Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * tuplestore.c
4 : * Generalized routines for temporary tuple storage.
5 : *
6 : * This module handles temporary storage of tuples for purposes such
7 : * as Materialize nodes, hashjoin batch files, etc. It is essentially
8 : * a dumbed-down version of tuplesort.c; it does no sorting of tuples
9 : * but can only store and regurgitate a sequence of tuples. However,
10 : * because no sort is required, it is allowed to start reading the sequence
11 : * before it has all been written. This is particularly useful for cursors,
12 : * because it allows random access within the already-scanned portion of
13 : * a query without having to process the underlying scan to completion.
14 : * Also, it is possible to support multiple independent read pointers.
15 : *
16 : * A temporary file is used to handle the data if it exceeds the
17 : * space limit specified by the caller.
18 : *
19 : * The (approximate) amount of memory allowed to the tuplestore is specified
20 : * in kilobytes by the caller. We absorb tuples and simply store them in an
21 : * in-memory array as long as we haven't exceeded maxKBytes. If we do exceed
22 : * maxKBytes, we dump all the tuples into a temp file and then read from that
23 : * when needed.
24 : *
25 : * Upon creation, a tuplestore supports a single read pointer, numbered 0.
26 : * Additional read pointers can be created using tuplestore_alloc_read_pointer.
27 : * Mark/restore behavior is supported by copying read pointers.
28 : *
29 : * When the caller requests backward-scan capability, we write the temp file
30 : * in a format that allows either forward or backward scan. Otherwise, only
31 : * forward scan is allowed. A request for backward scan must be made before
32 : * putting any tuples into the tuplestore. Rewind is normally allowed but
33 : * can be turned off via tuplestore_set_eflags; turning off rewind for all
34 : * read pointers enables truncation of the tuplestore at the oldest read point
35 : * for minimal memory usage. (The caller must explicitly call tuplestore_trim
36 : * at appropriate times for truncation to actually happen.)
37 : *
38 : * Note: in TSS_WRITEFILE state, the temp file's seek position is the
39 : * current write position, and the write-position variables in the tuplestore
40 : * aren't kept up to date. Similarly, in TSS_READFILE state the temp file's
41 : * seek position is the active read pointer's position, and that read pointer
42 : * isn't kept up to date. We update the appropriate variables using ftell()
43 : * before switching to the other state or activating a different read pointer.
44 : *
45 : *
46 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
47 : * Portions Copyright (c) 1994, Regents of the University of California
48 : *
49 : * IDENTIFICATION
50 : * src/backend/utils/sort/tuplestore.c
51 : *
52 : *-------------------------------------------------------------------------
53 : */
54 :
55 : #include "postgres.h"
56 :
57 : #include <limits.h>
58 :
59 : #include "access/htup_details.h"
60 : #include "commands/tablespace.h"
61 : #include "executor/executor.h"
62 : #include "miscadmin.h"
63 : #include "storage/buffile.h"
64 : #include "utils/memutils.h"
65 : #include "utils/resowner.h"
66 :
67 :
68 : /*
69 : * Possible states of a Tuplestore object. These denote the states that
70 : * persist between calls of Tuplestore routines.
71 : */
72 : typedef enum
73 : {
74 : TSS_INMEM, /* Tuples still fit in memory */
75 : TSS_WRITEFILE, /* Writing to temp file */
76 : TSS_READFILE, /* Reading from temp file */
77 : } TupStoreStatus;
78 :
79 : /*
80 : * State for a single read pointer. If we are in state INMEM then all the
81 : * read pointers' "current" fields denote the read positions. In state
82 : * WRITEFILE, the file/offset fields denote the read positions. In state
83 : * READFILE, inactive read pointers have valid file/offset, but the active
84 : * read pointer implicitly has position equal to the temp file's seek position.
85 : *
86 : * Special case: if eof_reached is true, then the pointer's read position is
87 : * implicitly equal to the write position, and current/file/offset aren't
88 : * maintained. This way we need not update all the read pointers each time
89 : * we write.
90 : */
91 : typedef struct
92 : {
93 : int eflags; /* capability flags */
94 : bool eof_reached; /* read has reached EOF */
95 : int current; /* next array index to read */
96 : int file; /* temp file# */
97 : off_t offset; /* byte offset in file */
98 : } TSReadPointer;
99 :
100 : /*
101 : * Private state of a Tuplestore operation.
102 : */
103 : struct Tuplestorestate
104 : {
105 : TupStoreStatus status; /* enumerated value as shown above */
106 : int eflags; /* capability flags (OR of pointers' flags) */
107 : bool backward; /* store extra length words in file? */
108 : bool interXact; /* keep open through transactions? */
109 : bool truncated; /* tuplestore_trim has removed tuples? */
110 : int64 availMem; /* remaining memory available, in bytes */
111 : int64 allowedMem; /* total memory allowed, in bytes */
112 : int64 tuples; /* number of tuples added */
113 : BufFile *myfile; /* underlying file, or NULL if none */
114 : MemoryContext context; /* memory context for holding tuples */
115 : ResourceOwner resowner; /* resowner for holding temp files */
116 :
117 : /*
118 : * These function pointers decouple the routines that must know what kind
119 : * of tuple we are handling from the routines that don't need to know it.
120 : * They are set up by the tuplestore_begin_xxx routines.
121 : *
122 : * (Although tuplestore.c currently only supports heap tuples, I've copied
123 : * this part of tuplesort.c so that extension to other kinds of objects
124 : * will be easy if it's ever needed.)
125 : *
126 : * Function to copy a supplied input tuple into palloc'd space. (NB: we
127 : * assume that a single pfree() is enough to release the tuple later, so
128 : * the representation must be "flat" in one palloc chunk.) state->availMem
129 : * must be decreased by the amount of space used.
130 : */
131 : void *(*copytup) (Tuplestorestate *state, void *tup);
132 :
133 : /*
134 : * Function to write a stored tuple onto tape. The representation of the
135 : * tuple on tape need not be the same as it is in memory; requirements on
136 : * the tape representation are given below. After writing the tuple,
137 : * pfree() it, and increase state->availMem by the amount of memory space
138 : * thereby released.
139 : */
140 : void (*writetup) (Tuplestorestate *state, void *tup);
141 :
142 : /*
143 : * Function to read a stored tuple from tape back into memory. 'len' is
144 : * the already-read length of the stored tuple. Create and return a
145 : * palloc'd copy, and decrease state->availMem by the amount of memory
146 : * space consumed.
147 : */
148 : void *(*readtup) (Tuplestorestate *state, unsigned int len);
149 :
150 : /*
151 : * This array holds pointers to tuples in memory if we are in state INMEM.
152 : * In states WRITEFILE and READFILE it's not used.
153 : *
154 : * When memtupdeleted > 0, the first memtupdeleted pointers are already
155 : * released due to a tuplestore_trim() operation, but we haven't expended
156 : * the effort to slide the remaining pointers down. These unused pointers
157 : * are set to NULL to catch any invalid accesses. Note that memtupcount
158 : * includes the deleted pointers.
159 : */
160 : void **memtuples; /* array of pointers to palloc'd tuples */
161 : int memtupdeleted; /* the first N slots are currently unused */
162 : int memtupcount; /* number of tuples currently present */
163 : int memtupsize; /* allocated length of memtuples array */
164 : bool growmemtuples; /* memtuples' growth still underway? */
165 :
166 : /*
167 : * These variables are used to keep track of the current positions.
168 : *
169 : * In state WRITEFILE, the current file seek position is the write point;
170 : * in state READFILE, the write position is remembered in writepos_xxx.
