Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * buffile.c
4 : * Management of large buffered temporary files.
5 : *
6 : * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * IDENTIFICATION
10 : * src/backend/storage/file/buffile.c
11 : *
12 : * NOTES:
13 : *
14 : * BufFiles provide a very incomplete emulation of stdio atop virtual Files
15 : * (as managed by fd.c). Currently, we only support the buffered-I/O
16 : * aspect of stdio: a read or write of the low-level File occurs only
17 : * when the buffer is filled or emptied. This is an even bigger win
18 : * for virtual Files than for ordinary kernel files, since reducing the
19 : * frequency with which a virtual File is touched reduces "thrashing"
20 : * of opening/closing file descriptors.
21 : *
22 : * Note that BufFile structs are allocated with palloc(), and therefore
23 : * will go away automatically at query/transaction end. Since the underlying
24 : * virtual Files are made with OpenTemporaryFile, all resources for
25 : * the file are certain to be cleaned up even if processing is aborted
26 : * by ereport(ERROR). The data structures required are made in the
27 : * palloc context that was current when the BufFile was created, and
28 : * any external resources such as temp files are owned by the ResourceOwner
29 : * that was current at that time.
30 : *
31 : * BufFile also supports temporary files that exceed the OS file size limit
32 : * (by opening multiple fd.c temporary files). This is an essential feature
33 : * for sorts and hashjoins on large amounts of data.
34 : *
35 : * BufFile supports temporary files that can be made read-only and shared with
36 : * other backends, as infrastructure for parallel execution. Such files need
37 : * to be created as a member of a SharedFileSet that all participants are
38 : * attached to.
39 : *-------------------------------------------------------------------------
40 : */
41 :
42 : #include "postgres.h"
43 :
44 : #include "commands/tablespace.h"
45 : #include "executor/instrument.h"
46 : #include "miscadmin.h"
47 : #include "pgstat.h"
48 : #include "storage/fd.h"
49 : #include "storage/buffile.h"
50 : #include "storage/buf_internals.h"
51 : #include "utils/resowner.h"
52 :
53 : /*
54 : * We break BufFiles into gigabyte-sized segments, regardless of RELSEG_SIZE.
55 : * The reason is that we'd like large BufFiles to be spread across multiple
56 : * tablespaces when available.
57 : */
58 : #define MAX_PHYSICAL_FILESIZE 0x40000000
59 : #define BUFFILE_SEG_SIZE (MAX_PHYSICAL_FILESIZE / BLCKSZ)
60 :
61 : /*
62 : * This data structure represents a buffered file that consists of one or
63 : * more physical files (each accessed through a virtual file descriptor
64 : * managed by fd.c).
65 : */
66 : struct BufFile
67 : {
68 : int numFiles; /* number of physical files in set */
69 : /* all files except the last have length exactly MAX_PHYSICAL_FILESIZE */
70 : File *files; /* palloc'd array with numFiles entries */
71 :
72 : bool isInterXact; /* keep open over transactions? */
73 : bool dirty; /* does buffer need to be written? */
74 : bool readOnly; /* has the file been set to read only? */
75 :
76 : SharedFileSet *fileset; /* space for segment files if shared */
77 : const char *name; /* name of this BufFile if shared */
78 :
79 : /*
80 : * resowner is the ResourceOwner to use for underlying temp files. (We
81 : * don't need to remember the memory context we're using explicitly,
82 : * because after creation we only repalloc our arrays larger.)
83 : */
84 : ResourceOwner resowner;
85 :
86 : /*
87 : * "current pos" is position of start of buffer within the logical file.
88 : * Position as seen by user of BufFile is (curFile, curOffset + pos).
