Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * libpq_source.c
4 : * Functions for fetching files from a remote server via libpq.
5 : *
6 : * Copyright (c) 2013-2025, PostgreSQL Global Development Group
7 : *
8 : *-------------------------------------------------------------------------
9 : */
10 : #include "postgres_fe.h"
11 :
12 : #include "catalog/pg_type_d.h"
13 : #include "common/connect.h"
14 : #include "file_ops.h"
15 : #include "filemap.h"
16 : #include "lib/stringinfo.h"
17 : #include "pg_rewind.h"
18 : #include "port/pg_bswap.h"
19 : #include "rewind_source.h"
20 :
21 : /*
22 : * Files are fetched MAX_CHUNK_SIZE bytes at a time, and with a
23 : * maximum of MAX_CHUNKS_PER_QUERY chunks in a single query.
24 : */
25 : #define MAX_CHUNK_SIZE (1024 * 1024)
26 : #define MAX_CHUNKS_PER_QUERY 1000
27 :
28 : /* represents a request to fetch a piece of a file from the source */
29 : typedef struct
30 : {
31 : const char *path; /* path relative to data directory root */
32 : off_t offset;
33 : size_t length;
34 : } fetch_range_request;
35 :
36 : typedef struct
37 : {
38 : rewind_source common; /* common interface functions */
39 :
40 : PGconn *conn;
41 :
42 : /*
43 : * Queue of chunks that have been requested with the queue_fetch_range()
44 : * function, but have not been fetched from the remote server yet.
45 : */
46 : int num_requests;
47 : fetch_range_request request_queue[MAX_CHUNKS_PER_QUERY];
48 :
49 : /* temporary space for process_queued_fetch_requests() */
50 : StringInfoData paths;
51 : StringInfoData offsets;
52 : StringInfoData lengths;
53 : } libpq_source;
54 :
55 : static void init_libpq_conn(PGconn *conn);
56 : static char *run_simple_query(PGconn *conn, const char *sql);
57 : static void run_simple_command(PGconn *conn, const char *sql);
58 : static void appendArrayEscapedString(StringInfo buf, const char *str);
59 :
60 : static void process_queued_fetch_requests(libpq_source *src);
61 :
62 : /* public interface functions */
63 : static void libpq_traverse_files(rewind_source *source,
64 : process_file_callback_t callback);
65 : static void libpq_queue_fetch_file(rewind_source *source, const char *path, size_t len);
66 : static void libpq_queue_fetch_range(rewind_source *source, const char *path,
67 : off_t off, size_t len);
68 : static void libpq_finish_fetch(rewind_source *source);
69 : static char *libpq_fetch_file(rewind_source *source, const char *path,
70 : size_t *filesize);
71 : static XLogRecPtr libpq_get_current_wal_insert_lsn(rewind_source *source);
72 : static void libpq_destroy(rewind_source *source);
73 :
74 : /*
75 : * Create a new libpq source.
76 : *
77 : * The caller has already established the connection, but should not try
78 : * to use it while the source is active.
79 : */
80 : rewind_source *
81 12 : init_libpq_source(PGconn *conn)
82 : {
83 : libpq_source *src;
84 :
85 12 : init_libpq_conn(conn);
86 :
87 12 : src = pg_malloc0(sizeof(libpq_source));
88 :
89 12 : src->common.traverse_files = libpq_traverse_files;
90 12 : src->common.fetch_file = libpq_fetch_file;
91 12 : src->common.queue_fetch_file = libpq_queue_fetch_file;
92 12 : src->common.queue_fetch_range = libpq_queue_fetch_range;
93 12 : src->common.finish_fetch = libpq_finish_fetch;
94 12 : src->common.get_current_wal_insert_lsn = libpq_get_current_wal_insert_lsn;
95 12 : src->common.destroy = libpq_destroy;
96 :
97 12 : src->conn = conn;
98 :
99 12 : initStringInfo(&src->paths);
100 12 : initStringInfo(&src->offsets);
101 12 : initStringInfo(&src->lengths);
102 :
103 12 : return &src->common;
104 : }
105 :
106 : /*
107 : * Initialize a libpq connection for use.