171 : * (The write position is the same as EOF, but since BufFileSeek doesn't
172 : * currently implement SEEK_END, we have to remember it explicitly.)
173 : */
174 : TSReadPointer *readptrs; /* array of read pointers */
175 : int activeptr; /* index of the active read pointer */
176 : int readptrcount; /* number of pointers currently valid */
177 : int readptrsize; /* allocated length of readptrs array */
178 :
179 : int writepos_file; /* file# (valid if READFILE state) */
180 : off_t writepos_offset; /* offset (valid if READFILE state) */
181 : };
182 :
183 : #define COPYTUP(state,tup) ((*(state)->copytup) (state, tup))
184 : #define WRITETUP(state,tup) ((*(state)->writetup) (state, tup))
185 : #define READTUP(state,len) ((*(state)->readtup) (state, len))
186 : #define LACKMEM(state) ((state)->availMem < 0)
187 : #define USEMEM(state,amt) ((state)->availMem -= (amt))
188 : #define FREEMEM(state,amt) ((state)->availMem += (amt))
189 :
190 : /*--------------------
191 : *
192 : * NOTES about on-tape representation of tuples:
193 : *
194 : * We require the first "unsigned int" of a stored tuple to be the total size
195 : * on-tape of the tuple, including itself (so it is never zero).
196 : * The remainder of the stored tuple
197 : * may or may not match the in-memory representation of the tuple ---
198 : * any conversion needed is the job of the writetup and readtup routines.
199 : *
200 : * If state->backward is true, then the stored representation of
201 : * the tuple must be followed by another "unsigned int" that is a copy of the
202 : * length --- so the total tape space used is actually sizeof(unsigned int)
203 : * more than the stored length value. This allows read-backwards. When
204 : * state->backward is not set, the write/read routines may omit the extra
205 : * length word.
206 : *
207 : * writetup is expected to write both length words as well as the tuple
208 : * data. When readtup is called, the tape is positioned just after the
209 : * front length word; readtup must read the tuple data and advance past
210 : * the back length word (if present).
211 : *
212 : * The write/read routines can make use of the tuple description data
213 : * stored in the Tuplestorestate record, if needed. They are also expected
214 : * to adjust state->availMem by the amount of memory space (not tape space!)
215 : * released or consumed. There is no error return from either writetup
216 : * or readtup; they should ereport() on failure.
217 : *
218 : *
219 : * NOTES about memory consumption calculations:
220 : *
221 : * We count space allocated for tuples against the maxKBytes limit,
222 : * plus the space used by the variable-size array memtuples.
223 : * Fixed-size space (primarily the BufFile I/O buffer) is not counted.
224 : * We don't worry about the size of the read pointer array, either.
225 : *
226 : * Note that we count actual space used (as shown by GetMemoryChunkSpace)
227 : * rather than the originally-requested size. This is important since
228 : * palloc can add substantial overhead. It's not a complete answer since
229 : * we won't count any wasted space in palloc allocation blocks, but it's
230 : * a lot better than what we were doing before 7.3.
231 : *
232 : *--------------------
233 : */
234 :
235 :
236 : static Tuplestorestate *tuplestore_begin_common(int eflags,
237 : bool interXact,
238 : int maxKBytes);
239 : static void tuplestore_puttuple_common(Tuplestorestate *state, void *tuple);
240 : static void dumptuples(Tuplestorestate *state);
241 : static unsigned int getlen(Tuplestorestate *state, bool eofOK);
242 : static void *copytup_heap(Tuplestorestate *state, void *tup);
243 : static void writetup_heap(Tuplestorestate *state, void *tup);
244 : static void *readtup_heap(Tuplestorestate *state, unsigned int len);
245 :
246 :
247 : /*
248 : * tuplestore_begin_xxx
249 : *
250 : * Initialize for a tuple store operation.
251 : */
252 : static Tuplestorestate *
253 246998 : tuplestore_begin_common(int eflags, bool interXact, int maxKBytes)
254 : {
255 : Tuplestorestate *state;
256 :
257 246998 : state = (Tuplestorestate *) palloc0(sizeof(Tuplestorestate));
258 :
259 246998 : state->status = TSS_INMEM;
260 246998 : state->eflags = eflags;
261 246998 : state->interXact = interXact;
262 246998 : state->truncated = false;
263 246998 : state->allowedMem = maxKBytes * 1024L;
264 246998 : state->availMem = state->allowedMem;
265 246998 : state->myfile = NULL;
266 246998 : state->context = CurrentMemoryContext;
267 246998 : state->resowner = CurrentResourceOwner;
268 :
269 246998 : state->memtupdeleted = 0;
270 246998 : state->memtupcount = 0;
271 246998 : state->tuples = 0;
272 :
273 : /*
274 : * Initial size of array must be more than ALLOCSET_SEPARATE_THRESHOLD;
275 : * see comments in grow_memtuples().
276 : */
277 246998 : state->memtupsize = Max(16384 / sizeof(void *),
278 : ALLOCSET_SEPARATE_THRESHOLD / sizeof(void *) + 1);
279 :
280 246998 : state->growmemtuples = true;
281 246998 : state->memtuples = (void **) palloc(state->memtupsize * sizeof(void *));
282 :
283 246998 : USEMEM(state, GetMemoryChunkSpace(state->memtuples));
284 :
285 246998 : state->activeptr = 0;
286 246998 : state->readptrcount = 1;
287 246998 : state->readptrsize = 8; /* arbitrary */
288 246998 : state->readptrs = (TSReadPointer *)
289 246998 : palloc(state->readptrsize * sizeof(TSReadPointer));
290 :
291 246998 : state->readptrs[0].eflags = eflags;
292 246998 : state->readptrs[0].eof_reached = false;
293 246998 : state->readptrs[0].current = 0;
294 :
295 246998 : return state;
296 : }
297 :
298 : /*
299 : * tuplestore_begin_heap
300 : *
301 : * Create a new tuplestore; other types of tuple stores (other than
302 : * "heap" tuple stores, for heap tuples) are possible, but not presently
303 : * implemented.
304 : *
305 : * randomAccess: if true, both forward and backward accesses to the
306 : * tuple store are allowed.
307 : *
308 : * interXact: if true, the files used for on-disk storage persist beyond the
309 : * end of the current transaction. NOTE: It's the caller's responsibility to
310 : * create such a tuplestore in a memory context and resource owner that will
311 : * also survive transaction boundaries, and to ensure the tuplestore is closed
312 : * when it's no longer wanted.
313 : *
314 : * maxKBytes: how much data to store in memory (any data beyond this
315 : * amount is paged to disk). When in doubt, use work_mem.
316 : */
317 : Tuplestorestate *
318 246998 : tuplestore_begin_heap(bool randomAccess, bool interXact, int maxKBytes)
319 : {
320 : Tuplestorestate *state;
321 : int eflags;
322 :
323 : /*
324 : * This interpretation of the meaning of randomAccess is compatible with
325 : * the pre-8.3 behavior of tuplestores.
326 : */
327 246998 : eflags = randomAccess ?
328 246998 : (EXEC_FLAG_BACKWARD | EXEC_FLAG_REWIND) :
329 : (EXEC_FLAG_REWIND);
330 :
331 246998 : state = tuplestore_begin_common(eflags, interXact, maxKBytes);
332 :
333 246998 : state->copytup = copytup_heap;
334 246998 : state->writetup = writetup_heap;
335 246998 : state->readtup = readtup_heap;
336 :
337 246998 : return state;
338 : }
339 :
340 : /*
341 : * tuplestore_set_eflags
342 : *
343 : * Set the capability flags for read pointer 0 at a finer grain than is
344 : * allowed by tuplestore_begin_xxx. This must be called before inserting
345 : * any data into the tuplestore.
