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/**
*
* 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.io.InterruptedIOException;
import java.util.ArrayList;
import java.util.List;
import java.util.NavigableSet;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.DoNotRetryIOException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.KeyValue.KVComparator;
import org.apache.hadoop.hbase.KeyValueUtil;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.client.IsolationLevel;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.executor.ExecutorService;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode;
import org.apache.hadoop.hbase.regionserver.ScannerContext.LimitScope;
import org.apache.hadoop.hbase.regionserver.ScannerContext.NextState;
import org.apache.hadoop.hbase.regionserver.handler.ParallelSeekHandler;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import com.google.common.annotations.VisibleForTesting;
/**
* Scanner scans both the memstore and the Store. Coalesce KeyValue stream
* into List<KeyValue> for a single row.
*/
@InterfaceAudience.Private
public class StoreScanner extends NonReversedNonLazyKeyValueScanner
implements KeyValueScanner, InternalScanner, ChangedReadersObserver {
private static final Log LOG = LogFactory.getLog(StoreScanner.class);
// In unit tests, the store could be null
protected final Store store;
protected ScanQueryMatcher matcher;
protected KeyValueHeap heap;
protected boolean cacheBlocks;
protected long countPerRow = 0;
protected int storeLimit = -1;
protected int storeOffset = 0;
// Used to indicate that the scanner has closed (see HBASE-1107)
// Doesnt need to be volatile because it's always accessed via synchronized methods
protected boolean closing = false;
protected final boolean get;
protected final boolean explicitColumnQuery;
protected final boolean useRowColBloom;
/**
* A flag that enables StoreFileScanner parallel-seeking
*/
protected boolean parallelSeekEnabled = false;
protected ExecutorService executor;
protected final Scan scan;
protected final NavigableSet columns;
protected final long oldestUnexpiredTS;
protected final long now;
protected final int minVersions;
protected final long maxRowSize;
protected final long cellsPerHeartbeatCheck;
/**
* The number of KVs seen by the scanner. Includes explicitly skipped KVs, but not
* KVs skipped via seeking to next row/column. TODO: estimate them?
*/
private long kvsScanned = 0;
private Cell prevCell = null;
/** We don't ever expect to change this, the constant is just for clarity. */
static final boolean LAZY_SEEK_ENABLED_BY_DEFAULT = true;
public static final String STORESCANNER_PARALLEL_SEEK_ENABLE =
"hbase.storescanner.parallel.seek.enable";
/** Used during unit testing to ensure that lazy seek does save seek ops */
protected static boolean lazySeekEnabledGlobally =
LAZY_SEEK_ENABLED_BY_DEFAULT;
/**
* The number of cells scanned in between timeout checks. Specifying a larger value means that
* timeout checks will occur less frequently. Specifying a small value will lead to more frequent
* timeout checks.
*/
public static final String HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK =
"hbase.cells.scanned.per.heartbeat.check";
/**
* Default value of {@link #HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK}.
*/
public static final long DEFAULT_HBASE_CELLS_SCANNED_PER_HEARTBEAT_CHECK = 10000;
// if heap == null and lastTop != null, you need to reseek given the key below
protected Cell lastTop = null;
// A flag whether use pread for scan
private boolean scanUsePread = false;
protected ReentrantLock lock = new ReentrantLock();
private final long readPt;
// used by the injection framework to test race between StoreScanner construction and compaction
enum StoreScannerCompactionRace {
BEFORE_SEEK,
AFTER_SEEK,
COMPACT_COMPLETE
}
/** An internal constructor. */
protected StoreScanner(Store store, Scan scan, final ScanInfo scanInfo,
final NavigableSet columns, long readPt, boolean cacheBlocks) {
this.readPt = readPt;
this.store = store;
this.cacheBlocks = cacheBlocks;
get = scan.isGetScan();
int numCol = columns == null ? 0 : columns.size();
explicitColumnQuery = numCol > 0;
this.scan = scan;
this.columns = columns;
this.now = EnvironmentEdgeManager.currentTime();
this.oldestUnexpiredTS = now - scanInfo.getTtl();
this.minVersions = scanInfo.getMinVersions();
// 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).
this.useRowColBloom = numCol > 1 || (!get && numCol == 1);
this.maxRowSize = scanInfo.getTableMaxRowSize();
this.scanUsePread = scan.isSmall()? true: scanInfo.isUsePread();
this.cellsPerHeartbeatCheck = scanInfo.getCellsPerTimeoutCheck();
// Parallel seeking is on if the config allows and more there is more than one store file.
if (this.store != null && this.store.getStorefilesCount() > 1) {
RegionServerServices rsService = ((HStore)store).getHRegion().getRegionServerServices();
if (rsService != null && scanInfo.isParallelSeekEnabled()) {
this.parallelSeekEnabled = true;
this.executor = rsService.getExecutorService();
}
}
}
/**
* 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(Store store, ScanInfo scanInfo, Scan scan, final NavigableSet columns,
long readPt)
throws IOException {
this(store, scan, scanInfo, columns, readPt, scan.getCacheBlocks());
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, now, store.getCoprocessorHost());
this.store.addChangedReaderObserver(this);
try {
// Pass columns to try to filter out unnecessary StoreFiles.