108 : */
109 : static void
110 12 : init_libpq_conn(PGconn *conn)
111 : {
112 : PGresult *res;
113 : char *str;
114 :
115 : /* disable all types of timeouts */
116 12 : run_simple_command(conn, "SET statement_timeout = 0");
117 12 : run_simple_command(conn, "SET lock_timeout = 0");
118 12 : run_simple_command(conn, "SET idle_in_transaction_session_timeout = 0");
119 12 : run_simple_command(conn, "SET transaction_timeout = 0");
120 :
121 : /*
122 : * we don't intend to do any updates, put the connection in read-only mode
123 : * to keep us honest
124 : */
125 12 : run_simple_command(conn, "SET default_transaction_read_only = on");
126 :
127 : /* secure search_path */
128 12 : res = PQexec(conn, ALWAYS_SECURE_SEARCH_PATH_SQL);
129 12 : if (PQresultStatus(res) != PGRES_TUPLES_OK)
130 0 : pg_fatal("could not clear \"search_path\": %s",
131 : PQresultErrorMessage(res));
132 12 : PQclear(res);
133 :
134 : /*
135 : * Also check that full_page_writes is enabled. We can get torn pages if
136 : * a page is modified while we read it with pg_read_binary_file(), and we
137 : * rely on full page images to fix them.
138 : */
139 12 : str = run_simple_query(conn, "SHOW full_page_writes");
140 12 : if (strcmp(str, "on") != 0)
141 0 : pg_fatal("\"full_page_writes\" must be enabled in the source server");
142 12 : pg_free(str);
143 :
144 : /* Prepare a statement we'll use to fetch files */
145 12 : res = PQprepare(conn, "fetch_chunks_stmt",
146 : "SELECT path, begin,\n"
147 : " pg_read_binary_file(path, begin, len, true) AS chunk\n"
148 : "FROM unnest ($1::text[], $2::int8[], $3::int4[]) as x(path, begin, len)",
149 : 3, NULL);
150 :
151 12 : if (PQresultStatus(res) != PGRES_COMMAND_OK)
152 0 : pg_fatal("could not prepare statement to fetch file contents: %s",
153 : PQresultErrorMessage(res));
154 12 : PQclear(res);
155 12 : }
156 :
157 : /*
158 : * Run a query that returns a single value.
159 : *
160 : * The result should be pg_free'd after use.
161 : */
162 : static char *
163 22 : run_simple_query(PGconn *conn, const char *sql)
164 : {
165 : PGresult *res;
166 : char *result;
167 :
168 22 : res = PQexec(conn, sql);
169 :
170 22 : if (PQresultStatus(res) != PGRES_TUPLES_OK)
171 0 : pg_fatal("error running query (%s) on source server: %s",
172 : sql, PQresultErrorMessage(res));
173 :
174 : /* sanity check the result set */
175 22 : if (PQnfields(res) != 1 || PQntuples(res) != 1 || PQgetisnull(res, 0, 0))
176 0 : pg_fatal("unexpected result set from query");
177 :
178 22 : result = pg_strdup(PQgetvalue(res, 0, 0));
179 :
180 22 : PQclear(res);
181 :
182 22 : return result;
183 : }
184 :
185 : /*
186 : * Run a command.
187 : *
188 : * In the event of a failure, exit immediately.
189 : */
190 : static void
191 60 : run_simple_command(PGconn *conn, const char *sql)
192 : {
193 : PGresult *res;
194 :
195 60 : res = PQexec(conn, sql);
196 :
197 60 : if (PQresultStatus(res) != PGRES_COMMAND_OK)
198 0 : pg_fatal("error running query (%s) in source server: %s",
199 : sql, PQresultErrorMessage(res));
200 :
201 60 : PQclear(res);
202 60 : }
203 :
204 : /*
205 : * Call the pg_current_wal_insert_lsn() function in the remote system.