346 : *
347 : * eflags is a bitmask following the meanings used for executor node
348 : * startup flags (see executor.h). tuplestore pays attention to these bits:
349 : * EXEC_FLAG_REWIND need rewind to start
350 : * EXEC_FLAG_BACKWARD need backward fetch
351 : * If tuplestore_set_eflags is not called, REWIND is allowed, and BACKWARD
352 : * is set per "randomAccess" in the tuplestore_begin_xxx call.
353 : *
354 : * NOTE: setting BACKWARD without REWIND means the pointer can read backwards,
355 : * but not further than the truncation point (the furthest-back read pointer
356 : * position at the time of the last tuplestore_trim call).
357 : */
358 : void
359 8212 : tuplestore_set_eflags(Tuplestorestate *state, int eflags)
360 : {
361 : int i;
362 :
363 8212 : if (state->status != TSS_INMEM || state->memtupcount != 0)
364 0 : elog(ERROR, "too late to call tuplestore_set_eflags");
365 :
366 8212 : state->readptrs[0].eflags = eflags;
367 8212 : for (i = 1; i < state->readptrcount; i++)
368 0 : eflags |= state->readptrs[i].eflags;
369 8212 : state->eflags = eflags;
370 8212 : }
371 :
372 : /*
373 : * tuplestore_alloc_read_pointer - allocate another read pointer.
374 : *
375 : * Returns the pointer's index.
376 : *
377 : * The new pointer initially copies the position of read pointer 0.
378 : * It can have its own eflags, but if any data has been inserted into
379 : * the tuplestore, these eflags must not represent an increase in
380 : * requirements.
381 : */
382 : int
383 12250 : tuplestore_alloc_read_pointer(Tuplestorestate *state, int eflags)
384 : {
385 : /* Check for possible increase of requirements */
386 12250 : if (state->status != TSS_INMEM || state->memtupcount != 0)
387 : {
388 614 : if ((state->eflags | eflags) != state->eflags)
389 0 : elog(ERROR, "too late to require new tuplestore eflags");
390 : }
391 :
392 : /* Make room for another read pointer if needed */
393 12250 : if (state->readptrcount >= state->readptrsize)
394 : {
395 12 : int newcnt = state->readptrsize * 2;
396 :
397 12 : state->readptrs = (TSReadPointer *)
398 12 : repalloc(state->readptrs, newcnt * sizeof(TSReadPointer));
399 12 : state->readptrsize = newcnt;
400 : }
401 :
402 : /* And set it up */
403 12250 : state->readptrs[state->readptrcount] = state->readptrs[0];
404 12250 : state->readptrs[state->readptrcount].eflags = eflags;
405 :
406 12250 : state->eflags |= eflags;
407 :
408 12250 : return state->readptrcount++;
409 : }
410 :
411 : /*
412 : * tuplestore_clear
413 : *
414 : * Delete all the contents of a tuplestore, and reset its read pointers
415 : * to the start.
416 : */
417 : void
418 122842 : tuplestore_clear(Tuplestorestate *state)
419 : {
420 : int i;
421 : TSReadPointer *readptr;
422 :
423 122842 : if (state->myfile)
424 0 : BufFileClose(state->myfile);
425 122842 : state->myfile = NULL;
426 122842 : if (state->memtuples)
427 : {
428 257178 : for (i = state->memtupdeleted; i < state->memtupcount; i++)
429 : {
430 134336 : FREEMEM(state, GetMemoryChunkSpace(state->memtuples[i]));
431 134336 : pfree(state->memtuples[i]);
432 : }
433 : }
434 122842 : state->status = TSS_INMEM;
435 122842 : state->truncated = false;
436 122842 : state->memtupdeleted = 0;
437 122842 : state->memtupcount = 0;
438 122842 : state->tuples = 0;
439 122842 : readptr = state->readptrs;
440 246368 : for (i = 0; i < state->readptrcount; readptr++, i++)
441 : {
442 123526 : readptr->eof_reached = false;
443 123526 : readptr->current = 0;
444 : }
445 122842 : }
446 :
447 : /*
448 : * tuplestore_end
449 : *
450 : * Release resources and clean up.
451 : */
452 : void
453 209098 : tuplestore_end(Tuplestorestate *state)
454 : {
455 : int i;
456 :
457 209098 : if (state->myfile)
458 104 : BufFileClose(state->myfile);
459 209098 : if (state->memtuples)
460 : {
461 10150194 : for (i = state->memtupdeleted; i < state->memtupcount; i++)
462 9941096 : pfree(state->memtuples[i]);
463 209098 : pfree(state->memtuples);
464 : }
465 209098 : pfree(state->readptrs);
466 209098 : pfree(state);
467 209098 : }
468 :
469 : /*
470 : * tuplestore_select_read_pointer - make the specified read pointer active
471 : */
472 : void
473 3813358 : tuplestore_select_read_pointer(Tuplestorestate *state, int ptr)
474 : {
475 : TSReadPointer *readptr;
476 : TSReadPointer *oldptr;
477 :
478 : Assert(ptr >= 0 && ptr < state->readptrcount);
479 :
480 : /* No work if already active */
481 3813358 : if (ptr == state->activeptr)
482 852080 : return;
483 :
484 2961278 : readptr = &state->readptrs[ptr];
485 2961278 : oldptr = &state->readptrs[state->activeptr];
486 :
487 2961278 : switch (state->status)
488 : {
489 2961278 : case TSS_INMEM:
490 : case TSS_WRITEFILE:
491 : /* no work */
492 2961278 : break;
493 0 : case TSS_READFILE:
494 :
495 : /*
496 : * First, save the current read position in the pointer about to
497 : * become inactive.
498 : */
499 0 : if (!oldptr->eof_reached)
500 0 : BufFileTell(state->myfile,
501 : &oldptr->file,
502 : &oldptr->offset);
503 :
504 : /*
505 : * We have to make the temp file's seek position equal to the
506 : * logical position of the new read pointer. In eof_reached
507 : * state, that's the EOF, which we have available from the saved
508 : * write position.
509 : */
510 0 : if (readptr->eof_reached)
511 : {
512 0 : if (BufFileSeek(state->myfile,
513 : state->writepos_file,
514 : state->writepos_offset,
515 : SEEK_SET) != 0)
516 0 : ereport(ERROR,
517 : (errcode_for_file_access(),
518 : errmsg("could not seek in tuplestore temporary file")));
519 : }
520 : else
521 : {
522 0 : if (BufFileSeek(state->myfile,
523 : readptr->file,
524 : readptr->offset,
525 : SEEK_SET) != 0)
526 0 : ereport(ERROR,
527 : (errcode_for_file_access(),
528 : errmsg("could not seek in tuplestore temporary file")));
529 : }
530 0 : break;
531 0 : default:
532 0 : elog(ERROR, "invalid tuplestore state");
533 : break;
534 : }
535 :
536 2961278 : state->activeptr = ptr;
537 : }
538 :
539 : /*
540 : * tuplestore_tuple_count
541 : *
542 : * Returns the number of tuples added since creation or the last
543 : * tuplestore_clear().
544 : */
545 : int64
546 6344 : tuplestore_tuple_count(Tuplestorestate *state)
547 : {
548 6344 : return state->tuples;
549 : }
550 :
551 : /*
552 : * tuplestore_ateof
553 : *
554 : * Returns the active read pointer's eof_reached state.
