apc_add() versus apc_store()

Question

I know that apc_store() overwrites the key if it already exists, so I know the difference, my question is just: What's the better method/best practice?

score 43 · Accepted Answer · answered Apr 05 '11 at 10:54

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The only difference between those two functions is that apc_add() will not overwrite an existing entry.
apc_store(), on the other hand, will overwrite an existing entry.

So, which one should your use, between apc_add() and apc_store() ?
Well, it all depends on your needs : do you want an existing entry to be overwritten, or not ?

answered Apr 05 '11 at 10:54

Pascal MARTIN

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A result of this difference might have major implications in concurrent environments: excessive locking, resulting with extremely high latencies or crashes (I've added another answer relating to this) – etov Nov 05 '14 at 09:47

score 2 · Answer 2 · edited Apr 13 '17 at 12:13

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In addition to what @Pascal MARTIN writes, there is a major practical difference between them.

In a heavily concurrent environment, e.g. when using apc for user objects in apache, the use of apc_store might lead to apc time bomb (the link is from 2007 but still relevant!), while apc_add mitigates this issue.

See also: https://serverfault.com/questions/342295/apc-keeps-crashing

edited Apr 13 '17 at 12:13

Community

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answered Nov 05 '14 at 09:46

etov

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score 1 · Answer 3 · answered Aug 21 '14 at 15:50

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you need apc_add() in case you like to implement an atomic counter in a concurrent environment. thats the main use-case IMO.

answered Aug 21 '14 at 15:50

staabm

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score 1 · Answer 4 · edited May 22 '19 at 09:32

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Really depends on the logic you need to apply: do you need to overwrite the key or not? It’s all up to you.

edited May 22 '19 at 09:32

TRiG

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answered Apr 05 '11 at 09:50

Poelinca Dorin

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Then there's a page fault in your memory. – DanMan Nov 17 '12 at 15:12

apc_add() versus apc_store()

4 Answers4