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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * hashpage.c
4 : : * Hash table page management code for the Postgres hash access method
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : *
10 : : * IDENTIFICATION
11 : : * src/backend/access/hash/hashpage.c
12 : : *
13 : : * NOTES
14 : : * Postgres hash pages look like ordinary relation pages. The opaque
15 : : * data at high addresses includes information about the page including
16 : : * whether a page is an overflow page or a true bucket, the bucket
17 : : * number, and the block numbers of the preceding and following pages
18 : : * in the same bucket.
19 : : *
20 : : * The first page in a hash relation, page zero, is special -- it stores
21 : : * information describing the hash table; it is referred to as the
22 : : * "meta page." Pages one and higher store the actual data.
23 : : *
24 : : * There are also bitmap pages, which are not manipulated here;
25 : : * see hashovfl.c.
26 : : *
27 : : *-------------------------------------------------------------------------
28 : : */
29 : : #include "postgres.h"
30 : :
31 : : #include "access/hash.h"
32 : : #include "access/hash_xlog.h"
33 : : #include "access/xloginsert.h"
34 : : #include "miscadmin.h"
35 : : #include "port/pg_bitutils.h"
36 : : #include "storage/predicate.h"
37 : : #include "storage/smgr.h"
38 : : #include "utils/rel.h"
39 : :
40 : : static bool _hash_alloc_buckets(Relation rel, BlockNumber firstblock,
41 : : uint32 nblocks);
42 : : static void _hash_splitbucket(Relation rel, Buffer metabuf,
43 : : Bucket obucket, Bucket nbucket,
44 : : Buffer obuf,
45 : : Buffer nbuf,
46 : : HTAB *htab,
47 : : uint32 maxbucket,
48 : : uint32 highmask, uint32 lowmask);
49 : : static void log_split_page(Relation rel, Buffer buf);
50 : :
51 : :
52 : : /*
53 : : * _hash_getbuf() -- Get a buffer by block number for read or write.
54 : : *
55 : : * 'access' must be HASH_READ, HASH_WRITE, or HASH_NOLOCK.
56 : : * 'flags' is a bitwise OR of the allowed page types.
57 : : *
58 : : * This must be used only to fetch pages that are expected to be valid
59 : : * already. _hash_checkpage() is applied using the given flags.
60 : : *
61 : : * When this routine returns, the appropriate lock is set on the
62 : : * requested buffer and its reference count has been incremented
63 : : * (ie, the buffer is "locked and pinned").
64 : : *
65 : : * P_NEW is disallowed because this routine can only be used
66 : : * to access pages that are known to be before the filesystem EOF.
67 : : * Extending the index should be done with _hash_getnewbuf.
68 : : */
69 : : Buffer
70 : 326355 : _hash_getbuf(Relation rel, BlockNumber blkno, int access, int flags)
71 : : {
72 : 326355 : Buffer buf;
73 : :
74 [ + - ]: 326355 : if (blkno == P_NEW)
75 [ # # # # ]: 0 : elog(ERROR, "hash AM does not use P_NEW");
76 : :
77 : 326355 : buf = ReadBuffer(rel, blkno);
78 : :
79 [ + + ]: 326355 : if (access != HASH_NOLOCK)
80 : 206735 : LockBuffer(buf, access);
81 : :
82 : : /* ref count and lock type are correct */
83 : :
84 : 326355 : _hash_checkpage(rel, buf, flags);
85 : :
86 : 652710 : return buf;
87 : 326355 : }
88 : :
89 : : /*
90 : : * _hash_getbuf_with_condlock_cleanup() -- Try to get a buffer for cleanup.
91 : : *
92 : : * We read the page and try to acquire a cleanup lock. If we get it,
93 : : * we return the buffer; otherwise, we return InvalidBuffer.
94 : : */
95 : : Buffer
96 : 221 : _hash_getbuf_with_condlock_cleanup(Relation rel, BlockNumber blkno, int flags)
97 : : {
98 : 221 : Buffer buf;
99 : :
100 [ + - ]: 221 : if (blkno == P_NEW)
101 [ # # # # ]: 0 : elog(ERROR, "hash AM does not use P_NEW");
102 : :
103 : 221 : buf = ReadBuffer(rel, blkno);
104 : :
105 [ + - ]: 221 : if (!ConditionalLockBufferForCleanup(buf))
106 : : {
107 : 0 : ReleaseBuffer(buf);
108 : 0 : return InvalidBuffer;
109 : : }
110 : :
111 : : /* ref count and lock type are correct */
112 : :
113 : 221 : _hash_checkpage(rel, buf, flags);
114 : :
115 : 221 : return buf;
116 : 221 : }
117 : :
118 : : /*
119 : : * _hash_getinitbuf() -- Get and initialize a buffer by block number.
120 : : *
121 : : * This must be used only to fetch pages that are known to be before
122 : : * the index's filesystem EOF, but are to be filled from scratch.
123 : : * _hash_pageinit() is applied automatically. Otherwise it has
124 : : * effects similar to _hash_getbuf() with access = HASH_WRITE.
125 : : *
126 : : * When this routine returns, a write lock is set on the
127 : : * requested buffer and its reference count has been incremented
128 : : * (ie, the buffer is "locked and pinned").
129 : : *
130 : : * P_NEW is disallowed because this routine can only be used
131 : : * to access pages that are known to be before the filesystem EOF.
132 : : * Extending the index should be done with _hash_getnewbuf.
133 : : */
134 : : Buffer
135 : 12 : _hash_getinitbuf(Relation rel, BlockNumber blkno)
136 : : {
137 : 12 : Buffer buf;
138 : :
139 [ + - ]: 12 : if (blkno == P_NEW)
140 [ # # # # ]: 0 : elog(ERROR, "hash AM does not use P_NEW");
141 : :
142 : 12 : buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_ZERO_AND_LOCK,
143 : : NULL);
144 : :
145 : : /* ref count and lock type are correct */
146 : :
147 : : /* initialize the page */
148 : 12 : _hash_pageinit(BufferGetPage(buf), BufferGetPageSize(buf));
149 : :
150 : 24 : return buf;
151 : 12 : }
152 : :
153 : : /*
154 : : * _hash_initbuf() -- Get and initialize a buffer by bucket number.
155 : : */
156 : : void
157 : 1200 : _hash_initbuf(Buffer buf, uint32 max_bucket, uint32 num_bucket, uint32 flag,
158 : : bool initpage)
159 : : {
160 : 1200 : HashPageOpaque pageopaque;
161 : 1200 : Page page;
162 : :
163 : 1200 : page = BufferGetPage(buf);
164 : :
165 : : /* initialize the page */
166 [ + - ]: 1200 : if (initpage)
167 : 0 : _hash_pageinit(page, BufferGetPageSize(buf));
168 : :
169 : 1200 : pageopaque = HashPageGetOpaque(page);
170 : :
171 : : /*
172 : : * Set hasho_prevblkno with current hashm_maxbucket. This value will be
173 : : * used to validate cached HashMetaPageData. See
174 : : * _hash_getbucketbuf_from_hashkey().
175 : : */
176 : 1200 : pageopaque->hasho_prevblkno = max_bucket;
177 : 1200 : pageopaque->hasho_nextblkno = InvalidBlockNumber;
178 : 1200 : pageopaque->hasho_bucket = num_bucket;
179 : 1200 : pageopaque->hasho_flag = flag;
180 : 1200 : pageopaque->hasho_page_id = HASHO_PAGE_ID;
181 : 1200 : }
182 : :
183 : : /*
184 : : * _hash_getnewbuf() -- Get a new page at the end of the index.
185 : : *
186 : : * This has the same API as _hash_getinitbuf, except that we are adding
187 : : * a page to the index, and hence expect the page to be past the
188 : : * logical EOF. (However, we have to support the case where it isn't,
189 : : * since a prior try might have crashed after extending the filesystem
190 : : * EOF but before updating the metapage to reflect the added page.)
191 : : *
192 : : * It is caller's responsibility to ensure that only one process can
193 : : * extend the index at a time. In practice, this function is called
194 : : * only while holding write lock on the metapage, because adding a page
195 : : * is always associated with an update of metapage data.
196 : : */
197 : : Buffer
198 : 1536 : _hash_getnewbuf(Relation rel, BlockNumber blkno, ForkNumber forkNum)
199 : : {
200 : 1536 : BlockNumber nblocks = RelationGetNumberOfBlocksInFork(rel, forkNum);
201 : 1536 : Buffer buf;
202 : :
203 [ + - ]: 1536 : if (blkno == P_NEW)
204 [ # # # # ]: 0 : elog(ERROR, "hash AM does not use P_NEW");
205 [ + - ]: 1536 : if (blkno > nblocks)
206 [ # # # # ]: 0 : elog(ERROR, "access to noncontiguous page in hash index \"%s\"",
207 : : RelationGetRelationName(rel));
208 : :
209 : : /* smgr insists we explicitly extend the relation */
210 [ + + ]: 1536 : if (blkno == nblocks)
211 : : {
212 : 1315 : buf = ExtendBufferedRel(BMR_REL(rel), forkNum, NULL,
213 : : EB_LOCK_FIRST | EB_SKIP_EXTENSION_LOCK);
214 [ + - ]: 1315 : if (BufferGetBlockNumber(buf) != blkno)
215 [ # # # # ]: 0 : elog(ERROR, "unexpected hash relation size: %u, should be %u",
216 : : BufferGetBlockNumber(buf), blkno);
217 : 1315 : }
218 : : else
219 : : {
220 : 221 : buf = ReadBufferExtended(rel, forkNum, blkno, RBM_ZERO_AND_LOCK,
221 : : NULL);
222 : : }
223 : :
224 : : /* ref count and lock type are correct */
225 : :
226 : : /* initialize the page */
227 : 1536 : _hash_pageinit(BufferGetPage(buf), BufferGetPageSize(buf));
228 : :
229 : 3072 : return buf;
230 : 1536 : }
231 : :
232 : : /*
233 : : * _hash_getbuf_with_strategy() -- Get a buffer with nondefault strategy.
