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sharedtuplestore.c
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1 /*-------------------------------------------------------------------------
2  *
3  * sharedtuplestore.c
4  * Simple mechanism for sharing tuples between backends.
5  *
6  * This module contains a shared temporary tuple storage mechanism providing
7  * a parallel-aware subset of the features of tuplestore.c. Multiple backends
8  * can write to a SharedTuplestore, and then multiple backends can later scan
9  * the stored tuples. Currently, the only scan type supported is a parallel
10  * scan where each backend reads an arbitrary subset of the tuples that were
11  * written.
12  *
13  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
14  * Portions Copyright (c) 1994, Regents of the University of California
15  *
16  * IDENTIFICATION
17  * src/backend/utils/sort/sharedtuplestore.c
18  *
19  *-------------------------------------------------------------------------
20  */
21 
22 #include "postgres.h"
23 
24 #include "access/htup.h"
25 #include "access/htup_details.h"
26 #include "miscadmin.h"
27 #include "storage/buffile.h"
28 #include "storage/lwlock.h"
29 #include "storage/sharedfileset.h"
30 #include "utils/sharedtuplestore.h"
31 
32 /*
33  * The size of chunks, in pages. This is somewhat arbitrarily set to match
34  * the size of HASH_CHUNK, so that Parallel Hash obtains new chunks of tuples
35  * at approximately the same rate as it allocates new chunks of memory to
36  * insert them into.
37  */
38 #define STS_CHUNK_PAGES 4
39 #define STS_CHUNK_HEADER_SIZE offsetof(SharedTuplestoreChunk, data)
40 #define STS_CHUNK_DATA_SIZE (STS_CHUNK_PAGES * BLCKSZ - STS_CHUNK_HEADER_SIZE)
41 
42 /* Chunk written to disk. */
43 typedef struct SharedTuplestoreChunk
44 {
45  int ntuples; /* Number of tuples in this chunk. */
46  int overflow; /* If overflow, how many including this one? */
49 
50 /* Per-participant shared state. */
52 {
54  BlockNumber read_page; /* Page number for next read. */
55  BlockNumber npages; /* Number of pages written. */
56  bool writing; /* Used only for assertions. */
58 
59 /* The control object that lives in shared memory. */
61 {
62  int nparticipants; /* Number of participants that can write. */
63  int flags; /* Flag bits from SHARED_TUPLESTORE_XXX */
64  size_t meta_data_size; /* Size of per-tuple header. */
65  char name[NAMEDATALEN]; /* A name for this tuplestore. */
66 
67  /* Followed by per-participant shared state. */
69 };
70 
71 /* Per-participant state that lives in backend-local memory. */
73 {
74  int participant; /* My participant number. */
75  SharedTuplestore *sts; /* The shared state. */
76  SharedFileSet *fileset; /* The SharedFileSet holding files. */
77  MemoryContext context; /* Memory context for buffers. */
78 
79  /* State for reading. */
80  int read_participant; /* The current participant to read from. */
81  BufFile *read_file; /* The current file to read from. */
82  int read_ntuples_available; /* The number of tuples in chunk. */
83  int read_ntuples; /* How many tuples have we read from chunk? */
84  size_t read_bytes; /* How many bytes have we read from chunk? */
85  char *read_buffer; /* A buffer for loading tuples. */
87  BlockNumber read_next_page; /* Lowest block we'll consider reading. */
88 
89  /* State for writing. */
90  SharedTuplestoreChunk *write_chunk; /* Buffer for writing. */
91  BufFile *write_file; /* The current file to write to. */
92  BlockNumber write_page; /* The next page to write to. */
93  char *write_pointer; /* Current write pointer within chunk. */
94  char *write_end; /* One past the end of the current chunk. */
95 };
96 
97 static void sts_filename(char *name, SharedTuplestoreAccessor *accessor,
98  int participant);
99 
100 /*
101  * Return the amount of shared memory required to hold SharedTuplestore for a
102  * given number of participants.
