Remove outdated workaround from columnar sort planning (timescale#9809)

We used to have a workaround there that added cost to account for
projection needed by Sort node. It proved to be more harmful than
useful, so it was removed, but some code was left over. Remove it too.

The main part removed here:
timescale#8416

This leads to some 6x speedups on some queries to partially compressed
tables.

Author: akuzm

tsl/src/nodes/columnar_scan/columnar_scan.c

@@ -1733,15 +1733,6 @@ build_on_single_compressed_path(PlannerInfo *root, const Chunk *chunk, RelOptInf
 			continue;
 		}
 
-		if (decompression_path == chunk_path_no_sort)
-		{
-			/*
-			 * We can't use the unsorted decompression path directly because it
-			 * doesn't have the sort projection cost workaround.
-			 */
-			continue;
-		}
-
 		if (!bms_is_empty(chunk_rel->lateral_relids) || !bms_is_empty(req_outer))
 		{
 			/*
@@ -1755,10 +1746,7 @@ build_on_single_compressed_path(PlannerInfo *root, const Chunk *chunk, RelOptInf
 			/*
 			 * We have to remove the explicit Sort, otherwise it will lead to
 			 * planning time regression because of double call of
-			 * prepare_sort_from_pathkeys() in MergeAppend plan creation. Still,
-			 * we have to use the copy of ColumnarScan path that we created
-			 * for explicit sorting, because it has the sort projection cost
-			 * workaround.
+			 * prepare_sort_from_pathkeys() in MergeAppend plan creation.
 			 */
 			decompression_path = castNode(SortPath, decompression_path)->subpath;
 		}

tsl/test/expected/columnar_index_scan-16.out

@@ -2010,11 +2010,13 @@ ORDER BY device;
 :PREFIX SELECT count(DISTINCT device) FROM metrics;
 --- QUERY PLAN ---
  Aggregate
-   ->  Sort
+   ->  Merge Append
          Sort Key: metrics.device
-         ->  Append
+         ->  Custom Scan (SkipScan) on _hyper_1_1_chunk
                ->  Custom Scan (ColumnarScan) on _hyper_1_1_chunk
-                     ->  Seq Scan on compress_hyper_2_2_chunk
+                     ->  Index Scan using compress_hyper_2_2_chunk_device_sensor__ts_meta_v2_last_tim_idx on compress_hyper_2_2_chunk
+         ->  Sort
+               Sort Key: _hyper_1_1_chunk.device
                ->  Seq Scan on _hyper_1_1_chunk
 
 :PREFIX SELECT first(DISTINCT value3, time) FROM metrics;
@@ -2462,19 +2464,15 @@ SET enable_partitionwise_aggregate = off;
          ->  Merge Append
                Sort Key: m1.device
                ->  Custom Scan (ColumnarScan) on _hyper_1_1_chunk m1_1
-                     ->  Sort
-                           Sort Key: compress_hyper_2_2_chunk.device
-                           ->  Seq Scan on compress_hyper_2_2_chunk
+                     ->  Index Scan using compress_hyper_2_2_chunk_device_sensor__ts_meta_v2_last_tim_idx on compress_hyper_2_2_chunk
                ->  Sort
                      Sort Key: m1_1.device
                      ->  Seq Scan on _hyper_1_1_chunk m1_1
          ->  Materialize
                ->  Merge Append
                      Sort Key: m2.device
                      ->  Custom Scan (ColumnarScan) on _hyper_1_1_chunk m2_1
-                           ->  Sort
-                                 Sort Key: compress_hyper_2_2_chunk_1.device
-                                 ->  Seq Scan on compress_hyper_2_2_chunk compress_hyper_2_2_chunk_1
+                           ->  Index Scan using compress_hyper_2_2_chunk_device_sensor__ts_meta_v2_last_tim_idx on compress_hyper_2_2_chunk compress_hyper_2_2_chunk_1
                      ->  Sort
                            Sort Key: m2_1.device
                            ->  Seq Scan on _hyper_1_1_chunk m2_1