234 : : *
235 : : * This is identical to _hash_getbuf() but also allows a buffer access
236 : : * strategy to be specified. We use this for VACUUM operations.
237 : : */
238 : : Buffer
239 : 199 : _hash_getbuf_with_strategy(Relation rel, BlockNumber blkno,
240 : : int access, int flags,
241 : : BufferAccessStrategy bstrategy)
242 : : {
243 : 199 : Buffer buf;
244 : :
245 [ + - ]: 199 : if (blkno == P_NEW)
246 [ # # # # ]: 0 : elog(ERROR, "hash AM does not use P_NEW");
247 : :
248 : 199 : buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, bstrategy);
249 : :
250 [ - + ]: 199 : if (access != HASH_NOLOCK)
251 : 199 : LockBuffer(buf, access);
252 : :
253 : : /* ref count and lock type are correct */
254 : :
255 : 199 : _hash_checkpage(rel, buf, flags);
256 : :
257 : 398 : return buf;
258 : 199 : }
259 : :
260 : : /*
261 : : * _hash_relbuf() -- release a locked buffer.
262 : : *
263 : : * Lock and pin (refcount) are both dropped.
264 : : */
265 : : void
266 : 192564 : _hash_relbuf(Relation rel, Buffer buf)
267 : : {
268 : 192564 : UnlockReleaseBuffer(buf);
269 : 192564 : }
270 : :
271 : : /*
272 : : * _hash_dropbuf() -- release an unlocked buffer.
273 : : *
274 : : * This is used to unpin a buffer on which we hold no lock.
275 : : */
276 : : void
277 : 135790 : _hash_dropbuf(Relation rel, Buffer buf)
278 : : {
279 : 135790 : ReleaseBuffer(buf);
280 : 135790 : }
281 : :
282 : : /*
283 : : * _hash_dropscanbuf() -- release buffers used in scan.
284 : : *
285 : : * This routine unpins the buffers used during scan on which we
286 : : * hold no lock.
287 : : */
288 : : void
289 : 134 : _hash_dropscanbuf(Relation rel, HashScanOpaque so)
290 : : {
291 : : /* release pin we hold on primary bucket page */
292 [ + + + + ]: 134 : if (BufferIsValid(so->hashso_bucket_buf) &&
293 : 60 : so->hashso_bucket_buf != so->currPos.buf)
294 : 21 : _hash_dropbuf(rel, so->hashso_bucket_buf);
295 : 134 : so->hashso_bucket_buf = InvalidBuffer;
296 : :
297 : : /* release pin we hold on primary bucket page of bucket being split */
298 [ - + # # ]: 134 : if (BufferIsValid(so->hashso_split_bucket_buf) &&
299 : 0 : so->hashso_split_bucket_buf != so->currPos.buf)
300 : 0 : _hash_dropbuf(rel, so->hashso_split_bucket_buf);
301 : 134 : so->hashso_split_bucket_buf = InvalidBuffer;
302 : :
303 : : /* release any pin we still hold */
304 [ + + ]: 134 : if (BufferIsValid(so->currPos.buf))
305 : 39 : _hash_dropbuf(rel, so->currPos.buf);
306 : 134 : so->currPos.buf = InvalidBuffer;
307 : :
308 : : /* reset split scan */
309 : 134 : so->hashso_buc_populated = false;
310 : 134 : so->hashso_buc_split = false;
311 : 134 : }
312 : :
313 : :
314 : : /*
315 : : * _hash_init() -- Initialize the metadata page of a hash index,
316 : : * the initial buckets, and the initial bitmap page.
317 : : *
318 : : * The initial number of buckets is dependent on num_tuples, an estimate
319 : : * of the number of tuples to be loaded into the index initially. The
320 : : * chosen number of buckets is returned.
321 : : *
322 : : * We are fairly cavalier about locking here, since we know that no one else
323 : : * could be accessing this index. In particular the rule about not holding
324 : : * multiple buffer locks is ignored.
325 : : */
326 : : uint32
327 : 30 : _hash_init(Relation rel, double num_tuples, ForkNumber forkNum)
328 : : {
329 : 30 : Buffer metabuf;
330 : 30 : Buffer buf;
331 : 30 : Buffer bitmapbuf;
332 : 30 : Page pg;
333 : 30 : HashMetaPage metap;
334 : 30 : RegProcedure procid;
335 : 30 : int32 data_width;
336 : 30 : int32 item_width;
337 : 30 : int32 ffactor;
338 : 30 : uint32 num_buckets;
339 : 30 : uint32 i;
340 : 30 : bool use_wal;
341 : :
342 : : /* safety check */
343 [ + - ]: 30 : if (RelationGetNumberOfBlocksInFork(rel, forkNum) != 0)
344 [ # # # # ]: 0 : elog(ERROR, "cannot initialize non-empty hash index \"%s\"",
345 : : RelationGetRelationName(rel));
346 : :
347 : : /*
348 : : * WAL log creation of pages if the relation is persistent, or this is the
349 : : * init fork. Init forks for unlogged relations always need to be WAL
350 : : * logged.
351 : : */
352 [ + + + - : 30 : use_wal = RelationNeedsWAL(rel) || forkNum == INIT_FORKNUM;
+ + + - ]
353 : :
354 : : /*
355 : : * Determine the target fill factor (in tuples per bucket) for this index.
356 : : * The idea is to make the fill factor correspond to pages about as full
357 : : * as the user-settable fillfactor parameter says. We can compute it
358 : : * exactly since the index datatype (i.e. uint32 hash key) is fixed-width.
359 : : */
360 : 30 : data_width = sizeof(uint32);
361 : 30 : item_width = MAXALIGN(sizeof(IndexTupleData)) + MAXALIGN(data_width) +
362 : : sizeof(ItemIdData); /* include the line pointer */
363 [ + - + + ]: 30 : ffactor = HashGetTargetPageUsage(rel) / item_width;
364 : : /* keep to a sane range */
365 [ + - ]: 30 : if (ffactor < 10)
366 : 0 : ffactor = 10;
367 : :
368 : 30 : procid = index_getprocid(rel, 1, HASHSTANDARD_PROC);
369 : :
370 : : /*
371 : : * We initialize the metapage, the first N bucket pages, and the first
372 : : * bitmap page in sequence, using _hash_getnewbuf to cause smgrextend()
373 : : * calls to occur. This ensures that the smgr level has the right idea of
374 : : * the physical index length.
375 : : *
376 : : * Critical section not required, because on error the creation of the
377 : : * whole relation will be rolled back.
378 : : */
379 : 30 : metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, forkNum);
380 : 30 : _hash_init_metabuffer(metabuf, num_tuples, procid, ffactor, false);
381 : 30 : MarkBufferDirty(metabuf);
382 : :
383 : 30 : pg = BufferGetPage(metabuf);
384 : 30 : metap = HashPageGetMeta(pg);
385 : :
386 : : /* XLOG stuff */
387 [ + + ]: 30 : if (use_wal)
388 : : {
389 : 1 : xl_hash_init_meta_page xlrec;
390 : 1 : XLogRecPtr recptr;
391 : :
392 : 1 : xlrec.num_tuples = num_tuples;
393 : 1 : xlrec.procid = metap->hashm_procid;
394 : 1 : xlrec.ffactor = metap->hashm_ffactor;
395 : :
396 : 1 : XLogBeginInsert();
397 : 1 : XLogRegisterData(&xlrec, SizeOfHashInitMetaPage);
398 : 1 : XLogRegisterBuffer(0, metabuf, REGBUF_WILL_INIT | REGBUF_STANDARD);
399 : :
400 : 1 : recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_INIT_META_PAGE);
401 : :
402 : 1 : PageSetLSN(BufferGetPage(metabuf), recptr);
403 : 1 : }
404 : :
405 : 30 : num_buckets = metap->hashm_maxbucket + 1;
406 : :
407 : : /*
408 : : * Release buffer lock on the metapage while we initialize buckets.
409 : : * Otherwise, we'll be in interrupt holdoff and the CHECK_FOR_INTERRUPTS
410 : : * won't accomplish anything. It's a bad idea to hold buffer locks for
411 : : * long intervals in any case, since that can block the bgwriter.
