TiFlashパフォーマンスの調整
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によって、 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。
リソースの計画
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の両方のデプロイ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確保し、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
JoinまたはUnion前の位置に集約関数を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
- より大きな実行同時実行数を設定する
tiflash_fine_grained_shuffle_stream_countを構成する
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 リソースを十分に活用できるため、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の 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、クエリの実行に 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を有効にする前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 TiKV からデータを読み取り、TiDB でJoinとAggregationを実行する必要があります。 tidb_enforce_mppが有効になった後、 JoinとAggregationがTiFlashにプッシュされます。さらに、オプティマイザは必ずしも MPP 実行計画を生成するとは限らないため、 tidb_enforce_mpp有効にすることで、オプティマイザに強制的に MPP 実行計画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 モードを有効にします。
mysql> set @@tidb_enforce_mpp = ON;
Query OK, 0 rows affected (0.00 sec)
MPP モードを有効にした後:
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)
JoinまたはUnion前の位置に集約関数をプッシュダウンする
集計操作をJoinまたはUnionの前の位置にプッシュダウンすることで、 JoinまたはUnion操作で処理するデータを減らすことができ、パフォーマンスが向上します。
変数tidb_opt_agg_push_down 、オプティマイザーが集約関数をJoinまたはUnionの前の位置に押し下げ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後のクエリ結果を示しています。この変数が有効になる前は、 HashJoin_41操作に続いてHashAgg_58操作が実行されます。この変数を有効にすると、新しく生成されたHashAgg_21およびHashAgg_32操作がHashJoin_76操作の前に実行されます。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ことで、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を実行する必要があります。この変数が有効になった後、 distinct aがTiFlashにプッシュされ、新しいgroup by列test.t.aが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。圧縮中に、削除された行のクリーンアップや、更新によって発生した複数のバージョンのデータのマージなど、ノード上の物理データが書き換えられます。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。以下に例を示します。
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は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、Broadcast Hash Join アルゴリズムが使用されます。それ以外の場合は、Shuffled Hash Join 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の結果セットのサイズを見積もることができません。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も少ない場合、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、Shuffled Hash Join 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を再構成する前後のクエリ結果を示しています。再構成前のExchangeType of ExchangeSender_29はHashPartitionです。この変数の値が10000000に変更された後、 ExchangeType / ExchangeSender_29がBroadcastに変更されます。
tidb_broadcast_join_threshold_sizeを再構成する前に:
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)
tidb_broadcast_join_threshold_size ～ 10000000を設定:
mysql> set @@tidb_broadcast_join_threshold_size = 10000000;
Query OK, 0 rows affected (0.00 sec)
tidb_broadcast_join_threshold_sizeが10000000に設定された後:
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)
より大きな実行同時実行数を設定する
実行の同時実行数が増えると、 TiFlash がシステムのより多くの CPU 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。
tidb_max_tiflash_threads変数は、 TiFlash がリクエストを実行する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を再構成する前後のクエリ結果を示しています。再構成前、すべてのTiFlashオペレーターの実行同時実行数は 24 です。この変数の値が20に変更された後、同時実行数は 60 になります。
tidb_max_tiflash_threadsを再構成する前に:
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)
tidb_max_tiflash_threads ～ 20を設定:
mysql> set @@tidb_max_tiflash_threads = 20;
Query OK, 0 rows affected (0.00 sec)
tidb_max_tiflash_threadsが20に設定された後:
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を構成する
ファイングレイン シャッフル機能のtiflash_fine_grained_shuffle_stream_countを構成することにより、ウィンドウ関数を実行するための同時実行性を高めることができます。このようにして、ウィンドウ関数の実行により多くのシステム リソースを占有できるため、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にプッシュされると、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後のクエリ結果を示しています。再構成前のstream_count [ExchangeSender_11, ExchangeReceiver_12, Sort_13, Window_22] 8 です。再構成後は、 stream_count 20 になります。
tiflash_fine_grained_shuffle_stream_countを再構成する前に:
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)
tiflash_fine_grained_shuffle_stream_count ～ 20を設定:
mysql> set @@tiflash_fine_grained_shuffle_stream_count = 20;
Query OK, 0 rows affected (0.00 sec)
tiflash_fine_grained_shuffle_stream_countが20に設定された後:
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)