TiFlash のパフォーマンスを調整する
このドキュメントでは、マシン リソースを適切に計画し、TiDB パラメータを調整することで、 TiFlashのパフォーマンスを調整する方法を紹介します。これらの方法に従うことで、 TiFlashクラスターは最適なパフォーマンスを実現できます。
リソースを計画する
マシンリソースを節約し、分離の要件がない場合は、 TiKV とTiFlashの両方の展開を組み合わせた方法を使用できます。 TiKV とTiFlashにそれぞれ十分なリソースを節約し、ディスクを共有しないことをお勧めします。
TiDBパラメータを調整する
このセクションでは、次のような TiDB パラメータを調整してTiFlash のパフォーマンスを向上させる方法について説明します。
- MPPモードを強制的に有効にする
- 集計関数を
JoinまたはUnion前の位置へプッシュダウンする Distinct最適化を有効にするALTER TABLE ... COMPACTステートメントを使用してデータを圧縮する- シャッフルハッシュ結合をブロードキャストハッシュ結合に置き換える
- 実行同時実行性を高める
tiflash_fine_grained_shuffle_stream_countを設定する
MPPモードを強制的に有効にする
MPP 実行プランは分散コンピューティング リソースを最大限に活用できるため、バッチ データ クエリの効率が大幅に向上します。オプティマイザーがクエリに対して MPP 実行プランを生成しない場合は、MPP モードを強制的に有効にすることができます。
変数tidb_enforce_mppは、オプティマイザのコスト見積もりを無視し、クエリ実行に TiFlash の MPP モードを強制的に使用するかどうかを制御します。MPP モードを強制的に有効にするには、次のコマンドを実行します。
set @@tidb_enforce_mpp = ON;
次の例は、 tidb_enforce_mpp有効にする前と有効にした後のクエリ結果を示しています。この変数を有効にする前は、 TiDB は TiKV からデータを読み取り、 TiDB でJoinとAggregation実行する必要があります。 tidb_enforce_mpp有効にすると、 JoinとAggregation TiFlashにプッシュダウンされます。 また、オプティマイザは必ずしも MPP 実行プランを生成するわけではないため、 tidb_enforce_mpp有効にすることで、オプティマイザに MPP 実行プランを生成させることができます。
MPP モードを有効にする前:
mysql> explain analyze select o_orderpriority, count(*) as order_count from orders where o_orderdate >= '1995-01-01' and o_orderdate < date_add('1995-01-01', interval '3' month) and exists (select * from lineitem where l_orderkey = o_orderkey and l_commitdate < l_receiptdate) group by o_orderpriority;
+--------------------------------------+--------------+-----------+-----------+---------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+--------------------------------------+--------------+-----------+-----------+---------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
| Projection_9 | 1.00 | 5 | root | | time:22.8s, loops:5, Concurrency:OFF | tpch_100.orders.o_orderpriority, Column#27 | 1016 Bytes | N/A |
| └─HashAgg_10 | 1.00 | 5 | root | | time:22.8s, loops:5, partial_worker:{wall_time:22.817403422s, concurrency:5, task_num:5027, tot_wait:1m52.560509138s, tot_exec:1.523754659s, tot_time:1m54.086196522s, max:22.817363394s, p95:22.817363394s}, final_worker:{wall_time:22.817416046s, concurrency:5, task_num:20, tot_wait:1m54.086784741s, tot_exec:155.94µs, tot_time:1m54.086948982s, max:22.817396284s, p95:22.817396284s} | group by:tpch_100.orders.o_orderpriority, funcs:count(1)->Column#27, funcs:firstrow(tpch_100.orders.o_orderpriority)->tpch_100.orders.o_orderpriority | 511.7 KB | N/A |
| └─IndexHashJoin_18 | 4429262.13 | 5145138 | root | | time:22.8s, loops:5028, inner:{total:1m52.6s, concurrency:5, task:227, construct:5.17s, fetch:1m40s, build:1.22s, join:7.49s} | semi join, inner:IndexLookUp_15, outer key:tpch_100.orders.o_orderkey, inner key:tpch_100.lineitem.l_orderkey, equal cond:eq(tpch_100.orders.o_orderkey, tpch_100.lineitem.l_orderkey) | 46.8 MB | N/A |
| ├─TableReader_37(Build) | 5536577.67 | 5610951 | root | | time:4.89s, loops:5467, cop_task: {num: 2127, max: 408.7ms, min: 277.5µs, avg: 81.6ms, p95: 249.7ms, max_proc_keys: 226272, p95_proc_keys: 220128, tot_proc: 2m50.2s, tot_wait: 40ms, rpc_num: 2127, rpc_time: 2m53.6s, copr_cache_hit_ratio: 0.02, distsql_concurrency: 15} | data:Selection_36 | 3.42 MB | N/A |
| │ └─Selection_36 | 5536577.67 | 5610951 | cop[tikv] | | tikv_task:{proc max:402ms, min:0s, avg: 79.7ms, p80:151ms, p95:245ms, iters:155122, tasks:2127}, scan_detail: {total_process_keys: 149478336, total_process_keys_size: 22705157593, total_keys: 149480413, get_snapshot_time: 187.9ms, rocksdb: {key_skipped_count: 149478336, block: {cache_hit_count: 393690}}} | ge(tpch_100.orders.o_orderdate, 1995-01-01 00:00:00.000000), lt(tpch_100.orders.o_orderdate, 1995-04-01 00:00:00.000000) | N/A | N/A |
| │ └─TableFullScan_35 | 150000000.00 | 150000000 | cop[tikv] | table:orders | tikv_task:{proc max:382ms, min:0s, avg: 74.6ms, p80:141ms, p95:229ms, iters:155122, tasks:2127} | keep order:false | N/A | N/A |
| └─IndexLookUp_15(Probe) | 22018496.89 | 14185840 | root | | time:1m33.4s, loops:14204, index_task: {total_time: 1m10.8s, fetch_handle: 1m10.7s, build: 3.9ms, wait: 13.3ms}, table_task: {total_time: 1m44.4s, num: 1989, concurrency: 5} | | 17.9 KB | N/A |
| ├─IndexRangeScan_12(Build) | 27523121.11 | 22441356 | cop[tikv] | table:lineitem, index:PRIMARY(L_ORDERKEY, L_LINENUMBER) | time:1m8.8s, loops:23635, cop_task: {num: 12537, max: 179.3ms, min: 331.4µs, avg: 22.7ms, p95: 66.9ms, max_proc_keys: 13755, p95_proc_keys: 5088, tot_proc: 3m44s, tot_wait: 129ms, rpc_num: 12537, rpc_time: 4m44s, copr_cache_hit_ratio: 0.06, distsql_concurrency: 15}, tikv_task:{proc max:170ms, min:0s, avg: 18.8ms, p80:29ms, p95:62ms, iters:68823, tasks:12537}, scan_detail: {total_process_keys: 21985403, total_process_keys_size: 1165226359, total_keys: 27492546, get_snapshot_time: 563.1ms, rocksdb: {key_skipped_count: 21985403, block: {cache_hit_count: 44004354}}} | range: decided by [eq(tpch_100.lineitem.l_orderkey, tpch_100.orders.o_orderkey)], keep order:false | N/A | N/A |
| └─Selection_14(Probe) | 22018496.89 | 14185840 | cop[tikv] | | time:1m34.8s, loops:16882, cop_task: {num: 12057, max: 240.4ms, min: 328.5µs, avg: 20.4ms, p95: 73.1ms, max_proc_keys: 15005, p95_proc_keys: 6118, tot_proc: 3m39.8s, tot_wait: 300ms, rpc_num: 12057, rpc_time: 4m5.7s, copr_cache_hit_ratio: 0.28, distsql_concurrency: 15}, tikv_task:{proc max:230ms, min:0s, avg: 27.5ms, p80:45ms, p95:82ms, iters:74165, tasks:12057}, scan_detail: {total_process_keys: 19916937, total_process_keys_size: 3957799619, total_keys: 24053143, get_snapshot_time: 1.07s, rocksdb: {key_skipped_count: 19254567, block: {cache_hit_count: 37816908}}} | lt(tpch_100.lineitem.l_commitdate, tpch_100.lineitem.l_receiptdate) | N/A | N/A |
