Skip to content

Commit c9ce4a1

Browse files
robertmhaasrobertmhaas
committed
Eliminate "parallel degree" terminology.
This terminology provoked widespread complaints. So, instead, rename the GUC max_parallel_degree to max_parallel_workers_per_gather (leaving room for a possible future GUC max_parallel_workers that acts as a system-wide limit), and rename the parallel_degree reloption to parallel_workers. Rename structure members to match. These changes create a dump/restore hazard for users of PostgreSQL 9.6beta1 who have set the reloption (or applied the GUC using ALTER USER or ALTER DATABASE).
1 parent 6581e93 commit c9ce4a1

File tree

19 files changed

+99
-99
lines changed

19 files changed

+99
-99
lines changed

‎doc/src/sgml/config.sgml

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1998,16 +1998,16 @@ include_dir 'conf.d'
19981998
</listitem>
19991999
</varlistentry>
20002000

2001-
<varlistentry id="guc-max-parallel-degree" xreflabel="max_parallel_degree">
2002-
<term><varname>max_parallel_degree</varname> (<type>integer</type>)
2001+
<varlistentry id="guc-max-parallel-workers-per-gather" xreflabel="max_parallel_workers_per_gather">
2002+
<term><varname>max_parallel_workers_per_gather</varname> (<type>integer</type>)
20032003
<indexterm>
2004-
<primary><varname>max_parallel_degree</> configuration parameter</primary>
2004+
<primary><varname>max_parallel_workers_per_gather</> configuration parameter</primary>
20052005
</indexterm>
20062006
</term>
20072007
<listitem>
20082008
<para>
2009-
Sets the maximum number of workers that can be started for an
2010-
individual parallel operation. Parallel workers are taken from the
2009+
Sets the maximum number of workers that can be started by a single
2010+
<literal>Gather</literal> node. Parallel workers are taken from the
20112011
pool of processes established by
20122012
<xref linkend="guc-max-worker-processes">. Note that the requested
20132013
number of workers may not actually be available at runtime. If this

‎doc/src/sgml/ref/create_table.sgml

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -909,14 +909,14 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
909909
</varlistentry>
910910

911911
<varlistentry>
912-
<term><literal>parallel_degree</> (<type>integer</>)</term>
912+
<term><literal>parallel_workers</> (<type>integer</>)</term>
913913
<listitem>
914914
<para>
915-
The parallel degree for a table is the number of workers that should
916-
be used to assist a parallel scan of that table. If not set, the
917-
system will determine a value based on the relation size. The actual
918-
number of workers chosen by the planner may be less, for example due to
919-
the setting of <xref linkend="guc-max-parallel-degree">.
915+
This sets the number of workers that should be used to assist a parallel
916+
scan of this table. If not set, the system will determine a value based
917+
on the relation size. The actual number of workers chosen by the planner
918+
may be less, for example due to
919+
the setting of <xref linkend="guc-max-worker-processes">.
920920
</para>
921921
</listitem>
922922
</varlistentry>

‎doc/src/sgml/release-9.6.sgml

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -153,7 +153,7 @@
153153
<para>
154154
Use of parallel query execution can be controlled through the new
155155
configuration parameters
156-
<xref linkend="guc-max-parallel-degree">,
156+
<xref linkend="guc-max-parallel-workers-per-gather">,
157157
<xref linkend="guc-force-parallel-mode">,
158158
<xref linkend="guc-parallel-setup-cost">, and
159159
<xref linkend="guc-parallel-tuple-cost">.