555 : */
556 : bool
557 2435872 : tuplestore_ateof(Tuplestorestate *state)
558 : {
559 2435872 : return state->readptrs[state->activeptr].eof_reached;
560 : }
561 :
562 : /*
563 : * Grow the memtuples[] array, if possible within our memory constraint. We
564 : * must not exceed INT_MAX tuples in memory or the caller-provided memory
565 : * limit. Return true if we were able to enlarge the array, false if not.
566 : *
567 : * Normally, at each increment we double the size of the array. When doing
568 : * that would exceed a limit, we attempt one last, smaller increase (and then
569 : * clear the growmemtuples flag so we don't try any more). That allows us to
570 : * use memory as fully as permitted; sticking to the pure doubling rule could
571 : * result in almost half going unused. Because availMem moves around with
572 : * tuple addition/removal, we need some rule to prevent making repeated small
573 : * increases in memtupsize, which would just be useless thrashing. The
574 : * growmemtuples flag accomplishes that and also prevents useless
575 : * recalculations in this function.
576 : */
577 : static bool
578 1888 : grow_memtuples(Tuplestorestate *state)
579 : {
580 : int newmemtupsize;
581 1888 : int memtupsize = state->memtupsize;
582 1888 : int64 memNowUsed = state->allowedMem - state->availMem;
583 :
584 : /* Forget it if we've already maxed out memtuples, per comment above */
585 1888 : if (!state->growmemtuples)
586 42 : return false;
587 :
588 : /* Select new value of memtupsize */
589 1846 : if (memNowUsed <= state->availMem)
590 : {
591 : /*
592 : * We've used no more than half of allowedMem; double our usage,
593 : * clamping at INT_MAX tuples.
594 : */
595 1780 : if (memtupsize < INT_MAX / 2)
596 1780 : newmemtupsize = memtupsize * 2;
597 : else
598 : {
599 0 : newmemtupsize = INT_MAX;
600 0 : state->growmemtuples = false;
601 : }
602 : }
603 : else
604 : {
605 : /*
606 : * This will be the last increment of memtupsize. Abandon doubling
607 : * strategy and instead increase as much as we safely can.
608 : *
609 : * To stay within allowedMem, we can't increase memtupsize by more
610 : * than availMem / sizeof(void *) elements. In practice, we want to
611 : * increase it by considerably less, because we need to leave some
612 : * space for the tuples to which the new array slots will refer. We
613 : * assume the new tuples will be about the same size as the tuples
614 : * we've already seen, and thus we can extrapolate from the space
615 : * consumption so far to estimate an appropriate new size for the
616 : * memtuples array. The optimal value might be higher or lower than
617 : * this estimate, but it's hard to know that in advance. We again
618 : * clamp at INT_MAX tuples.
619 : *
620 : * This calculation is safe against enlarging the array so much that
621 : * LACKMEM becomes true, because the memory currently used includes
622 : * the present array; thus, there would be enough allowedMem for the
623 : * new array elements even if no other memory were currently used.
624 : *
625 : * We do the arithmetic in float8, because otherwise the product of
626 : * memtupsize and allowedMem could overflow. Any inaccuracy in the
627 : * result should be insignificant; but even if we computed a
628 : * completely insane result, the checks below will prevent anything
629 : * really bad from happening.
630 : */
631 : double grow_ratio;
632 :
633 66 : grow_ratio = (double) state->allowedMem / (double) memNowUsed;
634 66 : if (memtupsize * grow_ratio < INT_MAX)
635 66 : newmemtupsize = (int) (memtupsize * grow_ratio);
636 : else
637 0 : newmemtupsize = INT_MAX;
638 :
639 : /* We won't make any further enlargement attempts */
640 66 : state->growmemtuples = false;
641 : }
642 :
643 : /* Must enlarge array by at least one element, else report failure */
644 1846 : if (newmemtupsize <= memtupsize)
645 0 : goto noalloc;
646 :
647 : /*
648 : * On a 32-bit machine, allowedMem could exceed MaxAllocHugeSize. Clamp
649 : * to ensure our request won't be rejected. Note that we can easily
650 : * exhaust address space before facing this outcome. (This is presently
651 : * impossible due to guc.c's MAX_KILOBYTES limitation on work_mem, but
652 : * don't rely on that at this distance.)
653 : */
654 1846 : if ((Size) newmemtupsize >= MaxAllocHugeSize / sizeof(void *))
655 : {
656 0 : newmemtupsize = (int) (MaxAllocHugeSize / sizeof(void *));
657 0 : state->growmemtuples = false; /* can't grow any more */
658 : }
659 :
660 : /*
661 : * We need to be sure that we do not cause LACKMEM to become true, else
662 : * the space management algorithm will go nuts. The code above should
663 : * never generate a dangerous request, but to be safe, check explicitly
664 : * that the array growth fits within availMem. (We could still cause
665 : * LACKMEM if the memory chunk overhead associated with the memtuples
666 : * array were to increase. That shouldn't happen because we chose the
667 : * initial array size large enough to ensure that palloc will be treating
668 : * both old and new arrays as separate chunks. But we'll check LACKMEM
669 : * explicitly below just in case.)
670 : */
671 1846 : if (state->availMem < (int64) ((newmemtupsize - memtupsize) * sizeof(void *)))
672 0 : goto noalloc;
673 :
674 : /* OK, do it */
675 1846 : FREEMEM(state, GetMemoryChunkSpace(state->memtuples));
676 1846 : state->memtupsize = newmemtupsize;
677 1846 : state->memtuples = (void **)
678 1846 : repalloc_huge(state->memtuples,
679 1846 : state->memtupsize * sizeof(void *));
680 1846 : USEMEM(state, GetMemoryChunkSpace(state->memtuples));
681 1846 : if (LACKMEM(state))
682 0 : elog(ERROR, "unexpected out-of-memory situation in tuplestore");
683 1846 : return true;
684 :
685 0 : noalloc:
686 : /* If for any reason we didn't realloc, shut off future attempts */
687 0 : state->growmemtuples = false;
688 0 : return false;
689 : }
690 :
691 : /*
692 : * Accept one tuple and append it to the tuplestore.
693 : *
694 : * Note that the input tuple is always copied; the caller need not save it.
695 : *
696 : * If the active read pointer is currently "at EOF", it remains so (the read
697 : * pointer implicitly advances along with the write pointer); otherwise the
698 : * read pointer is unchanged. Non-active read pointers do not move, which
699 : * means they are certain to not be "at EOF" immediately after puttuple.
700 : * This curious-seeming behavior is for the convenience of nodeMaterial.c and
701 : * nodeCtescan.c, which would otherwise need to do extra pointer repositioning
702 : * steps.
703 : *
704 : * tuplestore_puttupleslot() is a convenience routine to collect data from
705 : * a TupleTableSlot without an extra copy operation.
706 : */
707 : void
708 1960336 : tuplestore_puttupleslot(Tuplestorestate *state,
709 : TupleTableSlot *slot)
710 : {
711 : MinimalTuple tuple;
712 1960336 : MemoryContext oldcxt = MemoryContextSwitchTo(state->context);
713 :
714 : /*
715 : * Form a MinimalTuple in working memory
716 : */
717 1960336 : tuple = ExecCopySlotMinimalTuple(slot);
718 1960336 : USEMEM(state, GetMemoryChunkSpace(tuple));
719 :
720 1960336 : tuplestore_puttuple_common(state, (void *) tuple);
721 :
722 1960336 : MemoryContextSwitchTo(oldcxt);
723 1960336 : }
724 :
725 : /*
726 : * "Standard" case to copy from a HeapTuple. This is actually now somewhat
727 : * deprecated, but not worth getting rid of in view of the number of callers.