89 : */
90 : int curFile; /* file index (0..n) part of current pos */
91 : off_t curOffset; /* offset part of current pos */
92 : int pos; /* next read/write position in buffer */
93 : int nbytes; /* total # of valid bytes in buffer */
94 : PGAlignedBlock buffer;
95 : };
96 :
97 : static BufFile *makeBufFileCommon(int nfiles);
98 : static BufFile *makeBufFile(File firstfile);
99 : static void extendBufFile(BufFile *file);
100 : static void BufFileLoadBuffer(BufFile *file);
101 : static void BufFileDumpBuffer(BufFile *file);
102 : static int BufFileFlush(BufFile *file);
103 : static File MakeNewSharedSegment(BufFile *file, int segment);
104 :
105 : /*
106 : * Create BufFile and perform the common initialization.
107 : */
108 : static BufFile *
109 4678 : makeBufFileCommon(int nfiles)
110 : {
111 4678 : BufFile *file = (BufFile *) palloc(sizeof(BufFile));
112 :
113 4678 : file->numFiles = nfiles;
114 4678 : file->isInterXact = false;
115 4678 : file->dirty = false;
116 4678 : file->resowner = CurrentResourceOwner;
117 4678 : file->curFile = 0;
118 4678 : file->curOffset = 0L;
119 4678 : file->pos = 0;
120 4678 : file->nbytes = 0;
121 :
122 4678 : return file;
123 : }
124 :
125 : /*
126 : * Create a BufFile given the first underlying physical file.
127 : * NOTE: caller must set isInterXact if appropriate.
128 : */
129 : static BufFile *
130 1758 : makeBufFile(File firstfile)
131 : {
132 1758 : BufFile *file = makeBufFileCommon(1);
133 :
134 1758 : file->files = (File *) palloc(sizeof(File));
135 1758 : file->files[0] = firstfile;
136 1758 : file->readOnly = false;
137 1758 : file->fileset = NULL;
138 1758 : file->name = NULL;
139 :
140 1758 : return file;
141 : }
142 :
143 : /*
144 : * Add another component temp file.
145 : */
146 : static void
147 0 : extendBufFile(BufFile *file)
148 : {
149 : File pfile;
150 : ResourceOwner oldowner;
151 :
152 : /* Be sure to associate the file with the BufFile's resource owner */
153 0 : oldowner = CurrentResourceOwner;
154 0 : CurrentResourceOwner = file->resowner;
155 :
156 0 : if (file->fileset == NULL)
157 0 : pfile = OpenTemporaryFile(file->isInterXact);
158 : else
159 0 : pfile = MakeNewSharedSegment(file, file->numFiles);
160 :
161 : Assert(pfile >= 0);
162 :
163 0 : CurrentResourceOwner = oldowner;
164 :
165 0 : file->files = (File *) repalloc(file->files,
166 0 : (file->numFiles + 1) * sizeof(File));
167 0 : file->files[file->numFiles] = pfile;
168 0 : file->numFiles++;
169 0 : }
170 :
171 : /*
172 : * Create a BufFile for a new temporary file (which will expand to become
173 : * multiple temporary files if more than MAX_PHYSICAL_FILESIZE bytes are
174 : * written to it).
175 : *
176 : * If interXact is true, the temp file will not be automatically deleted
177 : * at end of transaction.
178 : *
179 : * Note: if interXact is true, the caller had better be calling us in a
180 : * memory context, and with a resource owner, that will survive across
181 : * transaction boundaries.
182 : */
183 : BufFile *
184 1758 : BufFileCreateTemp(bool interXact)
185 : {
186 : BufFile *file;
187 : File pfile;
188 :
189 : /*
190 : * Ensure that temp tablespaces are set up for OpenTemporaryFile to use.
191 : * Possibly the caller will have done this already, but it seems useful to
192 : * double-check here. Failure to do this at all would result in the temp
193 : * files always getting placed in the default tablespace, which is a
194 : * pretty hard-to-detect bug. Callers may prefer to do it earlier if they
195 : * want to be sure that any required catalog access is done in some other
196 : * resource context.