412 : : */
413 : 30 : LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
414 : :
415 : : /*
416 : : * Initialize and WAL Log the first N buckets
417 : : */
418 [ + + ]: 1230 : for (i = 0; i < num_buckets; i++)
419 : : {
420 : 1200 : BlockNumber blkno;
421 : :
422 : : /* Allow interrupts, in case N is huge */
423 [ + - ]: 1200 : CHECK_FOR_INTERRUPTS();
424 : :
425 [ + + ]: 1200 : blkno = BUCKET_TO_BLKNO(metap, i);
426 : 1200 : buf = _hash_getnewbuf(rel, blkno, forkNum);
427 : 1200 : _hash_initbuf(buf, metap->hashm_maxbucket, i, LH_BUCKET_PAGE, false);
428 : 1200 : MarkBufferDirty(buf);
429 : :
430 [ + + ]: 1200 : if (use_wal)
431 : 4 : log_newpage(&rel->rd_locator,
432 : 2 : forkNum,
433 : 2 : blkno,
434 : 2 : BufferGetPage(buf),
435 : : true);
436 : 1200 : _hash_relbuf(rel, buf);
437 : 1200 : }
438 : :
439 : : /* Now reacquire buffer lock on metapage */
440 : 30 : LockBuffer(metabuf, BUFFER_LOCK_EXCLUSIVE);
441 : :
442 : : /*
443 : : * Initialize bitmap page
444 : : */
445 : 30 : bitmapbuf = _hash_getnewbuf(rel, num_buckets + 1, forkNum);
446 : 30 : _hash_initbitmapbuffer(bitmapbuf, metap->hashm_bmsize, false);
447 : 30 : MarkBufferDirty(bitmapbuf);
448 : :
449 : : /* add the new bitmap page to the metapage's list of bitmaps */
450 : : /* metapage already has a write lock */
451 [ + - ]: 30 : if (metap->hashm_nmaps >= HASH_MAX_BITMAPS)
452 [ # # # # ]: 0 : ereport(ERROR,
453 : : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
454 : : errmsg("out of overflow pages in hash index \"%s\"",
455 : : RelationGetRelationName(rel))));
456 : :
457 : 30 : metap->hashm_mapp[metap->hashm_nmaps] = num_buckets + 1;
458 : :
459 : 30 : metap->hashm_nmaps++;
460 : 30 : MarkBufferDirty(metabuf);
461 : :
462 : : /* XLOG stuff */
463 [ + + ]: 30 : if (use_wal)
464 : : {
465 : 1 : xl_hash_init_bitmap_page xlrec;
466 : 1 : XLogRecPtr recptr;
467 : :
468 : 1 : xlrec.bmsize = metap->hashm_bmsize;
469 : :
470 : 1 : XLogBeginInsert();
471 : 1 : XLogRegisterData(&xlrec, SizeOfHashInitBitmapPage);
472 : 1 : XLogRegisterBuffer(0, bitmapbuf, REGBUF_WILL_INIT);
473 : :
474 : : /*
475 : : * This is safe only because nobody else can be modifying the index at
476 : : * this stage; it's only visible to the transaction that is creating
477 : : * it.
478 : : */
479 : 1 : XLogRegisterBuffer(1, metabuf, REGBUF_STANDARD);
480 : :
481 : 1 : recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_INIT_BITMAP_PAGE);
482 : :
483 : 1 : PageSetLSN(BufferGetPage(bitmapbuf), recptr);
484 : 1 : PageSetLSN(BufferGetPage(metabuf), recptr);
485 : 1 : }
486 : :
487 : : /* all done */
488 : 30 : _hash_relbuf(rel, bitmapbuf);
489 : 30 : _hash_relbuf(rel, metabuf);
490 : :
491 : 60 : return num_buckets;
492 : 30 : }
493 : :
494 : : /*
495 : : * _hash_init_metabuffer() -- Initialize the metadata page of a hash index.
496 : : */
497 : : void
498 : 30 : _hash_init_metabuffer(Buffer buf, double num_tuples, RegProcedure procid,
499 : : uint16 ffactor, bool initpage)
500 : : {
501 : 30 : HashMetaPage metap;
502 : 30 : HashPageOpaque pageopaque;
503 : 30 : Page page;
504 : 30 : double dnumbuckets;
505 : 30 : uint32 num_buckets;
506 : 30 : uint32 spare_index;
507 : 30 : uint32 lshift;
508 : :
509 : : /*
510 : : * Choose the number of initial bucket pages to match the fill factor
511 : : * given the estimated number of tuples. We round up the result to the
512 : : * total number of buckets which has to be allocated before using its
513 : : * hashm_spares element. However always force at least 2 bucket pages. The
514 : : * upper limit is determined by considerations explained in
515 : : * _hash_expandtable().
516 : : */
517 : 30 : dnumbuckets = num_tuples / ffactor;
518 [ + + ]: 30 : if (dnumbuckets <= 2.0)
519 : 7 : num_buckets = 2;
520 [ - + ]: 23 : else if (dnumbuckets >= (double) 0x40000000)
521 : 0 : num_buckets = 0x40000000;
522 : : else
523 : 23 : num_buckets = _hash_get_totalbuckets(_hash_spareindex(dnumbuckets));
524 : :
525 : 30 : spare_index = _hash_spareindex(num_buckets);
526 [ + - ]: 30 : Assert(spare_index < HASH_MAX_SPLITPOINTS);
527 : :
528 : 30 : page = BufferGetPage(buf);
529 [ + - ]: 30 : if (initpage)
530 : 0 : _hash_pageinit(page, BufferGetPageSize(buf));
531 : :
532 : 30 : pageopaque = HashPageGetOpaque(page);
533 : 30 : pageopaque->hasho_prevblkno = InvalidBlockNumber;
534 : 30 : pageopaque->hasho_nextblkno = InvalidBlockNumber;
535 : 30 : pageopaque->hasho_bucket = InvalidBucket;
536 : 30 : pageopaque->hasho_flag = LH_META_PAGE;
537 : 30 : pageopaque->hasho_page_id = HASHO_PAGE_ID;
538 : :
539 : 30 : metap = HashPageGetMeta(page);
540 : :
541 : 30 : metap->hashm_magic = HASH_MAGIC;
542 : 30 : metap->hashm_version = HASH_VERSION;
543 : 30 : metap->hashm_ntuples = 0;
544 : 30 : metap->hashm_nmaps = 0;
545 : 30 : metap->hashm_ffactor = ffactor;
546 : 30 : metap->hashm_bsize = HashGetMaxBitmapSize(page);
547 : :
548 : : /* find largest bitmap array size that will fit in page size */
549 : 30 : lshift = pg_leftmost_one_pos32(metap->hashm_bsize);
550 [ + - ]: 30 : Assert(lshift > 0);
551 : 30 : metap->hashm_bmsize = 1 << lshift;
552 : 30 : metap->hashm_bmshift = lshift + BYTE_TO_BIT;
553 [ + - ]: 30 : Assert((1 << BMPG_SHIFT(metap)) == (BMPG_MASK(metap) + 1));
554 : :
555 : : /*
556 : : * Label the index with its primary hash support function's OID. This is
557 : : * pretty useless for normal operation (in fact, hashm_procid is not used
558 : : * anywhere), but it might be handy for forensic purposes so we keep it.
559 : : */
560 : 30 : metap->hashm_procid = procid;
561 : :
562 : : /*
563 : : * We initialize the index with N buckets, 0 .. N-1, occupying physical
564 : : * blocks 1 to N. The first freespace bitmap page is in block N+1.
565 : : */
566 : 30 : metap->hashm_maxbucket = num_buckets - 1;
567 : :
568 : : /*
569 : : * Set highmask as next immediate ((2 ^ x) - 1), which should be
570 : : * sufficient to cover num_buckets.
571 : : */
572 : 30 : metap->hashm_highmask = pg_nextpower2_32(num_buckets + 1) - 1;
573 : 30 : metap->hashm_lowmask = (metap->hashm_highmask >> 1);
574 : :
575 [ - + # # : 30 : MemSet(metap->hashm_spares, 0, sizeof(metap->hashm_spares));
# # # # #
# ]
576 [ - + # # : 30 : MemSet(metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));
# # # # #
# ]
577 : :
578 : : /* Set up mapping for one spare page after the initial splitpoints */
579 : 30 : metap->hashm_spares[spare_index] = 1;
580 : 30 : metap->hashm_ovflpoint = spare_index;
581 : 30 : metap->hashm_firstfree = 0;
582 : :
583 : : /*
584 : : * Set pd_lower just past the end of the metadata. This is essential,
585 : : * because without doing so, metadata will be lost if xlog.c compresses
586 : : * the page.
587 : : */
588 : 30 : ((PageHeader) page)->pd_lower =
589 : 30 : ((char *) metap + sizeof(HashMetaPageData)) - (char *) page;
590 : 30 : }
591 : :
592 : : /*
593 : : * _hash_pageinit() -- Initialize a new hash index page.
594 : : */
595 : : void
596 : 1588 : _hash_pageinit(Page page, Size size)
597 : : {
598 : 1588 : PageInit(page, size, sizeof(HashPageOpaqueData));
599 : 1588 : }
600 : :
601 : : /*
602 : : * Attempt to expand the hash table by creating one new bucket.
603 : : *
604 : : * This will silently do nothing if we don't get cleanup lock on old or
605 : : * new bucket.
606 : : *
607 : : * Complete the pending splits and remove the tuples from old bucket,
608 : : * if there are any left over from the previous split.
609 : : *
610 : : * The caller must hold a pin, but no lock, on the metapage buffer.
611 : : * The buffer is returned in the same state.
612 : : */
613 : : void
614 : 221 : _hash_expandtable(Relation rel, Buffer metabuf)
615 : : {
616 : 221 : HashMetaPage metap;
617 : 221 : Bucket old_bucket;
618 : 221 : Bucket new_bucket;
619 : 221 : uint32 spare_ndx;
620 : 221 : BlockNumber start_oblkno;
621 : 221 : BlockNumber start_nblkno;
622 : 221 : Buffer buf_nblkno;
623 : 221 : Buffer buf_oblkno;
624 : 221 : Page opage;
625 : 221 : Page npage;
626 : 221 : HashPageOpaque oopaque;
627 : 221 : HashPageOpaque nopaque;
628 : 221 : uint32 maxbucket;
629 : 221 : uint32 highmask;
630 : 221 : uint32 lowmask;
631 : 221 : bool metap_update_masks = false;
632 : 221 : bool metap_update_splitpoint = false;
633 : :
634 : : restart_expand:
635 : :
636 : : /*
637 : : * Write-lock the meta page. It used to be necessary to acquire a
638 : : * heavyweight lock to begin a split, but that is no longer required.
