/**
*
* 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.NavigableSet;
import org.apache.hadoop.classification.InterfaceAudience;
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.filter.Filter.ReturnCode;
import org.apache.hadoop.hbase.io.TimeRange;
import org.apache.hadoop.hbase.regionserver.DeleteTracker.DeleteResult;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
/**
* A query matcher that is specifically designed for the scan case.
*/
@InterfaceAudience.Private
public class ScanQueryMatcher {
// Optimization so we can skip lots of compares when we decide to skip
// to the next row.
private boolean stickyNextRow;
private final byte[] stopRow;
private final TimeRange tr;
private final Filter filter;
/** Keeps track of deletes */
private final DeleteTracker deletes;
/*
* The following three booleans define how we deal with deletes.
* There are three different aspects:
* 1. Whether to keep delete markers. This is used in compactions.
* Minor compactions always keep delete markers.
* 2. Whether to keep deleted rows. This is also used in compactions,
* if the store is set to keep deleted rows. This implies keeping
* the delete markers as well.
* In this case deleted rows are subject to the normal max version
* and TTL/min version rules just like "normal" rows.
* 3. Whether a scan can do time travel queries even before deleted
* marker to reach deleted rows.
*/
/** whether to retain delete markers */
private final boolean retainDeletesInOutput;
/** whether to return deleted rows */
private final boolean keepDeletedCells;
/** whether time range queries can see rows "behind" a delete */
private final boolean seePastDeleteMarkers;
/** Keeps track of columns and versions */
private final ColumnTracker columns;
/** Key to seek to in memstore and StoreFiles */
private final KeyValue startKey;
/** Row comparator for the region this query is for */
private final KeyValue.KeyComparator rowComparator;
/* row is not private for tests */
/** Row the query is on */
byte [] row;
/**
* Oldest put in any of the involved store files
* Used to decide whether it is ok to delete
* family delete marker of this store keeps
* deleted KVs.
*/
private final long earliestPutTs;
/** readPoint over which the KVs are unconditionally included */
protected long maxReadPointToTrackVersions;
/**
* This variable shows whether there is an null column in the query. There
* always exists a null column in the wildcard column query.
* There maybe exists a null column in the explicit column query based on the
* first column.
* */
private boolean hasNullColumn = true;
// By default, when hbase.hstore.time.to.purge.deletes is 0ms, a delete
// marker is always removed during a major compaction. If set to non-zero
// value then major compaction will try to keep a delete marker around for
// the given number of milliseconds. We want to keep the delete markers
// around a bit longer because old puts might appear out-of-order. For
// example, during log replication between two clusters.
//
// If the delete marker has lived longer than its column-family's TTL then
// the delete marker will be removed even if time.to.purge.deletes has not
// passed. This is because all the Puts that this delete marker can influence
// would have also expired. (Removing of delete markers on col family TTL will
// not happen if min-versions is set to non-zero)
//
// But, if time.to.purge.deletes has not expired then a delete
// marker will not be removed just because there are no Puts that it is
// currently influencing. This is because Puts, that this delete can
// influence. may appear out of order.
private final long timeToPurgeDeletes;
private final boolean isUserScan;
/**
* Construct a QueryMatcher for a scan
* @param scan
* @param scanInfo The store's immutable scan info
* @param columns
* @param scanType Type of the scan
* @param earliestPutTs Earliest put seen in any of the store files.