197 : */
198 1758 : PrepareTempTablespaces();
199 :
200 1758 : pfile = OpenTemporaryFile(interXact);
201 : Assert(pfile >= 0);
202 :
203 1758 : file = makeBufFile(pfile);
204 1758 : file->isInterXact = interXact;
205 :
206 1758 : return file;
207 : }
208 :
209 : /*
210 : * Build the name for a given segment of a given BufFile.
211 : */
212 : static void
213 5840 : SharedSegmentName(char *name, const char *buffile_name, int segment)
214 : {
215 5840 : snprintf(name, MAXPGPATH, "%s.%d", buffile_name, segment);
216 5840 : }
217 :
218 : /*
219 : * Create a new segment file backing a shared BufFile.
220 : */
221 : static File
222 1486 : MakeNewSharedSegment(BufFile *buffile, int segment)
223 : {
224 : char name[MAXPGPATH];
225 : File file;
226 :
227 : /*
228 : * It is possible that there are files left over from before a crash
229 : * restart with the same name. In order for BufFileOpenShared() not to
230 : * get confused about how many segments there are, we'll unlink the next
231 : * segment number if it already exists.
232 : */
233 1486 : SharedSegmentName(name, buffile->name, segment + 1);
234 1486 : SharedFileSetDelete(buffile->fileset, name, true);
235 :
236 : /* Create the new segment. */
237 1486 : SharedSegmentName(name, buffile->name, segment);
238 1486 : file = SharedFileSetCreate(buffile->fileset, name);
239 :
240 : /* SharedFileSetCreate would've errored out */
241 : Assert(file > 0);
242 :
243 1486 : return file;
244 : }
245 :
246 : /*
247 : * Create a BufFile that can be discovered and opened read-only by other
248 : * backends that are attached to the same SharedFileSet using the same name.
249 : *
250 : * The naming scheme for shared BufFiles is left up to the calling code. The
251 : * name will appear as part of one or more filenames on disk, and might
252 : * provide clues to administrators about which subsystem is generating
253 : * temporary file data. Since each SharedFileSet object is backed by one or
254 : * more uniquely named temporary directory, names don't conflict with
255 : * unrelated SharedFileSet objects.
256 : */
257 : BufFile *
258 1486 : BufFileCreateShared(SharedFileSet *fileset, const char *name)
259 : {
260 : BufFile *file;
261 :
262 1486 : file = makeBufFileCommon(1);
263 1486 : file->fileset = fileset;
264 1486 : file->name = pstrdup(name);
265 1486 : file->files = (File *) palloc(sizeof(File));
266 1486 : file->files[0] = MakeNewSharedSegment(file, 0);
267 1486 : file->readOnly = false;
268 :
269 1486 : return file;
270 : }
271 :
272 : /*
273 : * Open a file that was previously created in another backend (or this one)
274 : * with BufFileCreateShared in the same SharedFileSet using the same name.
275 : * The backend that created the file must have called BufFileClose() or
276 : * BufFileExportShared() to make sure that it is ready to be opened by other
277 : * backends and render it read-only.
278 : */
279 : BufFile *
280 1434 : BufFileOpenShared(SharedFileSet *fileset, const char *name)
281 : {
282 : BufFile *file;
283 : char segment_name[MAXPGPATH];
284 1434 : Size capacity = 16;
285 : File *files;
286 1434 : int nfiles = 0;
287 :
288 1434 : files = palloc(sizeof(File) * capacity);
289 :
290 : /*
291 : * We don't know how many segments there are, so we'll probe the
292 : * filesystem to find out.