| └─TableRowIDScan_13 | 27523121.11 | 22441356 | cop[tikv] | table:lineitem | tikv_task:{proc max:230ms, min:0s, avg: 27.2ms, p80:45ms, p95:81ms, iters:74165, tasks:12057} | keep order:false | N/A | N/A |
+--------------------------------------+--------------+-----------+-----------+---------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
10 rows in set (22.82 sec)
MPP モードを有効にする:
mysql> set @@tidb_enforce_mpp = ON;
Query OK, 0 rows affected (0.00 sec)
MPP モードが有効になった後:
mysql> explain analyze select o_orderpriority, count(*) as order_count from orders where o_orderdate >= '1995-01-01' and o_orderdate < date_add('1995-01-01', interval '3' month) and exists (select * from lineitem where l_orderkey = o_orderkey and l_commitdate < l_receiptdate) group by o_orderpriority;
+--------------------------------------------------+--------------+-----------+--------------+----------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+--------------------------------------------------+--------------+-----------+--------------+----------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_59 | 1.00 | 5 | root | | time:5.97s, loops:2, cop_task: {num: 8, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_58 | N/A | N/A |
| └─ExchangeSender_58 | 1.00 | 5 | mpp[tiflash] | | tiflash_task:{proc max:5.97s, min:5.97s, avg: 5.97s, p80:5.97s, p95:5.97s, iters:5, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_10 | 1.00 | 5 | mpp[tiflash] | | tiflash_task:{proc max:5.97s, min:5.96s, avg: 5.97s, p80:5.97s, p95:5.97s, iters:5, tasks:3, threads:60} | tpch_100.orders.o_orderpriority, Column#27 | N/A | N/A |
| └─Projection_54 | 1.00 | 5 | mpp[tiflash] | | tiflash_task:{proc max:5.97s, min:5.96s, avg: 5.97s, p80:5.97s, p95:5.97s, iters:5, tasks:3, threads:60} | Column#27, tpch_100.orders.o_orderpriority | N/A | N/A |
| └─HashAgg_55 | 1.00 | 5 | mpp[tiflash] | | tiflash_task:{proc max:5.97s, min:5.96s, avg: 5.97s, p80:5.97s, p95:5.97s, iters:5, tasks:3, threads:60} | group by:tpch_100.orders.o_orderpriority, funcs:sum(Column#32)->Column#27, funcs:firstrow(tpch_100.orders.o_orderpriority)->tpch_100.orders.o_orderpriority, stream_count: 20 | N/A | N/A |
| └─ExchangeReceiver_57 | 1.00 | 15 | mpp[tiflash] | | tiflash_task:{proc max:5.97s, min:5.96s, avg: 5.97s, p80:5.97s, p95:5.97s, iters:5, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| └─ExchangeSender_56 | 1.00 | 15 | mpp[tiflash] | | tiflash_task:{proc max:5.96s, min:0s, avg: 1.99s, p80:5.96s, p95:5.96s, iters:768, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: tpch_100.orders.o_orderpriority, collate: utf8mb4_bin], stream_count: 20 | N/A | N/A |
| └─HashAgg_52 | 1.00 | 15 | mpp[tiflash] | | tiflash_task:{proc max:5.96s, min:0s, avg: 1.99s, p80:5.96s, p95:5.96s, iters:768, tasks:3, threads:60} | group by:tpch_100.orders.o_orderpriority, funcs:count(1)->Column#32 | N/A | N/A |
| └─HashJoin_41 | 4429262.13 | 5145138 | mpp[tiflash] | | tiflash_task:{proc max:5.95s, min:0s, avg: 1.98s, p80:5.95s, p95:5.95s, iters:118, tasks:3, threads:60} | semi join, equal:[eq(tpch_100.orders.o_orderkey, tpch_100.lineitem.l_orderkey)], stream_count: 20 | N/A | N/A |
| ├─ExchangeReceiver_26(Build) | 480030321.60 | 379356474 | mpp[tiflash] | | tiflash_task:{proc max:3.26s, min:0s, avg: 1.09s, p80:3.26s, p95:3.26s, iters:42469, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| │ └─ExchangeSender_25 | 480030321.60 | 379356474 | mpp[tiflash] | | tiflash_task:{proc max:3.37s, min:0s, avg: 1.12s, p80:3.37s, p95:3.37s, iters:9292, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: tpch_100.lineitem.l_orderkey, collate: binary], stream_count: 20 | N/A | N/A |
| │ └─Projection_60 | 480030321.60 | 379356474 | mpp[tiflash] | | tiflash_task:{proc max:819.1ms, min:0s, avg: 273ms, p80:819.1ms, p95:819.1ms, iters:9292, tasks:3, threads:60} | tpch_100.lineitem.l_orderkey | N/A | N/A |
| │ └─Selection_24 | 480030321.60 | 379356474 | mpp[tiflash] | | tiflash_task:{proc max:817.1ms, min:0s, avg: 272.4ms, p80:817.1ms, p95:817.1ms, iters:9292, tasks:3, threads:60} | lt(tpch_100.lineitem.l_commitdate, tpch_100.lineitem.l_receiptdate) | N/A | N/A |
| │ └─TableFullScan_23 | 600037902.00 | 600037902 | mpp[tiflash] | table:lineitem | tiflash_task:{proc max:328.1ms, min:0s, avg: 109.4ms, p80:328.1ms, p95:328.1ms, iters:9292, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73475, total_skipped_packs:13452, total_scanned_rows:600230532, total_skipped_rows:109887612, total_rs_index_load_time: 35ms, total_read_time: 34065ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
| └─ExchangeReceiver_22(Probe) | 5536577.67 | 5610951 | mpp[tiflash] | | tiflash_task:{proc max:2.5s, min:0s, avg: 833.7ms, p80:2.5s, p95:2.5s, iters:669, tasks:3, threads:60} | | N/A | N/A |
| └─ExchangeSender_21 | 5536577.67 | 5610951 | mpp[tiflash] | | tiflash_task:{proc max:5.93s, min:0s, avg: 1.98s, p80:5.93s, p95:5.93s, iters:2336, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: tpch_100.orders.o_orderkey, collate: binary] | N/A | N/A |
| └─Selection_20 | 5536577.67 | 5610951 | mpp[tiflash] | | tiflash_task:{proc max:325.5ms, min:0s, avg: 108.5ms, p80:325.5ms, p95:325.5ms, iters:2336, tasks:3, threads:60} | ge(tpch_100.orders.o_orderdate, 1995-01-01 00:00:00.000000), lt(tpch_100.orders.o_orderdate, 1995-04-01 00:00:00.000000) | N/A | N/A |