206 : */
207 : static XLogRecPtr
208 10 : libpq_get_current_wal_insert_lsn(rewind_source *source)
209 : {
210 10 : PGconn *conn = ((libpq_source *) source)->conn;
211 : XLogRecPtr result;
212 : uint32 hi;
213 : uint32 lo;
214 : char *val;
215 :
216 10 : val = run_simple_query(conn, "SELECT pg_current_wal_insert_lsn()");
217 :
218 10 : if (sscanf(val, "%X/%X", &hi, &lo) != 2)
219 0 : pg_fatal("unrecognized result \"%s\" for current WAL insert location", val);
220 :
221 10 : result = ((uint64) hi) << 32 | lo;
222 :
223 10 : pg_free(val);
224 :
225 10 : return result;
226 : }
227 :
228 : /*
229 : * Get a list of all files in the data directory.
230 : */
231 : static void
232 12 : libpq_traverse_files(rewind_source *source, process_file_callback_t callback)
233 : {
234 12 : PGconn *conn = ((libpq_source *) source)->conn;
235 : PGresult *res;
236 : const char *sql;
237 : int i;
238 :
239 : /*
240 : * Create a recursive directory listing of the whole data directory.
241 : *
242 : * The WITH RECURSIVE part does most of the work. The second part gets the
243 : * targets of the symlinks in pg_tblspc directory.
244 : *
245 : * XXX: There is no backend function to get a symbolic link's target in
246 : * general, so if the admin has put any custom symbolic links in the data
247 : * directory, they won't be copied correctly.
248 : */
249 12 : sql =
250 : "WITH RECURSIVE files (path, filename, size, isdir) AS (\n"
251 : " SELECT '' AS path, filename, size, isdir FROM\n"
252 : " (SELECT pg_ls_dir('.', true, false) AS filename) AS fn,\n"
253 : " pg_stat_file(fn.filename, true) AS this\n"
254 : " UNION ALL\n"
255 : " SELECT parent.path || parent.filename || '/' AS path,\n"
256 : " fn, this.size, this.isdir\n"
257 : " FROM files AS parent,\n"
258 : " pg_ls_dir(parent.path || parent.filename, true, false) AS fn,\n"
259 : " pg_stat_file(parent.path || parent.filename || '/' || fn, true) AS this\n"
260 : " WHERE parent.isdir = 't'\n"
261 : ")\n"
262 : "SELECT path || filename, size, isdir,\n"
263 : " pg_tablespace_location(pg_tablespace.oid) AS link_target\n"
264 : "FROM files\n"
265 : "LEFT OUTER JOIN pg_tablespace ON files.path = 'pg_tblspc/'\n"
266 : " AND oid::text = files.filename\n";
267 12 : res = PQexec(conn, sql);
268 :
269 12 : if (PQresultStatus(res) != PGRES_TUPLES_OK)
270 0 : pg_fatal("could not fetch file list: %s",
271 : PQresultErrorMessage(res));
272 :
273 : /* sanity check the result set */
274 12 : if (PQnfields(res) != 4)
275 0 : pg_fatal("unexpected result set while fetching file list");
276 :
277 : /* Read result to local variables */
278 13966 : for (i = 0; i < PQntuples(res); i++)
279 : {
280 : char *path;
281 : int64 filesize;
282 : bool isdir;
283 : char *link_target;
284 : file_type_t type;
285 :
286 13954 : if (PQgetisnull(res, i, 1))
287 : {
288 : /*
289 : * The file was removed from the server while the query was
290 : * running. Ignore it.