639 : : */
640 : 221 : LockBuffer(metabuf, BUFFER_LOCK_EXCLUSIVE);
641 : :
642 : 221 : _hash_checkpage(rel, metabuf, LH_META_PAGE);
643 : 221 : metap = HashPageGetMeta(BufferGetPage(metabuf));
644 : :
645 : : /*
646 : : * Check to see if split is still needed; someone else might have already
647 : : * done one while we waited for the lock.
648 : : *
649 : : * Make sure this stays in sync with _hash_doinsert()
650 : : */
651 [ + - + - ]: 442 : if (metap->hashm_ntuples <=
652 : 221 : (double) metap->hashm_ffactor * (metap->hashm_maxbucket + 1))
653 : 0 : goto fail;
654 : :
655 : : /*
656 : : * Can't split anymore if maxbucket has reached its maximum possible
657 : : * value.
658 : : *
659 : : * Ideally we'd allow bucket numbers up to UINT_MAX-1 (no higher because
660 : : * the calculation maxbucket+1 mustn't overflow). Currently we restrict
661 : : * to half that to prevent failure of pg_ceil_log2_32() and insufficient
662 : : * space in hashm_spares[]. It's moot anyway because an index with 2^32
663 : : * buckets would certainly overflow BlockNumber and hence
664 : : * _hash_alloc_buckets() would fail, but if we supported buckets smaller
665 : : * than a disk block then this would be an independent constraint.
666 : : *
667 : : * If you change this, see also the maximum initial number of buckets in
668 : : * _hash_init().
669 : : */
670 [ + - ]: 221 : if (metap->hashm_maxbucket >= (uint32) 0x7FFFFFFE)
671 : 0 : goto fail;
672 : :
673 : : /*
674 : : * Determine which bucket is to be split, and attempt to take cleanup lock
675 : : * on the old bucket. If we can't get the lock, give up.
676 : : *
677 : : * The cleanup lock protects us not only against other backends, but
678 : : * against our own backend as well.
679 : : *
680 : : * The cleanup lock is mainly to protect the split from concurrent
681 : : * inserts. See src/backend/access/hash/README, Lock Definitions for
682 : : * further details. Due to this locking restriction, if there is any
683 : : * pending scan, the split will give up which is not good, but harmless.
684 : : */
685 : 221 : new_bucket = metap->hashm_maxbucket + 1;
686 : :
687 : 221 : old_bucket = (new_bucket & metap->hashm_lowmask);
688 : :
689 [ + + ]: 221 : start_oblkno = BUCKET_TO_BLKNO(metap, old_bucket);
690 : :
691 : 221 : buf_oblkno = _hash_getbuf_with_condlock_cleanup(rel, start_oblkno, LH_BUCKET_PAGE);
692 [ - + ]: 221 : if (!buf_oblkno)
693 : 0 : goto fail;
694 : :
695 : 221 : opage = BufferGetPage(buf_oblkno);
696 : 221 : oopaque = HashPageGetOpaque(opage);
697 : :
698 : : /*
699 : : * We want to finish the split from a bucket as there is no apparent
700 : : * benefit by not doing so and it will make the code complicated to finish
701 : : * the split that involves multiple buckets considering the case where new
702 : : * split also fails. We don't need to consider the new bucket for
703 : : * completing the split here as it is not possible that a re-split of new
704 : : * bucket starts when there is still a pending split from old bucket.
705 : : */
706 [ - + ]: 221 : if (H_BUCKET_BEING_SPLIT(oopaque))
707 : : {
708 : : /*
709 : : * Copy bucket mapping info now; refer the comment in code below where
710 : : * we copy this information before calling _hash_splitbucket to see
711 : : * why this is okay.
712 : : */
713 : 0 : maxbucket = metap->hashm_maxbucket;
714 : 0 : highmask = metap->hashm_highmask;
715 : 0 : lowmask = metap->hashm_lowmask;
716 : :
717 : : /*
718 : : * Release the lock on metapage and old_bucket, before completing the
719 : : * split.
720 : : */
721 : 0 : LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
722 : 0 : LockBuffer(buf_oblkno, BUFFER_LOCK_UNLOCK);
723 : :
724 : 0 : _hash_finish_split(rel, metabuf, buf_oblkno, old_bucket, maxbucket,
725 : 0 : highmask, lowmask);
726 : :
727 : : /* release the pin on old buffer and retry for expand. */
728 : 0 : _hash_dropbuf(rel, buf_oblkno);
729 : :
730 : 0 : goto restart_expand;
731 : : }
732 : :
733 : : /*
734 : : * Clean the tuples remained from the previous split. This operation
735 : : * requires cleanup lock and we already have one on the old bucket, so
736 : : * let's do it. We also don't want to allow further splits from the bucket
737 : : * till the garbage of previous split is cleaned. This has two
738 : : * advantages; first, it helps in avoiding the bloat due to garbage and
739 : : * second is, during cleanup of bucket, we are always sure that the
740 : : * garbage tuples belong to most recently split bucket. On the contrary,
741 : : * if we allow cleanup of bucket after meta page is updated to indicate
742 : : * the new split and before the actual split, the cleanup operation won't
743 : : * be able to decide whether the tuple has been moved to the newly created
744 : : * bucket and ended up deleting such tuples.
745 : : */
746 [ - + ]: 221 : if (H_NEEDS_SPLIT_CLEANUP(oopaque))
747 : : {
748 : : /*
749 : : * Copy bucket mapping info now; refer to the comment in code below
750 : : * where we copy this information before calling _hash_splitbucket to
751 : : * see why this is okay.
752 : : */
753 : 0 : maxbucket = metap->hashm_maxbucket;
754 : 0 : highmask = metap->hashm_highmask;
755 : 0 : lowmask = metap->hashm_lowmask;
756 : :
757 : : /* Release the metapage lock. */
758 : 0 : LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
759 : :
760 : 0 : hashbucketcleanup(rel, old_bucket, buf_oblkno, start_oblkno, NULL,
761 : 0 : maxbucket, highmask, lowmask, NULL, NULL, true,
762 : : NULL, NULL);
763 : :
764 : 0 : _hash_dropbuf(rel, buf_oblkno);
765 : :
766 : 0 : goto restart_expand;
767 : : }
768 : :
769 : : /*
770 : : * There shouldn't be any active scan on new bucket.
771 : : *
772 : : * Note: it is safe to compute the new bucket's blkno here, even though we
773 : : * may still need to update the BUCKET_TO_BLKNO mapping. This is because
774 : : * the current value of hashm_spares[hashm_ovflpoint] correctly shows
775 : : * where we are going to put a new splitpoint's worth of buckets.
776 : : */
777 [ + - ]: 221 : start_nblkno = BUCKET_TO_BLKNO(metap, new_bucket);
778 : :
779 : : /*
780 : : * If the split point is increasing we need to allocate a new batch of
781 : : * bucket pages.
782 : : */
783 : 221 : spare_ndx = _hash_spareindex(new_bucket + 1);
784 [ + + ]: 221 : if (spare_ndx > metap->hashm_ovflpoint)
785 : : {
786 : 9 : uint32 buckets_to_add;
787 : :
788 [ + - ]: 9 : Assert(spare_ndx == metap->hashm_ovflpoint + 1);
789 : :
790 : : /*
791 : : * We treat allocation of buckets as a separate WAL-logged action.
792 : : * Even if we fail after this operation, won't leak bucket pages;
793 : : * rather, the next split will consume this space. In any case, even
794 : : * without failure we don't use all the space in one split operation.
795 : : */
796 : 9 : buckets_to_add = _hash_get_totalbuckets(spare_ndx) - new_bucket;
797 [ + - ]: 9 : if (!_hash_alloc_buckets(rel, start_nblkno, buckets_to_add))
798 : : {
799 : : /* can't split due to BlockNumber overflow */
800 : 0 : _hash_relbuf(rel, buf_oblkno);
801 : 0 : goto fail;
802 : : }
803 [ + - - ]: 9 : }
804 : :
805 : : /*
806 : : * Physically allocate the new bucket's primary page. We want to do this
807 : : * before changing the metapage's mapping info, in case we can't get the
808 : : * disk space.
809 : : *
810 : : * XXX It doesn't make sense to call _hash_getnewbuf first, zeroing the
811 : : * buffer, and then only afterwards check whether we have a cleanup lock.
812 : : * However, since no scan can be accessing the buffer yet, any concurrent
813 : : * accesses will just be from processes like the bgwriter or checkpointer
814 : : * which don't care about its contents, so it doesn't really matter.
815 : : */
816 : 221 : buf_nblkno = _hash_getnewbuf(rel, start_nblkno, MAIN_FORKNUM);
817 [ + - ]: 221 : if (!IsBufferCleanupOK(buf_nblkno))
818 : : {
819 : 0 : _hash_relbuf(rel, buf_oblkno);
820 : 0 : _hash_relbuf(rel, buf_nblkno);
821 : 0 : goto fail;
822 : : }
823 : :
824 : : /*
825 : : * Since we are scribbling on the pages in the shared buffers, establish a
826 : : * critical section. Any failure in this next code leaves us with a big
827 : : * problem: the metapage is effectively corrupt but could get written back
828 : : * to disk.
829 : : */
830 : 221 : START_CRIT_SECTION();
831 : :
832 : : /*
833 : : * Okay to proceed with split. Update the metapage bucket mapping info.