‎src/backend/access/common/reloptions.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -270,7 +270,7 @@ static relopt_int intRelOpts[] =
270270
},
271271
{
272272
{
273-
"parallel_degree",
273+
"parallel_workers",
274274
"Number of parallel processes that can be used per executor node for this relation.",
275275
RELOPT_KIND_HEAP,
276276
AccessExclusiveLock
@@ -1301,8 +1301,8 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
13011301
offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, analyze_scale_factor)},
13021302
{"user_catalog_table", RELOPT_TYPE_BOOL,
13031303
offsetof(StdRdOptions, user_catalog_table)},
1304-
{"parallel_degree", RELOPT_TYPE_INT,
1305-
offsetof(StdRdOptions, parallel_degree)}
1304+
{"parallel_workers", RELOPT_TYPE_INT,
1305+
offsetof(StdRdOptions, parallel_workers)}
13061306
};
13071307

13081308
options = parseRelOptions(reloptions, validate, kind, &numoptions);

‎src/backend/nodes/outfuncs.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1609,7 +1609,7 @@ _outPathInfo(StringInfo str, const Path *node)
16091609
_outBitmapset(str, NULL);
16101610
WRITE_BOOL_FIELD(parallel_aware);
16111611
WRITE_BOOL_FIELD(parallel_safe);
1612-
WRITE_INT_FIELD(parallel_degree);
1612+
WRITE_INT_FIELD(parallel_workers);
16131613
WRITE_FLOAT_FIELD(rows, "%.0f");
16141614
WRITE_FLOAT_FIELD(startup_cost, "%.2f");
16151615
WRITE_FLOAT_FIELD(total_cost, "%.2f");

‎src/backend/optimizer/path/allpaths.c

Lines changed: 17 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -669,26 +669,26 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
669669
static void
670670
create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
671671
{
672-
int parallel_degree = 1;
672+
int parallel_workers = 1;
673673

674674
/*
675-
* If the user has set the parallel_degree reloption, we decide what to do
675+
* If the user has set the parallel_workers reloption, we decide what to do
676676
* based on the value of that option. Otherwise, we estimate a value.
677677
*/
678-
if (rel->rel_parallel_degree != -1)
678+
if (rel->rel_parallel_workers != -1)
679679
{
680680
/*
681-
* If parallel_degree = 0 is set for this relation, bail out. The
681+
* If parallel_workers = 0 is set for this relation, bail out. The
682682
* user does not want a parallel path for this relation.
683683
*/
684-
if (rel->rel_parallel_degree == 0)
684+
if (rel->rel_parallel_workers == 0)
685685
return;
686686

687687
/*
688-
* Use the table parallel_degree, but don't go further than
689-
* max_parallel_degree.
688+
* Use the table parallel_workers, but don't go further than
689+
* max_parallel_workers_per_gather.
690690
*/
691-
parallel_degree = Min(rel->rel_parallel_degree, max_parallel_degree);
691+
parallel_workers = Min(rel->rel_parallel_workers, max_parallel_workers_per_gather);
692692
}
693693
else
694694
{
@@ -711,17 +711,17 @@ create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
711711
* sophisticated, but we need something here for now.
712712
*/
713713
while (rel->pages > parallel_threshold * 3 &&
714-
parallel_degree < max_parallel_degree)
714+
parallel_workers < max_parallel_workers_per_gather)
715715
{
716-
parallel_degree++;
716+
parallel_workers++;
717717
parallel_threshold *= 3;
718718
if (parallel_threshold >= PG_INT32_MAX / 3)
719719
break;
720720
}
721721
}
722722

723723
/* Add an unordered partial path based on a parallel sequential scan. */
724-
add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_degree));
724+
add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
725725
}
726726

727727
/*
@@ -1242,25 +1242,25 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
12421242
{
12431243
AppendPath *appendpath;
12441244
ListCell *lc;
1245-
int parallel_degree = 0;
1245+
int parallel_workers = 0;
12461246

12471247
/*
1248-
* Decide what parallel degree to request for this append path. For
1249-
* now, we just use the maximum parallel degree of any member. It
1248+
* Decide on the numebr of workers to request for this append path. For
1249+
* now, we just use the maximum value from among the members. It
12501250
* might be useful to use a higher number if the Append node were
12511251
* smart enough to spread out the workers, but it currently isn't.
12521252
*/
12531253
foreach(lc, partial_subpaths)
12541254
{
12551255
Path *path = lfirst(lc);
12561256

