matcher.row == null) || !kv.matchingRow(matcher.row)) {
this.countPerRow = 0;
matcher.reset();
matcher.setRow(kv.getRow());
}
}
@Override
public synchronized boolean reseek(KeyValue kv) throws IOException {
//Heap will not be null, if this is called from next() which.
//If called from RegionScanner.reseek(...) make sure the scanner
//stack is reset if needed.
checkReseek();
if (explicitColumnQuery && lazySeekEnabledGlobally) {
return heap.requestSeek(kv, true, useRowColBloom);
} else {
return heap.reseek(kv);
}
}
@Override
public long getSequenceID() {
return 0;
}
/**
* Used in testing.
* @return all scanners in no particular order
*/
List<KeyValueScanner> getAllScannersForTesting() {
List<KeyValueScanner> allScanners = new ArrayList<KeyValueScanner>();
KeyValueScanner current = heap.getCurrentForTesting();
if (current != null)
allScanners.add(current);
for (KeyValueScanner scanner : heap.getHeap())
allScanners.add(scanner);
return allScanners;
}
static void enableLazySeekGlobally(boolean enable) {
lazySeekEnabledGlobally = enable;
}
}