tsl/test/expected/columnar_index_scan-17.out

@@ -1315,16 +1315,15 @@ ORDER BY device_id;
 --- QUERY PLAN ---
  Finalize GroupAggregate
    Group Key: compression_insert.device_id
-   ->  Sort
+   ->  Merge Append
          Sort Key: compression_insert.device_id
-         ->  Append
-               ->  Partial GroupAggregate
-                     Group Key: _hyper_31_110_chunk.device_id
-                     ->  Custom Scan (ColumnarIndexScan) on _hyper_31_110_chunk
-                           ->  Index Scan using compress_hyper_32_111_chunk_device_id__ts_meta_v2_last_time_idx on compress_hyper_32_111_chunk
-               ->  Partial GroupAggregate
-                     Group Key: _hyper_31_110_chunk.device_id
-                     ->  Index Only Scan using _hyper_31_110_chunk_compression_insert_device_id_time_idx on _hyper_31_110_chunk
+         ->  Partial GroupAggregate
+               Group Key: _hyper_31_110_chunk.device_id
+               ->  Custom Scan (ColumnarIndexScan) on _hyper_31_110_chunk
+                     ->  Index Scan using compress_hyper_32_111_chunk_device_id__ts_meta_v2_last_time_idx on compress_hyper_32_111_chunk
+         ->  Partial GroupAggregate
+               Group Key: _hyper_31_110_chunk.device_id
+               ->  Index Only Scan using _hyper_31_110_chunk_compression_insert_device_id_time_idx on _hyper_31_110_chunk
 
 SELECT device_id, count(*)
 FROM compression_insert

tsl/test/expected/columnar_index_scan-18.out

@@ -2625,23 +2625,23 @@ EXPLAIN (buffers off, costs off) SELECT * FROM test_partials ORDER BY time;
    Order: test_partials."time"
    ->  Merge Append
          Sort Key: test_partials."time"
-         ->  Custom Scan (ColumnarScan) on _hyper_35_68_chunk
-               ->  Sort
-                     Sort Key: compress_hyper_36_71_chunk._ts_meta_v2_last_time, compress_hyper_36_71_chunk._ts_meta_v2_first_time
+         ->  Sort
+               Sort Key: _hyper_35_68_chunk."time"
+               ->  Custom Scan (ColumnarScan) on _hyper_35_68_chunk
                      ->  Seq Scan on compress_hyper_36_71_chunk
          ->  Index Scan Backward using _hyper_35_68_chunk_test_partials_time_idx on _hyper_35_68_chunk
    ->  Merge Append
          Sort Key: test_partials."time"
-         ->  Custom Scan (ColumnarScan) on _hyper_35_69_chunk
-               ->  Sort
-                     Sort Key: compress_hyper_36_72_chunk._ts_meta_v2_last_time, compress_hyper_36_72_chunk._ts_meta_v2_first_time
+         ->  Sort
+               Sort Key: _hyper_35_69_chunk."time"
+               ->  Custom Scan (ColumnarScan) on _hyper_35_69_chunk
                      ->  Seq Scan on compress_hyper_36_72_chunk
          ->  Index Scan Backward using _hyper_35_69_chunk_test_partials_time_idx on _hyper_35_69_chunk
    ->  Merge Append
          Sort Key: test_partials."time"
-         ->  Custom Scan (ColumnarScan) on _hyper_35_70_chunk
-               ->  Sort
-                     Sort Key: compress_hyper_36_73_chunk._ts_meta_v2_last_time, compress_hyper_36_73_chunk._ts_meta_v2_first_time
+         ->  Sort
+               Sort Key: _hyper_35_70_chunk."time"
+               ->  Custom Scan (ColumnarScan) on _hyper_35_70_chunk
                      ->  Seq Scan on compress_hyper_36_73_chunk
          ->  Index Scan Backward using _hyper_35_70_chunk_test_partials_time_idx on _hyper_35_70_chunk
 

tsl/test/expected/compression_ddl.out

@@ -313,8 +313,10 @@ INFO:  using tuplesort to scan rows from "_hyper_9_10_chunk" for converting to c
 
