1 /*
2 *
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 package org.apache.hadoop.hbase.client;
21
22 import java.io.IOException;
23 import java.util.ArrayList;
24 import java.util.Arrays;
25 import java.util.HashMap;
26 import java.util.List;
27 import java.util.Map;
28 import java.util.NavigableSet;
29 import java.util.TreeMap;
30 import java.util.TreeSet;
31
32 import org.apache.commons.logging.Log;
33 import org.apache.commons.logging.LogFactory;
34 import org.apache.hadoop.hbase.classification.InterfaceAudience;
35 import org.apache.hadoop.hbase.classification.InterfaceStability;
36 import org.apache.hadoop.hbase.HConstants;
37 import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
38 import org.apache.hadoop.hbase.filter.Filter;
39 import org.apache.hadoop.hbase.filter.IncompatibleFilterException;
40 import org.apache.hadoop.hbase.io.TimeRange;
41 import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
42 import org.apache.hadoop.hbase.security.access.Permission;
43 import org.apache.hadoop.hbase.security.visibility.Authorizations;
44 import org.apache.hadoop.hbase.util.Bytes;
45
46 /**
47 * Used to perform Scan operations.
48 * <p>
49 * All operations are identical to {@link Get} with the exception of
50 * instantiation. Rather than specifying a single row, an optional startRow
51 * and stopRow may be defined. If rows are not specified, the Scanner will
52 * iterate over all rows.
53 * <p>
54 * To scan everything for each row, instantiate a Scan object.
55 * <p>
56 * To modify scanner caching for just this scan, use {@link #setCaching(int) setCaching}.
57 * If caching is NOT set, we will use the caching value of the hosting {@link Table}.
58 * In addition to row caching, it is possible to specify a
59 * maximum result size, using {@link #setMaxResultSize(long)}. When both are used,
60 * single server requests are limited by either number of rows or maximum result size, whichever
61 * limit comes first.
62 * <p>
63 * To further define the scope of what to get when scanning, perform additional
64 * methods as outlined below.
65 * <p>
66 * To get all columns from specific families, execute {@link #addFamily(byte[]) addFamily}
67 * for each family to retrieve.
68 * <p>
69 * To get specific columns, execute {@link #addColumn(byte[], byte[]) addColumn}
70 * for each column to retrieve.
71 * <p>
72 * To only retrieve columns within a specific range of version timestamps,
73 * execute {@link #setTimeRange(long, long) setTimeRange}.
74 * <p>
75 * To only retrieve columns with a specific timestamp, execute
76 * {@link #setTimeStamp(long) setTimestamp}.
77 * <p>
78 * To limit the number of versions of each column to be returned, execute
79 * {@link #setMaxVersions(int) setMaxVersions}.
80 * <p>
81 * To limit the maximum number of values returned for each call to next(),
82 * execute {@link #setBatch(int) setBatch}.
83 * <p>
84 * To add a filter, execute {@link #setFilter(org.apache.hadoop.hbase.filter.Filter) setFilter}.
85 * <p>
86 * Expert: To explicitly disable server-side block caching for this scan,
87 * execute {@link #setCacheBlocks(boolean)}.
88 * <p><em>Note:</em> Usage alters Scan instances. Internally, attributes are updated as the Scan
89 * runs and if enabled, metrics accumulate in the Scan instance. Be aware this is the case when
90 * you go to clone a Scan instance or if you go to reuse a created Scan instance; safer is create
91 * a Scan instance per usage.
92 */
93 @InterfaceAudience.Public
94 @InterfaceStability.Stable
95 public class Scan extends Query {
96 private static final Log LOG = LogFactory.getLog(Scan.class);
97
98 private static final String RAW_ATTR = "_raw_";
99
100 private byte [] startRow = HConstants.EMPTY_START_ROW;
101 private byte [] stopRow = HConstants.EMPTY_END_ROW;
102 private int maxVersions = 1;
103 private int batch = -1;
104
105 /**
106 * Partial {@link Result}s are {@link Result}s must be combined to form a complete {@link Result}.
107 * The {@link Result}s had to be returned in fragments (i.e. as partials) because the size of the
108 * cells in the row exceeded max result size on the server. Typically partial results will be
109 * combined client side into complete results before being delivered to the caller. However, if
110 * this flag is set, the caller is indicating that they do not mind seeing partial results (i.e.