1257-
parallel_degree = Max(parallel_degree, path->parallel_degree);
1257+
parallel_workers = Max(parallel_workers, path->parallel_workers);
12581258
}
1259-
Assert(parallel_degree > 0);
1259+
Assert(parallel_workers > 0);
12601260

12611261
/* Generate a partial append path. */
12621262
appendpath = create_append_path(rel, partial_subpaths, NULL,
1263-
parallel_degree);
1263+
parallel_workers);
12641264
add_partial_path(rel, (Path *) appendpath);
12651265
}
12661266

‎src/backend/optimizer/path/costsize.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -113,7 +113,7 @@ int effective_cache_size = DEFAULT_EFFECTIVE_CACHE_SIZE;
113113

114114
Cost disable_cost = 1.0e10;
115115

116-
int max_parallel_degree = 2;
116+
int max_parallel_workers_per_gather = 2;
117117

118118
bool enable_seqscan = true;
119119
bool enable_indexscan = true;
@@ -229,9 +229,9 @@ cost_seqscan(Path *path, PlannerInfo *root,
229229
cpu_run_cost += path->pathtarget->cost.per_tuple * path->rows;
230230

231231
/* Adjust costing for parallelism, if used. */
232-
if (path->parallel_degree > 0)
232+
if (path->parallel_workers > 0)
233233
{
234-
double parallel_divisor = path->parallel_degree;
234+
double parallel_divisor = path->parallel_workers;
235235
double leader_contribution;
236236

237237
/*
@@ -245,7 +245,7 @@ cost_seqscan(Path *path, PlannerInfo *root,
245245
* estimate that the leader spends 30% of its time servicing each
246246
* worker, and the remainder executing the parallel plan.
247247
*/
248-
leader_contribution = 1.0 - (0.3 * path->parallel_degree);
248+
leader_contribution = 1.0 - (0.3 * path->parallel_workers);
249249
if (leader_contribution > 0)
250250
parallel_divisor += leader_contribution;
251251

‎src/backend/optimizer/plan/createplan.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1394,7 +1394,7 @@ create_gather_plan(PlannerInfo *root, GatherPath *best_path)
13941394

13951395
gather_plan = make_gather(tlist,
13961396
NIL,
1397-
best_path->path.parallel_degree,
1397+
best_path->path.parallel_workers,
13981398
best_path->single_copy,
13991399
subplan);
14001400

‎src/backend/optimizer/plan/planner.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -245,7 +245,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
245245
glob->parallelModeOK = (cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
246246
IsUnderPostmaster && dynamic_shared_memory_type != DSM_IMPL_NONE &&
247247
parse->commandType == CMD_SELECT && !parse->hasModifyingCTE &&
248-
parse->utilityStmt == NULL && max_parallel_degree > 0 &&
248+
parse->utilityStmt == NULL && max_parallel_workers_per_gather > 0 &&
249249
!IsParallelWorker() && !IsolationIsSerializable() &&
250250
!has_parallel_hazard((Node *) parse, true);
251251

@@ -3622,7 +3622,7 @@ create_grouping_paths(PlannerInfo *root,
36223622
if (grouped_rel->partial_pathlist)
36233623
{
36243624
Path *path = (Path *) linitial(grouped_rel->partial_pathlist);
3625-
double total_groups = path->rows * path->parallel_degree;
3625+
double total_groups = path->rows * path->parallel_workers;
36263626

36273627
path = (Path *) create_gather_path(root,
36283628
grouped_rel,
@@ -3717,7 +3717,7 @@ create_grouping_paths(PlannerInfo *root,
37173717

37183718
if (hashaggtablesize < work_mem * 1024L)
37193719
{
3720-
double total_groups = path->rows * path->parallel_degree;
3720+
double total_groups = path->rows * path->parallel_workers;
37213721

37223722
path = (Path *) create_gather_path(root,
37233723
grouped_rel,

0 commit comments

Comments
 (0)