1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
/*-------------------------------------------------------------------------
*
* hash.c--
* Implementation of Margo Seltzer's Hashing package for postgres.
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/hash/hash.c,v 1.9 1996/11/03 12:34:33 scrappy Exp $
*
* NOTES
* This file contains only the public interface routines.
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/relscan.h"
#include "access/hash.h"
#include "nodes/execnodes.h"
#include "executor/executor.h"
#include "access/heapam.h"
#include "access/genam.h"
#include "utils/palloc.h"
#include "catalog/index.h"
#ifndef HAVE_MEMMOVE
# include "regex/utils.h"
#else
# include <string.h>
#endif
#include "storage/bufmgr.h"
#include "miscadmin.h"
bool BuildingHash = false;
/*
* hashbuild() -- build a new hash index.
*
* We use a global variable to record the fact that we're creating
* a new index. This is used to avoid high-concurrency locking,
* since the index won't be visible until this transaction commits
* and since building is guaranteed to be single-threaded.
*/
void
hashbuild(Relation heap,
Relation index,
int natts,
AttrNumber *attnum,
IndexStrategy istrat,
uint16 pcount,
Datum *params,
FuncIndexInfo *finfo,
PredInfo *predInfo)
{
HeapScanDesc hscan;
Buffer buffer;
HeapTuple htup;
IndexTuple itup;
TupleDesc htupdesc, itupdesc;
Datum *attdata;
bool *nulls;
InsertIndexResult res;
int nhtups, nitups;
int i;
HashItem hitem;
#ifndef OMIT_PARTIAL_INDEX
ExprContext *econtext;
TupleTable tupleTable;
TupleTableSlot *slot;
#endif
Oid hrelid, irelid;
Node *pred, *oldPred;
/* note that this is a new btree */
BuildingHash = true;
pred = predInfo->pred;
oldPred = predInfo->oldPred;
/* initialize the hash index metadata page (if this is a new index) */
if (oldPred == NULL)
_hash_metapinit(index);
/* get tuple descriptors for heap and index relations */
htupdesc = RelationGetTupleDescriptor(heap);
itupdesc = RelationGetTupleDescriptor(index);
/* get space for data items that'll appear in the index tuple */
attdata = (Datum *) palloc(natts * sizeof(Datum));
nulls = (bool *) palloc(natts * sizeof(bool));
/*
* If this is a predicate (partial) index, we will need to evaluate the
* predicate using ExecQual, which requires the current tuple to be in a
* slot of a TupleTable. In addition, ExecQual must have an ExprContext
* referring to that slot. Here, we initialize dummy TupleTable and
* ExprContext objects for this purpose. --Nels, Feb '92
*/
#ifndef OMIT_PARTIAL_INDEX
if (pred != NULL || oldPred != NULL) {
tupleTable = ExecCreateTupleTable(1);
slot = ExecAllocTableSlot(tupleTable);
econtext = makeNode(ExprContext);
FillDummyExprContext(econtext, slot, htupdesc, buffer);
}
else /* quiet the compiler */
{
econtext = NULL;
tupleTable = 0;
slot = 0;
}
#endif /* OMIT_PARTIAL_INDEX */
/* start a heap scan */
hscan = heap_beginscan(heap, 0, NowTimeQual, 0, (ScanKey) NULL);
htup = heap_getnext(hscan, 0, &buffer);
/* build the index */
nhtups = nitups = 0;
for (; HeapTupleIsValid(htup); htup = heap_getnext(hscan, 0, &buffer)) {
nhtups++;
/*
* If oldPred != NULL, this is an EXTEND INDEX command, so skip
* this tuple if it was already in the existing partial index
*/
if (oldPred != NULL) {
/*SetSlotContents(slot, htup); */
#ifndef OMIT_PARTIAL_INDEX
slot->val = htup;
if (ExecQual((List*)oldPred, econtext) == true) {
nitups++;
continue;
}
#endif /* OMIT_PARTIAL_INDEX */
}
/* Skip this tuple if it doesn't satisfy the partial-index predicate */
if (pred != NULL) {
#ifndef OMIT_PARTIAL_INDEX
/*SetSlotContents(slot, htup); */
slot->val = htup;
if (ExecQual((List*)pred, econtext) == false)
continue;
#endif /* OMIT_PARTIAL_INDEX */
}
nitups++;
/*
* For the current heap tuple, extract all the attributes
* we use in this index, and note which are null.