111 * they understand that the results returned from the Scanner may only represent part of a
112 * particular row). In such a case, any attempt to combine the partials into a complete result on
113 * the client side will be skipped, and the caller will be able to see the exact results returned
114 * from the server.
115 */
116 private boolean allowPartialResults = false;
117
118 private int storeLimit = -1;
119 private int storeOffset = 0;
120 private boolean getScan;
121
122 /**
123 * @deprecated since 1.0.0. Use {@link #setScanMetricsEnabled(boolean)}
124 */
125 // Make private or remove.
126 @Deprecated
127 static public final String SCAN_ATTRIBUTES_METRICS_ENABLE = "scan.attributes.metrics.enable";
128
129 /**
130 * Use {@link #getScanMetrics()}
131 */
132 // Make this private or remove.
133 @Deprecated
134 static public final String SCAN_ATTRIBUTES_METRICS_DATA = "scan.attributes.metrics.data";
135
136 // If an application wants to use multiple scans over different tables each scan must
137 // define this attribute with the appropriate table name by calling
138 // scan.setAttribute(Scan.SCAN_ATTRIBUTES_TABLE_NAME, Bytes.toBytes(tableName))
139 static public final String SCAN_ATTRIBUTES_TABLE_NAME = "scan.attributes.table.name";
140
141 /**
142 * @deprecated without replacement
143 * This is now a no-op, SEEKs and SKIPs are optimizated automatically.
144 * Will be removed in 2.0+
145 */
146 @Deprecated
147 public static final String HINT_LOOKAHEAD = "_look_ahead_";
148
149 /*
150 * -1 means no caching
151 */
152 private int caching = -1;
153 private long maxResultSize = -1;
154 private boolean cacheBlocks = true;
155 private boolean reversed = false;
156 private TimeRange tr = new TimeRange();
157 private Map<byte [], NavigableSet<byte []>> familyMap =
158 new TreeMap<byte [], NavigableSet<byte []>>(Bytes.BYTES_COMPARATOR);
159 private Boolean loadColumnFamiliesOnDemand = null;
160
161 /**
162 * Set it true for small scan to get better performance
163 *
164 * Small scan should use pread and big scan can use seek + read
165 *
166 * seek + read is fast but can cause two problem (1) resource contention (2)
167 * cause too much network io
168 *
169 * [89-fb] Using pread for non-compaction read request
170 * https://issues.apache.org/jira/browse/HBASE-7266
171 *
172 * On the other hand, if setting it true, we would do
173 * openScanner,next,closeScanner in one RPC call. It means the better
174 * performance for small scan. [HBASE-9488].
175 *
176 * Generally, if the scan range is within one data block(64KB), it could be
177 * considered as a small scan.
178 */
179 private boolean small = false;
180
181 /**
182 * Create a Scan operation across all rows.
183 */
184 public Scan() {}
185
186 public Scan(byte [] startRow, Filter filter) {
187 this(startRow);
188 this.filter = filter;
189 }
190
191 /**
192 * Create a Scan operation starting at the specified row.
193 * <p>
194 * If the specified row does not exist, the Scanner will start from the
195 * next closest row after the specified row.
196 * @param startRow row to start scanner at or after
197 */
198 public Scan(byte [] startRow) {
199 this.startRow = startRow;
200 }
201
202 /**
203 * Create a Scan operation for the range of rows specified.
204 * @param startRow row to start scanner at or after (inclusive)
205 * @param stopRow row to stop scanner before (exclusive)
206 */
207 public Scan(byte [] startRow, byte [] stopRow) {
208 this.startRow = startRow;
209 this.stopRow = stopRow;
210 //if the startRow and stopRow both are empty, it is not a Get
211 this.getScan = isStartRowAndEqualsStopRow();
212 }
213
214 /**
215 * Creates a new instance of this class while copying all values.
216 *
217 * @param scan The scan instance to copy from.
218 * @throws IOException When copying the values fails.
219 */
220 public Scan(Scan scan) throws IOException {
221 startRow = scan.getStartRow();
222 stopRow = scan.getStopRow();
223 maxVersions = scan.getMaxVersions();
224 batch = scan.getBatch();
225 storeLimit = scan.getMaxResultsPerColumnFamily();
226 storeOffset = scan.getRowOffsetPerColumnFamily();
227 caching = scan.getCaching();
228 maxResultSize = scan.getMaxResultSize();
229 cacheBlocks = scan.getCacheBlocks();
230 getScan = scan.isGetScan();
231 filter = scan.getFilter(); // clone?