293 : */
294 : for (;;)
295 : {
296 : /* See if we need to expand our file segment array. */
297 4302 : if (nfiles + 1 > capacity)
298 : {
299 0 : capacity *= 2;
300 0 : files = repalloc(files, sizeof(File) * capacity);
301 : }
302 : /* Try to load a segment. */
303 2868 : SharedSegmentName(segment_name, name, nfiles);
304 2868 : files[nfiles] = SharedFileSetOpen(fileset, segment_name);
305 2868 : if (files[nfiles] <= 0)
306 1434 : break;
307 1434 : ++nfiles;
308 :
309 1434 : CHECK_FOR_INTERRUPTS();
310 : }
311 :
312 : /*
313 : * If we didn't find any files at all, then no BufFile exists with this
314 : * name.
315 : */
316 1434 : if (nfiles == 0)
317 0 : ereport(ERROR,
318 : (errcode_for_file_access(),
319 : errmsg("could not open temporary file \"%s\" from BufFile \"%s\": %m",
320 : segment_name, name)));
321 :
322 1434 : file = makeBufFileCommon(nfiles);
323 1434 : file->files = files;
324 1434 : file->readOnly = true; /* Can't write to files opened this way */
325 1434 : file->fileset = fileset;
326 1434 : file->name = pstrdup(name);
327 :
328 1434 : return file;
329 : }
330 :
331 : /*
332 : * Delete a BufFile that was created by BufFileCreateShared in the given
333 : * SharedFileSet using the given name.
334 : *
335 : * It is not necessary to delete files explicitly with this function. It is
336 : * provided only as a way to delete files proactively, rather than waiting for
337 : * the SharedFileSet to be cleaned up.
338 : *
339 : * Only one backend should attempt to delete a given name, and should know
340 : * that it exists and has been exported or closed.
341 : */
342 : void
343 0 : BufFileDeleteShared(SharedFileSet *fileset, const char *name)
344 : {
345 : char segment_name[MAXPGPATH];
346 0 : int segment = 0;
347 0 : bool found = false;
348 :
349 : /*
350 : * We don't know how many segments the file has. We'll keep deleting
351 : * until we run out. If we don't manage to find even an initial segment,
352 : * raise an error.
353 : */
354 : for (;;)
355 : {
356 0 : SharedSegmentName(segment_name, name, segment);
357 0 : if (!SharedFileSetDelete(fileset, segment_name, true))
358 0 : break;
359 0 : found = true;
360 0 : ++segment;
361 :
362 0 : CHECK_FOR_INTERRUPTS();
363 : }
364 :
365 0 : if (!found)
366 0 : elog(ERROR, "could not delete unknown shared BufFile \"%s\"", name);
367 0 : }
368 :
369 : /*
370 : * BufFileExportShared --- flush and make read-only, in preparation for sharing.
371 : */
372 : void
373 240 : BufFileExportShared(BufFile *file)
374 : {
375 : /* Must be a file belonging to a SharedFileSet. */
376 : Assert(file->fileset != NULL);
377 :
378 : /* It's probably a bug if someone calls this twice. */
379 : Assert(!file->readOnly);
380 :
381 240 : BufFileFlush(file);
382 240 : file->readOnly = true;
383 240 : }
384 :
385 : /*
386 : * Close a BufFile
387 : *
388 : * Like fclose(), this also implicitly FileCloses the underlying File.
389 : */
390 : void
391 4592 : BufFileClose(BufFile *file)
392 : {
393 : int i;
394 :
395 : /* flush any unwritten data */
396 4592 : BufFileFlush(file);
397 : /* close and delete the underlying file(s) */
398 9268 : for (i = 0; i < file->numFiles; i++)
399 4676 : FileClose(file->files[i]);
400 : /* release the buffer space */
401 4592 : pfree(file->files);
402 4592 : pfree(file);
403 4592 : }
404 :
405 : /*
406 : * BufFileLoadBuffer
407 : *
408 : * Load some data into buffer, if possible, starting from curOffset.
409 : * At call, must have dirty = false, pos and nbytes = 0.
410 : * On exit, nbytes is number of bytes loaded.
