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Reproduce debug_query_string==NULL on parallel workers. 

Certain background workers initiate parallel queries while
debug_query_string==NULL, at which point they attempted strlen(NULL) and
died to SIGSEGV.  Older debug_query_string observers allow NULL, so do
likewise in these newer ones.  Back-patch to v11, where commit
7de4a1bcc5 introduced the first of these.

Discussion: https://postgr.es/m/20201014022636.GA1962668@rfd.leadboat.com
This commit is contained in:
Noah Misch 2020-10-31 08:43:28 -07:00
parent 24d769b905
commit 0454666758
1 changed files with 17 additions and 8 deletions
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25
src/backend/access/nbtree/nbtsort.c
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@ -1245,7 +1245,6 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
BTLeader *btleader = (BTLeader *) palloc0(sizeof(BTLeader));
BufferUsage *bufferusage;
bool leaderparticipates = true;
char *sharedquery;
int querylen;
#ifdef DISABLE_LEADER_PARTICIPATION
@ -1308,9 +1307,14 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
shm_toc_estimate_keys(&pcxt->estimator, 1);
/* Finally, estimate PARALLEL_KEY_QUERY_TEXT space */
querylen = strlen(debug_query_string);
shm_toc_estimate_chunk(&pcxt->estimator, querylen + 1);
shm_toc_estimate_keys(&pcxt->estimator, 1);
if (debug_query_string)
{
querylen = strlen(debug_query_string);
shm_toc_estimate_chunk(&pcxt->estimator, querylen + 1);
shm_toc_estimate_keys(&pcxt->estimator, 1);
}
else
querylen = 0; /* keep compiler quiet */
/* Everyone's had a chance to ask for space, so now create the DSM */
InitializeParallelDSM(pcxt);
@ -1372,9 +1376,14 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
}
/* Store query string for workers */
sharedquery = (char *) shm_toc_allocate(pcxt->toc, querylen + 1);
memcpy(sharedquery, debug_query_string, querylen + 1);
shm_toc_insert(pcxt->toc, PARALLEL_KEY_QUERY_TEXT, sharedquery);
if (debug_query_string)
{
char *sharedquery;
sharedquery = (char *) shm_toc_allocate(pcxt->toc, querylen + 1);
memcpy(sharedquery, debug_query_string, querylen + 1);
shm_toc_insert(pcxt->toc, PARALLEL_KEY_QUERY_TEXT, sharedquery);
}
/* Allocate space for each worker's BufferUsage; no need to initialize */
bufferusage = shm_toc_allocate(pcxt->toc,
@ -1577,7 +1586,7 @@ _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc)
#endif /* BTREE_BUILD_STATS */
/* Set debug_query_string for individual workers first */
sharedquery = shm_toc_lookup(toc, PARALLEL_KEY_QUERY_TEXT, false);
sharedquery = shm_toc_lookup(toc, PARALLEL_KEY_QUERY_TEXT, true);
debug_query_string = sharedquery;
/* Report the query string from leader */