291 : */
292 0 : continue;
293 : }
294 :
295 13954 : path = PQgetvalue(res, i, 0);
296 13954 : filesize = atoll(PQgetvalue(res, i, 1));
297 13954 : isdir = (strcmp(PQgetvalue(res, i, 2), "t") == 0);
298 13954 : link_target = PQgetvalue(res, i, 3);
299 :
300 13954 : if (link_target[0])
301 : {
302 : /*
303 : * In-place tablespaces are directories located in pg_tblspc/ with
304 : * relative paths.
305 : */
306 2 : if (is_absolute_path(link_target))
307 0 : type = FILE_TYPE_SYMLINK;
308 : else
309 2 : type = FILE_TYPE_DIRECTORY;
310 : }
311 13952 : else if (isdir)
312 334 : type = FILE_TYPE_DIRECTORY;
313 : else
314 13618 : type = FILE_TYPE_REGULAR;
315 :
316 13954 : callback(path, type, filesize, link_target);
317 : }
318 12 : PQclear(res);
319 12 : }
320 :
321 : /*
322 : * Queue up a request to fetch a file from remote system.
323 : */
324 : static void
325 3918 : libpq_queue_fetch_file(rewind_source *source, const char *path, size_t len)
326 : {
327 : /*
328 : * Truncate the target file immediately, and queue a request to fetch it
329 : * from the source. If the file is small, smaller than MAX_CHUNK_SIZE,
330 : * request fetching a full-sized chunk anyway, so that if the file has
331 : * become larger in the source system, after we scanned the source
332 : * directory, we still fetch the whole file. This only works for files up
333 : * to MAX_CHUNK_SIZE, but that's good enough for small configuration files
334 : * and such that are changed every now and then, but not WAL-logged. For
335 : * larger files, we fetch up to the original size.
336 : *
337 : * Even with that mechanism, there is an inherent race condition if the
338 : * file is modified at the same instant that we're copying it, so that we
339 : * might copy a torn version of the file with one half from the old
340 : * version and another half from the new. But pg_basebackup has the same
341 : * problem, and it hasn't been a problem in practice.
342 : *
343 : * It might seem more natural to truncate the file later, when we receive
344 : * it from the source server, but then we'd need to track which
345 : * fetch-requests are for a whole file.
346 : */
347 3918 : open_target_file(path, true);
348 3918 : libpq_queue_fetch_range(source, path, 0, Max(len, MAX_CHUNK_SIZE));
349 3918 : }
350 :
351 : /*
352 : * Queue up a request to fetch a piece of a file from remote system.
353 : */
354 : static void
355 5560 : libpq_queue_fetch_range(rewind_source *source, const char *path, off_t off,
356 : size_t len)
357 : {
358 5560 : libpq_source *src = (libpq_source *) source;
359 :
360 : /*
361 : * Does this request happen to be a continuation of the previous chunk? If
362 : * so, merge it with the previous one.
363 : *
364 : * XXX: We use pointer equality to compare the path. That's good enough
365 : * for our purposes; the caller always passes the same pointer for the
366 : * same filename. If it didn't, we would fail to merge requests, but it
367 : * wouldn't affect correctness.
368 : */
369 5560 : if (src->num_requests > 0)
370 : {
371 5548 : fetch_range_request *prev = &src->request_queue[src->num_requests - 1];
372 :
373 5548 : if (prev->offset + prev->length == off &&
374 1244 : prev->length < MAX_CHUNK_SIZE &&
375 1244 : prev->path == path)
376 : {
377 : /*
378 : * Extend the previous request to cover as much of this new
379 : * request as possible, without exceeding MAX_CHUNK_SIZE.
380 : */
381 : size_t thislen;
382 :
383 1242 : thislen = Min(len, MAX_CHUNK_SIZE - prev->length);
384 1242 : prev->length += thislen;
385 :
386 1242 : off += thislen;
387 1242 : len -= thislen;
388 :
389 : /*
390 : * Fall through to create new requests for any remaining 'len'
391 : * that didn't fit in the previous chunk.