834 : : */
835 : 221 : metap->hashm_maxbucket = new_bucket;
836 : :
837 [ + + ]: 221 : if (new_bucket > metap->hashm_highmask)
838 : : {
839 : : /* Starting a new doubling */
840 : 3 : metap->hashm_lowmask = metap->hashm_highmask;
841 : 3 : metap->hashm_highmask = new_bucket | metap->hashm_lowmask;
842 : 3 : metap_update_masks = true;
843 : 3 : }
844 : :
845 : : /*
846 : : * If the split point is increasing we need to adjust the hashm_spares[]
847 : : * array and hashm_ovflpoint so that future overflow pages will be created
848 : : * beyond this new batch of bucket pages.
849 : : */
850 [ + + ]: 221 : if (spare_ndx > metap->hashm_ovflpoint)
851 : : {
852 : 9 : metap->hashm_spares[spare_ndx] = metap->hashm_spares[metap->hashm_ovflpoint];
853 : 9 : metap->hashm_ovflpoint = spare_ndx;
854 : 9 : metap_update_splitpoint = true;
855 : 9 : }
856 : :
857 : 221 : MarkBufferDirty(metabuf);
858 : :
859 : : /*
860 : : * Copy bucket mapping info now; this saves re-accessing the meta page
861 : : * inside _hash_splitbucket's inner loop. Note that once we drop the
862 : : * split lock, other splits could begin, so these values might be out of
863 : : * date before _hash_splitbucket finishes. That's okay, since all it
864 : : * needs is to tell which of these two buckets to map hashkeys into.
865 : : */
866 : 221 : maxbucket = metap->hashm_maxbucket;
867 : 221 : highmask = metap->hashm_highmask;
868 : 221 : lowmask = metap->hashm_lowmask;
869 : :
870 : 221 : opage = BufferGetPage(buf_oblkno);
871 : 221 : oopaque = HashPageGetOpaque(opage);
872 : :
873 : : /*
874 : : * Mark the old bucket to indicate that split is in progress. (At
875 : : * operation end, we will clear the split-in-progress flag.) Also, for a
876 : : * primary bucket page, hasho_prevblkno stores the number of buckets that
877 : : * existed as of the last split, so we must update that value here.
878 : : */
879 : 221 : oopaque->hasho_flag |= LH_BUCKET_BEING_SPLIT;
880 : 221 : oopaque->hasho_prevblkno = maxbucket;
881 : :
882 : 221 : MarkBufferDirty(buf_oblkno);
883 : :
884 : 221 : npage = BufferGetPage(buf_nblkno);
885 : :
886 : : /*
887 : : * initialize the new bucket's primary page and mark it to indicate that
888 : : * split is in progress.
889 : : */
890 : 221 : nopaque = HashPageGetOpaque(npage);
891 : 221 : nopaque->hasho_prevblkno = maxbucket;
892 : 221 : nopaque->hasho_nextblkno = InvalidBlockNumber;
893 : 221 : nopaque->hasho_bucket = new_bucket;
894 : 221 : nopaque->hasho_flag = LH_BUCKET_PAGE | LH_BUCKET_BEING_POPULATED;
895 : 221 : nopaque->hasho_page_id = HASHO_PAGE_ID;
896 : :
897 : 221 : MarkBufferDirty(buf_nblkno);
898 : :
899 : : /* XLOG stuff */
900 [ + - + - : 221 : if (RelationNeedsWAL(rel))
+ + + + ]
901 : : {
902 : 95 : xl_hash_split_allocate_page xlrec;
903 : 95 : XLogRecPtr recptr;
904 : :
905 : 95 : xlrec.new_bucket = maxbucket;
906 : 95 : xlrec.old_bucket_flag = oopaque->hasho_flag;
907 : 95 : xlrec.new_bucket_flag = nopaque->hasho_flag;
908 : 95 : xlrec.flags = 0;
909 : :
910 : 95 : XLogBeginInsert();
911 : :
912 : 95 : XLogRegisterBuffer(0, buf_oblkno, REGBUF_STANDARD);
913 : 95 : XLogRegisterBuffer(1, buf_nblkno, REGBUF_WILL_INIT);
914 : 95 : XLogRegisterBuffer(2, metabuf, REGBUF_STANDARD);
915 : :
916 [ + + ]: 95 : if (metap_update_masks)
917 : : {
918 : 3 : xlrec.flags |= XLH_SPLIT_META_UPDATE_MASKS;
919 : 3 : XLogRegisterBufData(2, &metap->hashm_lowmask, sizeof(uint32));
920 : 3 : XLogRegisterBufData(2, &metap->hashm_highmask, sizeof(uint32));
921 : 3 : }
922 : :
923 [ + + ]: 95 : if (metap_update_splitpoint)
924 : : {
925 : 5 : xlrec.flags |= XLH_SPLIT_META_UPDATE_SPLITPOINT;
926 : 5 : XLogRegisterBufData(2, &metap->hashm_ovflpoint,
927 : : sizeof(uint32));
928 : 5 : XLogRegisterBufData(2,
929 : 5 : &metap->hashm_spares[metap->hashm_ovflpoint],
930 : : sizeof(uint32));
931 : 5 : }
932 : :
933 : 95 : XLogRegisterData(&xlrec, SizeOfHashSplitAllocPage);
934 : :
935 : 95 : recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_ALLOCATE_PAGE);
936 : :
937 : 95 : PageSetLSN(BufferGetPage(buf_oblkno), recptr);
938 : 95 : PageSetLSN(BufferGetPage(buf_nblkno), recptr);
939 : 95 : PageSetLSN(BufferGetPage(metabuf), recptr);
940 : 95 : }
941 : :
942 [ + - ]: 221 : END_CRIT_SECTION();
943 : :
944 : : /* drop lock, but keep pin */
945 : 221 : LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
946 : :
947 : : /* Relocate records to the new bucket */
948 : 442 : _hash_splitbucket(rel, metabuf,
949 : 221 : old_bucket, new_bucket,
950 : 221 : buf_oblkno, buf_nblkno, NULL,
951 : 221 : maxbucket, highmask, lowmask);
952 : :
953 : : /* all done, now release the pins on primary buckets. */
954 : 221 : _hash_dropbuf(rel, buf_oblkno);
955 : 221 : _hash_dropbuf(rel, buf_nblkno);
956 : :
957 : 221 : return;
958 : :
959 : : /* Here if decide not to split or fail to acquire old bucket lock */
960 : : fail:
961 : :
962 : : /* We didn't write the metapage, so just drop lock */
963 : 0 : LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
964 [ - + ]: 221 : }
965 : :
966 : :
967 : : /*
968 : : * _hash_alloc_buckets -- allocate a new splitpoint's worth of bucket pages
969 : : *
970 : : * This does not need to initialize the new bucket pages; we'll do that as
971 : : * each one is used by _hash_expandtable(). But we have to extend the logical
972 : : * EOF to the end of the splitpoint; this keeps smgr's idea of the EOF in
973 : : * sync with ours, so that we don't get complaints from smgr.
974 : : *
975 : : * We do this by writing a page of zeroes at the end of the splitpoint range.
976 : : * We expect that the filesystem will ensure that the intervening pages read
977 : : * as zeroes too. On many filesystems this "hole" will not be allocated
978 : : * immediately, which means that the index file may end up more fragmented
979 : : * than if we forced it all to be allocated now; but since we don't scan
980 : : * hash indexes sequentially anyway, that probably doesn't matter.
981 : : *
982 : : * XXX It's annoying that this code is executed with the metapage lock held.
983 : : * We need to interlock against _hash_addovflpage() adding a new overflow page
984 : : * concurrently, but it'd likely be better to use LockRelationForExtension
985 : : * for the purpose. OTOH, adding a splitpoint is a very infrequent operation,
986 : : * so it may not be worth worrying about.
987 : : *
988 : : * Returns true if successful, or false if allocation failed due to
989 : : * BlockNumber overflow.
990 : : */
991 : : static bool
992 : 9 : _hash_alloc_buckets(Relation rel, BlockNumber firstblock, uint32 nblocks)
993 : : {
994 : 9 : BlockNumber lastblock;
995 : 9 : PGIOAlignedBlock zerobuf;
996 : 9 : Page page;
997 : 9 : HashPageOpaque ovflopaque;
998 : :
999 : 9 : lastblock = firstblock + nblocks - 1;
1000 : :
1001 : : /*
1002 : : * Check for overflow in block number calculation; if so, we cannot extend
1003 : : * the index anymore.
1004 : : */
1005 [ + - - + ]: 9 : if (lastblock < firstblock || lastblock == InvalidBlockNumber)
1006 : 0 : return false;
1007 : :
1008 : 9 : page = (Page) zerobuf.data;
1009 : :
1010 : : /*
1011 : : * Initialize the page. Just zeroing the page won't work; see
1012 : : * _hash_freeovflpage for similar usage. We take care to make the special
1013 : : * space valid for the benefit of tools such as pageinspect.