103  */
104 size_t
105 sts_estimate(int participants)
106 {
107  return offsetof(SharedTuplestore, participants) +
108  sizeof(SharedTuplestoreParticipant) * participants;
109 }
110 
111 /*
112  * Initialize a SharedTuplestore in existing shared memory. There must be
113  * space for sts_estimate(participants) bytes. If flags includes the value
114  * SHARED_TUPLESTORE_SINGLE_PASS, the files may in future be removed more
115  * eagerly (but this isn't yet implemented).
116  *
117  * Tuples that are stored may optionally carry a piece of fixed sized
118  * meta-data which will be retrieved along with the tuple. This is useful for
119  * the hash values used in multi-batch hash joins, but could have other
120  * applications.
121  *
122  * The caller must supply a SharedFileSet, which is essentially a directory
123  * that will be cleaned up automatically, and a name which must be unique
124  * across all SharedTuplestores created in the same SharedFileSet.
125  */
127 sts_initialize(SharedTuplestore *sts, int participants,
128  int my_participant_number,
129  size_t meta_data_size,
130  int flags,
131  SharedFileSet *fileset,
132  const char *name)
133 {
134  SharedTuplestoreAccessor *accessor;
135  int i;
136 
137  Assert(my_participant_number < participants);
138 
139  sts->nparticipants = participants;
140  sts->meta_data_size = meta_data_size;
141  sts->flags = flags;
142 
143  if (strlen(name) > sizeof(sts->name) - 1)
144  elog(ERROR, "SharedTuplestore name too long");
145  strcpy(sts->name, name);
146 
147  /*
148  * Limit meta-data so it + tuple size always fits into a single chunk.
149  * sts_puttuple() and sts_read_tuple() could be made to support scenarios
150  * where that's not the case, but it's not currently required. If so,
151  * meta-data size probably should be made variable, too.
152  */
153  if (meta_data_size + sizeof(uint32) >= STS_CHUNK_DATA_SIZE)
154  elog(ERROR, "meta-data too long");
155 
156  for (i = 0; i < participants; ++i)
157  {
160  sts->participants[i].read_page = 0;
161  sts->participants[i].writing = false;
162  }
163 
164  accessor = palloc0(sizeof(SharedTuplestoreAccessor));
165  accessor->participant = my_participant_number;
166  accessor->sts = sts;
167  accessor->fileset = fileset;
168  accessor->context = CurrentMemoryContext;
169 
170  return accessor;
171 }
172 
173 /*
174  * Attach to a SharedTuplestore that has been initialized by another backend,
175  * so that this backend can read and write tuples.
176  */
179  int my_participant_number,
180  SharedFileSet *fileset)
181 {
182  SharedTuplestoreAccessor *accessor;
183 
184  Assert(my_participant_number < sts->nparticipants);
185 
186  accessor = palloc0(sizeof(SharedTuplestoreAccessor));
187  accessor->participant = my_participant_number;
188  accessor->sts = sts;
189  accessor->fileset = fileset;
190  accessor->context = CurrentMemoryContext;
191 
192  return accessor;
193 }
194 
195 static void
197 {
198  size_t size;
199 
200  size = STS_CHUNK_PAGES * BLCKSZ;
201  BufFileWrite(accessor->write_file, accessor->write_chunk, size);
202  memset(accessor->write_chunk, 0, size);
203  accessor->write_pointer = &accessor->write_chunk->data[0];
204  accessor->sts->participants[accessor->participant].npages +=
206 }
207 
208 /*
209  * Finish writing tuples. This must be called by all backends that have
210  * written data before any backend begins reading it.
211  */
212 void
214 {
215  if (accessor->write_file != NULL)
216  {
217  sts_flush_chunk(accessor);
218  BufFileClose(accessor->write_file);
219  pfree(accessor->write_chunk);
220  accessor->write_chunk = NULL;
221  accessor->write_file = NULL;
222  accessor->sts->participants[accessor->participant].writing = false;
223  }
224 }
225 
226 /*
227  * Prepare to rescan. Only one participant must call this. After it returns,
228  * all participants may call sts_begin_parallel_scan() and then loop over
229  * sts_parallel_scan_next(). This function must not be called concurrently
230  * with a scan, and synchronization to avoid that is the caller's
231  * responsibility.
232  */
233 void
235 {
236  int i;
237 
238  /*
239  * Reset the shared read head for all participants' files. Also set the
240  * initial chunk size to the minimum (any increases from that size will be
241  * recorded in chunk_expansion_log).