232 loadColumnFamiliesOnDemand = scan.getLoadColumnFamiliesOnDemandValue();
233 consistency = scan.getConsistency();
234 reversed = scan.isReversed();
235 small = scan.isSmall();
236 allowPartialResults = scan.getAllowPartialResults();
237 TimeRange ctr = scan.getTimeRange();
238 tr = new TimeRange(ctr.getMin(), ctr.getMax());
239 Map<byte[], NavigableSet<byte[]>> fams = scan.getFamilyMap();
240 for (Map.Entry<byte[],NavigableSet<byte[]>> entry : fams.entrySet()) {
241 byte [] fam = entry.getKey();
242 NavigableSet<byte[]> cols = entry.getValue();
243 if (cols != null && cols.size() > 0) {
244 for (byte[] col : cols) {
245 addColumn(fam, col);
246 }
247 } else {
248 addFamily(fam);
249 }
250 }
251 for (Map.Entry<String, byte[]> attr : scan.getAttributesMap().entrySet()) {
252 setAttribute(attr.getKey(), attr.getValue());
253 }
254 }
255
256 /**
257 * Builds a scan object with the same specs as get.
258 * @param get get to model scan after
259 */
260 public Scan(Get get) {
261 this.startRow = get.getRow();
262 this.stopRow = get.getRow();
263 this.filter = get.getFilter();
264 this.cacheBlocks = get.getCacheBlocks();
265 this.maxVersions = get.getMaxVersions();
266 this.storeLimit = get.getMaxResultsPerColumnFamily();
267 this.storeOffset = get.getRowOffsetPerColumnFamily();
268 this.tr = get.getTimeRange();
269 this.familyMap = get.getFamilyMap();
270 this.getScan = true;
271 this.consistency = get.getConsistency();
272 this.setIsolationLevel(get.getIsolationLevel());
273 for (Map.Entry<String, byte[]> attr : get.getAttributesMap().entrySet()) {
274 setAttribute(attr.getKey(), attr.getValue());
275 }
276 }
277
278 public boolean isGetScan() {
279 return this.getScan || isStartRowAndEqualsStopRow();
280 }
281
282 private boolean isStartRowAndEqualsStopRow() {
283 return this.startRow != null && this.startRow.length > 0 &&
284 Bytes.equals(this.startRow, this.stopRow);
285 }
286 /**
287 * Get all columns from the specified family.
288 * <p>
289 * Overrides previous calls to addColumn for this family.
290 * @param family family name
291 * @return this
292 */
293 public Scan addFamily(byte [] family) {
294 familyMap.remove(family);
295 familyMap.put(family, null);
296 return this;
297 }
298
299 /**
300 * Get the column from the specified family with the specified qualifier.
301 * <p>
302 * Overrides previous calls to addFamily for this family.
303 * @param family family name
304 * @param qualifier column qualifier
305 * @return this
306 */
307 public Scan addColumn(byte [] family, byte [] qualifier) {
308 NavigableSet<byte []> set = familyMap.get(family);
309 if(set == null) {
310 set = new TreeSet<byte []>(Bytes.BYTES_COMPARATOR);
311 }
312 if (qualifier == null) {
313 qualifier = HConstants.EMPTY_BYTE_ARRAY;
314 }
315 set.add(qualifier);
316 familyMap.put(family, set);
317 return this;
318 }
319
320 /**
321 * Get versions of columns only within the specified timestamp range,
322 * [minStamp, maxStamp). Note, default maximum versions to return is 1. If
323 * your time range spans more than one version and you want all versions
324 * returned, up the number of versions beyond the default.
325 * @param minStamp minimum timestamp value, inclusive
326 * @param maxStamp maximum timestamp value, exclusive
327 * @throws IOException if invalid time range
328 * @see #setMaxVersions()
329 * @see #setMaxVersions(int)
330 * @return this
331 */
332 public Scan setTimeRange(long minStamp, long maxStamp)
333 throws IOException {
334 tr = new TimeRange(minStamp, maxStamp);
335 return this;
336 }
337
338 /**
339 * Get versions of columns with the specified timestamp. Note, default maximum
340 * versions to return is 1. If your time range spans more than one version
341 * and you want all versions returned, up the number of versions beyond the
342 * defaut.