1014 : : */
1015 : 9 : _hash_pageinit(page, BLCKSZ);
1016 : :
1017 : 9 : ovflopaque = HashPageGetOpaque(page);
1018 : :
1019 : 9 : ovflopaque->hasho_prevblkno = InvalidBlockNumber;
1020 : 9 : ovflopaque->hasho_nextblkno = InvalidBlockNumber;
1021 : 9 : ovflopaque->hasho_bucket = InvalidBucket;
1022 : 9 : ovflopaque->hasho_flag = LH_UNUSED_PAGE;
1023 : 9 : ovflopaque->hasho_page_id = HASHO_PAGE_ID;
1024 : :
1025 [ + - + - : 9 : if (RelationNeedsWAL(rel))
+ + + + ]
1026 : 10 : log_newpage(&rel->rd_locator,
1027 : : MAIN_FORKNUM,
1028 : 5 : lastblock,
1029 : 5 : zerobuf.data,
1030 : : true);
1031 : :
1032 : 9 : PageSetChecksumInplace(page, lastblock);
1033 : 9 : smgrextend(RelationGetSmgr(rel), MAIN_FORKNUM, lastblock, zerobuf.data,
1034 : : false);
1035 : :
1036 : 9 : return true;
1037 : 9 : }
1038 : :
1039 : :
1040 : : /*
1041 : : * _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
1042 : : *
1043 : : * This routine is used to partition the tuples between old and new bucket and
1044 : : * is used to finish the incomplete split operations. To finish the previously
1045 : : * interrupted split operation, the caller needs to fill htab. If htab is set,
1046 : : * then we skip the movement of tuples that exists in htab, otherwise NULL
1047 : : * value of htab indicates movement of all the tuples that belong to the new
1048 : : * bucket.
1049 : : *
1050 : : * We are splitting a bucket that consists of a base bucket page and zero
1051 : : * or more overflow (bucket chain) pages. We must relocate tuples that
1052 : : * belong in the new bucket.
1053 : : *
1054 : : * The caller must hold cleanup locks on both buckets to ensure that
1055 : : * no one else is trying to access them (see README).
1056 : : *
1057 : : * The caller must hold a pin, but no lock, on the metapage buffer.
1058 : : * The buffer is returned in the same state. (The metapage is only
1059 : : * touched if it becomes necessary to add or remove overflow pages.)
1060 : : *
1061 : : * Split needs to retain pin on primary bucket pages of both old and new
1062 : : * buckets till end of operation. This is to prevent vacuum from starting
1063 : : * while a split is in progress.
1064 : : *
1065 : : * In addition, the caller must have created the new bucket's base page,
1066 : : * which is passed in buffer nbuf, pinned and write-locked. The lock will be
1067 : : * released here and pin must be released by the caller. (The API is set up
1068 : : * this way because we must do _hash_getnewbuf() before releasing the metapage
1069 : : * write lock. So instead of passing the new bucket's start block number, we
1070 : : * pass an actual buffer.)
1071 : : */
1072 : : static void
1073 : 221 : _hash_splitbucket(Relation rel,
1074 : : Buffer metabuf,
1075 : : Bucket obucket,
1076 : : Bucket nbucket,
1077 : : Buffer obuf,
1078 : : Buffer nbuf,
1079 : : HTAB *htab,
1080 : : uint32 maxbucket,
1081 : : uint32 highmask,
1082 : : uint32 lowmask)
1083 : : {
1084 : 221 : Buffer bucket_obuf;
1085 : 221 : Buffer bucket_nbuf;
1086 : 221 : Page opage;
1087 : 221 : Page npage;
1088 : 221 : HashPageOpaque oopaque;
1089 : 221 : HashPageOpaque nopaque;
1090 : 221 : OffsetNumber itup_offsets[MaxIndexTuplesPerPage];
1091 : 221 : IndexTuple itups[MaxIndexTuplesPerPage];
1092 : 221 : Size all_tups_size = 0;
1093 : 221 : int i;
1094 : 221 : uint16 nitups = 0;
1095 : :
1096 : 221 : bucket_obuf = obuf;
1097 : 221 : opage = BufferGetPage(obuf);
1098 : 221 : oopaque = HashPageGetOpaque(opage);
1099 : :
1100 : 221 : bucket_nbuf = nbuf;
1101 : 221 : npage = BufferGetPage(nbuf);
1102 : 221 : nopaque = HashPageGetOpaque(npage);
1103 : :
1104 : : /* Copy the predicate locks from old bucket to new bucket. */
1105 : 442 : PredicateLockPageSplit(rel,
1106 : 221 : BufferGetBlockNumber(bucket_obuf),
1107 : 221 : BufferGetBlockNumber(bucket_nbuf));
1108 : :
1109 : : /*
1110 : : * Partition the tuples in the old bucket between the old bucket and the
1111 : : * new bucket, advancing along the old bucket's overflow bucket chain and
1112 : : * adding overflow pages to the new bucket as needed. Outer loop iterates
1113 : : * once per page in old bucket.
1114 : : */
1115 : 277 : for (;;)
1116 : : {
1117 : 277 : BlockNumber oblkno;
1118 : 277 : OffsetNumber ooffnum;
1119 : 277 : OffsetNumber omaxoffnum;
1120 : :
1121 : : /* Scan each tuple in old page */
1122 : 277 : omaxoffnum = PageGetMaxOffsetNumber(opage);
1123 [ + + ]: 50540 : for (ooffnum = FirstOffsetNumber;
1124 : 50540 : ooffnum <= omaxoffnum;
1125 : 50263 : ooffnum = OffsetNumberNext(ooffnum))
1126 : : {
1127 : 50263 : IndexTuple itup;
1128 : 50263 : Size itemsz;
1129 : 50263 : Bucket bucket;
1130 : 50263 : bool found = false;
1131 : :
1132 : : /* skip dead tuples */
1133 [ - + ]: 50263 : if (ItemIdIsDead(PageGetItemId(opage, ooffnum)))
1134 : 0 : continue;
1135 : :
1136 : : /*
1137 : : * Before inserting a tuple, probe the hash table containing TIDs
1138 : : * of tuples belonging to new bucket, if we find a match, then
1139 : : * skip that tuple, else fetch the item's hash key (conveniently
1140 : : * stored in the item) and determine which bucket it now belongs
1141 : : * in.
1142 : : */
1143 : 100526 : itup = (IndexTuple) PageGetItem(opage,
1144 : 50263 : PageGetItemId(opage, ooffnum));
1145 : :
1146 [ + - ]: 50263 : if (htab)
1147 : 0 : (void) hash_search(htab, &itup->t_tid, HASH_FIND, &found);
1148 : :
1149 [ - + ]: 50263 : if (found)
1150 : 0 : continue;
1151 : :
1152 : 100526 : bucket = _hash_hashkey2bucket(_hash_get_indextuple_hashkey(itup),
1153 : 50263 : maxbucket, highmask, lowmask);
1154 : :
1155 [ + + ]: 50263 : if (bucket == nbucket)
1156 : : {
1157 : 20512 : IndexTuple new_itup;
1158 : :
1159 : : /*
1160 : : * make a copy of index tuple as we have to scribble on it.
1161 : : */
1162 : 20512 : new_itup = CopyIndexTuple(itup);
1163 : :
1164 : : /*
1165 : : * mark the index tuple as moved by split, such tuples are
1166 : : * skipped by scan if there is split in progress for a bucket.
1167 : : */
1168 : 20512 : new_itup->t_info |= INDEX_MOVED_BY_SPLIT_MASK;
1169 : :
1170 : : /*
1171 : : * insert the tuple into the new bucket. if it doesn't fit on
1172 : : * the current page in the new bucket, we must allocate a new
1173 : : * overflow page and place the tuple on that page instead.
1174 : : */
1175 : 20512 : itemsz = IndexTupleSize(new_itup);
1176 : 20512 : itemsz = MAXALIGN(itemsz);
1177 : :
1178 [ + + ]: 20512 : if (PageGetFreeSpaceForMultipleTuples(npage, nitups + 1) < (all_tups_size + itemsz))
1179 : : {
1180 : : /*
1181 : : * Change the shared buffer state in critical section,
1182 : : * otherwise any error could make it unrecoverable.
1183 : : */
1184 : 13 : START_CRIT_SECTION();
1185 : :
1186 : 13 : _hash_pgaddmultitup(rel, nbuf, itups, itup_offsets, nitups);
1187 : 13 : MarkBufferDirty(nbuf);
1188 : : /* log the split operation before releasing the lock */
1189 : 13 : log_split_page(rel, nbuf);
1190 : :
1191 [ - + ]: 13 : END_CRIT_SECTION();
1192 : :
1193 : : /* drop lock, but keep pin */
1194 : 13 : LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
1195 : :
1196 : : /* be tidy */
1197 [ + + ]: 5304 : for (i = 0; i < nitups; i++)
1198 : 5291 : pfree(itups[i]);
1199 : 13 : nitups = 0;
1200 : 13 : all_tups_size = 0;
1201 : :
1202 : : /* chain to a new overflow page */
1203 : 13 : nbuf = _hash_addovflpage(rel, metabuf, nbuf, (nbuf == bucket_nbuf));
1204 : 13 : npage = BufferGetPage(nbuf);
1205 : 13 : nopaque = HashPageGetOpaque(npage);
1206 : 13 : }
1207 : :
1208 : 20512 : itups[nitups++] = new_itup;
1209 : 20512 : all_tups_size += itemsz;
1210 : 20512 : }
1211 : : else
1212 : : {
1213 : : /*
1214 : : * the tuple stays on this page, so nothing to do.
1215 : : */
1216 [ - + ]: 29751 : Assert(bucket == obucket);
1217 : : }
1218 [ - + ]: 50263 : }
1219 : :
1220 : 277 : oblkno = oopaque->hasho_nextblkno;
1221 : :
1222 : : /* retain the pin on the old primary bucket */
1223 [ + + ]: 277 : if (obuf == bucket_obuf)
1224 : 221 : LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
1225 : : else
1226 : 56 : _hash_relbuf(rel, obuf);
1227 : :
1228 : : /* Exit loop if no more overflow pages in old bucket */
1229 [ + + ]: 277 : if (!BlockNumberIsValid(oblkno))
1230 : : {
1231 : : /*
1232 : : * Change the shared buffer state in critical section, otherwise
1233 : : * any error could make it unrecoverable.