 INSERT INTO mytab_prep VALUES ('2023-01-01'::timestamptz, 2, 3, 2);
 VACUUM ANALYZE mytab_prep;
--- plan should be invalidated to return results from the uncompressed chunk also
-set enable_sort to off; /* penalize MergeAppend for predictable plans on PG < 17. */
+-- Plan should be invalidated to return results from the uncompressed chunk as well.
+-- Penalize MergeAppend for predictable plans on PG < 17.
+set enable_sort to off;
+set enable_indexscan to off;
 EXPLAIN (BUFFERS OFF, COSTS OFF) EXECUTE p1;
 --- QUERY PLAN ---
  Sort
@@ -332,6 +334,7 @@ EXECUTE p1;
  Sun Jan 01 00:00:00 2023 PST | 2 | 3 | 2
 
 reset enable_sort;
+reset enable_indexscan;
 -- check plan again after recompression
 SELECT compress_chunk(:'chunk_to_compress_prep');
 INFO:  Using index "compress_hyper_10_11_chunk_a_c__ts_meta_v2_last_time__ts_me_idx" for recompression

tsl/test/expected/compression_update_delete-16.out

@@ -65,14 +65,9 @@ OFFSET 5;
                      Chunk Status: PARTIAL
                      Reverse: true
                      Bulk Decompression: true
-                     ->  Sort (actual rows=2.00 loops=1)
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
                            Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                           Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                 Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                                 Filter: (compress_hyper_X_X_chunk.device_id = 1)
-                                 Rows Removed by Filter: 16
+                           Index Cond: (compress_hyper_X_X_chunk.device_id = 1)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _timescaledb_internal._hyper_X_X_chunk (actual rows=1598.00 loops=1)
                      Output: _hyper_X_X_chunk."time", _hyper_X_X_chunk.device_id, _hyper_X_X_chunk.v0
                      Filter: (_hyper_X_X_chunk.device_id = 1)
@@ -150,14 +145,9 @@ OFFSET 0;
                Chunk Status: PARTIAL
                Reverse: true
                Bulk Decompression: true
-               ->  Sort (actual rows=2.00 loops=1)
+               ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
                      Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                     Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                     Sort Method: quicksort 
-                     ->  Seq Scan on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                           Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                           Filter: (compress_hyper_X_X_chunk.device_id = 1)
-                           Rows Removed by Filter: 16
+                     Index Cond: (compress_hyper_X_X_chunk.device_id = 1)
          ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _timescaledb_internal._hyper_X_X_chunk (actual rows=1598.00 loops=1)
                Output: _hyper_X_X_chunk."time", _hyper_X_X_chunk.device_id, _hyper_X_X_chunk.v0
                Filter: (_hyper_X_X_chunk.device_id = 1)
@@ -196,14 +186,9 @@ LIMIT 10000;
                      Chunk Status: PARTIAL
                      Reverse: true
                      Bulk Decompression: true
-                     ->  Sort (actual rows=2.00 loops=1)
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
                            Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                           Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                 Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                                 Filter: (compress_hyper_X_X_chunk.device_id = 1)
-                                 Rows Removed by Filter: 16
+                           Index Cond: (compress_hyper_X_X_chunk.device_id = 1)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _timescaledb_internal._hyper_X_X_chunk (actual rows=1598.00 loops=1)
                      Output: _hyper_X_X_chunk."time", _hyper_X_X_chunk.device_id, _hyper_X_X_chunk.v0
                      Filter: (_hyper_X_X_chunk.device_id = 1)
@@ -242,14 +227,9 @@ OFFSET 10000;
                      Chunk Status: PARTIAL
                      Reverse: true
                      Bulk Decompression: true
-                     ->  Sort (actual rows=2.00 loops=1)
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
                            Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                           Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                 Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                                 Filter: (compress_hyper_X_X_chunk.device_id = 1)
-                                 Rows Removed by Filter: 16
+                           Index Cond: (compress_hyper_X_X_chunk.device_id = 1)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _timescaledb_internal._hyper_X_X_chunk (actual rows=1598.00 loops=1)
                      Output: _hyper_X_X_chunk."time", _hyper_X_X_chunk.device_id, _hyper_X_X_chunk.v0
                      Filter: (_hyper_X_X_chunk.device_id = 1)
@@ -288,14 +268,9 @@ LIMIT 100 OFFSET 100;
                      Chunk Status: PARTIAL
                      Reverse: true
                      Bulk Decompression: true
-                     ->  Sort (actual rows=1.00 loops=1)
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=1.00 loops=1)
                            Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                           Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on _timescaledb_internal.compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                 Output: compress_hyper_X_X_chunk."time", compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time, compress_hyper_X_X_chunk.device_id, compress_hyper_X_X_chunk.v0, compress_hyper_X_X_chunk._ts_meta_count
-                                 Filter: (compress_hyper_X_X_chunk.device_id = 1)
-                                 Rows Removed by Filter: 16
+                           Index Cond: (compress_hyper_X_X_chunk.device_id = 1)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _timescaledb_internal._hyper_X_X_chunk (actual rows=200.00 loops=1)
                      Output: _hyper_X_X_chunk."time", _hyper_X_X_chunk.device_id, _hyper_X_X_chunk.v0
                      Filter: (_hyper_X_X_chunk.device_id = 1)