411 : */
412 : static void
413 39430 : BufFileLoadBuffer(BufFile *file)
414 : {
415 : File thisfile;
416 :
417 : /*
418 : * Advance to next component file if necessary and possible.
419 : */
420 39430 : if (file->curOffset >= MAX_PHYSICAL_FILESIZE &&
421 0 : file->curFile + 1 < file->numFiles)
422 : {
423 0 : file->curFile++;
424 0 : file->curOffset = 0L;
425 : }
426 :
427 : /*
428 : * Read whatever we can get, up to a full bufferload.
429 : */
430 39430 : thisfile = file->files[file->curFile];
431 78860 : file->nbytes = FileRead(thisfile,
432 39430 : file->buffer.data,
433 : sizeof(file->buffer),
434 : file->curOffset,
435 : WAIT_EVENT_BUFFILE_READ);
436 39430 : if (file->nbytes < 0)
437 0 : file->nbytes = 0;
438 : /* we choose not to advance curOffset here */
439 :
440 39430 : if (file->nbytes > 0)
441 37682 : pgBufferUsage.temp_blks_read++;
442 39430 : }
443 :
444 : /*
445 : * BufFileDumpBuffer
446 : *
447 : * Dump buffer contents starting at curOffset.
448 : * At call, should have dirty = true, nbytes > 0.
449 : * On exit, dirty is cleared if successful write, and curOffset is advanced.
450 : */
451 : static void
452 45924 : BufFileDumpBuffer(BufFile *file)
453 : {
454 45924 : int wpos = 0;
455 : int bytestowrite;
456 : File thisfile;
457 :
458 : /*
459 : * Unlike BufFileLoadBuffer, we must dump the whole buffer even if it
460 : * crosses a component-file boundary; so we need a loop.
461 : */
462 137772 : while (wpos < file->nbytes)
463 : {
464 : off_t availbytes;
465 :
466 : /*
467 : * Advance to next component file if necessary and possible.
468 : */
469 45924 : if (file->curOffset >= MAX_PHYSICAL_FILESIZE)
470 : {
471 0 : while (file->curFile + 1 >= file->numFiles)
472 0 : extendBufFile(file);
473 0 : file->curFile++;
474 0 : file->curOffset = 0L;
475 : }
476 :
477 : /*
478 : * Determine how much we need to write into this file.
479 : */
480 45924 : bytestowrite = file->nbytes - wpos;
481 45924 : availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset;
482 :
483 45924 : if ((off_t) bytestowrite > availbytes)
484 0 : bytestowrite = (int) availbytes;
485 :
486 45924 : thisfile = file->files[file->curFile];
487 91848 : bytestowrite = FileWrite(thisfile,
488 45924 : file->buffer.data + wpos,
489 : bytestowrite,
490 : file->curOffset,
491 : WAIT_EVENT_BUFFILE_WRITE);
492 45924 : if (bytestowrite <= 0)
493 0 : return; /* failed to write */
494 45924 : file->curOffset += bytestowrite;
495 45924 : wpos += bytestowrite;
496 :
497 45924 : pgBufferUsage.temp_blks_written++;
498 : }
499 45924 : file->dirty = false;
500 :
501 : /*
502 : * At this point, curOffset has been advanced to the end of the buffer,
503 : * ie, its original value + nbytes. We need to make it point to the
504 : * logical file position, ie, original value + pos, in case that is less
505 : * (as could happen due to a small backwards seek in a dirty buffer!)
506 : */
507 45924 : file->curOffset -= (file->nbytes - file->pos);
508 45924 : if (file->curOffset < 0) /* handle possible segment crossing */
509 : {
510 0 : file->curFile--;
511 : Assert(file->curFile >= 0);
512 0 : file->curOffset += MAX_PHYSICAL_FILESIZE;
513 : }
514 :
515 : /*
516 : * Now we can set the buffer empty without changing the logical position
517 : */
518 45924 : file->pos = 0;
519 45924 : file->nbytes = 0;
520 : }
521 :
522 : /*
523 : * BufFileRead
524 : *
525 : * Like fread() except we assume 1-byte element size.