1234 : : */
1235 : 221 : START_CRIT_SECTION();
1236 : :
1237 : 221 : _hash_pgaddmultitup(rel, nbuf, itups, itup_offsets, nitups);
1238 : 221 : MarkBufferDirty(nbuf);
1239 : : /* log the split operation before releasing the lock */
1240 : 221 : log_split_page(rel, nbuf);
1241 : :
1242 [ - + ]: 221 : END_CRIT_SECTION();
1243 : :
1244 [ + + ]: 221 : if (nbuf == bucket_nbuf)
1245 : 220 : LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
1246 : : else
1247 : 1 : _hash_relbuf(rel, nbuf);
1248 : :
1249 : : /* be tidy */
1250 [ + + ]: 15442 : for (i = 0; i < nitups; i++)
1251 : 15221 : pfree(itups[i]);
1252 : 221 : break;
1253 : : }
1254 : :
1255 : : /* Else, advance to next old page */
1256 : 56 : obuf = _hash_getbuf(rel, oblkno, HASH_READ, LH_OVERFLOW_PAGE);
1257 : 56 : opage = BufferGetPage(obuf);
1258 : 56 : oopaque = HashPageGetOpaque(opage);
1259 [ + + ]: 277 : }
1260 : :
1261 : : /*
1262 : : * We're at the end of the old bucket chain, so we're done partitioning
1263 : : * the tuples. Mark the old and new buckets to indicate split is
1264 : : * finished.
1265 : : *
1266 : : * To avoid deadlocks due to locking order of buckets, first lock the old
1267 : : * bucket and then the new bucket.
1268 : : */
1269 : 221 : LockBuffer(bucket_obuf, BUFFER_LOCK_EXCLUSIVE);
1270 : 221 : opage = BufferGetPage(bucket_obuf);
1271 : 221 : oopaque = HashPageGetOpaque(opage);
1272 : :
1273 : 221 : LockBuffer(bucket_nbuf, BUFFER_LOCK_EXCLUSIVE);
1274 : 221 : npage = BufferGetPage(bucket_nbuf);
1275 : 221 : nopaque = HashPageGetOpaque(npage);
1276 : :
1277 : 221 : START_CRIT_SECTION();
1278 : :
1279 : 221 : oopaque->hasho_flag &= ~LH_BUCKET_BEING_SPLIT;
1280 : 221 : nopaque->hasho_flag &= ~LH_BUCKET_BEING_POPULATED;
1281 : :
1282 : : /*
1283 : : * After the split is finished, mark the old bucket to indicate that it
1284 : : * contains deletable tuples. We will clear split-cleanup flag after
1285 : : * deleting such tuples either at the end of split or at the next split
1286 : : * from old bucket or at the time of vacuum.
1287 : : */
1288 : 221 : oopaque->hasho_flag |= LH_BUCKET_NEEDS_SPLIT_CLEANUP;
1289 : :
1290 : : /*
1291 : : * now write the buffers, here we don't release the locks as caller is
1292 : : * responsible to release locks.
1293 : : */
1294 : 221 : MarkBufferDirty(bucket_obuf);
1295 : 221 : MarkBufferDirty(bucket_nbuf);
1296 : :
1297 [ + - + - : 221 : if (RelationNeedsWAL(rel))
+ + + + ]
1298 : : {
1299 : 95 : XLogRecPtr recptr;
1300 : 95 : xl_hash_split_complete xlrec;
1301 : :
1302 : 95 : xlrec.old_bucket_flag = oopaque->hasho_flag;
1303 : 95 : xlrec.new_bucket_flag = nopaque->hasho_flag;
1304 : :
1305 : 95 : XLogBeginInsert();
1306 : :
1307 : 95 : XLogRegisterData(&xlrec, SizeOfHashSplitComplete);
1308 : :
1309 : 95 : XLogRegisterBuffer(0, bucket_obuf, REGBUF_STANDARD);
1310 : 95 : XLogRegisterBuffer(1, bucket_nbuf, REGBUF_STANDARD);
1311 : :
1312 : 95 : recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_COMPLETE);
1313 : :
1314 : 95 : PageSetLSN(BufferGetPage(bucket_obuf), recptr);
1315 : 95 : PageSetLSN(BufferGetPage(bucket_nbuf), recptr);
1316 : 95 : }
1317 : :
1318 [ + - ]: 221 : END_CRIT_SECTION();
1319 : :
1320 : : /*
1321 : : * If possible, clean up the old bucket. We might not be able to do this
1322 : : * if someone else has a pin on it, but if not then we can go ahead. This
1323 : : * isn't absolutely necessary, but it reduces bloat; if we don't do it
1324 : : * now, VACUUM will do it eventually, but maybe not until new overflow
1325 : : * pages have been allocated. Note that there's no need to clean up the
1326 : : * new bucket.
1327 : : */
1328 [ + - ]: 221 : if (IsBufferCleanupOK(bucket_obuf))
1329 : : {
1330 : 221 : LockBuffer(bucket_nbuf, BUFFER_LOCK_UNLOCK);
1331 : 442 : hashbucketcleanup(rel, obucket, bucket_obuf,
1332 : 221 : BufferGetBlockNumber(bucket_obuf), NULL,
1333 : 221 : maxbucket, highmask, lowmask, NULL, NULL, true,
1334 : : NULL, NULL);
1335 : 221 : }
1336 : : else
1337 : : {
1338 : 0 : LockBuffer(bucket_nbuf, BUFFER_LOCK_UNLOCK);
1339 : 0 : LockBuffer(bucket_obuf, BUFFER_LOCK_UNLOCK);
1340 : : }
1341 : 221 : }
1342 : :
1343 : : /*
1344 : : * _hash_finish_split() -- Finish the previously interrupted split operation
1345 : : *
1346 : : * To complete the split operation, we form the hash table of TIDs in new
1347 : : * bucket which is then used by split operation to skip tuples that are
1348 : : * already moved before the split operation was previously interrupted.
1349 : : *
1350 : : * The caller must hold a pin, but no lock, on the metapage and old bucket's
1351 : : * primary page buffer. The buffers are returned in the same state. (The
1352 : : * metapage is only touched if it becomes necessary to add or remove overflow
1353 : : * pages.)
1354 : : */
1355 : : void
1356 : 0 : _hash_finish_split(Relation rel, Buffer metabuf, Buffer obuf, Bucket obucket,
1357 : : uint32 maxbucket, uint32 highmask, uint32 lowmask)
1358 : : {
1359 : 0 : HASHCTL hash_ctl;
1360 : 0 : HTAB *tidhtab;
1361 : 0 : Buffer bucket_nbuf = InvalidBuffer;
1362 : 0 : Buffer nbuf;
1363 : 0 : Page npage;
1364 : 0 : BlockNumber nblkno;
1365 : 0 : BlockNumber bucket_nblkno;
1366 : 0 : HashPageOpaque npageopaque;
1367 : 0 : Bucket nbucket;
1368 : 0 : bool found;
1369 : :
1370 : : /* Initialize hash tables used to track TIDs */
1371 : 0 : hash_ctl.keysize = sizeof(ItemPointerData);
1372 : 0 : hash_ctl.entrysize = sizeof(ItemPointerData);
1373 : 0 : hash_ctl.hcxt = CurrentMemoryContext;
1374 : :
1375 : 0 : tidhtab =
1376 : 0 : hash_create("bucket ctids",
1377 : : 256, /* arbitrary initial size */
1378 : : &hash_ctl,
1379 : : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
1380 : :
1381 : 0 : bucket_nblkno = nblkno = _hash_get_newblock_from_oldbucket(rel, obucket);
1382 : :
1383 : : /*
1384 : : * Scan the new bucket and build hash table of TIDs
1385 : : */
1386 : 0 : for (;;)
1387 : : {
1388 : 0 : OffsetNumber noffnum;
1389 : 0 : OffsetNumber nmaxoffnum;
1390 : :
1391 : 0 : nbuf = _hash_getbuf(rel, nblkno, HASH_READ,
1392 : : LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
1393 : :
1394 : : /* remember the primary bucket buffer to acquire cleanup lock on it. */
1395 [ # # ]: 0 : if (nblkno == bucket_nblkno)
1396 : 0 : bucket_nbuf = nbuf;
1397 : :
1398 : 0 : npage = BufferGetPage(nbuf);
1399 : 0 : npageopaque = HashPageGetOpaque(npage);
1400 : :
1401 : : /* Scan each tuple in new page */
1402 : 0 : nmaxoffnum = PageGetMaxOffsetNumber(npage);
1403 [ # # ]: 0 : for (noffnum = FirstOffsetNumber;
1404 : 0 : noffnum <= nmaxoffnum;
1405 : 0 : noffnum = OffsetNumberNext(noffnum))
1406 : : {
1407 : 0 : IndexTuple itup;
1408 : :
1409 : : /* Fetch the item's TID and insert it in hash table. */
1410 : 0 : itup = (IndexTuple) PageGetItem(npage,
1411 : 0 : PageGetItemId(npage, noffnum));
1412 : :
1413 : 0 : (void) hash_search(tidhtab, &itup->t_tid, HASH_ENTER, &found);
1414 : :
1415 [ # # ]: 0 : Assert(!found);
1416 : 0 : }
1417 : :
1418 : 0 : nblkno = npageopaque->hasho_nextblkno;
1419 : :
1420 : : /*
1421 : : * release our write lock without modifying buffer and ensure to
1422 : : * retain the pin on primary bucket.