| └─TableFullScan_19 | 150000000.00 | 150000000 | mpp[tiflash] | table:orders | tiflash_task:{proc max:238.5ms, min:0s, avg: 79.5ms, p80:238.5ms, p95:238.5ms, iters:2336, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:18541, total_skipped_packs:186, total_scanned_rows:150000611, total_skipped_rows:1513328, total_rs_index_load_time: 75ms, total_read_time: 11454ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+--------------------------------------------------+--------------+-----------+--------------+----------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------+------+
18 rows in set (6.00 sec)
集計関数をJoinまたはUnion前の位置へプッシュダウンする
集計操作をJoinまたはUnion前の位置にプッシュダウンすることで、 JoinまたはUnion操作で処理されるデータを削減し、パフォーマンスを向上させることができます。
変数tidb_opt_agg_push_downは、オプティマイザが集計関数をJoinまたはUnion前の位置にプッシュダウンする最適化操作を実行するかどうかを制御します。クエリで集計操作が非常に遅い場合は、この変数をONに設定できます。
set @@tidb_opt_agg_push_down = ON;
次の例は、 tidb_opt_agg_push_down変数を有効にする前と有効にした後のクエリ結果を示しています。この変数を有効にする前は、 HashJoin_41操作の後にHashAgg_58操作が実行されます。この変数を有効にすると、 HashJoin_76操作の前に新しく生成されたHashAgg_21操作とHashAgg_32操作が実行されます。これにより、 Join操作で処理されるデータが大幅に削減されます。
tidb_opt_agg_push_downが有効になる前:
mysql> explain analyze select count(*) from t1 join t2 where t1.a = t2.b group by t1.a;
+------------------------------------------+--------------+-----------+--------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+------------------------------------------+--------------+-----------+--------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+--------+------+
| TableReader_66 | 100450000.00 | 20 | root | | time:2.13s, loops:2, cop_task: {num: 21, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_65 | N/A | N/A |
| └─ExchangeSender_65 | 100450000.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:2.13s, min:2.08s, avg: 2.11s, p80:2.13s, p95:2.13s, iters:768, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_60 | 100450000.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:2.13s, min:2.08s, avg: 2.11s, p80:2.13s, p95:2.13s, iters:768, tasks:3, threads:60} | Column#43 | N/A | N/A |
| └─HashAgg_58 | 100450000.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:2.13s, min:2.08s, avg: 2.11s, p80:2.13s, p95:2.13s, iters:768, tasks:3, threads:60} | group by:test.t1.a, funcs:count(1)->Column#43 | N/A | N/A |
| └─HashJoin_41 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:1.77s, min:1.67s, avg: 1.73s, p80:1.77s, p95:1.77s, iters:10955, tasks:3, threads:60} | inner join, equal:[eq(test.t1.a, test.t2.b)], stream_count: 20 | N/A | N/A |
| ├─ExchangeReceiver_22(Build) | 100450000.00 | 99980000 | mpp[tiflash] | | tiflash_task:{proc max:171ms, min:127ms, avg: 154.5ms, p80:171ms, p95:171ms, iters:10440, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| │ └─ExchangeSender_21 | 100450000.00 | 99980000 | mpp[tiflash] | | tiflash_task:{proc max:498.7ms, min:0s, avg: 166.2ms, p80:498.7ms, p95:498.7ms, iters:1653, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t1.a, collate: binary], stream_count: 20 | N/A | N/A |
| │ └─Selection_20 | 100450000.00 | 99980000 | mpp[tiflash] | | tiflash_task:{proc max:83.7ms, min:0s, avg: 27.9ms, p80:83.7ms, p95:83.7ms, iters:1653, tasks:3, threads:60} | not(isnull(test.t1.a)) | N/A | N/A |
| │ └─TableFullScan_19 | 100450000.00 | 99980000 | mpp[tiflash] | table:t1 | tiflash_task:{proc max:41.7ms, min:0s, avg: 13.9ms, p80:41.7ms, p95:41.7ms, iters:1653, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:12336, total_skipped_packs:5759, total_scanned_rows:100083566, total_skipped_rows:46786721, total_rs_index_load_time: 5ms, total_read_time: 1105ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
| └─ExchangeReceiver_26(Probe) | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:373ms, min:71ms, avg: 253.2ms, p80:373ms, p95:373ms, iters:28135, tasks:3, threads:60} | | N/A | N/A |
| └─ExchangeSender_25 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:2.07s, min:0s, avg: 689.6ms, p80:2.07s, p95:2.07s, iters:9388, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t2.b, collate: binary] | N/A | N/A |
| └─Selection_24 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:146.9ms, min:0s, avg: 49ms, p80:146.9ms, p95:146.9ms, iters:9388, tasks:3, threads:60} | not(isnull(test.t2.b)) | N/A | N/A |
| └─TableFullScan_23 | 600000000.00 | 600000000 | mpp[tiflash] | table:t2 | tiflash_task:{proc max:63.8ms, min:0s, avg: 21.3ms, p80:63.8ms, p95:63.8ms, iters:9388, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73834, total_skipped_packs:439, total_scanned_rows:600007458, total_skipped_rows:3553131, total_rs_index_load_time: 12ms, total_read_time: 270ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+------------------------------------------+--------------+-----------+--------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+--------+------+
13 rows in set (2.15 sec)
有効化tidb_opt_agg_push_down :
mysql> set @@tidb_opt_agg_push_down = ON;
Query OK, 0 rows affected (0.00 sec)
tidb_opt_agg_push_downが有効になった後:
mysql> explain analyze select count(*) from t1 join t2 where t1.a = t2.b group by t1.a;
+------------------------------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+------------------------------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_85 | 20.00 | 20 | root | | time:432.4ms, loops:2, cop_task: {num: 19, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_84 | N/A | N/A |