List 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.
seekScanners(scanners, matcher.getStartKey(), explicitColumnQuery && lazySeekEnabledGlobally,
parallelSeekEnabled);
// set storeLimit
this.storeLimit = scan.getMaxResultsPerColumnFamily();
// set rowOffset
this.storeOffset = scan.getRowOffsetPerColumnFamily();
// Combine all seeked scanners with a heap
resetKVHeap(scanners, store.getComparator());
} catch (IOException e) {
// remove us from the HStore#changedReaderObservers here or we'll have no chance to
// and might cause memory leak
this.store.deleteChangedReaderObserver(this);
throw e;
}
}
/**
* Used for compactions.
*
* 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(Store store, ScanInfo scanInfo, Scan scan,
List scanners, ScanType scanType,
long smallestReadPoint, long earliestPutTs) throws IOException {
this(store, scanInfo, scan, scanners, scanType, smallestReadPoint, earliestPutTs, null, null);
}
/**
* Used for compactions that drop deletes from a limited range of rows.
*
* 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
* @param dropDeletesFromRow The inclusive left bound of the range; can be EMPTY_START_ROW.
* @param dropDeletesToRow The exclusive right bound of the range; can be EMPTY_END_ROW.
*/
public StoreScanner(Store store, ScanInfo scanInfo, Scan scan,
List scanners, long smallestReadPoint, long earliestPutTs,
byte[] dropDeletesFromRow, byte[] dropDeletesToRow) throws IOException {
this(store, scanInfo, scan, scanners, ScanType.COMPACT_RETAIN_DELETES, smallestReadPoint,
earliestPutTs, dropDeletesFromRow, dropDeletesToRow);
}
private StoreScanner(Store store, ScanInfo scanInfo, Scan scan,
List scanners, ScanType scanType, long smallestReadPoint,
long earliestPutTs, byte[] dropDeletesFromRow, byte[] dropDeletesToRow) throws IOException {
this(store, scan, scanInfo, null,
((HStore)store).getHRegion().getReadpoint(IsolationLevel.READ_COMMITTED), false);
if (dropDeletesFromRow == null) {
matcher = new ScanQueryMatcher(scan, scanInfo, null, scanType, smallestReadPoint,
earliestPutTs, oldestUnexpiredTS, now, store.getCoprocessorHost());
} else {
matcher = new ScanQueryMatcher(scan, scanInfo, null, smallestReadPoint, earliestPutTs,
oldestUnexpiredTS, now, dropDeletesFromRow, dropDeletesToRow, store.getCoprocessorHost());
}
// Filter the list of scanners using Bloom filters, time range, TTL, etc.
scanners = selectScannersFrom(scanners);
// Seek all scanners to the initial key
seekScanners(scanners, matcher.getStartKey(), false, parallelSeekEnabled);
// Combine all seeked scanners with a heap
resetKVHeap(scanners, store.getComparator());
}
@VisibleForTesting
StoreScanner(final Scan scan, ScanInfo scanInfo,
ScanType scanType, final NavigableSet columns,
final List scanners) throws IOException {
this(scan, scanInfo, scanType, columns, scanners,
HConstants.LATEST_TIMESTAMP,
// 0 is passed as readpoint because the test bypasses Store
0);
}
@VisibleForTesting
StoreScanner(final Scan scan, ScanInfo scanInfo,
ScanType scanType, final NavigableSet columns,
final List scanners, long earliestPutTs)
throws IOException {
this(scan, scanInfo, scanType, columns, scanners, earliestPutTs,
// 0 is passed as readpoint because the test bypasses Store
0);
}
private StoreScanner(final Scan scan, ScanInfo scanInfo,
ScanType scanType, final NavigableSet columns,
final List scanners, long earliestPutTs, long readPt)
throws IOException {
this(null, scan, scanInfo, columns, readPt, scan.getCacheBlocks());
this.matcher = new ScanQueryMatcher(scan, scanInfo, columns, scanType,
Long.MAX_VALUE, earliestPutTs, oldestUnexpiredTS, now, null);
// In unit tests, the store could be null
if (this.store != null) {
this.store.addChangedReaderObserver(this);
}
// Seek all scanners to the initial key
seekScanners(scanners, matcher.getStartKey(), false, parallelSeekEnabled);
resetKVHeap(scanners, scanInfo.getComparator());
}
/**
* Get a filtered list of scanners. Assumes we are not in a compaction.