392 : */
393 : }
394 : }
395 :
396 : /* Divide the request into pieces of MAX_CHUNK_SIZE bytes each */
397 10418 : while (len > 0)
398 : {
399 : int32 thislen;
400 :
401 : /* if the queue is full, perform all the work queued up so far */
402 4858 : if (src->num_requests == MAX_CHUNKS_PER_QUERY)
403 0 : process_queued_fetch_requests(src);
404 :
405 4858 : thislen = Min(len, MAX_CHUNK_SIZE);
406 4858 : src->request_queue[src->num_requests].path = path;
407 4858 : src->request_queue[src->num_requests].offset = off;
408 4858 : src->request_queue[src->num_requests].length = thislen;
409 4858 : src->num_requests++;
410 :
411 4858 : off += thislen;
412 4858 : len -= thislen;
413 : }
414 5560 : }
415 :
416 : /*
417 : * Fetch all the queued chunks and write them to the target data directory.
418 : */
419 : static void
420 12 : libpq_finish_fetch(rewind_source *source)
421 : {
422 12 : process_queued_fetch_requests((libpq_source *) source);
423 12 : }
424 :
425 : static void
426 12 : process_queued_fetch_requests(libpq_source *src)
427 : {
428 : const char *params[3];
429 : PGresult *res;
430 : int chunkno;
431 :
432 12 : if (src->num_requests == 0)
433 0 : return;
434 :
435 12 : pg_log_debug("getting %d file chunks", src->num_requests);
436 :
437 : /*
438 : * The prepared statement, 'fetch_chunks_stmt', takes three arrays with
439 : * the same length as parameters: paths, offsets and lengths. Construct
440 : * the string representations of them.
441 : */
442 12 : resetStringInfo(&src->paths);
443 12 : resetStringInfo(&src->offsets);
444 12 : resetStringInfo(&src->lengths);
445 :
446 12 : appendStringInfoChar(&src->paths, '{');
447 12 : appendStringInfoChar(&src->offsets, '{');
448 12 : appendStringInfoChar(&src->lengths, '{');
449 4870 : for (int i = 0; i < src->num_requests; i++)
450 : {
451 4858 : fetch_range_request *rq = &src->request_queue[i];
452 :
453 4858 : if (i > 0)
454 : {
455 4846 : appendStringInfoChar(&src->paths, ',');
456 4846 : appendStringInfoChar(&src->offsets, ',');
457 4846 : appendStringInfoChar(&src->lengths, ',');
458 : }
459 :
460 4858 : appendArrayEscapedString(&src->paths, rq->path);
461 4858 : appendStringInfo(&src->offsets, INT64_FORMAT, (int64) rq->offset);
462 4858 : appendStringInfo(&src->lengths, INT64_FORMAT, (int64) rq->length);
463 : }
464 12 : appendStringInfoChar(&src->paths, '}');
465 12 : appendStringInfoChar(&src->offsets, '}');
466 12 : appendStringInfoChar(&src->lengths, '}');
467 :
468 : /*
469 : * Execute the prepared statement.