| └─ExchangeSender_84 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:431.1ms, min:429.3ms, avg: 430.4ms, p80:431.1ms, p95:431.1ms, iters:16, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_83 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:430.1ms, min:429.3ms, avg: 429.7ms, p80:430.1ms, p95:430.1ms, iters:16, tasks:3, threads:60} | Column#43 | N/A | N/A |
| └─HashAgg_82 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:430.1ms, min:429.3ms, avg: 429.7ms, p80:430.1ms, p95:430.1ms, iters:16, tasks:3, threads:60} | group by:test.t1.a, funcs:count(Column#44)->Column#43, stream_count: 20 | N/A | N/A |
| └─ExchangeReceiver_78 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:430.1ms, min:429.3ms, avg: 429.7ms, p80:430.1ms, p95:430.1ms, iters:16, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| └─ExchangeSender_77 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:427ms, min:0s, avg: 142.3ms, p80:427ms, p95:427ms, iters:60, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t1.a, collate: binary], stream_count: 20 | N/A | N/A |
| └─HashJoin_76 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:426ms, min:0s, avg: 142ms, p80:426ms, p95:426ms, iters:60, tasks:3, threads:60} | inner join, equal:[eq(test.t1.a, test.t2.b)] | N/A | N/A |
| ├─ExchangeReceiver_36(Build) | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:374ms, min:0s, avg: 124.7ms, p80:374ms, p95:374ms, iters:46, tasks:3, threads:60} | | N/A | N/A |
| │ └─ExchangeSender_35 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:373.7ms, min:0s, avg: 124.6ms, p80:373.7ms, p95:373.7ms, iters:16, tasks:3, threads:60} | ExchangeType: Broadcast | N/A | N/A |
| │ └─Projection_31 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:373.7ms, min:0s, avg: 124.6ms, p80:373.7ms, p95:373.7ms, iters:16, tasks:3, threads:60} | Column#44, test.t2.b | N/A | N/A |
| │ └─HashAgg_32 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:373.7ms, min:0s, avg: 124.6ms, p80:373.7ms, p95:373.7ms, iters:16, tasks:3, threads:60} | group by:test.t2.b, funcs:sum(Column#45)->Column#44, funcs:firstrow(test.t2.b)->test.t2.b, stream_count: 20 | N/A | N/A |
| │ └─ExchangeReceiver_34 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:373.7ms, min:0s, avg: 124.6ms, p80:373.7ms, p95:373.7ms, iters:16, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| │ └─ExchangeSender_33 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:368.3ms, min:0s, avg: 122.8ms, p80:368.3ms, p95:368.3ms, iters:3, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t2.b, collate: binary], stream_count: 20 | N/A | N/A |
| │ └─HashAgg_21 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:367.3ms, min:0s, avg: 122.4ms, p80:367.3ms, p95:367.3ms, iters:3, tasks:3, threads:60} | group by:test.t2.b, funcs:count(1)->Column#45 | N/A | N/A |
| │ └─Selection_30 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:77.2ms, min:0s, avg: 25.7ms, p80:77.2ms, p95:77.2ms, iters:9389, tasks:3, threads:60} | not(isnull(test.t2.b)) | N/A | N/A |
| │ └─TableFullScan_29 | 600000000.00 | 600000000 | mpp[tiflash] | table:t2 | tiflash_task:{proc max:37.2ms, min:0s, avg: 12.4ms, p80:37.2ms, p95:37.2ms, iters:9389, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73834, total_skipped_packs:412, total_scanned_rows:600002896, total_skipped_rows:3342145, total_rs_index_load_time: 0ms, total_read_time: 45ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
| └─Selection_19(Probe) | 100450000.00 | 99980000 | mpp[tiflash] | | tiflash_task:{proc max:30ms, min:0s, avg: 10ms, p80:30ms, p95:30ms, iters:1645, tasks:3, threads:60} | not(isnull(test.t1.a)) | N/A | N/A |
| └─TableFullScan_18 | 100450000.00 | 99980000 | mpp[tiflash] | table:t1 | tiflash_task:{proc max:22ms, min:0s, avg: 7.34ms, p80:22ms, p95:22ms, iters:1645, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:12326, total_skipped_packs:4762, total_scanned_rows:100045535, total_skipped_rows:38651216, total_rs_index_load_time: 4ms, total_read_time: 355ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+------------------------------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
18 rows in set (0.46 sec)
Distinct最適化を有効にする
TiFlash は、 SumなどのDistinct列を受け入れる一部の集計関数をサポートしていません。デフォルトでは、集計関数全体が TiDB で計算されます。 Distinct最適化を有効にすると、一部の操作をTiFlashにプッシュダウンできるため、クエリのパフォーマンスが向上します。
クエリ内でdistinct操作の集計関数が遅い場合は、 tidb_opt_distinct_agg_push_down変数の値をONに設定することで、 Distinct ( select sum(distinct a) from tなど) の集計関数をコプロセッサーにプッシュダウンする最適化操作を有効にすることができます。
set @@tidb_opt_distinct_agg_push_down = ON;
次の例は、 tidb_opt_distinct_agg_push_down変数を有効にする前と有効にした後のクエリ結果を示しています。この変数を有効にする前に、TiDB はTiFlashからすべてのデータを読み取り、 TiDB でdistinct実行する必要があります。この変数を有効にすると、 distinct a TiFlashにプッシュダウンされ、新しいgroup by列test.t.a HashAgg_6に追加されます。クエリ結果の 2 つの警告は、集計関数をTiFlashに完全にプッシュダウンできないことを示しています。
tidb_opt_distinct_agg_push_downが有効になる前:
mysql> explain analyze select count(distinct a) from test.t;
+----------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+----------+---------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+----------+---------+
| HashAgg_6 | 1.00 | 1 | root | | time:2m23.2s, loops:2 | funcs:sum(distinct Column#23)->Column#22 | 41.3 KB | 0 Bytes |
| └─Projection_16 | 600000000.00 | 600000000 | root | | time:2.51s, loops:586548, Concurrency:5 | cast(test.t.a, decimal(10,0) BINARY)->Column#23 | 243.2 KB | N/A |
| └─TableReader_11 | 600000000.00 | 600000000 | root | | time:1.6s, loops:586548, cop_task: {num: 1173, max: 256.2ms, min: 25.1ms, avg: 46.9ms, p95: 63.5ms, rpc_num: 1173, rpc_time: 55s, copr_cache_hit_ratio: 0.00, distsql_concurrency: 15} | data:TableFullScan_10 | 70.2 MB | N/A |