728 : */
729 : void
730 1607768 : tuplestore_puttuple(Tuplestorestate *state, HeapTuple tuple)
731 : {
732 1607768 : MemoryContext oldcxt = MemoryContextSwitchTo(state->context);
733 :
734 : /*
735 : * Copy the tuple. (Must do this even in WRITEFILE case. Note that
736 : * COPYTUP includes USEMEM, so we needn't do that here.)
737 : */
738 1607768 : tuple = COPYTUP(state, tuple);
739 :
740 1607768 : tuplestore_puttuple_common(state, (void *) tuple);
741 :
742 1607768 : MemoryContextSwitchTo(oldcxt);
743 1607768 : }
744 :
745 : /*
746 : * Similar to tuplestore_puttuple(), but work from values + nulls arrays.
747 : * This avoids an extra tuple-construction operation.
748 : */
749 : void
750 16381224 : tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
751 : const Datum *values, const bool *isnull)
752 : {
753 : MinimalTuple tuple;
754 16381224 : MemoryContext oldcxt = MemoryContextSwitchTo(state->context);
755 :
756 16381224 : tuple = heap_form_minimal_tuple(tdesc, values, isnull);
757 16381224 : USEMEM(state, GetMemoryChunkSpace(tuple));
758 :
759 16381224 : tuplestore_puttuple_common(state, (void *) tuple);
760 :
761 16381224 : MemoryContextSwitchTo(oldcxt);
762 16381224 : }
763 :
764 : static void
765 19949328 : tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
766 : {
767 : TSReadPointer *readptr;
768 : int i;
769 : ResourceOwner oldowner;
770 :
771 19949328 : state->tuples++;
772 :
773 19949328 : switch (state->status)
774 : {
775 13801174 : case TSS_INMEM:
776 :
777 : /*
778 : * Update read pointers as needed; see API spec above.
779 : */
780 13801174 : readptr = state->readptrs;
781 29867718 : for (i = 0; i < state->readptrcount; readptr++, i++)
782 : {
783 16066544 : if (readptr->eof_reached && i != state->activeptr)
784 : {
785 454 : readptr->eof_reached = false;
786 454 : readptr->current = state->memtupcount;
787 : }
788 : }
789 :
790 : /*
791 : * Grow the array as needed. Note that we try to grow the array
792 : * when there is still one free slot remaining --- if we fail,
793 : * there'll still be room to store the incoming tuple, and then
794 : * we'll switch to tape-based operation.
795 : */
796 13801174 : if (state->memtupcount >= state->memtupsize - 1)
797 : {
798 1888 : (void) grow_memtuples(state);
799 : Assert(state->memtupcount < state->memtupsize);
800 : }
801 :
802 : /* Stash the tuple in the in-memory array */
803 13801174 : state->memtuples[state->memtupcount++] = tuple;
804 :
805 : /*
806 : * Done if we still fit in available memory and have array slots.
807 : */
808 13801174 : if (state->memtupcount < state->memtupsize && !LACKMEM(state))
809 13801066 : return;
810 :
811 : /*
812 : * Nope; time to switch to tape-based operation. Make sure that
813 : * the temp file(s) are created in suitable temp tablespaces.
814 : */
815 108 : PrepareTempTablespaces();
816 :
817 : /* associate the file with the store's resource owner */
818 108 : oldowner = CurrentResourceOwner;
819 108 : CurrentResourceOwner = state->resowner;
820 :
821 108 : state->myfile = BufFileCreateTemp(state->interXact);
822 :
823 108 : CurrentResourceOwner = oldowner;
824 :
825 : /*
826 : * Freeze the decision about whether trailing length words will be
827 : * used. We can't change this choice once data is on tape, even
828 : * though callers might drop the requirement.
829 : */
830 108 : state->backward = (state->eflags & EXEC_FLAG_BACKWARD) != 0;
831 108 : state->status = TSS_WRITEFILE;
832 108 : dumptuples(state);
833 108 : break;
834 6148154 : case TSS_WRITEFILE:
835 :
836 : /*
837 : * Update read pointers as needed; see API spec above. Note:
838 : * BufFileTell is quite cheap, so not worth trying to avoid
839 : * multiple calls.
840 : */
841 6148154 : readptr = state->readptrs;
842 12296308 : for (i = 0; i < state->readptrcount; readptr++, i++)
843 : {
844 6148154 : if (readptr->eof_reached && i != state->activeptr)
845 : {
846 0 : readptr->eof_reached = false;
847 0 : BufFileTell(state->myfile,
848 : &readptr->file,
849 : &readptr->offset);
850 : }
851 : }
852 :
853 6148154 : WRITETUP(state, tuple);
854 6148154 : break;
855 0 : case TSS_READFILE:
856 :
857 : /*
858 : * Switch from reading to writing.
859 : */
860 0 : if (!state->readptrs[state->activeptr].eof_reached)
861 0 : BufFileTell(state->myfile,
862 0 : &state->readptrs[state->activeptr].file,
863 0 : &state->readptrs[state->activeptr].offset);
864 0 : if (BufFileSeek(state->myfile,
865 : state->writepos_file, state->writepos_offset,
866 : SEEK_SET) != 0)
867 0 : ereport(ERROR,
868 : (errcode_for_file_access(),
869 : errmsg("could not seek in tuplestore temporary file")));
870 0 : state->status = TSS_WRITEFILE;
871 :
872 : /*
873 : * Update read pointers as needed; see API spec above.
874 : */
875 0 : readptr = state->readptrs;
876 0 : for (i = 0; i < state->readptrcount; readptr++, i++)
877 : {
878 0 : if (readptr->eof_reached && i != state->activeptr)
879 : {
880 0 : readptr->eof_reached = false;
881 0 : readptr->file = state->writepos_file;
882 0 : readptr->offset = state->writepos_offset;
883 : }
884 : }
885 :
886 0 : WRITETUP(state, tuple);
887 0 : break;
888 0 : default:
889 0 : elog(ERROR, "invalid tuplestore state");
890 : break;
891 : }
892 : }
893 :
894 : /*
895 : * Fetch the next tuple in either forward or back direction.
896 : * Returns NULL if no more tuples. If should_free is set, the
897 : * caller must pfree the returned tuple when done with it.
898 : *
899 : * Backward scan is only allowed if randomAccess was set true or
900 : * EXEC_FLAG_BACKWARD was specified to tuplestore_set_eflags().
901 : */
902 : static void *
903 20437344 : tuplestore_gettuple(Tuplestorestate *state, bool forward,
904 : bool *should_free)
905 : {
906 20437344 : TSReadPointer *readptr = &state->readptrs[state->activeptr];
907 : unsigned int tuplen;
908 : void *tup;
909 :
910 : Assert(forward || (readptr->eflags & EXEC_FLAG_BACKWARD));
911 :
912 20437344 : switch (state->status)
913 : {
914 14263448 : case TSS_INMEM:
915 14263448 : *should_free = false;
916 14263448 : if (forward)
917 : {
918 14088196 : if (readptr->eof_reached)
919 180 : return NULL;
920 14088016 : if (readptr->current < state->memtupcount)
921 : {
922 : /* We have another tuple, so return it */
923 13737684 : return state->memtuples[readptr->current++];
924 : }
925 350332 : readptr->eof_reached = true;
926 350332 : return NULL;
927 : }
928 : else
929 : {
930 : /*
931 : * if all tuples are fetched already then we return last
932 : * tuple, else tuple before last returned.
