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From "Mamta A. Satoor (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1822) LOCK TABLE example and description in reference manual should get replaced by a 'real' example
Date Thu, 28 Sep 2006 18:09:51 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1822?page=comments#action_12438514 ] 
            
Mamta A. Satoor commented on DERBY-1822:
----------------------------------------

Laura, I looked at the latest patch and following line needs rewording. 
"To lock the entire FlightsAvailable table in exclusive mode for a transaction that will update
many rows, but where no single statement will update enough rows, acquire an exclusive table
lock on the table. "

Here is what the example is trying to do, please feel free to word it as seems appropriate.
Consider a trasnaction with multiple update statements, each one of which acquires couple
row locks here and there. Since each individual update statement acquires only few row level
locks, the transaction will not automatically upgrade the locks to a table level lock. But
all of the update statements collectively endup getting and releasing large number of locks
and may even run into deadlocks. For such transactions, it might be better to just acquire
a table level lock at the beginning of the transaction. This way, individual updatement statements
won't have to keep acquiring and releasing row level locks.

One suggestion for the rewording of the above statement
"Lock the entire FlightsAvailable table in exclusive mode for the transaction that will update
many rows, but where no single update statement will update enough rows to acquire an exclusive
table lock on the table. "


> LOCK TABLE example and description in reference manual should get replaced by a 'real'
example
> ----------------------------------------------------------------------------------------------
>
>                 Key: DERBY-1822
>                 URL: http://issues.apache.org/jira/browse/DERBY-1822
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation
>    Affects Versions: 10.2.1.5, 10.3.0.0
>            Reporter: Myrna van Lunteren
>         Assigned To: Laura Stewart
>            Priority: Minor
>             Fix For: 10.3.0.0
>
>         Attachments: derby1822.diff, derby1822_2.diff, rrefsqlj40506.html, rrefsqlj40506.html
>
>
> The Example in the documentation for LOCK TABLE looks jumbled.
> It looks like part of it is based on a demo that was part of the pre-quel to Derby. The
current toursdb demo is based on it, and thus includes reference to the table 'Flights', so
it looks as if the queries *might* be possible, but the table listed (HotelAvailability) does
not exist. 
> Then there is mention of the table People, which doesn't exist either, 
> A proper example needs to be put in place.
> Note that the description above the example mentions Hotels, this probably was supposed
to be removed also.

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