* @param oldestUnexpiredTS the oldest timestamp we are interested in,
* based on TTL
*/
public ScanQueryMatcher(Scan scan, HStore.ScanInfo scanInfo,
NavigableSet<byte[]> columns, ScanType scanType,
long readPointToUse, long earliestPutTs, long oldestUnexpiredTS) {
this.tr = scan.getTimeRange();
this.rowComparator = scanInfo.getComparator().getRawComparator();
this.deletes = new ScanDeleteTracker();
this.stopRow = scan.getStopRow();
this.startKey = KeyValue.createFirstDeleteFamilyOnRow(scan.getStartRow(),
scanInfo.getFamily());
this.filter = scan.getFilter();
this.earliestPutTs = earliestPutTs;
this.maxReadPointToTrackVersions = readPointToUse;
this.timeToPurgeDeletes = scanInfo.getTimeToPurgeDeletes();
/* how to deal with deletes */
this.isUserScan = scanType == ScanType.USER_SCAN;
// keep deleted cells: if compaction or raw scan
this.keepDeletedCells = (scanInfo.getKeepDeletedCells() && !isUserScan) || scan.isRaw();
// retain deletes: if minor compaction or raw scan
this.retainDeletesInOutput = scanType == ScanType.MINOR_COMPACT || scan.isRaw();
// seePastDeleteMarker: user initiated scans
this.seePastDeleteMarkers = scanInfo.getKeepDeletedCells() && isUserScan;
int maxVersions = Math.min(scan.getMaxVersions(), scanInfo.getMaxVersions());
// Single branch to deal with two types of reads (columns vs all in family)
if (columns == null || columns.size() == 0) {
// there is always a null column in the wildcard column query.
hasNullColumn = true;
// use a specialized scan for wildcard column tracker.
this.columns = new ScanWildcardColumnTracker(
scanInfo.getMinVersions(), maxVersions, oldestUnexpiredTS);
} else {
// whether there is null column in the explicit column query
hasNullColumn = (columns.first().length == 0);
// We can share the ExplicitColumnTracker, diff is we reset
// between rows, not between storefiles.
this.columns = new ExplicitColumnTracker(columns,
scanInfo.getMinVersions(), maxVersions, oldestUnexpiredTS);
}
}
/*
* Constructor for tests
*/
ScanQueryMatcher(Scan scan, HStore.ScanInfo scanInfo,
NavigableSet<byte[]> columns, long oldestUnexpiredTS) {
this(scan, scanInfo, columns, ScanType.USER_SCAN,
Long.MAX_VALUE, /* max Readpoint to track versions */
HConstants.LATEST_TIMESTAMP, oldestUnexpiredTS);
}
/**
*
* @return whether there is an null column in the query
*/
public boolean hasNullColumnInQuery() {
return hasNullColumn;
}
/**
* Determines if the caller should do one of several things:
* - seek/skip to the next row (MatchCode.SEEK_NEXT_ROW)
* - seek/skip to the next column (MatchCode.SEEK_NEXT_COL)
* - include the current KeyValue (MatchCode.INCLUDE)
* - ignore the current KeyValue (MatchCode.SKIP)
* - got to the next row (MatchCode.DONE)
*
* @param kv KeyValue to check
* @return The match code instance.
* @throws IOException in case there is an internal consistency problem
* caused by a data corruption.
*/
public MatchCode match(KeyValue kv) throws IOException {
if (filter != null && filter.filterAllRemaining()) {
return MatchCode.DONE_SCAN;
}
byte [] bytes = kv.getBuffer();
int offset = kv.getOffset();
int initialOffset = offset;
int keyLength = Bytes.toInt(bytes, offset, Bytes.SIZEOF_INT);
offset += KeyValue.ROW_OFFSET;
short rowLength = Bytes.toShort(bytes, offset, Bytes.SIZEOF_SHORT);
offset += Bytes.SIZEOF_SHORT;
int ret = this.rowComparator.compareRows(row, 0, row.length,
bytes, offset, rowLength);
if (ret <= -1) {
return MatchCode.DONE;
} else if (ret >= 1) {
// could optimize this, if necessary?
// Could also be called SEEK_TO_CURRENT_ROW, but this
// should be rare/never happens.
return MatchCode.SEEK_NEXT_ROW;
}
// optimize case.
if (this.stickyNextRow)
return MatchCode.SEEK_NEXT_ROW;
if (this.columns.done()) {
stickyNextRow = true;
return MatchCode.SEEK_NEXT_ROW;
}
//Passing rowLength
offset += rowLength;
//Skipping family
byte familyLength = bytes [offset];
offset += familyLength + 1;
int qualLength = keyLength + KeyValue.ROW_OFFSET -
(offset - initialOffset) - KeyValue.TIMESTAMP_TYPE_SIZE;
long timestamp = kv.getTimestamp();
// check for early out based on timestamp alone
if (columns.isDone(timestamp)) {
return columns.getNextRowOrNextColumn(bytes, offset, qualLength);
}
/*
* The delete logic is pretty complicated now.
