Optimize getPartitionEndRow for window function

[gengliqi]

Enhancement

1. isDifferentFromPrevPartition has some useless copies.
   

   tiflash/dbms/src/DataStreams/WindowBlockInputStream.cpp

   Lines 127 to 132 in 2dd8483

   	const auto reference_columns = inputAt(prev_frame_start);
   	const auto compared_columns = inputAt(partition_end);
   	for (size_t i = 0; i < partition_column_indices.size(); ++i)
   	{
   	const auto reference_column = reference_columns[partition_column_indices[i]];

2. compare several times first to speed up the case that the partition end is very close.

If the partition key has a high cardinal number, the partition number will be huge and the performance lost by above mentioned is very significant.

Test step

create table win(s varchar(20));
insert into 50000000 lines where `s` are all different.
explain analyze select row_number() over (partition by s) rn from win;

v6.5.0

mysql> explain analyze select row_number() over (partition by s) rn from win;
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
| id                                 | estRows     | actRows  | task         | access object | execution info                                                                                                                                                                                                                                                         | operator info                                                                                                  | memory | disk |
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_25                     | 50000000.00 | 50000000 | root         |               | time:18.7s, loops:48833, cop_task: {num: 769, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00}                                                                                                                                                          | data:ExchangeSender_24                                                                                         | N/A    | N/A  |
| └─ExchangeSender_24                | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:18.7s, loops:768, threads:8}                                                                                                                                                                                                                        | ExchangeType: PassThrough                                                                                      | N/A    | N/A  |
|   └─Projection_8                   | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:18.5s, loops:768, threads:8}                                                                                                                                                                                                                        | Column#4, stream_count: 8                                                                                      | N/A    | N/A  |
|     └─Window_23                    | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:18.5s, loops:768, threads:8}                                                                                                                                                                                                                        | row_number()->Column#4 over(partition by test.win.s rows between current row and current row), stream_count: 8 | N/A    | N/A  |
|       └─Sort_14                    | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:7.85s, loops:768, threads:8}                                                                                                                                                                                                                        | test.win.s, stream_count: 8                                                                                    | N/A    | N/A  |
|         └─ExchangeReceiver_13      | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:203.9ms, loops:3992, threads:8}                                                                                                                                                                                                                     | stream_count: 8                                                                                                | N/A    | N/A  |
|           └─ExchangeSender_12      | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:1.62s, loops:789, threads:20}                                                                                                                                                                                                                       | ExchangeType: HashPartition, Hash Cols: [name: test.win.s, collate: utf8mb4_bin], stream_count: 8              | N/A    | N/A  |
|             └─TableFullScan_11     | 50000000.00 | 50000000 | mpp[tiflash] | table:win     | tiflash_task:{time:28.2ms, loops:789, threads:20}, tiflash_scan:{dtfile:{total_scanned_packs:6145, total_skipped_packs:0, total_scanned_rows:50000000, total_skipped_rows:0, total_rs_index_load_time: 1ms, total_read_time: 2843ms}, total_create_snapshot_time: 0ms} | keep order:false                                                                                               | N/A    | N/A  |
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
8 rows in set (18.66 sec)

Applying #6625.

mysql> explain analyze select row_number() over (partition by s) rn from win;
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
| id                                 | estRows     | actRows  | task         | access object | execution info                                                                                                                                                                                                                                                         | operator info                                                                                                  | memory | disk |
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_25                     | 50000000.00 | 50000000 | root         |               | time:8.71s, loops:48833, cop_task: {num: 769, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00}                                                                                                                                                          | data:ExchangeSender_24                                                                                         | N/A    | N/A  |
| └─ExchangeSender_24                | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:8.71s, loops:768, threads:8}                                                                                                                                                                                                                        | ExchangeType: PassThrough                                                                                      | N/A    | N/A  |
|   └─Projection_8                   | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:8.55s, loops:768, threads:8}                                                                                                                                                                                                                        | Column#4, stream_count: 8                                                                                      | N/A    | N/A  |
|     └─Window_23                    | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:8.55s, loops:768, threads:8}                                                                                                                                                                                                                        | row_number()->Column#4 over(partition by test.win.s rows between current row and current row), stream_count: 8 | N/A    | N/A  |
|       └─Sort_14                    | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:7.88s, loops:768, threads:8}                                                                                                                                                                                                                        | test.win.s, stream_count: 8                                                                                    | N/A    | N/A  |
|         └─ExchangeReceiver_13      | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:263ms, loops:4016, threads:8}                                                                                                                                                                                                                       | stream_count: 8                                                                                                | N/A    | N/A  |
|           └─ExchangeSender_12      | 50000000.00 | 50000000 | mpp[tiflash] |               | tiflash_task:{time:1.73s, loops:789, threads:20}                                                                                                                                                                                                                       | ExchangeType: HashPartition, Hash Cols: [name: test.win.s, collate: utf8mb4_bin], stream_count: 8              | N/A    | N/A  |
|             └─TableFullScan_11     | 50000000.00 | 50000000 | mpp[tiflash] | table:win     | tiflash_task:{time:16.5ms, loops:789, threads:20}, tiflash_scan:{dtfile:{total_scanned_packs:6145, total_skipped_packs:0, total_scanned_rows:50000000, total_skipped_rows:0, total_rs_index_load_time: 0ms, total_read_time: 2331ms}, total_create_snapshot_time: 0ms} | keep order:false                                                                                               | N/A    | N/A  |
+------------------------------------+-------------+----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------+--------+------+
8 rows in set (8.71 sec)