343 * @param timestamp version timestamp
344 * @see #setMaxVersions()
345 * @see #setMaxVersions(int)
346 * @return this
347 */
348 public Scan setTimeStamp(long timestamp)
349 throws IOException {
350 try {
351 tr = new TimeRange(timestamp, timestamp+1);
352 } catch(IOException e) {
353 // This should never happen, unless integer overflow or something extremely wrong...
354 LOG.error("TimeRange failed, likely caused by integer overflow. ", e);
355 throw e;
356 }
357 return this;
358 }
359
360 /**
361 * Set the start row of the scan.
362 * @param startRow row to start scan on (inclusive)
363 * Note: In order to make startRow exclusive add a trailing 0 byte
364 * @return this
365 */
366 public Scan setStartRow(byte [] startRow) {
367 this.startRow = startRow;
368 return this;
369 }
370
371 /**
372 * Set the stop row.
373 * @param stopRow row to end at (exclusive)
374 * <p><b>Note:</b> In order to make stopRow inclusive add a trailing 0 byte</p>
375 * <p><b>Note:</b> When doing a filter for a rowKey <u>Prefix</u>
376 * use {@link #setRowPrefixFilter(byte[])}.
377 * The 'trailing 0' will not yield the desired result.</p>
378 * @return this
379 */
380 public Scan setStopRow(byte [] stopRow) {
381 this.stopRow = stopRow;
382 return this;
383 }
384
385 /**
386 * <p>Set a filter (using stopRow and startRow) so the result set only contains rows where the
387 * rowKey starts with the specified prefix.</p>
388 * <p>This is a utility method that converts the desired rowPrefix into the appropriate values
389 * for the startRow and stopRow to achieve the desired result.</p>
390 * <p>This can safely be used in combination with setFilter.</p>
391 * <p><b>NOTE: Doing a {@link #setStartRow(byte[])} and/or {@link #setStopRow(byte[])}
392 * after this method will yield undefined results.</b></p>
393 * @param rowPrefix the prefix all rows must start with. (Set <i>null</i> to remove the filter.)
394 * @return this
395 */
396 public Scan setRowPrefixFilter(byte[] rowPrefix) {
397 if (rowPrefix == null) {
398 setStartRow(HConstants.EMPTY_START_ROW);
399 setStopRow(HConstants.EMPTY_END_ROW);
400 } else {
401 this.setStartRow(rowPrefix);
402 this.setStopRow(calculateTheClosestNextRowKeyForPrefix(rowPrefix));
403 }
404 return this;
405 }
406
407 /**
408 * <p>When scanning for a prefix the scan should stop immediately after the the last row that
409 * has the specified prefix. This method calculates the closest next rowKey immediately following
410 * the given rowKeyPrefix.</p>
411 * <p><b>IMPORTANT: This converts a rowKey<u>Prefix</u> into a rowKey</b>.</p>
412 * <p>If the prefix is an 'ASCII' string put into a byte[] then this is easy because you can
413 * simply increment the last byte of the array.
414 * But if your application uses real binary rowids you may run into the scenario that your
415 * prefix is something like:</p>
416 * <b>{ 0x12, 0x23, 0xFF, 0xFF }</b><br/>
417 * Then this stopRow needs to be fed into the actual scan<br/>
418 * <b>{ 0x12, 0x24 }</b> (Notice that it is shorter now)<br/>
419 * This method calculates the correct stop row value for this usecase.
420 *
421 * @param rowKeyPrefix the rowKey<u>Prefix</u>.
422 * @return the closest next rowKey immediately following the given rowKeyPrefix.
423 */
424 private byte[] calculateTheClosestNextRowKeyForPrefix(byte[] rowKeyPrefix) {
425 // Essentially we are treating it like an 'unsigned very very long' and doing +1 manually.
426 // Search for the place where the trailing 0xFFs start
427 int offset = rowKeyPrefix.length;
428 while (offset > 0) {
429 if (rowKeyPrefix[offset - 1] != (byte) 0xFF) {
430 break;
431 }
432 offset--;
433 }
434
435 if (offset == 0) {
436 // We got an 0xFFFF... (only FFs) stopRow value which is
437 // the last possible prefix before the end of the table.