* This is corroborated by the following:
* 1. The store might be instructed to keep deleted rows around.
* 2. A scan can optionally see past a delete marker now.
* 3. If deleted rows are kept, we have to find out when we can
* remove the delete markers.
* 4. Family delete markers are always first (regardless of their TS)
* 5. Delete markers should not be counted as version
* 6. Delete markers affect puts of the *same* TS
* 7. Delete marker need to be version counted together with puts
* they affect
*/
byte type = kv.getType();
if (kv.isDelete()) {
if (!keepDeletedCells) {
// first ignore delete markers if the scanner can do so, and the
// range does not include the marker
//
// during flushes and compactions also ignore delete markers newer
// than the readpoint of any open scanner, this prevents deleted
// rows that could still be seen by a scanner from being collected
boolean includeDeleteMarker = seePastDeleteMarkers ?
tr.withinTimeRange(timestamp) :
tr.withinOrAfterTimeRange(timestamp);
if (includeDeleteMarker
&& kv.getMemstoreTS() <= maxReadPointToTrackVersions) {
this.deletes.add(bytes, offset, qualLength, timestamp, type);
}
// Can't early out now, because DelFam come before any other keys
}
if (retainDeletesInOutput
|| (!isUserScan && (EnvironmentEdgeManager.currentTimeMillis() - timestamp) <= timeToPurgeDeletes)
|| kv.getMemstoreTS() > maxReadPointToTrackVersions) {
// always include or it is not time yet to check whether it is OK
// to purge deltes or not
return MatchCode.INCLUDE;
} else if (keepDeletedCells) {
if (timestamp < earliestPutTs) {
// keeping delete rows, but there are no puts older than
// this delete in the store files.
return columns.getNextRowOrNextColumn(bytes, offset, qualLength);
}
// else: fall through and do version counting on the
// delete markers
} else {
return MatchCode.SKIP;
}
// note the following next else if...
// delete marker are not subject to other delete markers
} else if (!this.deletes.isEmpty()) {
DeleteResult deleteResult = deletes.isDeleted(bytes, offset, qualLength,
timestamp);
switch (deleteResult) {
case FAMILY_DELETED:
case COLUMN_DELETED:
return columns.getNextRowOrNextColumn(bytes, offset, qualLength);
case VERSION_DELETED:
return MatchCode.SKIP;
case NOT_DELETED:
break;
default:
throw new RuntimeException("UNEXPECTED");
}
}
int timestampComparison = tr.compare(timestamp);
if (timestampComparison >= 1) {
return MatchCode.SKIP;
} else if (timestampComparison <= -1) {
return columns.getNextRowOrNextColumn(bytes, offset, qualLength);
}
/**
* Filters should be checked before checking column trackers. If we do
* otherwise, as was previously being done, ColumnTracker may increment its
* counter for even that KV which may be discarded later on by Filter. This
* would lead to incorrect results in certain cases.
*/
ReturnCode filterResponse = ReturnCode.SKIP;
if (filter != null) {
filterResponse = filter.filterKeyValue(kv);
if (filterResponse == ReturnCode.SKIP) {
return MatchCode.SKIP;
} else if (filterResponse == ReturnCode.NEXT_COL) {
return columns.getNextRowOrNextColumn(bytes, offset, qualLength);
} else if (filterResponse == ReturnCode.NEXT_ROW) {
stickyNextRow = true;
return MatchCode.SEEK_NEXT_ROW;
} else if (filterResponse == ReturnCode.SEEK_NEXT_USING_HINT) {
return MatchCode.SEEK_NEXT_USING_HINT;
}
}
MatchCode colChecker = columns.checkColumn(bytes, offset, qualLength,
timestamp, type, kv.getMemstoreTS() > maxReadPointToTrackVersions);
/*
* According to current implementation, colChecker can only be
* SEEK_NEXT_COL, SEEK_NEXT_ROW, SKIP or INCLUDE. Therefore, always return
* the MatchCode. If it is SEEK_NEXT_ROW, also set stickyNextRow.