933 : */
934 175252 : if (readptr->eof_reached)
935 : {
936 2596 : readptr->current = state->memtupcount;
937 2596 : readptr->eof_reached = false;
938 : }
939 : else
940 : {
941 172656 : if (readptr->current <= state->memtupdeleted)
942 : {
943 : Assert(!state->truncated);
944 0 : return NULL;
945 : }
946 172656 : readptr->current--; /* last returned tuple */
947 : }
948 175252 : if (readptr->current <= state->memtupdeleted)
949 : {
950 : Assert(!state->truncated);
951 30 : return NULL;
952 : }
953 175222 : return state->memtuples[readptr->current - 1];
954 : }
955 : break;
956 :
957 106 : case TSS_WRITEFILE:
958 : /* Skip state change if we'll just return NULL */
959 106 : if (readptr->eof_reached && forward)
960 0 : return NULL;
961 :
962 : /*
963 : * Switch from writing to reading.
964 : */
965 106 : BufFileTell(state->myfile,
966 : &state->writepos_file, &state->writepos_offset);
967 106 : if (!readptr->eof_reached)
968 106 : if (BufFileSeek(state->myfile,
969 : readptr->file, readptr->offset,
970 : SEEK_SET) != 0)
971 0 : ereport(ERROR,
972 : (errcode_for_file_access(),
973 : errmsg("could not seek in tuplestore temporary file")));
974 106 : state->status = TSS_READFILE;
975 : /* FALLTHROUGH */
976 :
977 6173896 : case TSS_READFILE:
978 6173896 : *should_free = true;
979 6173896 : if (forward)
980 : {
981 6173884 : if ((tuplen = getlen(state, true)) != 0)
982 : {
983 6173790 : tup = READTUP(state, tuplen);
984 6173790 : return tup;
985 : }
986 : else
987 : {
988 94 : readptr->eof_reached = true;
989 94 : return NULL;
990 : }
991 : }
992 :
993 : /*
994 : * Backward.
995 : *
996 : * if all tuples are fetched already then we return last tuple,
997 : * else tuple before last returned.
998 : *
999 : * Back up to fetch previously-returned tuple's ending length
1000 : * word. If seek fails, assume we are at start of file.
1001 : */
1002 12 : if (BufFileSeek(state->myfile, 0, -(long) sizeof(unsigned int),
1003 : SEEK_CUR) != 0)
1004 : {
1005 : /* even a failed backwards fetch gets you out of eof state */
1006 0 : readptr->eof_reached = false;
1007 : Assert(!state->truncated);
1008 0 : return NULL;
1009 : }
1010 12 : tuplen = getlen(state, false);
1011 :
1012 12 : if (readptr->eof_reached)
1013 : {
1014 6 : readptr->eof_reached = false;
1015 : /* We will return the tuple returned before returning NULL */
1016 : }
1017 : else
1018 : {
1019 : /*
1020 : * Back up to get ending length word of tuple before it.
1021 : */
1022 6 : if (BufFileSeek(state->myfile, 0,
1023 6 : -(long) (tuplen + 2 * sizeof(unsigned int)),
1024 : SEEK_CUR) != 0)
1025 : {
1026 : /*
1027 : * If that fails, presumably the prev tuple is the first
1028 : * in the file. Back up so that it becomes next to read
1029 : * in forward direction (not obviously right, but that is
1030 : * what in-memory case does).
1031 : */
1032 0 : if (BufFileSeek(state->myfile, 0,
1033 0 : -(long) (tuplen + sizeof(unsigned int)),
1034 : SEEK_CUR) != 0)
1035 0 : ereport(ERROR,
1036 : (errcode_for_file_access(),
1037 : errmsg("could not seek in tuplestore temporary file")));
1038 : Assert(!state->truncated);
1039 0 : return NULL;
1040 : }
1041 6 : tuplen = getlen(state, false);
1042 : }
1043 :
1044 : /*
1045 : * Now we have the length of the prior tuple, back up and read it.
1046 : * Note: READTUP expects we are positioned after the initial
1047 : * length word of the tuple, so back up to that point.
1048 : */
1049 12 : if (BufFileSeek(state->myfile, 0,
1050 12 : -(long) tuplen,
1051 : SEEK_CUR) != 0)
1052 0 : ereport(ERROR,
1053 : (errcode_for_file_access(),
1054 : errmsg("could not seek in tuplestore temporary file")));
1055 12 : tup = READTUP(state, tuplen);
1056 12 : return tup;
1057 :
1058 0 : default:
1059 0 : elog(ERROR, "invalid tuplestore state");
1060 : return NULL; /* keep compiler quiet */
1061 : }
1062 : }
1063 :
1064 : /*
1065 : * tuplestore_gettupleslot - exported function to fetch a MinimalTuple
1066 : *
1067 : * If successful, put tuple in slot and return true; else, clear the slot
1068 : * and return false.
1069 : *
1070 : * If copy is true, the slot receives a copied tuple (allocated in current
1071 : * memory context) that will stay valid regardless of future manipulations of
1072 : * the tuplestore's state. If copy is false, the slot may just receive a
1073 : * pointer to a tuple held within the tuplestore. The latter is more
1074 : * efficient but the slot contents may be corrupted if additional writes to
1075 : * the tuplestore occur. (If using tuplestore_trim, see comments therein.)
1076 : */
1077 : bool
1078 20265080 : tuplestore_gettupleslot(Tuplestorestate *state, bool forward,
1079 : bool copy, TupleTableSlot *slot)
1080 : {
1081 : MinimalTuple tuple;
1082 : bool should_free;
1083 :
1084 20265080 : tuple = (MinimalTuple) tuplestore_gettuple(state, forward, &should_free);
1085 :
1086 20265080 : if (tuple)
1087 : {
1088 19916992 : if (copy && !should_free)
1089 : {
1090 1752320 : tuple = heap_copy_minimal_tuple(tuple);
1091 1752320 : should_free = true;
1092 : }
1093 19916992 : ExecStoreMinimalTuple(tuple, slot, should_free);
1094 19916992 : return true;
1095 : }
1096 : else
1097 : {
1098 348088 : ExecClearTuple(slot);
1099 348088 : return false;
1100 : }
1101 : }
1102 :
1103 : /*
1104 : * tuplestore_advance - exported function to adjust position without fetching
1105 : *
1106 : * We could optimize this case to avoid palloc/pfree overhead, but for the
1107 : * moment it doesn't seem worthwhile.
1108 : */
1109 : bool
1110 172252 : tuplestore_advance(Tuplestorestate *state, bool forward)
1111 : {
1112 : void *tuple;
1113 : bool should_free;
1114 :
1115 172252 : tuple = tuplestore_gettuple(state, forward, &should_free);
1116 :
1117 172252 : if (tuple)
1118 : {
1119 169704 : if (should_free)
1120 0 : pfree(tuple);
1121 169704 : return true;
1122 : }
1123 : else
1124 : {
1125 2548 : return false;
1126 : }
1127 : }
1128 :
1129 : /*
1130 : * Advance over N tuples in either forward or back direction,
1131 : * without returning any data. N<=0 is a no-op.
1132 : * Returns true if successful, false if ran out of tuples.