526 : */
527 : size_t
528 20752906 : BufFileRead(BufFile *file, void *ptr, size_t size)
529 : {
530 20752906 : size_t nread = 0;
531 : size_t nthistime;
532 :
533 20752906 : if (file->dirty)
534 : {
535 456 : if (BufFileFlush(file) != 0)
536 0 : return 0; /* could not flush... */
537 : Assert(!file->dirty);
538 : }
539 :
540 62272514 : while (size > 0)
541 : {
542 20768450 : if (file->pos >= file->nbytes)
543 : {
544 : /* Try to load more data into buffer. */
545 39430 : file->curOffset += file->pos;
546 39430 : file->pos = 0;
547 39430 : file->nbytes = 0;
548 39430 : BufFileLoadBuffer(file);
549 39430 : if (file->nbytes <= 0)
550 1748 : break; /* no more data available */
551 : }
552 :
553 20766702 : nthistime = file->nbytes - file->pos;
554 20766702 : if (nthistime > size)
555 20731152 : nthistime = size;
556 : Assert(nthistime > 0);
557 :
558 20766702 : memcpy(ptr, file->buffer.data + file->pos, nthistime);
559 :
560 20766702 : file->pos += nthistime;
561 20766702 : ptr = (void *) ((char *) ptr + nthistime);
562 20766702 : size -= nthistime;
563 20766702 : nread += nthistime;
564 : }
565 :
566 20752906 : return nread;
567 : }
568 :
569 : /*
570 : * BufFileWrite
571 : *
572 : * Like fwrite() except we assume 1-byte element size.
573 : */
574 : size_t
575 21979136 : BufFileWrite(BufFile *file, void *ptr, size_t size)
576 : {
577 21979136 : size_t nwritten = 0;
578 : size_t nthistime;
579 :
580 : Assert(!file->readOnly);
581 :
582 65964062 : while (size > 0)
583 : {
584 22005790 : if (file->pos >= BLCKSZ)
585 : {
586 : /* Buffer full, dump it out */
587 42658 : if (file->dirty)
588 : {
589 42658 : BufFileDumpBuffer(file);
590 42658 : if (file->dirty)
591 0 : break; /* I/O error */
592 : }
593 : else
594 : {
595 : /* Hmm, went directly from reading to writing? */
596 0 : file->curOffset += file->pos;
597 0 : file->pos = 0;
598 0 : file->nbytes = 0;
599 : }
600 : }
601 :
602 22005790 : nthistime = BLCKSZ - file->pos;
603 22005790 : if (nthistime > size)
604 21961618 : nthistime = size;
605 : Assert(nthistime > 0);
606 :
607 22005790 : memcpy(file->buffer.data + file->pos, ptr, nthistime);
608 :
609 22005790 : file->dirty = true;
610 22005790 : file->pos += nthistime;
611 22005790 : if (file->nbytes < file->pos)
612 22005790 : file->nbytes = file->pos;
613 22005790 : ptr = (void *) ((char *) ptr + nthistime);
614 22005790 : size -= nthistime;
615 22005790 : nwritten += nthistime;
616 : }
617 :
618 21979136 : return nwritten;
619 : }
620 :
621 : /*
622 : * BufFileFlush
623 : *
624 : * Like fflush()
625 : */
626 : static int
627 7066 : BufFileFlush(BufFile *file)
628 : {
629 7066 : if (file->dirty)
630 : {
631 3266 : BufFileDumpBuffer(file);
632 3266 : if (file->dirty)
633 0 : return EOF;
634 : }
635 :
636 7066 : return 0;
637 : }
638 :
639 : /*
640 : * BufFileSeek
641 : *
642 : * Like fseek(), except that target position needs two values in order to
643 : * work when logical filesize exceeds maximum value representable by off_t.