tsl/test/expected/recompress_chunk_segmentwise.out

@@ -1928,12 +1928,8 @@ ORDER BY o1.time;
          ->  Merge Append (actual rows=3598.00 loops=1)
                Sort Key: o2."time"
                ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o2_1 (actual rows=3598.00 loops=1)
-                     ->  Sort (actual rows=4.00 loops=1)
-                           Sort Key: compress_hyper_X_X_chunk_1._ts_meta_v2_last_time, compress_hyper_X_X_chunk_1._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on compress_hyper_X_X_chunk compress_hyper_X_X_chunk_1 (actual rows=4.00 loops=1)
-                                 Filter: (device_id = 2)
-                                 Rows Removed by Filter: 14
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on compress_hyper_X_X_chunk compress_hyper_X_X_chunk_1 (actual rows=4.00 loops=1)
+                           Index Cond: (device_id = 2)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_device_id_time_idx on _hyper_X_X_chunk o2_1 (actual rows=0.00 loops=1)
                      Index Cond: (device_id = 2)
          ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o2_2 (actual rows=5038.00 loops=1)
@@ -1948,12 +1944,8 @@ ORDER BY o1.time;
                ->  Merge Append (actual rows=3598.00 loops=1)
                      Sort Key: o1."time"
                      ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o1_1 (actual rows=2000.00 loops=1)
-                           ->  Sort (actual rows=2.00 loops=1)
-                                 Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                                 Sort Method: quicksort 
-                                 ->  Seq Scan on compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                       Filter: (device_id = 1)
-                                       Rows Removed by Filter: 16
+                           ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
+                                 Index Cond: (device_id = 1)
                      ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _hyper_X_X_chunk o1_1 (actual rows=1598.00 loops=1)
                            Filter: (device_id = 1)
                ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o1_2 (actual rows=5038.00 loops=1)
@@ -2038,12 +2030,8 @@ ORDER BY time;
          ->  Merge Append (actual rows=3598.00 loops=1)
                Sort Key: o1."time"
                ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o1_1 (actual rows=2000.00 loops=1)
-                     ->  Sort (actual rows=2.00 loops=1)
-                           Sort Key: compress_hyper_X_X_chunk._ts_meta_v2_last_time, compress_hyper_X_X_chunk._ts_meta_v2_first_time
-                           Sort Method: quicksort 
-                           ->  Seq Scan on compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
-                                 Filter: (device_id = 1)
-                                 Rows Removed by Filter: 16
+                     ->  Index Scan Backward using compress_hyper_X_X_chunk_device_id__ts_meta_v2_last_time___idx on compress_hyper_X_X_chunk (actual rows=2.00 loops=1)
+                           Index Cond: (device_id = 1)
                ->  Index Scan using _hyper_X_X_chunk_metrics_compressed_time_idx on _hyper_X_X_chunk o1_1 (actual rows=1598.00 loops=1)
                      Filter: (device_id = 1)
          ->  Custom Scan (ColumnarScan) on _hyper_X_X_chunk o1_2 (actual rows=5038.00 loops=1)