1133 : */
1134 : bool
1135 1281186 : tuplestore_skiptuples(Tuplestorestate *state, int64 ntuples, bool forward)
1136 : {
1137 1281186 : TSReadPointer *readptr = &state->readptrs[state->activeptr];
1138 :
1139 : Assert(forward || (readptr->eflags & EXEC_FLAG_BACKWARD));
1140 :
1141 1281186 : if (ntuples <= 0)
1142 18 : return true;
1143 :
1144 1281168 : switch (state->status)
1145 : {
1146 1281162 : case TSS_INMEM:
1147 1281162 : if (forward)
1148 : {
1149 1278454 : if (readptr->eof_reached)
1150 0 : return false;
1151 1278454 : if (state->memtupcount - readptr->current >= ntuples)
1152 : {
1153 1278364 : readptr->current += ntuples;
1154 1278364 : return true;
1155 : }
1156 90 : readptr->current = state->memtupcount;
1157 90 : readptr->eof_reached = true;
1158 90 : return false;
1159 : }
1160 : else
1161 : {
1162 2708 : if (readptr->eof_reached)
1163 : {
1164 0 : readptr->current = state->memtupcount;
1165 0 : readptr->eof_reached = false;
1166 0 : ntuples--;
1167 : }
1168 2708 : if (readptr->current - state->memtupdeleted > ntuples)
1169 : {
1170 2708 : readptr->current -= ntuples;
1171 2708 : return true;
1172 : }
1173 : Assert(!state->truncated);
1174 0 : readptr->current = state->memtupdeleted;
1175 0 : return false;
1176 : }
1177 : break;
1178 :
1179 6 : default:
1180 : /* We don't currently try hard to optimize other cases */
1181 18 : while (ntuples-- > 0)
1182 : {
1183 : void *tuple;
1184 : bool should_free;
1185 :
1186 12 : tuple = tuplestore_gettuple(state, forward, &should_free);
1187 :
1188 12 : if (tuple == NULL)
1189 0 : return false;
1190 12 : if (should_free)
1191 12 : pfree(tuple);
1192 12 : CHECK_FOR_INTERRUPTS();
1193 : }
1194 6 : return true;
1195 : }
1196 : }
1197 :
1198 : /*
1199 : * dumptuples - remove tuples from memory and write to tape
1200 : *
1201 : * As a side effect, we must convert each read pointer's position from
1202 : * "current" to file/offset format. But eof_reached pointers don't
1203 : * need to change state.
1204 : */
1205 : static void
1206 108 : dumptuples(Tuplestorestate *state)
1207 : {
1208 : int i;
1209 :
1210 108 : for (i = state->memtupdeleted;; i++)
1211 2835724 : {
1212 2835832 : TSReadPointer *readptr = state->readptrs;
1213 : int j;
1214 :
1215 5671664 : for (j = 0; j < state->readptrcount; readptr++, j++)
1216 : {
1217 2835832 : if (i == readptr->current && !readptr->eof_reached)
1218 108 : BufFileTell(state->myfile,
1219 : &readptr->file, &readptr->offset);
1220 : }
1221 2835832 : if (i >= state->memtupcount)
1222 108 : break;
1223 2835724 : WRITETUP(state, state->memtuples[i]);
1224 : }
1225 108 : state->memtupdeleted = 0;
1226 108 : state->memtupcount = 0;
1227 108 : }
1228 :
1229 : /*
1230 : * tuplestore_rescan - rewind the active read pointer to start
1231 : */
1232 : void
1233 287076 : tuplestore_rescan(Tuplestorestate *state)
1234 : {
1235 287076 : TSReadPointer *readptr = &state->readptrs[state->activeptr];
1236 :
1237 : Assert(readptr->eflags & EXEC_FLAG_REWIND);
1238 : Assert(!state->truncated);
1239 :
1240 287076 : switch (state->status)
1241 : {
1242 286970 : case TSS_INMEM:
1243 286970 : readptr->eof_reached = false;
1244 286970 : readptr->current = 0;
1245 286970 : break;
1246 106 : case TSS_WRITEFILE:
1247 106 : readptr->eof_reached = false;
1248 106 : readptr->file = 0;
1249 106 : readptr->offset = 0;
1250 106 : break;
1251 0 : case TSS_READFILE:
1252 0 : readptr->eof_reached = false;
1253 0 : if (BufFileSeek(state->myfile, 0, 0, SEEK_SET) != 0)
1254 0 : ereport(ERROR,
1255 : (errcode_for_file_access(),
1256 : errmsg("could not seek in tuplestore temporary file")));
1257 0 : break;
1258 0 : default:
1259 0 : elog(ERROR, "invalid tuplestore state");
1260 : break;
1261 : }
1262 287076 : }
1263 :
1264 : /*
1265 : * tuplestore_copy_read_pointer - copy a read pointer's state to another
1266 : */
1267 : void
1268 60932 : tuplestore_copy_read_pointer(Tuplestorestate *state,
1269 : int srcptr, int destptr)
1270 : {
1271 60932 : TSReadPointer *sptr = &state->readptrs[srcptr];
1272 60932 : TSReadPointer *dptr = &state->readptrs[destptr];
1273 :
1274 : Assert(srcptr >= 0 && srcptr < state->readptrcount);
1275 : Assert(destptr >= 0 && destptr < state->readptrcount);
1276 :
1277 : /* Assigning to self is a no-op */
1278 60932 : if (srcptr == destptr)
1279 0 : return;
1280 :
1281 60932 : if (dptr->eflags != sptr->eflags)
1282 : {
1283 : /* Possible change of overall eflags, so copy and then recompute */
1284 : int eflags;
1285 : int i;
1286 :
1287 0 : *dptr = *sptr;
1288 0 : eflags = state->readptrs[0].eflags;
1289 0 : for (i = 1; i < state->readptrcount; i++)
1290 0 : eflags |= state->readptrs[i].eflags;
1291 0 : state->eflags = eflags;
1292 : }
1293 : else
1294 60932 : *dptr = *sptr;
1295 :
1296 60932 : switch (state->status)
1297 : {
1298 60932 : case TSS_INMEM:
1299 : case TSS_WRITEFILE:
1300 : /* no work */
1301 60932 : break;
1302 0 : case TSS_READFILE:
1303 :
1304 : /*
1305 : * This case is a bit tricky since the active read pointer's
1306 : * position corresponds to the seek point, not what is in its
1307 : * variables. Assigning to the active requires a seek, and
1308 : * assigning from the active requires a tell, except when
1309 : * eof_reached.
1310 : */
1311 0 : if (destptr == state->activeptr)
1312 : {
1313 0 : if (dptr->eof_reached)
1314 : {
1315 0 : if (BufFileSeek(state->myfile,
1316 : state->writepos_file,
1317 : state->writepos_offset,
1318 : SEEK_SET) != 0)
1319 0 : ereport(ERROR,
1320 : (errcode_for_file_access(),
1321 : errmsg("could not seek in tuplestore temporary file")));
1322 : }
1323 : else
1324 : {
1325 0 : if (BufFileSeek(state->myfile,
1326 : dptr->file, dptr->offset,
1327 : SEEK_SET) != 0)
1328 0 : ereport(ERROR,
1329 : (errcode_for_file_access(),
1330 : errmsg("could not seek in tuplestore temporary file")));
1331 : }
1332 : }
1333 0 : else if (srcptr == state->activeptr)
1334 : {
1335 0 : if (!dptr->eof_reached)
1336 0 : BufFileTell(state->myfile,
1337 : &dptr->file,
1338 : &dptr->offset);
1339 : }
1340 0 : break;
1341 0 : default:
1342 0 : elog(ERROR, "invalid tuplestore state");
1343 : break;
1344 : }
1345 : }
1346 :
1347 : /*
1348 : * tuplestore_trim - remove all no-longer-needed tuples
1349 : *
1350 : * Calling this function authorizes the tuplestore to delete all tuples
1351 : * before the oldest read pointer, if no read pointer is marked as requiring
1352 : * REWIND capability.
1353 : *
1354 : * Note: this is obviously safe if no pointer has BACKWARD capability either.
1355 : * If a pointer is marked as BACKWARD but not REWIND capable, it means that
1356 : * the pointer can be moved backward but not before the oldest other read
1357 : * pointer.