242  */
243  for (i = 0; i < accessor->sts->nparticipants; ++i)
244  {
245  accessor->sts->participants[i].read_page = 0;
246  }
247 }
248 
249 /*
250  * Begin scanning the contents in parallel.
251  */
252 void
254 {
256 
257  /* End any existing scan that was in progress. */
258  sts_end_parallel_scan(accessor);
259 
260  /*
261  * Any backend that might have written into this shared tuplestore must
262  * have called sts_end_write(), so that all buffers are flushed and the
263  * files have stopped growing.
264  */
265  for (i = 0; i < accessor->sts->nparticipants; ++i)
266  Assert(!accessor->sts->participants[i].writing);
267 
268  /*
269  * We will start out reading the file that THIS backend wrote. There may
270  * be some caching locality advantage to that.
271  */
272  accessor->read_participant = accessor->participant;
273  accessor->read_file = NULL;
274  accessor->read_next_page = 0;
275 }
276 
277 /*
278  * Finish a parallel scan, freeing associated backend-local resources.
279  */
280 void
282 {
283  /*
284  * Here we could delete all files if SHARED_TUPLESTORE_SINGLE_PASS, but
285  * we'd probably need a reference count of current parallel scanners so we
286  * could safely do it only when the reference count reaches zero.
287  */
288  if (accessor->read_file != NULL)
289  {
290  BufFileClose(accessor->read_file);
291  accessor->read_file = NULL;
292  }
293 }
294 
295 /*
296  * Write a tuple. If a meta-data size was provided to sts_initialize, then a
297  * pointer to meta data of that size must be provided.
298  */
299 void
300 sts_puttuple(SharedTuplestoreAccessor *accessor, void *meta_data,
301  MinimalTuple tuple)
302 {
303  size_t size;
304 
305  /* Do we have our own file yet? */
306  if (accessor->write_file == NULL)
307  {
308  SharedTuplestoreParticipant *participant;
309  char name[MAXPGPATH];
310 
311  /* Create one. Only this backend will write into it. */
312  sts_filename(name, accessor, accessor->participant);
313  accessor->write_file = BufFileCreateShared(accessor->fileset, name);
314 
315  /* Set up the shared state for this backend's file. */
316  participant = &accessor->sts->participants[accessor->participant];
317  participant->writing = true; /* for assertions only */
318  }
319 
320  /* Do we have space? */
321  size = accessor->sts->meta_data_size + tuple->t_len;
322  if (accessor->write_pointer + size >= accessor->write_end)
323  {
324  if (accessor->write_chunk == NULL)
325  {
326  /* First time through. Allocate chunk. */
327  accessor->write_chunk = (SharedTuplestoreChunk *)
329  STS_CHUNK_PAGES * BLCKSZ);
330  accessor->write_chunk->ntuples = 0;
331  accessor->write_pointer = &accessor->write_chunk->data[0];
332  accessor->write_end = (char *)
333  accessor->write_chunk + STS_CHUNK_PAGES * BLCKSZ;
334  }
335  else
336  {
337  /* See if flushing helps. */
338  sts_flush_chunk(accessor);
339  }
340 
341  /* It may still not be enough in the case of a gigantic tuple. */
342  if (accessor->write_pointer + size >= accessor->write_end)
343  {
344  size_t written;
345 
346  /*
347  * We'll write the beginning of the oversized tuple, and then
348  * write the rest in some number of 'overflow' chunks.
349  *
350  * sts_initialize() verifies that the size of the tuple +
351  * meta-data always fits into a chunk. Because the chunk has been
352  * flushed above, we can be sure to have all of a chunk's usable
353  * space available.
354  */
355  Assert(accessor->write_pointer + accessor->sts->meta_data_size +
356  sizeof(uint32) < accessor->write_end);
357 
358  /* Write the meta-data as one chunk. */
359  if (accessor->sts->meta_data_size > 0)
360  memcpy(accessor->write_pointer, meta_data,
361  accessor->sts->meta_data_size);
362 
363  /*
364  * Write as much of the tuple as we can fit. This includes the
365  * tuple's size at the start.