438 // So set it to stop at the 'end of the table'
439 return HConstants.EMPTY_END_ROW;
440 }
441
442 // Copy the right length of the original
443 byte[] newStopRow = Arrays.copyOfRange(rowKeyPrefix, 0, offset);
444 // And increment the last one
445 newStopRow[newStopRow.length - 1]++;
446 return newStopRow;
447 }
448
449 /**
450 * Get all available versions.
451 * @return this
452 */
453 public Scan setMaxVersions() {
454 this.maxVersions = Integer.MAX_VALUE;
455 return this;
456 }
457
458 /**
459 * Get up to the specified number of versions of each column.
460 * @param maxVersions maximum versions for each column
461 * @return this
462 */
463 public Scan setMaxVersions(int maxVersions) {
464 this.maxVersions = maxVersions;
465 return this;
466 }
467
468 /**
469 * Set the maximum number of values to return for each call to next()
470 * @param batch the maximum number of values
471 */
472 public Scan setBatch(int batch) {
473 if (this.hasFilter() && this.filter.hasFilterRow()) {
474 throw new IncompatibleFilterException(
475 "Cannot set batch on a scan using a filter" +
476 " that returns true for filter.hasFilterRow");
477 }
478 this.batch = batch;
479 return this;
480 }
481
482 /**
483 * Set the maximum number of values to return per row per Column Family
484 * @param limit the maximum number of values returned / row / CF
485 */
486 public Scan setMaxResultsPerColumnFamily(int limit) {
487 this.storeLimit = limit;
488 return this;
489 }
490
491 /**
492 * Set offset for the row per Column Family.
493 * @param offset is the number of kvs that will be skipped.
494 */
495 public Scan setRowOffsetPerColumnFamily(int offset) {
496 this.storeOffset = offset;
497 return this;
498 }
499
500 /**
501 * Set the number of rows for caching that will be passed to scanners.
502 * If not set, the Configuration setting {@link HConstants#HBASE_CLIENT_SCANNER_CACHING} will
503 * apply.
504 * Higher caching values will enable faster scanners but will use more memory.
505 * @param caching the number of rows for caching
506 */
507 public Scan setCaching(int caching) {
508 this.caching = caching;
509 return this;
510 }
511
512 /**
513 * @return the maximum result size in bytes. See {@link #setMaxResultSize(long)}
514 */
515 public long getMaxResultSize() {
516 return maxResultSize;
517 }
518
519 /**
520 * Set the maximum result size. The default is -1; this means that no specific
521 * maximum result size will be set for this scan, and the global configured
522 * value will be used instead. (Defaults to unlimited).
523 *
524 * @param maxResultSize The maximum result size in bytes.
525 */
526 public Scan setMaxResultSize(long maxResultSize) {
527 this.maxResultSize = maxResultSize;
528 return this;
529 }
530
531 @Override
532 public Scan setFilter(Filter filter) {
533 super.setFilter(filter);
534 return this;
535 }
536
537 /**
538 * Setting the familyMap
539 * @param familyMap map of family to qualifier
540 * @return this
541 */
542 public Scan setFamilyMap(Map<byte [], NavigableSet<byte []>> familyMap) {
543 this.familyMap = familyMap;
544 return this;
545 }
546
547 /**
548 * Getting the familyMap
549 * @return familyMap
550 */
551 public Map<byte [], NavigableSet<byte []>> getFamilyMap() {
552 return this.familyMap;
553 }
554
555 /**
556 * @return the number of families in familyMap
557 */
558 public int numFamilies() {
559 if(hasFamilies()) {
560 return this.familyMap.size();
561 }
562 return 0;
563 }
564
565 /**
566 * @return true if familyMap is non empty, false otherwise
567 */
568 public boolean hasFamilies() {
569 return !this.familyMap.isEmpty();
570 }
571
572 /**
573 * @return the keys of the familyMap
574 */
575 public byte[][] getFamilies() {
576 if(hasFamilies()) {
577 return this.familyMap.keySet().toArray(new byte[0][0]);
578 }
579 return null;
580 }
581
582 /**
583 * @return the startrow
584 */
585 public byte [] getStartRow() {
586 return this.startRow;
587 }
588
589 /**
590 * @return the stoprow
591 */
592 public byte [] getStopRow() {
593 return this.stopRow;
594 }
595
596 /**
597 * @return the max number of versions to fetch
598 */
599 public int getMaxVersions() {
600 return this.maxVersions;
601 }
602
603 /**
604 * @return maximum number of values to return for a single call to next()