644 : * We do not support relative seeks across more than that, however.
645 : *
646 : * Result is 0 if OK, EOF if not. Logical position is not moved if an
647 : * impossible seek is attempted.
648 : */
649 : int
650 22732 : BufFileSeek(BufFile *file, int fileno, off_t offset, int whence)
651 : {
652 : int newFile;
653 : off_t newOffset;
654 :
655 22732 : switch (whence)
656 : {
657 : case SEEK_SET:
658 22712 : if (fileno < 0)
659 0 : return EOF;
660 22712 : newFile = fileno;
661 22712 : newOffset = offset;
662 22712 : break;
663 : case SEEK_CUR:
664 :
665 : /*
666 : * Relative seek considers only the signed offset, ignoring
667 : * fileno. Note that large offsets (> 1 gig) risk overflow in this
668 : * add, unless we have 64-bit off_t.
669 : */
670 20 : newFile = file->curFile;
671 20 : newOffset = (file->curOffset + file->pos) + offset;
672 20 : break;
673 : #ifdef NOT_USED
674 : case SEEK_END:
675 : /* could be implemented, not needed currently */
676 : break;
677 : #endif
678 : default:
679 0 : elog(ERROR, "invalid whence: %d", whence);
680 : return EOF;
681 : }
682 45464 : while (newOffset < 0)
683 : {
684 0 : if (--newFile < 0)
685 0 : return EOF;
686 0 : newOffset += MAX_PHYSICAL_FILESIZE;
687 : }
688 45380 : if (newFile == file->curFile &&
689 43692 : newOffset >= file->curOffset &&
690 21044 : newOffset <= file->curOffset + file->nbytes)
691 : {
692 : /*
693 : * Seek is to a point within existing buffer; we can just adjust
694 : * pos-within-buffer, without flushing buffer. Note this is OK
695 : * whether reading or writing, but buffer remains dirty if we were
696 : * writing.
697 : */
698 20954 : file->pos = (int) (newOffset - file->curOffset);
699 20954 : return 0;
700 : }
701 : /* Otherwise, must reposition buffer, so flush any dirty data */
702 1778 : if (BufFileFlush(file) != 0)
703 0 : return EOF;
704 :
705 : /*
706 : * At this point and no sooner, check for seek past last segment. The
707 : * above flush could have created a new segment, so checking sooner would
708 : * not work (at least not with this code).
709 : */
710 :
711 : /* convert seek to "start of next seg" to "end of last seg" */
712 1778 : if (newFile == file->numFiles && newOffset == 0)
713 : {
714 0 : newFile--;
715 0 : newOffset = MAX_PHYSICAL_FILESIZE;
716 : }
717 3556 : while (newOffset > MAX_PHYSICAL_FILESIZE)
718 : {
719 0 : if (++newFile >= file->numFiles)
720 0 : return EOF;
721 0 : newOffset -= MAX_PHYSICAL_FILESIZE;
722 : }
723 1778 : if (newFile >= file->numFiles)
724 0 : return EOF;
725 : /* Seek is OK! */
726 1778 : file->curFile = newFile;
727 1778 : file->curOffset = newOffset;
728 1778 : file->pos = 0;
729 1778 : file->nbytes = 0;
730 1778 : return 0;
731 : }
732 :
733 : void
734 90 : BufFileTell(BufFile *file, int *fileno, off_t *offset)
735 : {
736 90 : *fileno = file->curFile;
737 90 : *offset = file->curOffset + file->pos;
738 90 : }
739 :
740 : /*
741 : * BufFileSeekBlock --- block-oriented seek
742 : *
743 : * Performs absolute seek to the start of the n'th BLCKSZ-sized block of
744 : * the file. Note that users of this interface will fail if their files
745 : * exceed BLCKSZ * LONG_MAX bytes, but that is quite a lot; we don't work
746 : * with tables bigger than that, either...