366  */
367  written = accessor->write_end - accessor->write_pointer -
368  accessor->sts->meta_data_size;
369  memcpy(accessor->write_pointer + accessor->sts->meta_data_size,
370  tuple, written);
371  ++accessor->write_chunk->ntuples;
372  size -= accessor->sts->meta_data_size;
373  size -= written;
374  /* Now write as many overflow chunks as we need for the rest. */
375  while (size > 0)
376  {
377  size_t written_this_chunk;
378 
379  sts_flush_chunk(accessor);
380 
381  /*
382  * How many overflow chunks to go? This will allow readers to
383  * skip all of them at once instead of reading each one.
384  */
385  accessor->write_chunk->overflow = (size + STS_CHUNK_DATA_SIZE - 1) /
387  written_this_chunk =
388  Min(accessor->write_end - accessor->write_pointer, size);
389  memcpy(accessor->write_pointer, (char *) tuple + written,
390  written_this_chunk);
391  accessor->write_pointer += written_this_chunk;
392  size -= written_this_chunk;
393  written += written_this_chunk;
394  }
395  return;
396  }
397  }
398 
399  /* Copy meta-data and tuple into buffer. */
400  if (accessor->sts->meta_data_size > 0)
401  memcpy(accessor->write_pointer, meta_data,
402  accessor->sts->meta_data_size);
403  memcpy(accessor->write_pointer + accessor->sts->meta_data_size, tuple,
404  tuple->t_len);
405  accessor->write_pointer += size;
406  ++accessor->write_chunk->ntuples;
407 }
408 
409 static MinimalTuple
410 sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
411 {
412  MinimalTuple tuple;
413  uint32 size;
414  size_t remaining_size;
415  size_t this_chunk_size;
416  char *destination;
417 
418  /*
419  * We'll keep track of bytes read from this chunk so that we can detect an
420  * overflowing tuple and switch to reading overflow pages.
421  */
422  if (accessor->sts->meta_data_size > 0)
423  {
424  if (BufFileRead(accessor->read_file,
425  meta_data,
426  accessor->sts->meta_data_size) !=
427  accessor->sts->meta_data_size)
428  ereport(ERROR,
430  errmsg("could not read from shared tuplestore temporary file"),
431  errdetail_internal("Short read while reading meta-data.")));
432  accessor->read_bytes += accessor->sts->meta_data_size;
433  }
434  if (BufFileRead(accessor->read_file,
435  &size,
436  sizeof(size)) != sizeof(size))
437  ereport(ERROR,
439  errmsg("could not read from shared tuplestore temporary file"),
440  errdetail_internal("Short read while reading size.")));
441  accessor->read_bytes += sizeof(size);
442  if (size > accessor->read_buffer_size)
443  {
444  size_t new_read_buffer_size;
445 
446  if (accessor->read_buffer != NULL)
447  pfree(accessor->read_buffer);
448  new_read_buffer_size = Max(size, accessor->read_buffer_size * 2);
449  accessor->read_buffer =
450  MemoryContextAlloc(accessor->context, new_read_buffer_size);
451  accessor->read_buffer_size = new_read_buffer_size;
452  }
453  remaining_size = size - sizeof(uint32);
454  this_chunk_size = Min(remaining_size,
455  BLCKSZ * STS_CHUNK_PAGES - accessor->read_bytes);
456  destination = accessor->read_buffer + sizeof(uint32);
457  if (BufFileRead(accessor->read_file,
458  destination,
459  this_chunk_size) != this_chunk_size)
460  ereport(ERROR,
462  errmsg("could not read from shared tuplestore temporary file"),
463  errdetail_internal("Short read while reading tuple.")));
464  accessor->read_bytes += this_chunk_size;
465  remaining_size -= this_chunk_size;
466  destination += this_chunk_size;
467  ++accessor->read_ntuples;
468 
469  /* Check if we need to read any overflow chunks. */
470  while (remaining_size > 0)
471  {
472  /* We are now positioned at the start of an overflow chunk. */
473  SharedTuplestoreChunk chunk_header;
474 
475  if (BufFileRead(accessor->read_file, &chunk_header, STS_CHUNK_HEADER_SIZE) !=
477  ereport(ERROR,
479  errmsg("could not read from shared tuplestore temporary file"),
480  errdetail_internal("Short read while reading overflow chunk header.")));
481  accessor->read_bytes = STS_CHUNK_HEADER_SIZE;
482  if (chunk_header.overflow == 0)
483  ereport(ERROR,
485  errmsg("unexpected chunk in shared tuplestore temporary file"),
486  errdetail_internal("Expected overflow chunk.")));
487  accessor->read_next_page += STS_CHUNK_PAGES;
488  this_chunk_size = Min(remaining_size,
489  BLCKSZ * STS_CHUNK_PAGES -
491  if (BufFileRead(accessor->read_file,
492  destination,
493  this_chunk_size) != this_chunk_size)
494  ereport(ERROR,
496  errmsg("could not read from shared tuplestore temporary file"),
497  errdetail_internal("Short read while reading tuple.")));
498  accessor->read_bytes += this_chunk_size;
499  remaining_size -= this_chunk_size;
500  destination += this_chunk_size;
501 
502  /*
503  * These will be used to count regular tuples following the oversized
504  * tuple that spilled into this overflow chunk.
