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Diffstat (limited to 'doc/FAQ_DEV')
| -rw-r--r-- | doc/FAQ_DEV | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/doc/FAQ_DEV b/doc/FAQ_DEV index 31b27ee73ec..5f9f0788348 100644 --- a/doc/FAQ_DEV +++ b/doc/FAQ_DEV @@ -26,6 +26,7 @@ 10) What is elog()? 11) What is configure all about? 12) How do I add a new port? + 13) What is CommandCounterIncrement()? _________________________________________________________________ 1) What tools are available for developers? @@ -414,3 +415,15 @@ c-mode) src/include/storage/s_lock.h for your CPU. There is also a src/makefiles directory for port-specific Makefile handling. There is a backend/port directory if you need special files for your OS. + + 13) What is CommandCounterIncrement()? + + Normally, transactions can not see the rows they modify. This allows + UPDATE foo SET x = x + 1 to work correctly. + + However, there are cases where a transactions needs to see rows + affected in previous parts of the transaction. This is accomplished + using a Command Counter. Incrementing the counter allows transactions + to be broken into pieces so each piece can see rows modified by + previous pieces. CommandCounterIncrement() increments the Command + Counter, creating a new piece of the transaction. |