605 */
606 public int getBatch() {
607 return this.batch;
608 }
609
610 /**
611 * @return maximum number of values to return per row per CF
612 */
613 public int getMaxResultsPerColumnFamily() {
614 return this.storeLimit;
615 }
616
617 /**
618 * Method for retrieving the scan's offset per row per column
619 * family (#kvs to be skipped)
620 * @return row offset
621 */
622 public int getRowOffsetPerColumnFamily() {
623 return this.storeOffset;
624 }
625
626 /**
627 * @return caching the number of rows fetched when calling next on a scanner
628 */
629 public int getCaching() {
630 return this.caching;
631 }
632
633 /**
634 * @return TimeRange
635 */
636 public TimeRange getTimeRange() {
637 return this.tr;
638 }
639
640 /**
641 * @return RowFilter
642 */
643 @Override
644 public Filter getFilter() {
645 return filter;
646 }
647
648 /**
649 * @return true is a filter has been specified, false if not
650 */
651 public boolean hasFilter() {
652 return filter != null;
653 }
654
655 /**
656 * Set whether blocks should be cached for this Scan.
657 * <p>
658 * This is true by default. When true, default settings of the table and
659 * family are used (this will never override caching blocks if the block
660 * cache is disabled for that family or entirely).
661 *
662 * @param cacheBlocks if false, default settings are overridden and blocks
663 * will not be cached
664 */
665 public Scan setCacheBlocks(boolean cacheBlocks) {
666 this.cacheBlocks = cacheBlocks;
667 return this;
668 }
669
670 /**
671 * Get whether blocks should be cached for this Scan.
672 * @return true if default caching should be used, false if blocks should not
673 * be cached
674 */
675 public boolean getCacheBlocks() {
676 return cacheBlocks;
677 }
678
679 /**
680 * Set whether this scan is a reversed one
681 * <p>
682 * This is false by default which means forward(normal) scan.
683 *
684 * @param reversed if true, scan will be backward order
685 * @return this
686 */
687 public Scan setReversed(boolean reversed) {
688 this.reversed = reversed;
689 return this;
690 }
691
692 /**
693 * Get whether this scan is a reversed one.
694 * @return true if backward scan, false if forward(default) scan
695 */
696 public boolean isReversed() {
697 return reversed;
698 }
699
700 /**
701 * Setting whether the caller wants to see the partial results that may be returned from the
702 * server. By default this value is false and the complete results will be assembled client side
703 * before being delivered to the caller.
704 * @param allowPartialResults
705 * @return this
706 */
707 public Scan setAllowPartialResults(final boolean allowPartialResults) {
708 this.allowPartialResults = allowPartialResults;
709 return this;
710 }
711
712 /**
713 * @return true when the constructor of this scan understands that the results they will see may
714 * only represent a partial portion of a row. The entire row would be retrieved by
715 * subsequent calls to {@link ResultScanner#next()}
716 */
717 public boolean getAllowPartialResults() {
718 return allowPartialResults;
719 }
720
721 /**
722 * Set the value indicating whether loading CFs on demand should be allowed (cluster
723 * default is false). On-demand CF loading doesn't load column families until necessary, e.g.
724 * if you filter on one column, the other column family data will be loaded only for the rows
725 * that are included in result, not all rows like in normal case.
726 * With column-specific filters, like SingleColumnValueFilter w/filterIfMissing == true,
727 * this can deliver huge perf gains when there's a cf with lots of data; however, it can
728 * also lead to some inconsistent results, as follows:
729 * - if someone does a concurrent update to both column families in question you may get a row
730 * that never existed, e.g. for { rowKey = 5, { cat_videos => 1 }, { video => "my cat" } }
731 * someone puts rowKey 5 with { cat_videos => 0 }, { video => "my dog" }, concurrent scan
732 * filtering on "cat_videos == 1" can get { rowKey = 5, { cat_videos => 1 },
733 * { video => "my dog" } }.
734 * - if there's a concurrent split and you have more than 2 column families, some rows may be
735 * missing some column families.
