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Tara2
Posted: Thursday, January 21, 2021 4:17:18 AM

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How is the definition below fit in the following text?

Quote:
pre-emption (n.)
also preemption, c. 1600, "a purchase by one before an opportunity is offered to others," originally as a right; literally "a purchasing before others," from pre- "before" + emption "purchase."



The second approach for preventing deadlocks is to use preemption and transaction rollbacks. In preemption, when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.
thar
Posted: Thursday, January 21, 2021 4:51:39 AM

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This is being used as a technical term. It is in fact the original meaning of the word in Latin. empt = to buy. Pre = before.

But now 'pre-empt' has a wider meaning in modern English.
This writer is now using the noun with that modern meaning. It may be a technical term in computing, I don't know.

More useful for a definition is the adjective or verb which are far more common in modern English. They have that wider meaning of taking some action before something else becomes a problem.

pre-emptive
Quote:
adjective
serving or intended to pre-empt or forestall something, especially to prevent attack by disabling the enemy.
"a pre-emptive strike"


pre-empt
Quote:
If you pre-empt an action, you prevent it from happening by doing something which makes it unnecessary or impossible. You can pre-empt pain by taking a painkiller at the first warning sign.


ie you fix the problem before it becomes a problem, by seeing it before it happens and taking action. Planning ahead to prevent a problem arising.



Here it explains what pre-emption is:
In preemption, when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.
I don't know what that means, but it does involve the system recognising that there is a problem ahead. If it continues with the process it will get deadlocked. So it executes a prevention process. This pre-empts the problem and does something so that the problem never appears. Things happen in an order that keeps the process moving and it doesn't get deadlocked.

In Drago's example of locked traffic, the pre-emptive action would be to have put in traffic lights. They only allow flow in one direction at a time. That means that the situation of all the cars being jammed together and stuck there never arises. You have pre-empted the problem by taking some action, and this prevented the problem from ever occurring.



Tara2
Posted: Thursday, January 21, 2021 8:13:30 AM

Rank: Advanced Member

Joined: 11/8/2017
Posts: 3,447
Neurons: 12,606
thar wrote:
This is being used as a technical term. It is in fact the original meaning of the word in Latin. empt = to buy. Pre = before.

But now 'pre-empt' has a wider meaning in modern English.
This writer is now using the noun with that modern meaning. It may be a technical term in computing, I don't know.

More useful for a definition is the adjective or verb which are far more common in modern English. They have that wider meaning of taking some action before something else becomes a problem.

pre-emptive
Quote:
adjective
serving or intended to pre-empt or forestall something, especially to prevent attack by disabling the enemy.
"a pre-emptive strike"


pre-empt
Quote:
If you pre-empt an action, you prevent it from happening by doing something which makes it unnecessary or impossible. You can pre-empt pain by taking a painkiller at the first warning sign.


ie you fix the problem before it becomes a problem, by seeing it before it happens and taking action. Planning ahead to prevent a problem arising.



Here it explains what pre-emption is:
In preemption, when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.
I don't know what that means, but it does involve the system recognising that there is a problem ahead. If it continues with the process it will get deadlocked. So it executes a prevention process. This pre-empts the problem and does something so that the problem never appears. Things happen in an order that keeps the process moving and it doesn't get deadlocked.

In Drago's example of locked traffic, the pre-emptive action would be to have put in traffic lights. They only allow flow in one direction at a time. That means that the situation of all the cars being jammed together and stuck there never arises. You have pre-empted the problem by taking some action, and this prevented the problem from ever occurring.




Many, many thanks for such excellent explanation!!!
Tara2
Posted: Thursday, January 21, 2021 1:49:53 PM

Rank: Advanced Member

Joined: 11/8/2017
Posts: 3,447
Neurons: 12,606
Sorry thar, this word is difficult, its meaning here I can't get. Shouldn't it mean 'take back' here, please?

when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.
coag
Posted: Thursday, January 21, 2021 4:17:44 PM

Rank: Advanced Member

Joined: 3/27/2010
Posts: 1,618
Neurons: 8,806
Tara2 wrote:
The second approach for preventing deadlocks is to use preemption and transaction rollbacks. In preemption, when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.

I think that "preemption" in this case means that transaction Tj has a higher priority than transaction Ti, that is, that Tj can interrupt Ti. This meaning of "preemption" is close to the Latin origin of the word:
originally as a right; literally "a purchasing before others," (Online Etymology Dictionary)

preemption
3a : a doctrine in law according to which federal law supersedes state law when federal law is in conflict with a state law
Even without an express provision for preemption, we have found that state law must yield to a congressional Act in at least two circumstances. (Webster)
thar
Posted: Thursday, January 21, 2021 4:54:43 PM

Rank: Advanced Member

Joined: 7/8/2010
Posts: 23,708
Neurons: 96,171
It is an odd use - really it is taken back, not "pre-" anything.
Tara2
Posted: Thursday, January 21, 2021 4:59:37 PM

Rank: Advanced Member

Joined: 11/8/2017
Posts: 3,447
Neurons: 12,606
coag wrote:
Tara2 wrote:
The second approach for preventing deadlocks is to use preemption and transaction rollbacks. In preemption, when a transaction Tj requests a lock that transaction Ti holds, the lock granted to Ti may be preempted by rolling back of Ti, and granting of the lock to Tj.

I think that "preemption" in this case means that transaction Tj has a higher priority than transaction Ti, that is, that Tj can interrupt Ti. This meaning of "preemption" is close to the Latin origin of the word:
originally as a right; literally "a purchasing before others," (Online Etymology Dictionary)

preemption
3a : a doctrine in law according to which federal law supersedes state law when federal law is in conflict with a state law
Even without an express provision for preemption, we have found that state law must yield to a congressional Act in at least two circumstances. (Webster)

Thank you so much!!!
Tara2
Posted: Thursday, January 21, 2021 5:01:00 PM

Rank: Advanced Member

Joined: 11/8/2017
Posts: 3,447
Neurons: 12,606
thar wrote:
It is an odd use - really it is taken back, not "pre-" anything.

Many thanks!!!
Sorry thar, so do you mean that the meaning that coag said here is correct not the modern use of it (preemption)?
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