470 : */
471 12 : params[0] = src->paths.data;
472 12 : params[1] = src->offsets.data;
473 12 : params[2] = src->lengths.data;
474 :
475 12 : if (PQsendQueryPrepared(src->conn, "fetch_chunks_stmt", 3, params, NULL, NULL, 1) != 1)
476 0 : pg_fatal("could not send query: %s", PQerrorMessage(src->conn));
477 :
478 12 : if (PQsetSingleRowMode(src->conn) != 1)
479 0 : pg_fatal("could not set libpq connection to single row mode");
480 :
481 : /*----
482 : * The result set is of format:
483 : *
484 : * path text -- path in the data directory, e.g "base/1/123"
485 : * begin int8 -- offset within the file
486 : * chunk bytea -- file content
487 : *----
488 : */
489 12 : chunkno = 0;
490 4882 : while ((res = PQgetResult(src->conn)) != NULL)
491 : {
492 4870 : fetch_range_request *rq = &src->request_queue[chunkno];
493 : char *filename;
494 : int filenamelen;
495 : int64 chunkoff;
496 : int chunksize;
497 : char *chunk;
498 :
499 4870 : switch (PQresultStatus(res))
500 : {
501 4858 : case PGRES_SINGLE_TUPLE:
502 4858 : break;
503 :
504 12 : case PGRES_TUPLES_OK:
505 12 : PQclear(res);
506 12 : continue; /* final zero-row result */
507 :
508 0 : default:
509 0 : pg_fatal("unexpected result while fetching remote files: %s",
510 : PQresultErrorMessage(res));
511 : }
512 :
513 4858 : if (chunkno > src->num_requests)
514 0 : pg_fatal("received more data chunks than requested");
515 :
516 : /* sanity check the result set */
517 4858 : if (PQnfields(res) != 3 || PQntuples(res) != 1)
518 0 : pg_fatal("unexpected result set size while fetching remote files");
519 :
520 9716 : if (PQftype(res, 0) != TEXTOID ||
521 9716 : PQftype(res, 1) != INT8OID ||
522 4858 : PQftype(res, 2) != BYTEAOID)
523 : {
524 0 : pg_fatal("unexpected data types in result set while fetching remote files: %u %u %u",
525 : PQftype(res, 0), PQftype(res, 1), PQftype(res, 2));
526 : }
527 :
528 4858 : if (PQfformat(res, 0) != 1 &&
529 0 : PQfformat(res, 1) != 1 &&
530 0 : PQfformat(res, 2) != 1)
531 : {
532 0 : pg_fatal("unexpected result format while fetching remote files");
533 : }
534 :
535 9716 : if (PQgetisnull(res, 0, 0) ||
536 4858 : PQgetisnull(res, 0, 1))
537 : {
538 0 : pg_fatal("unexpected null values in result while fetching remote files");
539 : }
540 :
541 4858 : if (PQgetlength(res, 0, 1) != sizeof(int64))
542 0 : pg_fatal("unexpected result length while fetching remote files");
543 :
544 : /* Read result set to local variables */
545 4858 : memcpy(&chunkoff, PQgetvalue(res, 0, 1), sizeof(int64));
546 4858 : chunkoff = pg_ntoh64(chunkoff);
547 4858 : chunksize = PQgetlength(res, 0, 2);
548 :
549 4858 : filenamelen = PQgetlength(res, 0, 0);
550 4858 : filename = pg_malloc(filenamelen + 1);
551 4858 : memcpy(filename, PQgetvalue(res, 0, 0), filenamelen);
552 4858 : filename[filenamelen] = '\0';
553 :
554 4858 : chunk = PQgetvalue(res, 0, 2);
555 :
556 : /*
557 : * If a file has been deleted on the source, remove it on the target
558 : * as well. Note that multiple unlink() calls may happen on the same
559 : * file if multiple data chunks are associated with it, hence ignore
560 : * unconditionally anything missing.
561 : */
562 4858 : if (PQgetisnull(res, 0, 2))
563 : {
564 0 : pg_log_debug("received null value for chunk for file \"%s\", file has been deleted",
565 : filename);
566 0 : remove_target_file(filename, true);
567 : }
568 : else
569 : {
570 4858 : pg_log_debug("received chunk for file \"%s\", offset %" PRId64 ", size %d",
571 : filename, chunkoff, chunksize);
572 :
573 4858 : if (strcmp(filename, rq->path) != 0)
574 : {
575 0 : pg_fatal("received data for file \"%s\", when requested for \"%s\"",
576 : filename, rq->path);
577 : }
578 4858 : if (chunkoff != rq->offset)
579 0 : pg_fatal("received data at offset %" PRId64 " of file \"%s\", when requested for offset %lld",
580 : chunkoff, rq->path, (long long int) rq->offset);
581 :
582 : /*
583 : * We should not receive more data than we requested, or
584 : * pg_read_binary_file() messed up. We could receive less,
585 : * though, if the file was truncated in the source after we
586 : * checked its size. That's OK, there should be a WAL record of
587 : * the truncation, which will get replayed when you start the
588 : * target system for the first time after pg_rewind has completed.