736 */
737 public Scan setLoadColumnFamiliesOnDemand(boolean value) {
738 this.loadColumnFamiliesOnDemand = value;
739 return this;
740 }
741
742 /**
743 * Get the raw loadColumnFamiliesOnDemand setting; if it's not set, can be null.
744 */
745 public Boolean getLoadColumnFamiliesOnDemandValue() {
746 return this.loadColumnFamiliesOnDemand;
747 }
748
749 /**
750 * Get the logical value indicating whether on-demand CF loading should be allowed.
751 */
752 public boolean doLoadColumnFamiliesOnDemand() {
753 return (this.loadColumnFamiliesOnDemand != null)
754 && this.loadColumnFamiliesOnDemand.booleanValue();
755 }
756
757 /**
758 * Compile the table and column family (i.e. schema) information
759 * into a String. Useful for parsing and aggregation by debugging,
760 * logging, and administration tools.
761 * @return Map
762 */
763 @Override
764 public Map<String, Object> getFingerprint() {
765 Map<String, Object> map = new HashMap<String, Object>();
766 List<String> families = new ArrayList<String>();
767 if(this.familyMap.size() == 0) {
768 map.put("families", "ALL");
769 return map;
770 } else {
771 map.put("families", families);
772 }
773 for (Map.Entry<byte [], NavigableSet<byte[]>> entry :
774 this.familyMap.entrySet()) {
775 families.add(Bytes.toStringBinary(entry.getKey()));
776 }
777 return map;
778 }
779
780 /**
781 * Compile the details beyond the scope of getFingerprint (row, columns,
782 * timestamps, etc.) into a Map along with the fingerprinted information.
783 * Useful for debugging, logging, and administration tools.
784 * @param maxCols a limit on the number of columns output prior to truncation
785 * @return Map
786 */
787 @Override
788 public Map<String, Object> toMap(int maxCols) {
789 // start with the fingerpring map and build on top of it
790 Map<String, Object> map = getFingerprint();
791 // map from families to column list replaces fingerprint's list of families
792 Map<String, List<String>> familyColumns =
793 new HashMap<String, List<String>>();
794 map.put("families", familyColumns);
795 // add scalar information first
796 map.put("startRow", Bytes.toStringBinary(this.startRow));
797 map.put("stopRow", Bytes.toStringBinary(this.stopRow));
798 map.put("maxVersions", this.maxVersions);
799 map.put("batch", this.batch);
800 map.put("caching", this.caching);
801 map.put("maxResultSize", this.maxResultSize);
802 map.put("cacheBlocks", this.cacheBlocks);
803 map.put("loadColumnFamiliesOnDemand", this.loadColumnFamiliesOnDemand);
804 List<Long> timeRange = new ArrayList<Long>();
805 timeRange.add(this.tr.getMin());
806 timeRange.add(this.tr.getMax());
807 map.put("timeRange", timeRange);
808 int colCount = 0;
809 // iterate through affected families and list out up to maxCols columns
810 for (Map.Entry<byte [], NavigableSet<byte[]>> entry :
811 this.familyMap.entrySet()) {
812 List<String> columns = new ArrayList<String>();
813 familyColumns.put(Bytes.toStringBinary(entry.getKey()), columns);
814 if(entry.getValue() == null) {
815 colCount++;
816 --maxCols;
817 columns.add("ALL");
818 } else {
819 colCount += entry.getValue().size();
820 if (maxCols <= 0) {
821 continue;
822 }
823 for (byte [] column : entry.getValue()) {
824 if (--maxCols <= 0) {
825 continue;
826 }
827 columns.add(Bytes.toStringBinary(column));
828 }
829 }
830 }
831 map.put("totalColumns", colCount);
832 if (this.filter != null) {
833 map.put("filter", this.filter.toString());
834 }
835 // add the id if set
836 if (getId() != null) {
837 map.put("id", getId());
838 }
839 return map;
840 }
841
842 /**
843 * Enable/disable "raw" mode for this scan.
844 * If "raw" is enabled the scan will return all
845 * delete marker and deleted rows that have not
846 * been collected, yet.
847 * This is mostly useful for Scan on column families
848 * that have KEEP_DELETED_ROWS enabled.
849 * It is an error to specify any column when "raw" is set.
850 * @param raw True/False to enable/disable "raw" mode.
