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Do not produce partial aggregation plans for the only chunk
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It doesn't make much sense.
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@akuzm
akuzm committed Dec 14, 2023
1 parent e0a3e30 commit 9a4eb12
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Showing 16 changed files with 171 additions and 193 deletions.
17 changes: 17 additions & 0 deletions src/planner/partialize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -461,6 +461,15 @@ generate_agg_pushdown_path(PlannerInfo *root, Path *cheapest_total_path, RelOptI
if (subpaths == NIL)
return;

if (list_length(subpaths) < 2)
{
/*
* Doesn't make sense to add per-chunk aggregation paths if there's
* only one chunk.
*/
return;
}

/* Generate agg paths on top of the append children */
List *sorted_subpaths = NIL;
List *hashed_subpaths = NIL;
Expand Down Expand Up @@ -580,6 +589,14 @@ generate_partial_agg_pushdown_path(PlannerInfo *root, Path *cheapest_partial_pat
if (subpaths == NIL)
return;

if (list_length(subpaths) < 2)
{
/*
* Doesn't make sense to add per-chunk aggregation paths if there's
* only one chunk.
*/
return;
}
/* Generate agg paths on top of the append children */
ListCell *lc;
List *sorted_subpaths = NIL;
Expand Down
130 changes: 50 additions & 80 deletions test/expected/agg_bookends.out
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Original file line number Diff line number Diff line change
Expand Up @@ -77,116 +77,92 @@ SELECT setting, current_setting(setting) AS value from (VALUES ('timescaledb.ena
(5 rows)

:PREFIX SELECT last(temp, time_alt) FROM btest;
QUERY PLAN
------------------------------------------------------------------
Finalize HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Partial HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(5 rows)
QUERY PLAN
------------------------------------------------------------
Aggregate (actual rows=1 loops=1)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(2 rows)

:PREFIX SELECT first(temp, time_alt) FROM btest;
QUERY PLAN
------------------------------------------------------------------
Finalize HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Partial HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(5 rows)
QUERY PLAN
------------------------------------------------------------
Aggregate (actual rows=1 loops=1)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(2 rows)

:PREFIX SELECT gp, last(temp, time) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

:PREFIX SELECT gp, first(temp, time) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

--check whole row
:PREFIX SELECT gp, first(btest, time) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

--check toasted col
:PREFIX SELECT gp, left(last(strid, time), 10) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

:PREFIX SELECT gp, last(temp, strid) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

:PREFIX SELECT gp, last(strid, temp) FROM btest GROUP BY gp ORDER BY gp;
QUERY PLAN
------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------
Sort (actual rows=2 loops=1)
Sort Key: _hyper_1_1_chunk.gp
Sort Method: quicksort
-> Finalize HashAggregate (actual rows=2 loops=1)
-> HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Partial HashAggregate (actual rows=2 loops=1)
Group Key: _hyper_1_1_chunk.gp
Batches: 1
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(10 rows)
-> Seq Scan on _hyper_1_1_chunk (actual rows=6 loops=1)
(7 rows)

BEGIN;
--check null value as last element
Expand Down Expand Up @@ -849,24 +825,18 @@ INSERT INTO btest_numeric VALUES('2018-01-20T09:00:43', NULL);
(5 rows)

:PREFIX SELECT first(time, quantity) FROM btest_numeric;
QUERY PLAN
------------------------------------------------------------------
Finalize HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Partial HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Seq Scan on _hyper_2_8_chunk (actual rows=2 loops=1)
(5 rows)
QUERY PLAN
------------------------------------------------------------
Aggregate (actual rows=1 loops=1)
-> Seq Scan on _hyper_2_8_chunk (actual rows=2 loops=1)
(2 rows)

:PREFIX SELECT last(time, quantity) FROM btest_numeric;
QUERY PLAN
------------------------------------------------------------------
Finalize HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Partial HashAggregate (actual rows=1 loops=1)
Batches: 1
-> Seq Scan on _hyper_2_8_chunk (actual rows=2 loops=1)
(5 rows)
QUERY PLAN
------------------------------------------------------------
Aggregate (actual rows=1 loops=1)
-> Seq Scan on _hyper_2_8_chunk (actual rows=2 loops=1)
(2 rows)