589 : */
590 4858 : if (chunksize > rq->length)
591 0 : pg_fatal("received more than requested for file \"%s\"", rq->path);
592 :
593 4858 : open_target_file(filename, false);
594 :
595 4858 : write_target_range(chunk, chunkoff, chunksize);
596 : }
597 :
598 4858 : pg_free(filename);
599 :
600 4858 : PQclear(res);
601 4858 : chunkno++;
602 : }
603 12 : if (chunkno != src->num_requests)
604 0 : pg_fatal("unexpected number of data chunks received");
605 :
606 12 : src->num_requests = 0;
607 : }
608 :
609 : /*
610 : * Escape a string to be used as element in a text array constant
611 : */
612 : static void
613 4858 : appendArrayEscapedString(StringInfo buf, const char *str)
614 : {
615 4858 : appendStringInfoCharMacro(buf, '\"');
616 88636 : while (*str)
617 : {
618 83778 : char ch = *str;
619 :
620 83778 : if (ch == '"' || ch == '\\')
621 0 : appendStringInfoCharMacro(buf, '\\');
622 :
623 83778 : appendStringInfoCharMacro(buf, ch);
624 :
625 83778 : str++;
626 : }
627 4858 : appendStringInfoCharMacro(buf, '\"');
628 4858 : }
629 :
630 : /*
631 : * Fetch a single file as a malloc'd buffer.
632 : */
633 : static char *
634 34 : libpq_fetch_file(rewind_source *source, const char *path, size_t *filesize)
635 : {
636 34 : PGconn *conn = ((libpq_source *) source)->conn;
637 : PGresult *res;
638 : char *result;
639 : int len;
640 : const char *paramValues[1];
641 :
642 34 : paramValues[0] = path;
643 34 : res = PQexecParams(conn, "SELECT pg_read_binary_file($1)",
644 : 1, NULL, paramValues, NULL, NULL, 1);
645 :
646 34 : if (PQresultStatus(res) != PGRES_TUPLES_OK)
647 0 : pg_fatal("could not fetch remote file \"%s\": %s",
648 : path, PQresultErrorMessage(res));
649 :
650 : /* sanity check the result set */
651 34 : if (PQntuples(res) != 1 || PQgetisnull(res, 0, 0))
652 0 : pg_fatal("unexpected result set while fetching remote file \"%s\"",
653 : path);
654 :
655 : /* Read result to local variables */
656 34 : len = PQgetlength(res, 0, 0);
657 34 : result = pg_malloc(len + 1);
658 34 : memcpy(result, PQgetvalue(res, 0, 0), len);
659 34 : result[len] = '\0';
660 :
661 34 : PQclear(res);
662 :
663 34 : pg_log_debug("fetched file \"%s\", length %d", path, len);
664 :
665 34 : if (filesize)
666 24 : *filesize = len;
667 34 : return result;
668 : }
669 :
670 : /*
671 : * Close a libpq source.
672 : */
673 : static void
674 12 : libpq_destroy(rewind_source *source)
675 : {
676 12 : libpq_source *src = (libpq_source *) source;
677 :
678 12 : pfree(src->paths.data);
679 12 : pfree(src->offsets.data);
680 12 : pfree(src->lengths.data);
681 12 : pfree(src);
682 :
683 : /* NOTE: we don't close the connection here, as it was not opened by us. */
684 12 : }
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