1423 : : */
1424 [ # # ]: 0 : if (nbuf == bucket_nbuf)
1425 : 0 : LockBuffer(nbuf, BUFFER_LOCK_UNLOCK);
1426 : : else
1427 : 0 : _hash_relbuf(rel, nbuf);
1428 : :
1429 : : /* Exit loop if no more overflow pages in new bucket */
1430 [ # # ]: 0 : if (!BlockNumberIsValid(nblkno))
1431 : 0 : break;
1432 [ # # ]: 0 : }
1433 : :
1434 : : /*
1435 : : * Conditionally get the cleanup lock on old and new buckets to perform
1436 : : * the split operation. If we don't get the cleanup locks, silently give
1437 : : * up and next insertion on old bucket will try again to complete the
1438 : : * split.
1439 : : */
1440 [ # # ]: 0 : if (!ConditionalLockBufferForCleanup(obuf))
1441 : : {
1442 : 0 : hash_destroy(tidhtab);
1443 : 0 : return;
1444 : : }
1445 [ # # ]: 0 : if (!ConditionalLockBufferForCleanup(bucket_nbuf))
1446 : : {
1447 : 0 : LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
1448 : 0 : hash_destroy(tidhtab);
1449 : 0 : return;
1450 : : }
1451 : :
1452 : 0 : npage = BufferGetPage(bucket_nbuf);
1453 : 0 : npageopaque = HashPageGetOpaque(npage);
1454 : 0 : nbucket = npageopaque->hasho_bucket;
1455 : :
1456 : 0 : _hash_splitbucket(rel, metabuf, obucket,
1457 : 0 : nbucket, obuf, bucket_nbuf, tidhtab,
1458 : 0 : maxbucket, highmask, lowmask);
1459 : :
1460 : 0 : _hash_dropbuf(rel, bucket_nbuf);
1461 : 0 : hash_destroy(tidhtab);
1462 : 0 : }
1463 : :
1464 : : /*
1465 : : * log_split_page() -- Log the split operation
1466 : : *
1467 : : * We log the split operation when the new page in new bucket gets full,
1468 : : * so we log the entire page.
1469 : : *
1470 : : * 'buf' must be locked by the caller which is also responsible for unlocking
1471 : : * it.
1472 : : */
1473 : : static void
1474 : 234 : log_split_page(Relation rel, Buffer buf)
1475 : : {
1476 [ + - + - : 234 : if (RelationNeedsWAL(rel))
+ + + + ]
1477 : : {
1478 : 108 : XLogRecPtr recptr;
1479 : :
1480 : 108 : XLogBeginInsert();
1481 : :
1482 : 108 : XLogRegisterBuffer(0, buf, REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
1483 : :
1484 : 108 : recptr = XLogInsert(RM_HASH_ID, XLOG_HASH_SPLIT_PAGE);
1485 : :
1486 : 108 : PageSetLSN(BufferGetPage(buf), recptr);
1487 : 108 : }
1488 : 234 : }
1489 : :
1490 : : /*
1491 : : * _hash_getcachedmetap() -- Returns cached metapage data.
1492 : : *
1493 : : * If metabuf is not InvalidBuffer, caller must hold a pin, but no lock, on
1494 : : * the metapage. If not set, we'll set it before returning if we have to
1495 : : * refresh the cache, and return with a pin but no lock on it; caller is
1496 : : * responsible for releasing the pin.
1497 : : *
1498 : : * We refresh the cache if it's not initialized yet or force_refresh is true.
1499 : : */
1500 : : HashMetaPage
1501 : 119787 : _hash_getcachedmetap(Relation rel, Buffer *metabuf, bool force_refresh)
1502 : : {
1503 : 119787 : Page page;
1504 : :
1505 [ + - ]: 119787 : Assert(metabuf);
1506 [ + + + + ]: 119787 : if (force_refresh || rel->rd_amcache == NULL)
1507 : : {
1508 : 143 : char *cache = NULL;
1509 : :
1510 : : /*
1511 : : * It's important that we don't set rd_amcache to an invalid value.
1512 : : * Either MemoryContextAlloc or _hash_getbuf could fail, so don't
1513 : : * install a pointer to the newly-allocated storage in the actual
1514 : : * relcache entry until both have succeeded.
1515 : : */
1516 [ + + ]: 143 : if (rel->rd_amcache == NULL)
1517 : 36 : cache = MemoryContextAlloc(rel->rd_indexcxt,
1518 : : sizeof(HashMetaPageData));
1519 : :
1520 : : /* Read the metapage. */
1521 [ - + ]: 143 : if (BufferIsValid(*metabuf))
1522 : 0 : LockBuffer(*metabuf, BUFFER_LOCK_SHARE);
1523 : : else
1524 : 143 : *metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ,
1525 : : LH_META_PAGE);
1526 : 143 : page = BufferGetPage(*metabuf);
1527 : :
1528 : : /* Populate the cache. */
1529 [ + + ]: 143 : if (rel->rd_amcache == NULL)
1530 : 36 : rel->rd_amcache = cache;
1531 : 143 : memcpy(rel->rd_amcache, HashPageGetMeta(page),
1532 : : sizeof(HashMetaPageData));
1533 : :
1534 : : /* Release metapage lock, but keep the pin. */
1535 : 143 : LockBuffer(*metabuf, BUFFER_LOCK_UNLOCK);
1536 : 143 : }
1537 : :
1538 : 239574 : return (HashMetaPage) rel->rd_amcache;
1539 : 119787 : }
1540 : :
1541 : : /*
1542 : : * _hash_getbucketbuf_from_hashkey() -- Get the bucket's buffer for the given
1543 : : * hashkey.
1544 : : *
1545 : : * Bucket pages do not move or get removed once they are allocated. This give
1546 : : * us an opportunity to use the previously saved metapage contents to reach
1547 : : * the target bucket buffer, instead of reading from the metapage every time.
1548 : : * This saves one buffer access every time we want to reach the target bucket
1549 : : * buffer, which is very helpful savings in bufmgr traffic and contention.
1550 : : *
1551 : : * The access type parameter (HASH_READ or HASH_WRITE) indicates whether the
1552 : : * bucket buffer has to be locked for reading or writing.
1553 : : *
1554 : : * The out parameter cachedmetap is set with metapage contents used for
1555 : : * hashkey to bucket buffer mapping. Some callers need this info to reach the
1556 : : * old bucket in case of bucket split, see _hash_doinsert().
1557 : : */
1558 : : Buffer
1559 : 119676 : _hash_getbucketbuf_from_hashkey(Relation rel, uint32 hashkey, int access,
1560 : : HashMetaPage *cachedmetap)
1561 : : {
1562 : 119676 : HashMetaPage metap;
1563 : 119676 : Buffer buf;
1564 : 119676 : Buffer metabuf = InvalidBuffer;
1565 : 119676 : Page page;
1566 : 119676 : Bucket bucket;
1567 : 119676 : BlockNumber blkno;
1568 : 119676 : HashPageOpaque opaque;
1569 : :
1570 : : /* We read from target bucket buffer, hence locking is must. */
1571 [ + + + - ]: 119676 : Assert(access == HASH_READ || access == HASH_WRITE);
1572 : :
1573 : 119676 : metap = _hash_getcachedmetap(rel, &metabuf, false);
1574 [ + - ]: 119676 : Assert(metap != NULL);
1575 : :
1576 : : /*
1577 : : * Loop until we get a lock on the correct target bucket.
1578 : : */
1579 : 119783 : for (;;)
1580 : : {
1581 : : /*
1582 : : * Compute the target bucket number, and convert to block number.
1583 : : */
1584 : 239566 : bucket = _hash_hashkey2bucket(hashkey,
1585 : 119783 : metap->hashm_maxbucket,
1586 : 119783 : metap->hashm_highmask,
1587 : 119783 : metap->hashm_lowmask);
1588 : :
1589 [ + + ]: 119783 : blkno = BUCKET_TO_BLKNO(metap, bucket);
1590 : :
1591 : : /* Fetch the primary bucket page for the bucket */
1592 : 119783 : buf = _hash_getbuf(rel, blkno, access, LH_BUCKET_PAGE);
1593 : 119783 : page = BufferGetPage(buf);
1594 : 119783 : opaque = HashPageGetOpaque(page);
1595 [ + - ]: 119783 : Assert(opaque->hasho_bucket == bucket);
1596 [ + - ]: 119783 : Assert(opaque->hasho_prevblkno != InvalidBlockNumber);
1597 : :
1598 : : /*
1599 : : * If this bucket hasn't been split, we're done.
1600 : : */
1601 [ + + ]: 119783 : if (opaque->hasho_prevblkno <= metap->hashm_maxbucket)
1602 : 119676 : break;
1603 : :
1604 : : /* Drop lock on this buffer, update cached metapage, and retry. */
1605 : 107 : _hash_relbuf(rel, buf);
1606 : 107 : metap = _hash_getcachedmetap(rel, &metabuf, true);
1607 [ + - ]: 107 : Assert(metap != NULL);
1608 : : }
1609 : :
1610 [ + + ]: 119676 : if (BufferIsValid(metabuf))
1611 : 143 : _hash_dropbuf(rel, metabuf);
1612 : :
1613 [ + + ]: 119676 : if (cachedmetap)
1614 : 119616 : *cachedmetap = metap;
1615 : :
1616 : 239352 : return buf;
1617 : 119676 : }
|