-- NULL values followed by non-NULL values
INSERT INTO btest_numeric VALUES('2019-01-20T09:00:43', 1);
Expand Down
10 changes: 5 additions & 5 deletions test/expected/parallel-13.out
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Original file line number Diff line number Diff line change
Expand Up @@ -641,11 +641,11 @@ SET max_parallel_workers_per_gather TO 2;
Finalize Aggregate
-> Gather
Workers Planned: 2
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Partial Aggregate
-> Partial Aggregate
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Seq Scan on _hyper_1_2_chunk
Expand Down
10 changes: 5 additions & 5 deletions test/expected/parallel-14.out
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Original file line number Diff line number Diff line change
Expand Up @@ -641,11 +641,11 @@ SET max_parallel_workers_per_gather TO 2;
Finalize Aggregate
-> Gather
Workers Planned: 2
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Partial Aggregate
-> Partial Aggregate
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Seq Scan on _hyper_1_2_chunk
Expand Down
10 changes: 5 additions & 5 deletions test/expected/parallel-15.out
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Original file line number Diff line number Diff line change
Expand Up @@ -642,11 +642,11 @@ SET max_parallel_workers_per_gather TO 2;
Finalize Aggregate
-> Gather
Workers Planned: 2
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Partial Aggregate
-> Partial Aggregate
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Seq Scan on _hyper_1_2_chunk
Expand Down
10 changes: 5 additions & 5 deletions test/expected/parallel-16.out
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Original file line number Diff line number Diff line change
Expand Up @@ -643,11 +643,11 @@ SET max_parallel_workers_per_gather TO 2;
Finalize Aggregate
-> Gather
Workers Planned: 2
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Partial Aggregate
-> Partial Aggregate
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Custom Scan (ChunkAppend) on test
Chunks excluded during startup: 0
-> Result
One-Time Filter: (length(version()) > 0)
-> Parallel Seq Scan on _hyper_1_2_chunk
Expand Down
17 changes: 7 additions & 10 deletions test/expected/partitionwise-13.out
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Original file line number Diff line number Diff line change
Expand Up @@ -889,18 +889,15 @@ FROM hyper_timepart
WHERE device = 1
GROUP BY 1
LIMIT 10;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------
Limit
Output: _hyper_3_8_chunk.device, (avg(_hyper_3_8_chunk.temp))
-> Finalize GroupAggregate
-> GroupAggregate
Output: _hyper_3_8_chunk.device, avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Partial GroupAggregate
Output: _hyper_3_8_chunk.device, PARTIAL avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(11 rows)
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(8 rows)

17 changes: 7 additions & 10 deletions test/expected/partitionwise-14.out
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Original file line number Diff line number Diff line change
Expand Up @@ -889,18 +889,15 @@ FROM hyper_timepart
WHERE device = 1
GROUP BY 1
LIMIT 10;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------
Limit
Output: _hyper_3_8_chunk.device, (avg(_hyper_3_8_chunk.temp))
-> Finalize GroupAggregate
-> GroupAggregate
Output: _hyper_3_8_chunk.device, avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Partial GroupAggregate
Output: _hyper_3_8_chunk.device, PARTIAL avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(11 rows)
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(8 rows)

17 changes: 7 additions & 10 deletions test/expected/partitionwise-15.out
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Original file line number Diff line number Diff line change
Expand Up @@ -889,18 +889,15 @@ FROM hyper_timepart
WHERE device = 1
GROUP BY 1
LIMIT 10;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------
Limit
Output: _hyper_3_8_chunk.device, (avg(_hyper_3_8_chunk.temp))
-> Finalize GroupAggregate
-> GroupAggregate
Output: _hyper_3_8_chunk.device, avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Partial GroupAggregate
Output: _hyper_3_8_chunk.device, PARTIAL avg(_hyper_3_8_chunk.temp)
Group Key: _hyper_3_8_chunk.device
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(11 rows)
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(8 rows)

16 changes: 7 additions & 9 deletions test/expected/partitionwise-16.out
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Original file line number Diff line number Diff line change
Expand Up @@ -889,16 +889,14 @@ FROM hyper_timepart
WHERE device = 1
GROUP BY 1
LIMIT 10;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------
Limit
Output: _hyper_3_8_chunk.device, (avg(_hyper_3_8_chunk.temp))
-> Finalize GroupAggregate
-> GroupAggregate
Output: _hyper_3_8_chunk.device, avg(_hyper_3_8_chunk.temp)
-> Partial GroupAggregate
Output: _hyper_3_8_chunk.device, PARTIAL avg(_hyper_3_8_chunk.temp)
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(9 rows)
-> Index Scan using _hyper_3_8_chunk_hyper_timepart_device_expr_idx on _timescaledb_internal._hyper_3_8_chunk
Output: _hyper_3_8_chunk.device, _hyper_3_8_chunk.temp
Index Cond: (_hyper_3_8_chunk.device = 1)
(7 rows)

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