*/
if (colChecker == MatchCode.SEEK_NEXT_ROW) {
stickyNextRow = true;
} else if (filter != null && colChecker == MatchCode.INCLUDE &&
filterResponse == ReturnCode.INCLUDE_AND_NEXT_COL) {
return MatchCode.INCLUDE_AND_SEEK_NEXT_COL;
}
return colChecker;
}
public boolean moreRowsMayExistAfter(KeyValue kv) {
if (!Bytes.equals(stopRow , HConstants.EMPTY_END_ROW) &&
rowComparator.compareRows(kv.getBuffer(),kv.getRowOffset(),
kv.getRowLength(), stopRow, 0, stopRow.length) >= 0) {
// KV >= STOPROW
// then NO there is nothing left.
return false;
} else {
return true;
}
}
/**
* Set current row
* @param row
*/
public void setRow(byte [] row) {
this.row = row;
reset();
}
public void reset() {
this.deletes.reset();
this.columns.reset();
stickyNextRow = false;
}
/**
*
* @return the start key
*/
public KeyValue getStartKey() {
return this.startKey;
}
/**
*
* @return the Filter
*/
Filter getFilter() {
return this.filter;
}
public KeyValue getNextKeyHint(KeyValue kv) {
if (filter == null) {
return null;
} else {
return filter.getNextKeyHint(kv);
}
}
public KeyValue getKeyForNextColumn(KeyValue kv) {
ColumnCount nextColumn = columns.getColumnHint();
if (nextColumn == null) {
return KeyValue.createLastOnRow(
kv.getBuffer(), kv.getRowOffset(), kv.getRowLength(),
kv.getBuffer(), kv.getFamilyOffset(), kv.getFamilyLength(),
kv.getBuffer(), kv.getQualifierOffset(), kv.getQualifierLength());
} else {
return KeyValue.createFirstOnRow(
kv.getBuffer(), kv.getRowOffset(), kv.getRowLength(),
kv.getBuffer(), kv.getFamilyOffset(), kv.getFamilyLength(),
nextColumn.getBuffer(), nextColumn.getOffset(), nextColumn.getLength());
}
}
public KeyValue getKeyForNextRow(KeyValue kv) {
return KeyValue.createLastOnRow(
kv.getBuffer(), kv.getRowOffset(), kv.getRowLength(),
null, 0, 0,
null, 0, 0);
}
/**
* {@link #match} return codes. These instruct the scanner moving through
* memstores and StoreFiles what to do with the current KeyValue.
* <p>
* Additionally, this contains "early-out" language to tell the scanner to
* move on to the next File (memstore or Storefile), or to return immediately.
*/
public static enum MatchCode {
/**
* Include KeyValue in the returned result
*/
INCLUDE,
/**
* Do not include KeyValue in the returned result
*/
SKIP,
/**
* Do not include, jump to next StoreFile or memstore (in time order)
*/
NEXT,
/**
* Do not include, return current result
*/
DONE,
/**
* These codes are used by the ScanQueryMatcher
*/
/**
* Done with the row, seek there.
*/
SEEK_NEXT_ROW,
/**
* Done with column, seek to next.
*/
SEEK_NEXT_COL,
/**
* Done with scan, thanks to the row filter.
*/
DONE_SCAN,
/*
* Seek to next key which is given as hint.
*/
SEEK_NEXT_USING_HINT,
/**
* Include KeyValue and done with column, seek to next.
*/
INCLUDE_AND_SEEK_NEXT_COL,
/**
* Include KeyValue and done with row, seek to next.
*/
INCLUDE_AND_SEEK_NEXT_ROW,
}
}