Relaxed Guide to memory_order_relaxed Hans Boehm Paul E. McKenney Google Facebook CPPCON 2020std::atomic/std::atomic_ref and memory_order_relaxed ● C++ atomic operations simple threads-as-interleaving semantics ● by passing memory_order enum values to explicit atomic operations. ● In particular, memory_order_relaxed allows arbitrary visibility reordering with respect memory_order_relaxed? ● Just a load, just a store: Full control, excellent efficiency and scalability! ○ Assuming aligned machine-sized atomic objects, that is…What is Not to Like About memory_order_relaxed

256 Iteration Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Group‐by Merger . . 309 7.7.21 21. [Other] Why does Oracle database throw“Order by value must implements Comparable”exception when using Timestamp Order By? . . . . . . . . . . . 309 ix 7.7.22 22. [Other] In Windows Adaptor 12 Apache ShardingSphere document, v5.0.0 more freely. 3.2 Mode 3.2.1 Background In order to meet the different needs of users for quick test startup, stand‐alone running and cluster running

495 /metadata/${databaseName}/rules/sharding/tables/t_order/versions/0 . . . . . . 496 /metadata/databaseName/schemas/{schemaName}/tables/t_order/versions/0 . . 496 /nodes/compute_nodes . . . . . . 521 Traversal Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521 Group‐by Merger . . . . . 553 13.6.4 Other Why does Oracle database throw“Order by value must implements Com‐ parable”exception when using Timestamp Order By? . . . . . . . . . . . . . . 554 13.6.5 Other In Windows

382 Traversal Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382 Group‐by Merger . . . . . 461 8.6.4 Other Why does Oracle database throw“Order by value must implements Com‐ parable”exception when using Timestamp Order By? . . . . . . . . . . . . . . 461 8.6.5 Other In Windows into different databases. The diagram below has presented the solution to assign user tables and order tables to different databases by vertical sharding according to business need. Vertical sharding

viii Iteration Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 Group‐by Merger . . . . 364 7.8.24 [Other] Why does Oracle database throw“Order by value must implements Com‐ parable”exception when using Timestamp Order By? . . . . . . . . . . . . . . 364 7.8.25 [Other] In Windows most applicable one to their needs to conduct business more freely. 3.2 Mode 3.2.1 Background In order to meet the different needs of users for quick test startup, stand‐alone running and cluster running

409 Traversal Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 Group‐by Merger . . . . . 500 8.6.4 Other Why does Oracle database throw“Order by value must implements Com‐ parable”exception when using Timestamp Order By? . . . . . . . . . . . . . . 500 8.6.5 Other In Windows into different databases. The diagram below has presented the solution to assign user tables and order tables to different databases by vertical sharding according to business need. Vertical sharding

. . . . . . 295 vii 7.10 Why does Oracle database throw “Order by value must implements Comparable”ex‐ ception when using Timestamp Order By? . . . . . . . . . . . . . . . . . . . . . . . . . 296 7 into different databases. The diagram below has presented the solution to assign user tables and order tables to different databases by vertical sharding according to business need. Vertical sharding The change of table name after sharding, or misconducts caused by operations such as pagination, order by or aggregated group by are just the case in point. 3.1. Sharding 10 Apache ShardingSphere document

266 Iteration Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Order‐by Merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Group‐by Merger . . . . 352 7.8.24 [Other] Why does Oracle database throw“Order by value must implements Com‐ parable”exception when using Timestamp Order By? . . . . . . . . . . . . . . 352 7.8.25 [Other] In Windows Adaptor 12 Apache ShardingSphere document, v5.1.1 more freely. 3.2 Mode 3.2.1 Background In order to meet the different needs of users for quick test startup, stand‐alone running and cluster running

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 8. Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 8.1.2. Create Order Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 8.1.3. Order Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 8.1.4. Update Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 7. Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 7.1.2. Create Order Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 7.1.3. Order Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 7.1.4. Update Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .