[elephant-ticket] Re: #24: Prevalence-style storage options

[elephant]

#24: Prevalence-style storage options
--------------------------+-------------------------------------------------
  Reporter:  ieslick      |       Owner:  ieslick
      Type:  enhancement  |      Status:  new    
  Priority:  major        |   Milestone:         
 Component:  system-wide  |     Version:         
Resolution:               |    Keywords:         
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Changes (by ieslick):

  * milestone:  Release 0.9.2 =>
  * priority:  critical => major

Old description:

> Make storage policy decisions on per-class (or per-instance) basis
>
> Concurrent mode
>  * The existing all transactions to memory
>  * For backends that allow multiple processes to connect
>  * Full ACID functionality
>
> Single-threaded objects
>  * Cache values in instance slots for fast reads
>  * Writes update slots and write to disk as normal
>  * Violates consistency and isolation; users must enforce single operator
>
> Prevalence mode
>  * Standard object model (user enforced ACID properties)
>  * Read/write to normal slots
>  * Backup slot values on object creation and explicit synch calls on
> class or instances
>  * In-memory slot indexing?  Write-through disk class indexing?

New description:

 Make storage policy decisions on per-class (or per-instance) basis

 Concurrent mode
  * The existing "all transactions read/write disk"
  * For backends that allow multiple processes to connect
  * Full ACID functionality

 Single-threaded objects
  * Cache values in instance slots for fast reads
  * Writes update memory slots and also write to disk as normal
  * Violates consistency and isolation; users must enforce single operation

 Prevalence mode
  * Standard object model (user enforced ACID properties)
  * Read/write to normal slots
  * Backup slot values on object creation and explicit synch calls on class
 or instances
  * In-memory slot indexing?  Write-through disk class indexing?

Comment:

 This has some significant implications, but the total code size should not
 be that high so we can look at this _if_ we get some customer requests for
 prevalence style data models.

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Ticket URL: <http://trac.common-lisp.net/elephant/ticket/24>
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