| └─TableFullScan_10 | 600000000.00 | 600000000 | cop[tiflash] | table:t | tiflash_task:{proc max:9ms, min:531µs, avg: 4.49ms, p80:5.55ms, p95:6.74ms, iters:9390, tasks:1173, threads:1173}, tiflash_scan:{dtfile:{total_scanned_packs:73834, total_skipped_packs:1231, total_scanned_rows:600010914, total_skipped_rows:9988978, total_rs_index_load_time: 0ms, total_read_time: 16ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+----------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+----------+---------+
4 rows in set, 2 warnings (2 min 23.21 sec)
有効化tidb_opt_distinct_agg_push_down :
mysql> set @@tidb_opt_distinct_agg_push_down = ON;
Query OK, 0 rows affected (0.00 sec)
tidb_opt_distinct_agg_push_downが有効になった後:
mysql> explain analyze select count(distinct a) from test.t;
+-----------------------------+--------------+-----------+-------------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+-----------+---------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+-----------------------------+--------------+-----------+-------------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+-----------+---------+
| HashAgg_10 | 1.00 | 1 | root | | time:233.8ms, loops:2 | funcs:sum(distinct Column#23)->Column#22 | 2.42 KB | 0 Bytes |
| └─Projection_12 | 1.00 | 3 | root | | time:233.7ms, loops:2, Concurrency:OFF | cast(test.c.a, decimal(10,0) BINARY)->Column#23 | 380 Bytes | N/A |
| └─TableReader_11 | 1.00 | 3 | root | | time:233.7ms, loops:2, cop_task: {num: 6, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00, distsql_concurrency: 15} | data:HashAgg_6 | 100 Bytes | N/A |
| └─HashAgg_6 | 1.00 | 3 | batchCop[tiflash] | | tiflash_task:{proc max:225.8ms, min:210.7ms, avg: 216.9ms, p80:225.8ms, p95:225.8ms, iters:3, tasks:3, threads:60} | group by:test.t.a, | N/A | N/A |
| └─TableFullScan_9 | 600000000.00 | 600000000 | batchCop[tiflash] | table:t | tiflash_task:{proc max:50.3ms, min:33.7ms, avg: 44.6ms, p80:50.3ms, p95:50.3ms, iters:9387, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73833, total_skipped_packs:475, total_scanned_rows:600000000, total_skipped_rows:3852098, total_rs_index_load_time: 0ms, total_read_time: 84ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+-----------------------------+--------------+-----------+-------------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------+-----------+---------+
5 rows in set, 2 warnings (0.24 sec)
ALTER TABLE ... COMPACTステートメントを使用してデータを圧縮する
ALTER TABLE ... COMPACTステートメントを実行すると、 TiFlashノード上の特定のテーブルまたはパーティションの圧縮を開始できます。圧縮中は、ノード上の物理データが書き換えられ、削除された行がクリーンアップされ、更新によって発生した複数のバージョンのデータがマージされます。これにより、アクセス パフォーマンスが向上し、ディスク使用量が削減されます。次に例を示します。
ALTER TABLE employees COMPACT TIFLASH REPLICA;
ALTER TABLE employees COMPACT PARTITION pNorth, pEast TIFLASH REPLICA;
シャッフルハッシュ結合をブロードキャストハッシュ結合に置き換える
小さなテーブルでのJoin操作の場合、ブロードキャスト ハッシュ結合アルゴリズムにより大きなテーブルの転送を回避できるため、コンピューティング パフォーマンスが向上します。
tidb_broadcast_join_threshold_size変数は、ブロードキャスト ハッシュ結合アルゴリズムを使用するかどうかを制御します。テーブル サイズ (単位: バイト) がこの変数の値より小さい場合は、ブロードキャスト ハッシュ結合アルゴリズムが使用されます。それ以外の場合は、シャッフル ハッシュ結合アルゴリズムが使用されます。set @@tidb_broadcast_join_threshold_size = 2000000;tidb_broadcast_join_threshold_count変数は、ブロードキャスト ハッシュ結合アルゴリズムを使用するかどうかも制御します。結合操作のオブジェクトがサブクエリに属している場合、オプティマイザはサブクエリ結果セットのサイズを推定できません。この場合、サイズは結果セットの行数によって決まります。サブクエリの推定行数がこの変数の値より少ない場合、ブロードキャスト ハッシュ結合アルゴリズムが使用されます。それ以外の場合は、シャッフル ハッシュ結合アルゴリズムが使用されます。set @@tidb_broadcast_join_threshold_count = 100000;
次の例は、 tidb_broadcast_join_threshold_sizeが再構成される前と再構成された後のクエリ結果を示しています。再構成前は、 ExchangeSender_29のうちExchangeType HashPartitionです。この変数の値が10000000に変更されると、 ExchangeSender_29のうちExchangeType Broadcastに変わります。
tidb_broadcast_join_threshold_size再構成される前:
mysql> explain analyze select max(l_shipdate), max(l_commitdate), max(l_receiptdate) from supplier,lineitem where s_suppkey = l_suppkey;
+------------------------------------------+--------------+-----------+--------------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+------------------------------------------+--------------+-----------+--------------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
| HashAgg_45 | 1.00 | 1 | root | | time:3.8s, loops:2, partial_worker:{wall_time:3.798284809s, concurrency:5, task_num:1, tot_wait:18.99079929s, tot_exec:8.193µs, tot_time:18.990819019s, max:3.798181723s, p95:3.798181723s}, final_worker:{wall_time:0s, concurrency:5, task_num:1, tot_wait:18.991291379s, tot_exec:197.45µs, tot_time:18.991494363s, max:3.798334972s, p95:3.798334972s} | funcs:max(Column#28)->Column#25, funcs:max(Column#29)->Column#26, funcs:max(Column#30)->Column#27 | 17.3 KB | N/A |
| └─TableReader_47 | 1.00 | 3 | root | | time:3.8s, loops:2, cop_task: {num: 6, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_46 | N/A | N/A |
| └─ExchangeSender_46 | 1.00 | 3 | mpp[tiflash] | | tiflash_task:{proc max:3.79s, min:3.78s, avg: 3.78s, p80:3.79s, p95:3.79s, iters:3, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─HashAgg_13 | 1.00 | 3 | mpp[tiflash] | | tiflash_task:{proc max:3.79s, min:3.78s, avg: 3.78s, p80:3.79s, p95:3.79s, iters:3, tasks:3, threads:60} | funcs:max(tpch_100.lineitem.l_shipdate)->Column#28, funcs:max(tpch_100.lineitem.l_commitdate)->Column#29, funcs:max(tpch_100.lineitem.l_receiptdate)->Column#30 | N/A | N/A |
| └─HashJoin_44 | 600845438.27 | 600037902 | mpp[tiflash] | | tiflash_task:{proc max:3.17s, min:3.12s, avg: 3.14s, p80:3.17s, p95:3.17s, iters:11143, tasks:3, threads:60} | inner join, equal:[eq(tpch_100.supplier.s_suppkey, tpch_100.lineitem.l_suppkey)], stream_count: 20 | N/A | N/A |
