The transaction cache statement enables or disables the transaction read cache.
transaction cache [on|off|exp]
| on | Enables the transaction read cache. |
| off | Disables the transaction read cache. |
| exp | The transaction read cache is turned on if the expression evaluates to nonzero (true) and turned off if it evaluates to 0 (false). |
Normally, all read operations within a transaction first query the list of uncommitted updates. This allows the re-reading of an item already written.
Users can turn this cache off if they are confident that the transaction does not attempt this activity. Turning the cache off can improve the performance of reads within a transaction, especially if the transaction is particularly long.
Once the cache is turned off, it remains off until the program completes.
transaction start transaction cache on else msg="6 cache"; goto fail write "1" on "1" read xx from "1" else msg="6 read"; goto fail transaction rollback read xx from "1" then msg="6 read2"; goto fail delete 1 transaction start transaction cache off else msg="7 cache"; goto fail write "1" on "1" read xx from "1" then msg="7 read"; goto fail transaction commit read xx from "1" else msg="7 read2"; goto fail delete 1