*/
for (i = 1; i <= natts; i++) {
int attoff;
bool attnull;
/*
* Offsets are from the start of the tuple, and are
* zero-based; indices are one-based. The next call
* returns i - 1. That's data hiding for you.
*/
/* attoff = i - 1 */
attoff = AttrNumberGetAttrOffset(i);
/* below, attdata[attoff] set to equal some datum &
* attnull is changed to indicate whether or not the attribute
* is null for this tuple
*/
attdata[attoff] = GetIndexValue(htup,
htupdesc,
attoff,
attnum,
finfo,
&attnull,
buffer);
nulls[attoff] = (attnull ? 'n' : ' ');
}
/* form an index tuple and point it at the heap tuple */
itup = index_formtuple(itupdesc, attdata, nulls);
/*
* If the single index key is null, we don't insert it into
* the index. Hash tables support scans on '='.
* Relational algebra says that A = B
* returns null if either A or B is null. This
* means that no qualification used in an index scan could ever
* return true on a null attribute. It also means that indices
* can't be used by ISNULL or NOTNULL scans, but that's an
* artifact of the strategy map architecture chosen in 1986, not
* of the way nulls are handled here.
*/
if (itup->t_info & INDEX_NULL_MASK) {
pfree(itup);
continue;
}
itup->t_tid = htup->t_ctid;
hitem = _hash_formitem(itup);
res = _hash_doinsert(index, hitem);
pfree(hitem);
pfree(itup);
pfree(res);
}
/* okay, all heap tuples are indexed */
heap_endscan(hscan);
if (pred != NULL || oldPred != NULL) {
#ifndef OMIT_PARTIAL_INDEX
ExecDestroyTupleTable(tupleTable, true);
pfree(econtext);
#endif /* OMIT_PARTIAL_INDEX */
}
/*
* Since we just counted the tuples in the heap, we update its
* stats in pg_class to guarantee that the planner takes advantage
* of the index we just created. Finally, only update statistics
* during normal index definitions, not for indices on system catalogs
* created during bootstrap processing. We must close the relations
* before updatings statistics to guarantee that the relcache entries
* are flushed when we increment the command counter in UpdateStats().
*/
if (IsNormalProcessingMode())
{
hrelid = heap->rd_id;
irelid = index->rd_id;
heap_close(heap);
index_close(index);
UpdateStats(hrelid, nhtups, true);
UpdateStats(irelid, nitups, false);
if (oldPred != NULL) {
if (nitups == nhtups) pred = NULL;
UpdateIndexPredicate(irelid, oldPred, pred);
}
}
/* be tidy */
pfree(nulls);
pfree(attdata);
/* all done */
BuildingHash = false;
}
/*
* hashinsert() -- insert an index tuple into a hash table.
*
* Hash on the index tuple's key, find the appropriate location
* for the new tuple, put it there, and return an InsertIndexResult
* to the caller.
*/
InsertIndexResult
hashinsert(Relation rel, Datum *datum, char *nulls, ItemPointer ht_ctid)
{
HashItem hitem;
IndexTuple itup;
InsertIndexResult res;
/* generate an index tuple */
itup = index_formtuple(RelationGetTupleDescriptor(rel), datum, nulls);
itup->t_tid = *ht_ctid;
if (itup->t_info & INDEX_NULL_MASK)
return ((InsertIndexResult) NULL);
hitem = _hash_formitem(itup);
res = _hash_doinsert(rel, hitem);
pfree(hitem);
pfree(itup);
return (res);
}
/*
* hashgettuple() -- Get the next tuple in the scan.
*/
char *
hashgettuple(IndexScanDesc scan, ScanDirection dir)
{
RetrieveIndexResult res;
/*
* If we've already initialized this scan, we can just advance it
* in the appropriate direction. If we haven't done so yet, we
* call a routine to get the first item in the scan.