| ├─ExchangeReceiver_30(Build) | 1000000.00 | 1000000 | mpp[tiflash] | | tiflash_task:{proc max:23.3ms, min:21ms, avg: 22.5ms, p80:23.3ms, p95:23.3ms, iters:120, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| │ └─ExchangeSender_29 | 1000000.00 | 1000000 | mpp[tiflash] | | tiflash_task:{proc max:22.7ms, min:0s, avg: 7.57ms, p80:22.7ms, p95:22.7ms, iters:16, tasks:3, threads:2} | ExchangeType: HashPartition, Hash Cols: [name: tpch_100.supplier.s_suppkey, collate: binary], stream_count: 20 | N/A | N/A |
| │ └─TableFullScan_28 | 1000000.00 | 1000000 | mpp[tiflash] | table:supplier | tiflash_task:{proc max:9.71ms, min:0s, avg: 3.24ms, p80:9.71ms, p95:9.71ms, iters:16, tasks:3, threads:2}, tiflash_scan:{dtfile:{total_scanned_packs:123, total_skipped_packs:0, total_scanned_rows:1000000, total_skipped_rows:0, total_rs_index_load_time: 0ms, total_read_time: 2ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
| └─ExchangeReceiver_33(Probe) | 600037902.00 | 600037902 | mpp[tiflash] | | tiflash_task:{proc max:564.3ms, min:340ms, avg: 438.5ms, p80:564.3ms, p95:564.3ms, iters:27583, tasks:3, threads:60} | | N/A | N/A |
| └─ExchangeSender_32 | 600037902.00 | 600037902 | mpp[tiflash] | | tiflash_task:{proc max:3.69s, min:0s, avg: 1.23s, p80:3.69s, p95:3.69s, iters:9298, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: tpch_100.lineitem.l_suppkey, collate: binary] | N/A | N/A |
| └─TableFullScan_31 | 600037902.00 | 600037902 | mpp[tiflash] | table:lineitem | tiflash_task:{proc max:62.8ms, min:0s, avg: 20.9ms, p80:62.8ms, p95:62.8ms, iters:9298, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73465, total_skipped_packs:13060, total_scanned_rows:600168663, total_skipped_rows:106699256, total_rs_index_load_time: 16ms, total_read_time: 27979ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+------------------------------------------+--------------+-----------+--------------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
11 rows in set (3.83 sec)
セットtidb_broadcast_join_threshold_size ～ 10000000 :
mysql> set @@tidb_broadcast_join_threshold_size = 10000000;
Query OK, 0 rows affected (0.00 sec)
tidb_broadcast_join_threshold_size 10000000に設定した後:
mysql> explain analyze select max(l_shipdate), max(l_commitdate), max(l_receiptdate) from supplier,lineitem where s_suppkey = l_suppkey;
+------------------------------------------+--------------+-----------+--------------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+------------------------------------------+--------------+-----------+--------------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
| HashAgg_43 | 1.00 | 1 | root | | time:2.75s, loops:2, partial_worker:{wall_time:2.748445779s, concurrency:5, task_num:1, tot_wait:13.74202679s, tot_exec:8.012µs, tot_time:13.742045721s, max:2.748414915s, p95:2.748414915s}, final_worker:{wall_time:2.74848039s, concurrency:5, task_num:1, tot_wait:13.742157526s, tot_exec:53.191µs, tot_time:13.742214417s, max:2.748462393s, p95:2.748462393s} | funcs:max(Column#28)->Column#25, funcs:max(Column#29)->Column#26, funcs:max(Column#30)->Column#27 | 17.3 KB | N/A |
| └─TableReader_45 | 1.00 | 3 | root | | time:2.75s, loops:2, cop_task: {num: 6, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_44 | N/A | N/A |
| └─ExchangeSender_44 | 1.00 | 3 | mpp[tiflash] | | tiflash_task:{proc max:2.74s, min:2.65s, avg: 2.7s, p80:2.74s, p95:2.74s, iters:3, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─HashAgg_13 | 1.00 | 3 | mpp[tiflash] | | tiflash_task:{proc max:2.74s, min:2.65s, avg: 2.7s, p80:2.74s, p95:2.74s, iters:3, tasks:3, threads:60} | funcs:max(tpch_100.lineitem.l_shipdate)->Column#28, funcs:max(tpch_100.lineitem.l_commitdate)->Column#29, funcs:max(tpch_100.lineitem.l_receiptdate)->Column#30 | N/A | N/A |
| └─HashJoin_42 | 600845438.27 | 600037902 | mpp[tiflash] | | tiflash_task:{proc max:2.15s, min:2.06s, avg: 2.11s, p80:2.15s, p95:2.15s, iters:9286, tasks:3, threads:60} | inner join, equal:[eq(tpch_100.supplier.s_suppkey, tpch_100.lineitem.l_suppkey)] | N/A | N/A |
| ├─ExchangeReceiver_30(Build) | 1000000.00 | 3000000 | mpp[tiflash] | | tiflash_task:{proc max:28.1ms, min:24.9ms, avg: 27ms, p80:28.1ms, p95:28.1ms, iters:48, tasks:3, threads:60} | | N/A | N/A |
| │ └─ExchangeSender_29 | 1000000.00 | 1000000 | mpp[tiflash] | | tiflash_task:{proc max:14ms, min:0s, avg: 4.67ms, p80:14ms, p95:14ms, iters:16, tasks:3, threads:2} | ExchangeType: Broadcast | N/A | N/A |
| │ └─TableFullScan_28 | 1000000.00 | 1000000 | mpp[tiflash] | table:supplier | tiflash_task:{proc max:9ms, min:0s, avg: 3ms, p80:9ms, p95:9ms, iters:16, tasks:3, threads:2}, tiflash_scan:{dtfile:{total_scanned_packs:123, total_skipped_packs:0, total_scanned_rows:1000000, total_skipped_rows:0, total_rs_index_load_time: 0ms, total_read_time: 2ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
| └─TableFullScan_31(Probe) | 600037902.00 | 600037902 | mpp[tiflash] | table:lineitem | tiflash_task:{proc max:57.9ms, min:42.9ms, avg: 51.3ms, p80:57.9ms, p95:57.9ms, iters:9297, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73464, total_skipped_packs:12985, total_scanned_rows:600169085, total_skipped_rows:106014866, total_rs_index_load_time: 23ms, total_read_time: 21667ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+------------------------------------------+--------------+-----------+--------------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+---------+------+