851 */
852 public Scan setRaw(boolean raw) {
853 setAttribute(RAW_ATTR, Bytes.toBytes(raw));
854 return this;
855 }
856
857 /**
858 * @return True if this Scan is in "raw" mode.
859 */
860 public boolean isRaw() {
861 byte[] attr = getAttribute(RAW_ATTR);
862 return attr == null ? false : Bytes.toBoolean(attr);
863 }
864
865
866
867 /**
868 * Set whether this scan is a small scan
869 * <p>
870 * Small scan should use pread and big scan can use seek + read
871 *
872 * seek + read is fast but can cause two problem (1) resource contention (2)
873 * cause too much network io
874 *
875 * [89-fb] Using pread for non-compaction read request
876 * https://issues.apache.org/jira/browse/HBASE-7266
877 *
878 * On the other hand, if setting it true, we would do
879 * openScanner,next,closeScanner in one RPC call. It means the better
880 * performance for small scan. [HBASE-9488].
881 *
882 * Generally, if the scan range is within one data block(64KB), it could be
883 * considered as a small scan.
884 *
885 * @param small
886 */
887 public Scan setSmall(boolean small) {
888 this.small = small;
889 return this;
890 }
891
892 /**
893 * Get whether this scan is a small scan
894 * @return true if small scan
895 */
896 public boolean isSmall() {
897 return small;
898 }
899
900 @Override
901 public Scan setAttribute(String name, byte[] value) {
902 return (Scan) super.setAttribute(name, value);
903 }
904
905 @Override
906 public Scan setId(String id) {
907 return (Scan) super.setId(id);
908 }
909
910 @Override
911 public Scan setAuthorizations(Authorizations authorizations) {
912 return (Scan) super.setAuthorizations(authorizations);
913 }
914
915 @Override
916 public Scan setACL(Map<String, Permission> perms) {
917 return (Scan) super.setACL(perms);
918 }
919
920 @Override
921 public Scan setACL(String user, Permission perms) {
922 return (Scan) super.setACL(user, perms);
923 }
924
925 @Override
926 public Scan setConsistency(Consistency consistency) {
927 return (Scan) super.setConsistency(consistency);
928 }
929
930 @Override
931 public Scan setReplicaId(int Id) {
932 return (Scan) super.setReplicaId(Id);
933 }
934
935 @Override
936 public Scan setIsolationLevel(IsolationLevel level) {
937 return (Scan) super.setIsolationLevel(level);
938 }
939
940 /**
941 * Utility that creates a Scan that will do a small scan in reverse from passed row
942 * looking for next closest row.
943 * @param row
944 * @param family
945 * @return An instance of Scan primed with passed <code>row</code> and <code>family</code> to
946 * scan in reverse for one row only.
947 */
948 static Scan createGetClosestRowOrBeforeReverseScan(byte[] row) {
949 // Below does not work if you add in family; need to add the family qualifier that is highest
950 // possible family qualifier. Do we have such a notion? Would have to be magic.
951 Scan scan = new Scan(row);
952 scan.setSmall(true);
953 scan.setReversed(true);
954 scan.setCaching(1);
955 return scan;
956 }
957
958 /**
959 * Enable collection of {@link ScanMetrics}. For advanced users.
960 * @param enabled Set to true to enable accumulating scan metrics
961 */
962 public Scan setScanMetricsEnabled(final boolean enabled) {
963 setAttribute(Scan.SCAN_ATTRIBUTES_METRICS_ENABLE, Bytes.toBytes(Boolean.valueOf(enabled)));
964 return this;
965 }
966
967 /**
968 * @return True if collection of scan metrics is enabled. For advanced users.
969 */
970 public boolean isScanMetricsEnabled() {
971 byte[] attr = getAttribute(Scan.SCAN_ATTRIBUTES_METRICS_ENABLE);
972 return attr == null ? false : Bytes.toBoolean(attr);
973 }
974
975 /**
976 * @return Metrics on this Scan, if metrics were enabled.
977 * @see #setScanMetricsEnabled(boolean)
978 */
979 public ScanMetrics getScanMetrics() {
980 byte [] bytes = getAttribute(Scan.SCAN_ATTRIBUTES_METRICS_DATA);
981 if (bytes == null) return null;
982 return ProtobufUtil.toScanMetrics(bytes);
983 }
984 }