1358 : */
1359 : void
1360 826800 : tuplestore_trim(Tuplestorestate *state)
1361 : {
1362 : int oldest;
1363 : int nremove;
1364 : int i;
1365 :
1366 : /*
1367 : * Truncation is disallowed if any read pointer requires rewind
1368 : * capability.
1369 : */
1370 826800 : if (state->eflags & EXEC_FLAG_REWIND)
1371 0 : return;
1372 :
1373 : /*
1374 : * We don't bother trimming temp files since it usually would mean more
1375 : * work than just letting them sit in kernel buffers until they age out.
1376 : */
1377 826800 : if (state->status != TSS_INMEM)
1378 0 : return;
1379 :
1380 : /* Find the oldest read pointer */
1381 826800 : oldest = state->memtupcount;
1382 3564342 : for (i = 0; i < state->readptrcount; i++)
1383 : {
1384 2737542 : if (!state->readptrs[i].eof_reached)
1385 2708326 : oldest = Min(oldest, state->readptrs[i].current);
1386 : }
1387 :
1388 : /*
1389 : * Note: you might think we could remove all the tuples before the oldest
1390 : * "current", since that one is the next to be returned. However, since
1391 : * tuplestore_gettuple returns a direct pointer to our internal copy of
1392 : * the tuple, it's likely that the caller has still got the tuple just
1393 : * before "current" referenced in a slot. So we keep one extra tuple
1394 : * before the oldest "current". (Strictly speaking, we could require such
1395 : * callers to use the "copy" flag to tuplestore_gettupleslot, but for
1396 : * efficiency we allow this one case to not use "copy".)
1397 : */
1398 826800 : nremove = oldest - 1;
1399 826800 : if (nremove <= 0)
1400 7102 : return; /* nothing to do */
1401 :
1402 : Assert(nremove >= state->memtupdeleted);
1403 : Assert(nremove <= state->memtupcount);
1404 :
1405 : /* Release no-longer-needed tuples */
1406 1640450 : for (i = state->memtupdeleted; i < nremove; i++)
1407 : {
1408 820752 : FREEMEM(state, GetMemoryChunkSpace(state->memtuples[i]));
1409 820752 : pfree(state->memtuples[i]);
1410 820752 : state->memtuples[i] = NULL;
1411 : }
1412 819698 : state->memtupdeleted = nremove;
1413 :
1414 : /* mark tuplestore as truncated (used for Assert crosschecks only) */
1415 819698 : state->truncated = true;
1416 :
1417 : /*
1418 : * If nremove is less than 1/8th memtupcount, just stop here, leaving the
1419 : * "deleted" slots as NULL. This prevents us from expending O(N^2) time
1420 : * repeatedly memmove-ing a large pointer array. The worst case space
1421 : * wastage is pretty small, since it's just pointers and not whole tuples.
1422 : */
1423 819698 : if (nremove < state->memtupcount / 8)
1424 112680 : return;
1425 :
1426 : /*
1427 : * Slide the array down and readjust pointers.
1428 : *
1429 : * In mergejoin's current usage, it's demonstrable that there will always
1430 : * be exactly one non-removed tuple; so optimize that case.
1431 : */
1432 707018 : if (nremove + 1 == state->memtupcount)
1433 630254 : state->memtuples[0] = state->memtuples[nremove];
1434 : else
1435 76764 : memmove(state->memtuples, state->memtuples + nremove,
1436 76764 : (state->memtupcount - nremove) * sizeof(void *));
1437 :
1438 707018 : state->memtupdeleted = 0;
1439 707018 : state->memtupcount -= nremove;
1440 3071712 : for (i = 0; i < state->readptrcount; i++)
1441 : {
1442 2364694 : if (!state->readptrs[i].eof_reached)
1443 2360444 : state->readptrs[i].current -= nremove;
1444 : }
1445 : }
1446 :
1447 : /*
1448 : * tuplestore_in_memory
1449 : *
1450 : * Returns true if the tuplestore has not spilled to disk.
1451 : *
1452 : * XXX exposing this is a violation of modularity ... should get rid of it.
1453 : */
1454 : bool
1455 1553382 : tuplestore_in_memory(Tuplestorestate *state)
1456 : {
1457 1553382 : return (state->status == TSS_INMEM);
1458 : }
1459 :
1460 :
1461 : /*
1462 : * Tape interface routines
1463 : */
1464 :
1465 : static unsigned int
1466 6173902 : getlen(Tuplestorestate *state, bool eofOK)
1467 : {
1468 : unsigned int len;
1469 : size_t nbytes;
1470 :
1471 6173902 : nbytes = BufFileReadMaybeEOF(state->myfile, &len, sizeof(len), eofOK);
1472 6173902 : if (nbytes == 0)
1473 94 : return 0;
1474 : else
1475 6173808 : return len;
1476 : }
1477 :
1478 :
1479 : /*
1480 : * Routines specialized for HeapTuple case
1481 : *
1482 : * The stored form is actually a MinimalTuple, but for largely historical
1483 : * reasons we allow COPYTUP to work from a HeapTuple.
1484 : *
1485 : * Since MinimalTuple already has length in its first word, we don't need
1486 : * to write that separately.
1487 : */
1488 :
1489 : static void *
1490 1607768 : copytup_heap(Tuplestorestate *state, void *tup)
1491 : {
1492 : MinimalTuple tuple;
1493 :
1494 1607768 : tuple = minimal_tuple_from_heap_tuple((HeapTuple) tup);
1495 1607768 : USEMEM(state, GetMemoryChunkSpace(tuple));
1496 1607768 : return (void *) tuple;
1497 : }
1498 :
1499 : static void
1500 8983878 : writetup_heap(Tuplestorestate *state, void *tup)
1501 : {
1502 8983878 : MinimalTuple tuple = (MinimalTuple) tup;
1503 :
1504 : /* the part of the MinimalTuple we'll write: */
1505 8983878 : char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
1506 8983878 : unsigned int tupbodylen = tuple->t_len - MINIMAL_TUPLE_DATA_OFFSET;
1507 :
1508 : /* total on-disk footprint: */
1509 8983878 : unsigned int tuplen = tupbodylen + sizeof(int);
1510 :
1511 8983878 : BufFileWrite(state->myfile, &tuplen, sizeof(tuplen));
1512 8983878 : BufFileWrite(state->myfile, tupbody, tupbodylen);
1513 8983878 : if (state->backward) /* need trailing length word? */
1514 60000 : BufFileWrite(state->myfile, &tuplen, sizeof(tuplen));
1515 :
1516 8983878 : FREEMEM(state, GetMemoryChunkSpace(tuple));
1517 8983878 : heap_free_minimal_tuple(tuple);
1518 8983878 : }
1519 :
1520 : static void *
1521 6173802 : readtup_heap(Tuplestorestate *state, unsigned int len)
1522 : {
1523 6173802 : unsigned int tupbodylen = len - sizeof(int);
1524 6173802 : unsigned int tuplen = tupbodylen + MINIMAL_TUPLE_DATA_OFFSET;
1525 6173802 : MinimalTuple tuple = (MinimalTuple) palloc(tuplen);
1526 6173802 : char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
1527 :
1528 6173802 : USEMEM(state, GetMemoryChunkSpace(tuple));
1529 : /* read in the tuple proper */
1530 6173802 : tuple->t_len = tuplen;
1531 6173802 : BufFileReadExact(state->myfile, tupbody, tupbodylen);
1532 6173802 : if (state->backward) /* need trailing length word? */
1533 60018 : BufFileReadExact(state->myfile, &tuplen, sizeof(tuplen));
1534 6173802 : return (void *) tuple;
1535 : }
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