* @return list of scanners to seek
*/
protected List getScannersNoCompaction() throws IOException {
final boolean isCompaction = false;
boolean usePread = get || scanUsePread;
return selectScannersFrom(store.getScanners(cacheBlocks, get, usePread,
isCompaction, matcher, scan.getStartRow(), scan.getStopRow(), this.readPt));
}
/**
* Seek the specified scanners with the given key
* @param scanners
* @param seekKey
* @param isLazy true if using lazy seek
* @param isParallelSeek true if using parallel seek
* @throws IOException
*/
protected void seekScanners(List scanners,
Cell seekKey, boolean isLazy, boolean isParallelSeek)
throws IOException {
// 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 (isLazy) {
for (KeyValueScanner scanner : scanners) {
scanner.requestSeek(seekKey, false, true);
}
} else {
if (!isParallelSeek) {
long totalScannersSoughtBytes = 0;
for (KeyValueScanner scanner : scanners) {
if (totalScannersSoughtBytes >= maxRowSize) {
throw new RowTooBigException("Max row size allowed: " + maxRowSize
+ ", but row is bigger than that");
}
scanner.seek(seekKey);
Cell c = scanner.peek();
if (c != null) {
totalScannersSoughtBytes += CellUtil.estimatedSerializedSizeOf(c);
}
}
} else {
parallelSeek(scanners, seekKey);
}
}
}
protected void resetKVHeap(List scanners,
KVComparator comparator) throws IOException {
// Combine all seeked scanners with a heap
heap = new KeyValueHeap(scanners, comparator);
}
/**
* Filters the given list of scanners using Bloom filter, time range, and
* TTL.
*/
protected List selectScannersFrom(
final List 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 scanners =
new ArrayList(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, store, expiredTimestampCutoff)) {
scanners.add(kvs);
}
}
return scanners;
}
@Override
public Cell peek() {
lock.lock();
try {
if (this.heap == null) {
return this.lastTop;
}
return this.heap.peek();
} finally {
lock.unlock();
}
}
@Override
public KeyValue next() {
// throw runtime exception perhaps?
throw new RuntimeException("Never call StoreScanner.next()");
}
@Override
public void close() {
lock.lock();
try {
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.
} finally {
lock.unlock();
}
}
@Override
public boolean seek(Cell key) throws IOException {
lock.lock();
try {
// reset matcher state, in case that underlying store changed
checkReseek();
return this.heap.seek(key);
} finally {
lock.unlock();
}
}
@Override
public boolean next(List outResult) throws IOException {
return next(outResult, NoLimitScannerContext.getInstance());
}
/**
* Get the next row of values from this Store.
* @param outResult
* @param scannerContext
* @return true if there are more rows, false if scanner is done
*/
@Override
public boolean next(List outResult, ScannerContext scannerContext) throws IOException {
lock.lock();
try {
if (scannerContext == null) {
throw new IllegalArgumentException("Scanner context cannot be null");
}
if (checkReseek()) {
return scannerContext.setScannerState(NextState.MORE_VALUES).hasMoreValues();
}
// if the heap was left null, then the scanners had previously run out anyways, close and
// return.
if (this.heap == null) {
close();
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
}
Cell cell = this.heap.peek();
if (cell == null) {
close();
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
}
// only call setRow if the row changes; avoids confusing the query matcher
// if scanning intra-row
byte[] row = cell.getRowArray();
int offset = cell.getRowOffset();
short length = cell.getRowLength();
// If no limits exists in the scope LimitScope.Between_Cells then we are sure we are changing
// rows. Else it is possible we are still traversing the same row so we must perform the row
// comparison.
if (!scannerContext.hasAnyLimit(LimitScope.BETWEEN_CELLS) || matcher.row == null) {
this.countPerRow = 0;
matcher.setRow(row, offset, length);
}
// Clear progress away unless invoker has indicated it should be kept.
if (!scannerContext.getKeepProgress()) scannerContext.clearProgress();
// Only do a sanity-check if store and comparator are available.
