On Sat, Oct 17, 2020 at 08:39:35AM -0700, Peter Geoghegan wrote:
> On Tue, Oct 13, 2020 at 7:26 PM Noah Misch <n...@leadboat.com> wrote:
> > 1. Disable parallelism for the index build under ExecuteTruncateGuts().
> > Nobody will mourn a performance loss from declining parallelism for an
> > empty index, but I feel like this is fixing in the wrong place.
> > 2. Make _bt_begin_parallel() and begin_parallel_vacuum() recognize the
> > debug_query_string==NULL case and reproduce it on the worker.
> > 3. Require bgworkers to set debug_query_string before entering code of
> > vacuum,
> > truncate, etc. Logical replication might synthesize a DDL statement, or
> > it
> > might just use a constant string.
> >
> > I tend to prefer (2), but (3) isn't bad. Opinions?
>
> I also prefer 2.
Thanks. Here is the pair of patches I plan to use. The second is equivalent
to v0; I just added a log message.
Author: Noah Misch <n...@leadboat.com>
Commit: Noah Misch <n...@leadboat.com>
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
7de4a1bcc56f494acbd0d6e70781df877dc8ecb5 introduced the first of these.
Reviewed by FIXME.
Discussion: https://postgr.es/m/20201014022636.ga1962...@rfd.leadboat.com
diff --git a/src/backend/access/heap/vacuumlazy.c
b/src/backend/access/heap/vacuumlazy.c
index 4f2f381..34ae8aa 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -3238,7 +3238,6 @@ begin_parallel_vacuum(Oid relid, Relation *Irel,
LVRelStats *vacrelstats,
WalUsage *wal_usage;
bool *can_parallel_vacuum;
long maxtuples;
- char *sharedquery;
Size est_shared;
Size est_deadtuples;
int nindexes_mwm = 0;
@@ -3335,9 +3334,14 @@ begin_parallel_vacuum(Oid relid, Relation *Irel,
LVRelStats *vacrelstats,
shm_toc_estimate_keys(&pcxt->estimator, 1);
/* Finally, estimate PARALLEL_VACUUM_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 */
InitializeParallelDSM(pcxt);
@@ -3382,10 +3386,16 @@ begin_parallel_vacuum(Oid relid, Relation *Irel,
LVRelStats *vacrelstats,
lps->wal_usage = wal_usage;
/* Store query string for workers */
- sharedquery = (char *) shm_toc_allocate(pcxt->toc, querylen + 1);
- memcpy(sharedquery, debug_query_string, querylen + 1);
- sharedquery[querylen] = '\0';
- shm_toc_insert(pcxt->toc, PARALLEL_VACUUM_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);
+ sharedquery[querylen] = '\0';
+ shm_toc_insert(pcxt->toc,
+ PARALLEL_VACUUM_KEY_QUERY_TEXT,
sharedquery);
+ }
pfree(can_parallel_vacuum);
return lps;
@@ -3528,7 +3538,7 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
elog(DEBUG1, "starting parallel vacuum worker for bulk delete");
/* Set debug_query_string for individual workers */
- sharedquery = shm_toc_lookup(toc, PARALLEL_VACUUM_KEY_QUERY_TEXT,
false);
+ sharedquery = shm_toc_lookup(toc, PARALLEL_VACUUM_KEY_QUERY_TEXT, true);
debug_query_string = sharedquery;
pgstat_report_activity(STATE_RUNNING, debug_query_string);
diff --git a/src/backend/access/nbtree/nbtsort.c
b/src/backend/access/nbtree/nbtsort.c
index efee867..8730de2 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -1466,7 +1466,6 @@ _bt_begin_parallel(BTBuildState *buildstate, bool
isconcurrent, int request)
WalUsage *walusage;
BufferUsage *bufferusage;
bool leaderparticipates = true;
- char *sharedquery;
int querylen;
#ifdef DISABLE_LEADER_PARTICIPATION
@@ -1533,9 +1532,14 @@ _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);
@@ -1599,9 +1603,14 @@ _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 WalUsage and BufferUsage; no need to
@@ -1806,7 +1815,7 @@ _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 */
Author: Noah Misch <n...@leadboat.com>
Commit: Noah Misch <n...@leadboat.com>
Set debug_query_string in worker_spi.
This makes elog.c emit the string, which is good practice for a
background worker that executes SQL strings.
Reviewed by FIXME.
Discussion: https://postgr.es/m/20201014022636.ga1962...@rfd.leadboat.com
diff --git a/src/test/modules/worker_spi/worker_spi.c
b/src/test/modules/worker_spi/worker_spi.c
index 1c7b17c..daf6c1d 100644
--- a/src/test/modules/worker_spi/worker_spi.c
+++ b/src/test/modules/worker_spi/worker_spi.c
@@ -113,16 +113,17 @@ initialize_worker_spi(worktable *table)
SPI_connect();
PushActiveSnapshot(GetTransactionSnapshot());
pgstat_report_activity(STATE_RUNNING, "initializing worker_spi schema");
/* XXX could we use CREATE SCHEMA IF NOT EXISTS? */
initStringInfo(&buf);
appendStringInfo(&buf, "select count(*) from pg_namespace where nspname
= '%s'",
table->schema);
+ debug_query_string = buf.data;
ret = SPI_execute(buf.data, true, 0);
if (ret != SPI_OK_SELECT)
elog(FATAL, "SPI_execute failed: error code %d", ret);
if (SPI_processed != 1)
elog(FATAL, "not a singleton result");
@@ -138,30 +139,32 @@ initialize_worker_spi(worktable *table)
appendStringInfo(&buf,
"CREATE SCHEMA \"%s\" "
"CREATE TABLE \"%s\" ("
" type text CHECK
(type IN ('total', 'delta')), "
" value
integer)"
"CREATE UNIQUE INDEX
\"%s_unique_total\" ON \"%s\" (type) "
"WHERE type = 'total'",
table->schema, table->name,
table->name, table->name);
+ debug_query_string = buf.data;
/* set statement start time */
SetCurrentStatementStartTimestamp();
ret = SPI_execute(buf.data, false, 0);
if (ret != SPI_OK_UTILITY)
elog(FATAL, "failed to create my schema");
}
SPI_finish();
PopActiveSnapshot();
CommitTransactionCommand();
pgstat_report_activity(STATE_IDLE, NULL);
+ debug_query_string = NULL;
}
void
worker_spi_main(Datum main_arg)
{
int index = DatumGetInt32(main_arg);
worktable *table;
StringInfoData buf;
@@ -206,16 +209,17 @@ worker_spi_main(Datum main_arg)
"UPDATE %s.%s "
"SET value = %s.value + total.sum "
"FROM total WHERE type = 'total' "
"RETURNING %s.value",
table->schema, table->name,
table->schema, table->name,
table->name,
table->name);
+ debug_query_string = buf.data;
/*
* Main loop: do this until the SIGTERM handler tells us to terminate
*/
while (!got_sigterm)
{
int ret;