747 : *
748 : * Result is 0 if OK, EOF if not. Logical position is not moved if an
749 : * impossible seek is attempted.
750 : */
751 : int
752 20960 : BufFileSeekBlock(BufFile *file, long blknum)
753 : {
754 41920 : return BufFileSeek(file,
755 20960 : (int) (blknum / BUFFILE_SEG_SIZE),
756 20960 : (off_t) (blknum % BUFFILE_SEG_SIZE) * BLCKSZ,
757 : SEEK_SET);
758 : }
759 :
760 : #ifdef NOT_USED
761 : /*
762 : * BufFileTellBlock --- block-oriented tell
763 : *
764 : * Any fractional part of a block in the current seek position is ignored.
765 : */
766 : long
767 : BufFileTellBlock(BufFile *file)
768 : {
769 : long blknum;
770 :
771 : blknum = (file->curOffset + file->pos) / BLCKSZ;
772 : blknum += file->curFile * BUFFILE_SEG_SIZE;
773 : return blknum;
774 : }
775 :
776 : #endif
777 :
778 : /*
779 : * Return the current shared BufFile size.
780 : *
781 : * Counts any holes left behind by BufFileAppend as part of the size.
782 : * ereport()s on failure.
783 : */
784 : int64
785 168 : BufFileSize(BufFile *file)
786 : {
787 : int64 lastFileSize;
788 :
789 : Assert(file->fileset != NULL);
790 :
791 : /* Get the size of the last physical file. */
792 168 : lastFileSize = FileSize(file->files[file->numFiles - 1]);
793 168 : if (lastFileSize < 0)
794 0 : ereport(ERROR,
795 : (errcode_for_file_access(),
796 : errmsg("could not determine size of temporary file \"%s\" from BufFile \"%s\": %m",
797 : FilePathName(file->files[file->numFiles - 1]),
798 : file->name)));
799 :
800 168 : return ((file->numFiles - 1) * (int64) MAX_PHYSICAL_FILESIZE) +
801 : lastFileSize;
802 : }
803 :
804 : /*
805 : * Append the contents of source file (managed within shared fileset) to
806 : * end of target file (managed within same shared fileset).
807 : *
808 : * Note that operation subsumes ownership of underlying resources from
809 : * "source". Caller should never call BufFileClose against source having
810 : * called here first. Resource owners for source and target must match,
811 : * too.
812 : *
813 : * This operation works by manipulating lists of segment files, so the
814 : * file content is always appended at a MAX_PHYSICAL_FILESIZE-aligned
815 : * boundary, typically creating empty holes before the boundary. These
816 : * areas do not contain any interesting data, and cannot be read from by
817 : * caller.
818 : *
819 : * Returns the block number within target where the contents of source
820 : * begins. Caller should apply this as an offset when working off block
821 : * positions that are in terms of the original BufFile space.
822 : */
823 : long
824 84 : BufFileAppend(BufFile *target, BufFile *source)
825 : {
826 84 : long startBlock = target->numFiles * BUFFILE_SEG_SIZE;
827 84 : int newNumFiles = target->numFiles + source->numFiles;
828 : int i;
829 :
830 : Assert(target->fileset != NULL);
831 : Assert(source->readOnly);
832 : Assert(!source->dirty);
833 : Assert(source->fileset != NULL);
834 :
835 84 : if (target->resowner != source->resowner)
836 0 : elog(ERROR, "could not append BufFile with non-matching resource owner");
837 :
838 84 : target->files = (File *)
839 84 : repalloc(target->files, sizeof(File) * newNumFiles);
840 168 : for (i = target->numFiles; i < newNumFiles; i++)
841 84 : target->files[i] = source->files[i - target->numFiles];
842 84 : target->numFiles = newNumFiles;
843 :
844 84 : return startBlock;
845 : }
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