KeyValue.KVComparator comparator =
store != null ? store.getComparator() : null;
int count = 0;
long totalBytesRead = 0;
LOOP: do {
// Update and check the time limit based on the configured value of cellsPerTimeoutCheck
if ((kvsScanned % cellsPerHeartbeatCheck == 0)) {
scannerContext.updateTimeProgress();
if (scannerContext.checkTimeLimit(LimitScope.BETWEEN_CELLS)) {
return scannerContext.setScannerState(NextState.TIME_LIMIT_REACHED).hasMoreValues();
}
}
if (prevCell != cell) ++kvsScanned; // Do object compare - we set prevKV from the same heap.
checkScanOrder(prevCell, cell, comparator);
prevCell = cell;
ScanQueryMatcher.MatchCode qcode = matcher.match(cell);
qcode = optimize(qcode, cell);
switch(qcode) {
case INCLUDE:
case INCLUDE_AND_SEEK_NEXT_ROW:
case INCLUDE_AND_SEEK_NEXT_COL:
Filter f = matcher.getFilter();
if (f != null) {
// TODO convert Scan Query Matcher to be Cell instead of KV based ?
cell = f.transformCell(cell);
}
this.countPerRow++;
if (storeLimit > -1 &&
this.countPerRow > (storeLimit + storeOffset)) {
// do what SEEK_NEXT_ROW does.
if (!matcher.moreRowsMayExistAfter(cell)) {
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
}
// Setting the matcher.row = null, will mean that after the subsequent seekToNextRow()
// the heap.peek() will any way be in the next row. So the SQM.match(cell) need do
// another compareRow to say the current row is DONE
matcher.row = null;
seekToNextRow(cell);
break LOOP;
}
// add to results only if we have skipped #storeOffset kvs
// also update metric accordingly
if (this.countPerRow > storeOffset) {
outResult.add(cell);
// Update local tracking information
count++;
totalBytesRead += CellUtil.estimatedSerializedSizeOf(cell);
// Update the progress of the scanner context
scannerContext.incrementSizeProgress(CellUtil.estimatedHeapSizeOfWithoutTags(cell));
scannerContext.incrementBatchProgress(1);
if (totalBytesRead > maxRowSize) {
throw new RowTooBigException("Max row size allowed: " + maxRowSize
+ ", but the row is bigger than that.");
}
}
if (qcode == ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_ROW) {
if (!matcher.moreRowsMayExistAfter(cell)) {
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
}
// Setting the matcher.row = null, will mean that after the subsequent seekToNextRow()
// the heap.peek() will any way be in the next row. So the SQM.match(cell) need do
// another compareRow to say the current row is DONE
matcher.row = null;
seekToNextRow(cell);
} else if (qcode == ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_COL) {
seekAsDirection(matcher.getKeyForNextColumn(cell));
} else {
this.heap.next();
}
if (scannerContext.checkBatchLimit(LimitScope.BETWEEN_CELLS)) {
break LOOP;
}
if (scannerContext.checkSizeLimit(LimitScope.BETWEEN_CELLS)) {
break LOOP;
}
continue;
case DONE:
// We are sure that this row is done and we are in the next row.
// So subsequent StoresScanner.next() call need not do another compare
// and set the matcher.row
matcher.row = null;
return scannerContext.setScannerState(NextState.MORE_VALUES).hasMoreValues();
case DONE_SCAN:
close();
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
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(cell)) {
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
}
// Setting the matcher.row = null, will mean that after the subsequent seekToNextRow()
// the heap.peek() will any way be in the next row. So the SQM.match(cell) need do
// another compareRow to say the current row is DONE
matcher.row = null;
seekToNextRow(cell);
break;
case SEEK_NEXT_COL:
seekAsDirection(matcher.getKeyForNextColumn(cell));
break;
case SKIP:
this.heap.next();
break;
case SEEK_NEXT_USING_HINT:
// TODO convert resee to Cell?
Cell nextKV = matcher.getNextKeyHint(cell);
if (nextKV != null) {
seekAsDirection(nextKV);
} else {
heap.next();
}
break;
default:
throw new RuntimeException("UNEXPECTED");
}
} while((cell = this.heap.peek()) != null);
if (count > 0) {
return scannerContext.setScannerState(NextState.MORE_VALUES).hasMoreValues();
}
// No more keys
close();
return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
} finally {
lock.unlock();
}
}
/*
* See if we should actually SEEK or rather just SKIP to the next Cell.