*/
if (ItemPointerIsValid(&(scan->currentItemData)))
res = _hash_next(scan, dir);
else
res = _hash_first(scan, dir);
return ((char *) res);
}
/*
* hashbeginscan() -- start a scan on a hash index
*/
char *
hashbeginscan(Relation rel,
bool fromEnd,
uint16 keysz,
ScanKey scankey)
{
IndexScanDesc scan;
HashScanOpaque so;
scan = RelationGetIndexScan(rel, fromEnd, keysz, scankey);
so = (HashScanOpaque) palloc(sizeof(HashScanOpaqueData));
so->hashso_curbuf = so->hashso_mrkbuf = InvalidBuffer;
scan->opaque = so;
scan->flags = 0x0;
/* register scan in case we change pages it's using */
_hash_regscan(scan);
return ((char *) scan);
}
/*
* hashrescan() -- rescan an index relation
*/
void
hashrescan(IndexScanDesc scan, bool fromEnd, ScanKey scankey)
{
ItemPointer iptr;
HashScanOpaque so;
so = (HashScanOpaque) scan->opaque;
/* we hold a read lock on the current page in the scan */
if (ItemPointerIsValid(iptr = &(scan->currentItemData))) {
_hash_relbuf(scan->relation, so->hashso_curbuf, HASH_READ);
so->hashso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
if (ItemPointerIsValid(iptr = &(scan->currentMarkData))) {
_hash_relbuf(scan->relation, so->hashso_mrkbuf, HASH_READ);
so->hashso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* reset the scan key */
if (scan->numberOfKeys > 0) {
memmove(scan->keyData,
scankey,
scan->numberOfKeys * sizeof(ScanKeyData));
}
}
/*
* hashendscan() -- close down a scan
*/
void
hashendscan(IndexScanDesc scan)
{
ItemPointer iptr;
HashScanOpaque so;
so = (HashScanOpaque) scan->opaque;
/* release any locks we still hold */
if (ItemPointerIsValid(iptr = &(scan->currentItemData))) {
_hash_relbuf(scan->relation, so->hashso_curbuf, HASH_READ);
so->hashso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
if (ItemPointerIsValid(iptr = &(scan->currentMarkData))) {
if (BufferIsValid(so->hashso_mrkbuf))
_hash_relbuf(scan->relation, so->hashso_mrkbuf, HASH_READ);
so->hashso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* don't need scan registered anymore */
_hash_dropscan(scan);
/* be tidy */
pfree (scan->opaque);
}
/*
* hashmarkpos() -- save current scan position
*
*/
void
hashmarkpos(IndexScanDesc scan)
{
ItemPointer iptr;
HashScanOpaque so;
/* see if we ever call this code. if we do, then so_mrkbuf a
* useful element in the scan->opaque structure. if this procedure
* is never called, so_mrkbuf should be removed from the scan->opaque
* structure.
*/
elog(NOTICE, "Hashmarkpos() called.");
so = (HashScanOpaque) scan->opaque;
/* release lock on old marked data, if any */
if (ItemPointerIsValid(iptr = &(scan->currentMarkData))) {
_hash_relbuf(scan->relation, so->hashso_mrkbuf, HASH_READ);
so->hashso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* bump lock on currentItemData and copy to currentMarkData */
if (ItemPointerIsValid(&(scan->currentItemData))) {
so->hashso_mrkbuf = _hash_getbuf(scan->relation,
BufferGetBlockNumber(so->hashso_curbuf),
HASH_READ);
scan->currentMarkData = scan->currentItemData;
}
}
/*
* hashrestrpos() -- restore scan to last saved position
*/
void
hashrestrpos(IndexScanDesc scan)
{
ItemPointer iptr;
HashScanOpaque so;
/* see if we ever call this code. if we do, then so_mrkbuf a
* useful element in the scan->opaque structure. if this procedure
* is never called, so_mrkbuf should be removed from the scan->opaque
* structure.
*/
elog(NOTICE, "Hashrestrpos() called.");
so = (HashScanOpaque) scan->opaque;
/* release lock on current data, if any */
if (ItemPointerIsValid(iptr = &(scan->currentItemData))) {
_hash_relbuf(scan->relation, so->hashso_curbuf, HASH_READ);
so->hashso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* bump lock on currentMarkData and copy to currentItemData */
if (ItemPointerIsValid(&(scan->currentMarkData))) {
so->hashso_curbuf =
_hash_getbuf(scan->relation,
BufferGetBlockNumber(so->hashso_mrkbuf),
HASH_READ);
scan->currentItemData = scan->currentMarkData;
}
}
/* stubs */
void
hashdelete(Relation rel, ItemPointer tid)
{
/* adjust any active scans that will be affected by this deletion */
_hash_adjscans(rel, tid);
/* delete the data from the page */
_hash_pagedel(rel, tid);
}