Steal: 允许Buffer Pool里未提交事务所修改的脏页刷回到持久存储 No-steal: 不允许Buffer Pool里未提交事务所修改的脏页刷到持久存储中 缓冲区管理策略Buffer Management Policy 13 ■ Force策略的问题 对持久存储器进行频繁的随机写操作，性能下降。 ■ No-Steal策略的问题 不允许未提交事务的脏页换出，系统的并发量不高。 ▪ No-Force 协调者故障 如果协调者发生故障，参与者必 须决定提交或者撤 销事务，在某些情况下 ，参与者并不知道是否提交事 务，所以必须等协调者从失败中恢复。 27 两阶段提交存在的问题 1. Uncertainty Period 2. Blocking 图片来源：Bernstein的著作Principles of Transaction Processing 28 ● 事务的实现原理和Write

subselect’s search condition may evolve to NULL for certain rows, but that doesn’t cause any uncertainty: such a row won’t be included in the subresult set.  In reality, the subselect doesn’t return

...................................................................343 9.26.7. Database Object Management Functions........................................................347 9.26.8. Index Maintenance Issues.......................................................................478 15.7.1.4. Memory Management ........................................................................479 15.7.2. Cygwin... ..............................................................................570 18.12. Lock Management...............................................................................................

...................................................................357 9.26.7. Database Object Management Functions........................................................361 9.26.8. Index Maintenance Issues.......................................................................502 16.7.1.4. Memory Management ........................................................................503 16.7.2. Cygwin... ..............................................................................600 19.12. Lock Management...............................................................................................

Defaults ...................................................................... 583 19.12. Lock Management .................................................................................. 592 19.13. Version Functions ..................................................................... 1316 46.3. Memory Management ............................................................................. 1324 46.4. Visibility .......................................................................... 355 9.86. Collation Management Functions ................................................................................ 355

Defaults ...................................................................... 669 20.12. Lock Management .................................................................................. 679 20.13. Version ....................................................................... 1350 43.8. Transaction Management ......................................................................... 1356 43.9. Errors and in PL/Tcl ............................................................ 1396 44.10. Transaction Management ....................................................................... 1397 44.11. PL/Tcl Configuration

Defaults ...................................................................... 652 19.12. Lock Management .................................................................................. 661 19.13. Version ....................................................................... 1308 42.8. Transaction Management ......................................................................... 1314 42.9. Errors and in PL/Tcl ............................................................ 1355 43.10. Transaction Management ....................................................................... 1356 43.11. PL/Tcl Configuration

Defaults ...................................................................... 648 19.12. Lock Management .................................................................................. 657 19.13. Version ....................................................................... 1307 42.8. Transaction Management ......................................................................... 1313 42.9. Errors and in PL/Tcl ............................................................ 1353 43.10. Transaction Management ....................................................................... 1354 43.11. PL/Tcl Configuration

Defaults ...................................................................... 619 19.12. Lock Management .................................................................................. 628 19.13. Version ....................................................................... 1271 43.8. Transaction Management ......................................................................... 1277 43.9. Errors and in PL/Tcl ............................................................ 1316 44.10. Transaction Management ....................................................................... 1317 44.11. PL/Tcl Configuration

..............................................................................379 18.11. Lock Management..............................................................................................380 .............................................................................831 42.3. Memory Management ..........................................................................................832 to PostgreSQL developers. 1. What is PostgreSQL? PostgreSQL is an object-relational database management system (ORDBMS) based on POSTGRES, Version 4.21, developed at the University of California at Berkeley