505  */
506  accessor->read_ntuples = 0;
507  accessor->read_ntuples_available = chunk_header.ntuples;
508  }
509 
510  tuple = (MinimalTuple) accessor->read_buffer;
511  tuple->t_len = size;
512 
513  return tuple;
514 }
515 
516 /*
517  * Get the next tuple in the current parallel scan.
518  */
521 {
523  BlockNumber read_page;
524  bool eof;
525 
526  for (;;)
527  {
528  /* Can we read more tuples from the current chunk? */
529  if (accessor->read_ntuples < accessor->read_ntuples_available)
530  return sts_read_tuple(accessor, meta_data);
531 
532  /* Find the location of a new chunk to read. */
533  p = &accessor->sts->participants[accessor->read_participant];
534 
536  /* We can skip directly past overflow pages we know about. */
537  if (p->read_page < accessor->read_next_page)
538  p->read_page = accessor->read_next_page;
539  eof = p->read_page >= p->npages;
540  if (!eof)
541  {
542  /* Claim the next chunk. */
543  read_page = p->read_page;
544  /* Advance the read head for the next reader. */
546  accessor->read_next_page = p->read_page;
547  }
548  LWLockRelease(&p->lock);
549 
550  if (!eof)
551  {
552  SharedTuplestoreChunk chunk_header;
553  size_t nread;
554 
555  /* Make sure we have the file open. */
556  if (accessor->read_file == NULL)
557  {
558  char name[MAXPGPATH];
559 
560  sts_filename(name, accessor, accessor->read_participant);
561  accessor->read_file =
562  BufFileOpenShared(accessor->fileset, name, O_RDONLY);
563  }
564 
565  /* Seek and load the chunk header. */
566  if (BufFileSeekBlock(accessor->read_file, read_page) != 0)
567  ereport(ERROR,
569  errmsg("could not seek to block %u in shared tuplestore temporary file",
570  read_page)));
571  nread = BufFileRead(accessor->read_file, &chunk_header,
573  if (nread != STS_CHUNK_HEADER_SIZE)
574  ereport(ERROR,
576  errmsg("could not read from shared tuplestore temporary file: read only %zu of %zu bytes",
577  nread, STS_CHUNK_HEADER_SIZE)));
578 
579  /*
580  * If this is an overflow chunk, we skip it and any following
581  * overflow chunks all at once.
582  */
583  if (chunk_header.overflow > 0)
584  {
585  accessor->read_next_page = read_page +
586  chunk_header.overflow * STS_CHUNK_PAGES;
587  continue;
588  }
589 
590  accessor->read_ntuples = 0;
591  accessor->read_ntuples_available = chunk_header.ntuples;
592  accessor->read_bytes = STS_CHUNK_HEADER_SIZE;
593 
594  /* Go around again, so we can get a tuple from this chunk. */
595  }
596  else
597  {
598  if (accessor->read_file != NULL)
599  {
600  BufFileClose(accessor->read_file);
601  accessor->read_file = NULL;
602  }
603 
604  /*
605  * Try the next participant's file. If we've gone full circle,
606  * we're done.
607  */
608  accessor->read_participant = (accessor->read_participant + 1) %
609  accessor->sts->nparticipants;
610  if (accessor->read_participant == accessor->participant)
611  break;
612  accessor->read_next_page = 0;
613 
614  /* Go around again, so we can get a chunk from this file. */
615  }
616  }
617 
618  return NULL;
619 }
620 
621 /*
622  * Create the name used for the BufFile that a given participant will write.
623  */
624 static void
625 sts_filename(char *name, SharedTuplestoreAccessor *accessor, int participant)
626 {
627  snprintf(name, MAXPGPATH, "%s.p%d", accessor->sts->name, participant);
628 }
char name[NAMEDATALEN]
Definition: lwlock.h:31
SharedTuplestoreAccessor * sts_initialize(SharedTuplestore *sts, int participants, int my_participant_number, size_t meta_data_size, int flags, SharedFileSet *fileset, const char *name)
void sts_puttuple(SharedTuplestoreAccessor *accessor, void *meta_data, MinimalTuple tuple)
size_t sts_estimate(int participants)
#define Min(x, y)
Definition: c.h:927
static void sts_flush_chunk(SharedTuplestoreAccessor *accessor)
SharedTuplestoreParticipant participants[FLEXIBLE_ARRAY_MEMBER]
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:283
static void sts_filename(char *name, SharedTuplestoreAccessor *accessor, int participant)
uint32 BlockNumber
Definition: block.h:31
SharedTuplestore * sts
void BufFileClose(BufFile *file)
Definition: buffile.c:395
int errdetail_internal(const char *fmt,...)
Definition: elog.c:984
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1812
#define NAMEDATALEN
void pfree(void *pointer)
Definition: mcxt.c:1057
#define STS_CHUNK_HEADER_SIZE
#define ERROR
Definition: elog.h:43
void sts_end_parallel_scan(SharedTuplestoreAccessor *accessor)
#define MAXPGPATH
struct SharedTuplestoreChunk SharedTuplestoreChunk
BufFile * BufFileCreateShared(SharedFileSet *fileset, const char *name)
Definition: buffile.c:262
MinimalTupleData * MinimalTuple
Definition: htup.h:27
int errcode_for_file_access(void)
Definition: elog.c:633
SharedTuplestoreAccessor * sts_attach(SharedTuplestore *sts, int my_participant_number, SharedFileSet *fileset)
unsigned int uint32
Definition: c.h:374
MemoryContext CurrentMemoryContext
Definition: mcxt.c:38
void sts_begin_parallel_scan(SharedTuplestoreAccessor *accessor)
static MinimalTuple sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
struct SharedTuplestoreParticipant SharedTuplestoreParticipant
BufFile * BufFileOpenShared(SharedFileSet *fileset, const char *name, int mode)
Definition: buffile.c:284
void LWLockInitialize(LWLock *lock, int tranche_id)
Definition: lwlock.c:745
void * palloc0(Size size)
Definition: mcxt.c:981
int BufFileSeekBlock(BufFile *file, long blknum)
Definition: buffile.c:761
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:840
#define ereport(elevel,...)
Definition: elog.h:144
#define Max(x, y)
Definition: c.h:921
#define Assert(condition)
Definition: c.h:745
#define STS_CHUNK_DATA_SIZE
SharedTuplestoreChunk * write_chunk
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1208
const char * name
Definition: encode.c:561
void sts_reinitialize(SharedTuplestoreAccessor *accessor)
#define STS_CHUNK_PAGES
int errmsg(const char *fmt,...)
Definition: elog.c:824
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:797
#define elog(elevel,...)
Definition: elog.h:214
int i
size_t BufFileRead(BufFile *file, void *ptr, size_t size)
Definition: buffile.c:543
MinimalTuple sts_parallel_scan_next(SharedTuplestoreAccessor *accessor, void *meta_data)
void BufFileWrite(BufFile *file, void *ptr, size_t size)
Definition: buffile.c:586
char data[FLEXIBLE_ARRAY_MEMBER]
#define snprintf
Definition: port.h:193
#define offsetof(type, field)
Definition: c.h:668
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
void sts_end_write(SharedTuplestoreAccessor *accessor)