9 rows in set (2.76 sec)
実行同時実行性を高める
実行の同時実行性が高まると、 TiFlash はシステムの CPU リソースをより多く占有できるようになり、クエリ パフォーマンスが向上します。
tidb_max_tiflash_threads変数は、 TiFlash がリクエストを実行するための最大同時実行数を設定するために使用されます。単位はスレッドです。
set @@tidb_max_tiflash_threads = 20;
次の例は、 tidb_max_tiflash_threads再設定する前と後のクエリ結果を示しています。 tidb_max_tiflash_threadsを設定する前は、単一のTiFlashインスタンスの要求実行の同時実行は 8 スレッドです。 クラスターには合計 3 つのTiFlashインスタンスがあるため、すべてのTiFlashインスタンスでの要求実行のスレッドの合計数は 24 (8 × 3) です。 tidb_max_tiflash_threadsを20に設定した後は、すべてのTiFlashインスタンスでの要求実行のスレッドの合計数は 60 (20 × 3) です。
tidb_max_tiflash_threads再構成される前:
mysql> explain analyze select a, count(*) from t group by a;
+--------------------------------------+--------------+-----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+--------------------------------------+--------------+-----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_44 | 20.00 | 20 | root | | time:655.9ms, loops:2, cop_task: {num: 14, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_43 | N/A | N/A |
| └─ExchangeSender_43 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:654.6ms, min:652.4ms, avg: 653.8ms, p80:654.6ms, p95:654.6ms, iters:11, tasks:3, threads:24} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_5 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:654.3ms, min:651.4ms, avg: 653.1ms, p80:654.3ms, p95:654.3ms, iters:11, tasks:3, threads:24} | test.t.a, Column#22 | N/A | N/A |
| └─Projection_39 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:654.3ms, min:651.4ms, avg: 653.1ms, p80:654.3ms, p95:654.3ms, iters:11, tasks:3, threads:24} | Column#22, test.t.a | N/A | N/A |
| └─HashAgg_40 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:654.3ms, min:651.4ms, avg: 653.1ms, p80:654.3ms, p95:654.3ms, iters:11, tasks:3, threads:24} | group by:test.t.a, funcs:sum(Column#29)->Column#22, funcs:firstrow(test.t.a)->test.t.a, stream_count: 8 | N/A | N/A |
| └─ExchangeReceiver_42 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:654.3ms, min:651.4ms, avg: 653.1ms, p80:654.3ms, p95:654.3ms, iters:11, tasks:3, threads:24} | stream_count: 8 | N/A | N/A |
| └─ExchangeSender_41 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:649ms, min:0s, avg: 216.3ms, p80:649ms, p95:649ms, iters:3, tasks:3, threads:24} | ExchangeType: HashPartition, Hash Cols: [name: test.t.a, collate: binary], stream_count: 8 | N/A | N/A |
| └─HashAgg_37 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:649ms, min:0s, avg: 216.3ms, p80:649ms, p95:649ms, iters:3, tasks:3, threads:24} | group by:test.t.a, funcs:count(1)->Column#29 | N/A | N/A |
| └─TableFullScan_26 | 600000000.00 | 600000000 | mpp[tiflash] | table:t | tiflash_task:{proc max:40ms, min:0s, avg: 13.3ms, p80:40ms, p95:40ms, iters:9386, tasks:3, threads:24}, tiflash_scan:{dtfile:{total_scanned_packs:73833, total_skipped_packs:174, total_scanned_rows:600000000, total_skipped_rows:1402537, total_rs_index_load_time: 0ms, total_read_time: 4ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+--------------------------------------+--------------+-----------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------+--------+------+
9 rows in set (0.67 sec)
セットtidb_max_tiflash_threads ～ 20 :
mysql> set @@tidb_max_tiflash_threads = 20;
Query OK, 0 rows affected (0.00 sec)
tidb_max_tiflash_threads 20に設定した後:
mysql> explain analyze select a, count(*) from t group by a;
+--------------------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+--------------------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_44 | 20.00 | 20 | root | | time:357.7ms, loops:2, cop_task: {num: 19, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_43 | N/A | N/A |
| └─ExchangeSender_43 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:355.3ms, min:354.6ms, avg: 355ms, p80:355.3ms, p95:355.3ms, iters:16, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_5 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:354.3ms, min:353.6ms, avg: 354ms, p80:354.3ms, p95:354.3ms, iters:16, tasks:3, threads:60} | test.t.a, Column#22 | N/A | N/A |
| └─Projection_39 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:354.3ms, min:353.6ms, avg: 354ms, p80:354.3ms, p95:354.3ms, iters:16, tasks:3, threads:60} | Column#22, test.t.a | N/A | N/A |
| └─HashAgg_40 | 20.00 | 20 | mpp[tiflash] | | tiflash_task:{proc max:354.3ms, min:353.6ms, avg: 354ms, p80:354.3ms, p95:354.3ms, iters:16, tasks:3, threads:60} | group by:test.t.a, funcs:sum(Column#29)->Column#22, funcs:firstrow(test.t.a)->test.t.a, stream_count: 20 | N/A | N/A |
| └─ExchangeReceiver_42 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:354.3ms, min:353.6ms, avg: 354ms, p80:354.3ms, p95:354.3ms, iters:16, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| └─ExchangeSender_41 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:349.6ms, min:0s, avg: 116.5ms, p80:349.6ms, p95:349.6ms, iters:3, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t.a, collate: binary], stream_count: 20 | N/A | N/A |
| └─HashAgg_37 | 20.00 | 60 | mpp[tiflash] | | tiflash_task:{proc max:347.6ms, min:0s, avg: 115.9ms, p80:347.6ms, p95:347.6ms, iters:3, tasks:3, threads:60} | group by:test.t.a, funcs:count(1)->Column#29 | N/A | N/A |
| └─TableFullScan_26 | 600000000.00 | 600000000 | mpp[tiflash] | table:t | tiflash_task:{proc max:36.6ms, min:0s, avg: 12.2ms, p80:36.6ms, p95:36.6ms, iters:9389, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73833, total_skipped_packs:418, total_scanned_rows:600001386, total_skipped_rows:3381854, total_rs_index_load_time: 10ms, total_read_time: 61ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+--------------------------------------+--------------+-----------+--------------+---------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+--------+------+