* (see HBASE-13109)
*/
private ScanQueryMatcher.MatchCode optimize(ScanQueryMatcher.MatchCode qcode, Cell cell) {
switch(qcode) {
case INCLUDE_AND_SEEK_NEXT_COL:
case SEEK_NEXT_COL:
{
Cell nextIndexedKey = getNextIndexedKey();
if (nextIndexedKey != null && nextIndexedKey != KeyValueScanner.NO_NEXT_INDEXED_KEY
&& matcher.compareKeyForNextColumn(nextIndexedKey, cell) >= 0) {
return qcode == MatchCode.SEEK_NEXT_COL ? MatchCode.SKIP : MatchCode.INCLUDE;
}
break;
}
case INCLUDE_AND_SEEK_NEXT_ROW:
case SEEK_NEXT_ROW:
{
Cell nextIndexedKey = getNextIndexedKey();
if (nextIndexedKey != null && nextIndexedKey != KeyValueScanner.NO_NEXT_INDEXED_KEY
&& matcher.compareKeyForNextRow(nextIndexedKey, cell) >= 0) {
return qcode == MatchCode.SEEK_NEXT_ROW ? MatchCode.SKIP : MatchCode.INCLUDE;
}
break;
}
default:
break;
}
return qcode;
}
// Implementation of ChangedReadersObserver
@Override
public void updateReaders() throws IOException {
lock.lock();
try {
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
} finally {
lock.unlock();
}
}
/**
* @return true if top of heap has changed (and KeyValueHeap has to try the
* next KV)
* @throws IOException
*/
protected boolean checkReseek() throws IOException {
if (this.heap == null && this.lastTop != null) {
resetScannerStack(this.lastTop);
if (this.heap.peek() == null
|| store.getComparator().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;
}
protected void resetScannerStack(Cell 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 scanners = getScannersNoCompaction();
// Seek all scanners to the initial key
seekScanners(scanners, lastTopKey, false, parallelSeekEnabled);
// Combine all seeked scanners with a heap
resetKVHeap(scanners, store.getComparator());
// 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.
Cell kv = heap.peek();
if (kv == null) {
kv = lastTopKey;
}
byte[] row = kv.getRowArray();
int offset = kv.getRowOffset();
short length = kv.getRowLength();
if ((matcher.row == null) || !Bytes.equals(row, offset, length, matcher.row,
matcher.rowOffset, matcher.rowLength)) {
this.countPerRow = 0;
matcher.reset();
matcher.setRow(row, offset, length);
}
}
/**
* Check whether scan as expected order
* @param prevKV
* @param kv
* @param comparator
* @throws IOException
*/
protected void checkScanOrder(Cell prevKV, Cell kv,
KeyValue.KVComparator comparator) throws IOException {
// 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;
}
protected boolean seekToNextRow(Cell kv) throws IOException {
return reseek(KeyValueUtil.createLastOnRow(kv));
}
/**
* Do a reseek in a normal StoreScanner(scan forward)
* @param kv
* @return true if scanner has values left, false if end of scanner
* @throws IOException
*/
protected boolean seekAsDirection(Cell kv)
throws IOException {
return reseek(kv);
}
@Override
public boolean reseek(Cell kv) throws IOException {
lock.lock();
try {
//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);
}
return heap.reseek(kv);
} finally {
lock.unlock();
}
}
@Override
public long getSequenceID() {
return 0;
}
/**
* Seek storefiles in parallel to optimize IO latency as much as possible
* @param scanners the list {@link KeyValueScanner}s to be read from
* @param kv the KeyValue on which the operation is being requested
* @throws IOException
*/
private void parallelSeek(final List
scanners, final Cell kv) throws IOException {
if (scanners.isEmpty()) return;
int storeFileScannerCount = scanners.size();
CountDownLatch latch = new CountDownLatch(storeFileScannerCount);
List handlers =
new ArrayList(storeFileScannerCount);
for (KeyValueScanner scanner : scanners) {
if (scanner instanceof StoreFileScanner) {
ParallelSeekHandler seekHandler = new ParallelSeekHandler(scanner, kv,
this.readPt, latch);
executor.submit(seekHandler);
handlers.add(seekHandler);
} else {
scanner.seek(kv);
latch.countDown();
}
}
try {
latch.await();
} catch (InterruptedException ie) {
throw (InterruptedIOException)new InterruptedIOException().initCause(ie);
}
for (ParallelSeekHandler handler : handlers) {
if (handler.getErr() != null) {
throw new IOException(handler.getErr());
}
}
}
/**
* Used in testing.
* @return all scanners in no particular order
*/
List getAllScannersForTesting() {
List allScanners = new ArrayList();
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;
}
/**
* @return The estimated number of KVs seen by this scanner (includes some skipped KVs).
*/
public long getEstimatedNumberOfKvsScanned() {
return this.kvsScanned;
}
@Override
public Cell getNextIndexedKey() {
return this.heap.getNextIndexedKey();
}
}
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