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Skip ChunkAppend if AppendPath has no children

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Since postgres has optimizations for Append paths without children
we do not replace those paths with ChunkAppend. While this will
prevent ChunkAppendPaths without children during planning, in the
executor it is still possible for ChunkAppend to have no children
as run-time exclusion may remove all of them.
This commit is contained in:
Sven Klemm 2021-04-22 00:08:52 +02:00 committed by Sven Klemm
parent 8fd4ecbdd9
commit fc3f8305e3
5 changed files with 21 additions and 15 deletions
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8
src/planner.c
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@ -483,8 +483,13 @@ should_chunk_append(Hypertable *ht, PlannerInfo *root, RelOptInfo *rel, Path *pa
* Params this Path might benefit from startup or runtime exclusion
*/
{
AppendPath *append = castNode(AppendPath, path);
ListCell *lc;
/* Don't create ChunkAppend with no children */
if (list_length(append->subpaths) == 0)
return false;
foreach (lc, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
@ -501,10 +506,11 @@ should_chunk_append(Hypertable *ht, PlannerInfo *root, RelOptInfo *rel, Path *pa
* Can we do ordered append
*/
{
MergeAppendPath *merge = castNode(MergeAppendPath, path);
PathKey *pk;
ListCell *lc;
if (!ordered || path->pathkeys == NIL)
if (!ordered || path->pathkeys == NIL || list_length(merge->subpaths) == 0)
return false;
pk = linitial_node(PathKey, path->pathkeys);

6
test/expected/append-12.out
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@ -329,14 +329,14 @@ AND date_part('dow', time) between 1 and 5
GROUP BY t
ORDER BY t DESC;
QUERY PLAN
------------------------------------------------------------------------------
-----------------------------------------------------------
GroupAggregate (actual rows=0 loops=1)
Group Key: (date_trunc('year'::text, "time"))
-> Sort (actual rows=0 loops=1)
Sort Key: (date_trunc('year'::text, "time")) DESC
Sort Method: quicksort
-> Custom Scan (ChunkAppend) on append_test (actual rows=0 loops=1)
Chunks excluded during startup: 0
-> Result (actual rows=0 loops=1)
One-Time Filter: false
(7 rows)
-- a parameterized query can safely constify params, so won't be

6
test/expected/append-13.out
View File

@ -329,14 +329,14 @@ AND date_part('dow', time) between 1 and 5
GROUP BY t
ORDER BY t DESC;
QUERY PLAN
------------------------------------------------------------------------------
-----------------------------------------------------------
GroupAggregate (actual rows=0 loops=1)
Group Key: (date_trunc('year'::text, "time"))
-> Sort (actual rows=0 loops=1)
Sort Key: (date_trunc('year'::text, "time")) DESC
Sort Method: quicksort
-> Custom Scan (ChunkAppend) on append_test (actual rows=0 loops=1)
Chunks excluded during startup: 0
-> Result (actual rows=0 loops=1)
One-Time Filter: false
(7 rows)
-- a parameterized query can safely constify params, so won't be

6
tsl/test/expected/continuous_aggs_union_view-12.out
View File

@ -366,9 +366,9 @@ SELECT _timescaledb_internal.cagg_watermark(:boundary_view_id);
----------------------------------------------------------------------------------------------------------------------------------
Append (actual rows=4 loops=1)
-> HashAggregate (actual rows=0 loops=1)
Group Key: _materialized_hypertable_6.time_bucket
-> Custom Scan (ChunkAppend) on _materialized_hypertable_6 (actual rows=0 loops=1)
Chunks excluded during startup: 0
Group Key: time_bucket
-> Result (actual rows=0 loops=1)
One-Time Filter: false
-> HashAggregate (actual rows=4 loops=1)
Group Key: time_bucket(10, boundary_test."time")
-> Custom Scan (ChunkAppend) on boundary_test (actual rows=4 loops=1)

6
tsl/test/expected/continuous_aggs_union_view-13.out
View File

@ -366,10 +366,10 @@ SELECT _timescaledb_internal.cagg_watermark(:boundary_view_id);
----------------------------------------------------------------------------------------------------------------------------------
Append (actual rows=4 loops=1)
-> HashAggregate (actual rows=0 loops=1)
Group Key: _materialized_hypertable_6.time_bucket
Group Key: time_bucket
Batches: 1
-> Custom Scan (ChunkAppend) on _materialized_hypertable_6 (actual rows=0 loops=1)
Chunks excluded during startup: 0
-> Result (actual rows=0 loops=1)
One-Time Filter: false
-> HashAggregate (actual rows=4 loops=1)
Group Key: time_bucket(10, boundary_test."time")
Batches: 1