9 rows in set (0.37 sec)
tiflash_fine_grained_shuffle_stream_countを設定する
Fine Grained Shuffle 機能のtiflash_fine_grained_shuffle_stream_count構成することで、ウィンドウ関数の実行の同時実行性を高めることができます。これにより、ウィンドウ関数の実行でより多くのシステム リソースを占有できるようになり、クエリのパフォーマンスが向上します。
ウィンドウ関数が実行のためにTiFlashにプッシュダウンされるときに、この変数を使用してウィンドウ関数実行の同時実行レベルを制御できます。単位はスレッドです。
set @@tiflash_fine_grained_shuffle_stream_count = 20;
次の例は、 tiflash_fine_grained_shuffle_stream_count変数が再構成される前と後のクエリ結果を示しています。再構成前は、 [ExchangeSender_11, ExchangeReceiver_12, Sort_13, Window_22]のうちstream_countは 8 です。再構成後は、 stream_countが 20 になります。
tiflash_fine_grained_shuffle_stream_count再構成される前:
mysql> explain analyze select *, row_number() over (partition by a) from t;
+----------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_24 | 600000000.00 | 600000000 | root | | time:4m30.5s, loops:585941, cop_task: {num: 9163, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_23 | N/A | N/A |
| └─ExchangeSender_23 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:4m30.5s, min:3m4.8s, avg: 3m36.1s, p80:4m30.5s, p95:4m30.5s, iters:9160, tasks:3, threads:24} | ExchangeType: PassThrough | N/A | N/A |
| └─Window_22 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:3m31.6s, min:2m26.2s, avg: 2m50.7s, p80:3m31.6s, p95:3m31.6s, iters:9160, tasks:3, threads:24} | row_number()->Column#23 over(partition by test.t.a rows between current row and current row), stream_count: 8 | N/A | N/A |
| └─Sort_13 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:3m28.6s, min:2m24.2s, avg: 2m48.4s, p80:3m28.6s, p95:3m28.6s, iters:9160, tasks:3, threads:24} | test.t.a, stream_count: 8 | N/A | N/A |
| └─ExchangeReceiver_12 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:32.4s, min:32s, avg: 32.1s, p80:32.4s, p95:32.4s, iters:49307, tasks:3, threads:24} | stream_count: 8 | N/A | N/A |
| └─ExchangeSender_11 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:32s, min:0s, avg: 10.7s, p80:32s, p95:32s, iters:9386, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t.a, collate: binary], stream_count: 8 | N/A | N/A |
| └─TableFullScan_10 | 600000000.00 | 600000000 | mpp[tiflash] | table:t | tiflash_task:{proc max:113.9ms, min:0s, avg: 38ms, p80:113.9ms, p95:113.9ms, iters:9386, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73834, total_skipped_packs:190, total_scanned_rows:600000000, total_skipped_rows:1536382, total_rs_index_load_time: 16ms, total_read_time: 166324ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+----------------------------------+--------------+-----------+--------------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------+--------+------+
7 rows in set (4 min 30.59 sec)
セットtiflash_fine_grained_shuffle_stream_count ～ 20 :
mysql> set @@tiflash_fine_grained_shuffle_stream_count = 20;
Query OK, 0 rows affected (0.00 sec)
tiflash_fine_grained_shuffle_stream_count 20に設定した後:
mysql> explain analyze select *, row_number() over (partition by a) from t;
+----------------------------------+--------------+-----------+--------------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+--------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------------+--------------+-----------+--------------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+--------+------+
| TableReader_24 | 600000000.00 | 600000000 | root | | time:2m55s, loops:585941, cop_task: {num: 9163, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_23 | N/A | N/A |
| └─ExchangeSender_23 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:2m55s, min:1m37s, avg: 2m28.7s, p80:2m55s, p95:2m55s, iters:9160, tasks:3, threads:60} | ExchangeType: PassThrough | N/A | N/A |
| └─Window_22 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:2m12.9s, min:1m17s, avg: 1m54.2s, p80:2m12.9s, p95:2m12.9s, iters:9160, tasks:3, threads:60} | row_number()->Column#23 over(partition by test.t.a rows between current row and current row), stream_count: 20 | N/A | N/A |
| └─Sort_13 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:2m10.9s, min:1m16s, avg: 1m52.5s, p80:2m10.9s, p95:2m10.9s, iters:9160, tasks:3, threads:60} | test.t.a, stream_count: 20 | N/A | N/A |
| └─ExchangeReceiver_12 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:27.2s, min:25.5s, avg: 26.6s, p80:27.2s, p95:27.2s, iters:49602, tasks:3, threads:60} | stream_count: 20 | N/A | N/A |
| └─ExchangeSender_11 | 600000000.00 | 600000000 | mpp[tiflash] | | tiflash_task:{proc max:25.5s, min:0s, avg: 8.51s, p80:25.5s, p95:25.5s, iters:9388, tasks:3, threads:60} | ExchangeType: HashPartition, Hash Cols: [name: test.t.a, collate: binary], stream_count: 20 | N/A | N/A |
| └─TableFullScan_10 | 600000000.00 | 600000000 | mpp[tiflash] | table:t | tiflash_task:{proc max:167.3ms, min:0s, avg: 55.8ms, p80:167.3ms, p95:167.3ms, iters:9388, tasks:3, threads:60}, tiflash_scan:{dtfile:{total_scanned_packs:73834, total_skipped_packs:408, total_scanned_rows:600002896, total_skipped_rows:3307316, total_rs_index_load_time: 20ms, total_read_time: 179431ms}, total_create_snapshot_time: 0ms} | keep order:false | N/A | N/A |
+----------------------------------+--------------+-----------+--------------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+--------+------+
7 rows in set (2 min 55.09 sec)