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db: added notes about custodians and connection-pool, virtual-connection

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This commit is contained in:
Ryan Culpepper 2012-08-22 11:05:25 -04:00
parent c7a6272f4b
commit c4edc684eb
1 changed files with 9 additions and 4 deletions
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collects/db/scribblings/connect.scrbl
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@ -344,9 +344,10 @@ connections.
Creates a @tech{connection pool}. The pool consists of up to Creates a @tech{connection pool}. The pool consists of up to
@racket[max-connections], divided between leased connections and up to @racket[max-connections], divided between leased connections and up to
@racket[max-idle-connections] idle connections. The pool uses @racket[max-idle-connections] idle connections. The pool uses
@racket[connect] to create new connections when needed; the @racket[connect] to create new connections when needed. The
@racket[connect] function must return a fresh connection each time it @racket[connect] function is called with the same
is called. @racket[current-custodian] value as when the connection pool was
created, and it must return a fresh connection each time it is called.
@examples[#:eval the-eval @examples[#:eval the-eval
(eval:alts (eval:alts
@ -417,7 +418,11 @@ automatically releases them when they are no longer needed.
Creates a @tech{virtual connection} that creates actual connections on Creates a @tech{virtual connection} that creates actual connections on
demand using the @racket[connect] function, or by calling demand using the @racket[connect] function, or by calling
@racket[(connection-pool-lease connect)] if @racket[connect] is a @racket[(connection-pool-lease connect)] if @racket[connect] is a
@tech{connection pool}. A virtual connection encapsulates a mapping @tech{connection pool}. If @racket[connect] is a function, it is
called with the same @racket[current-custodian] value as when the
virtual connection was created.
A virtual connection encapsulates a mapping
of threads to actual connections. When a query function is called with of threads to actual connections. When a query function is called with
a virtual connection, the current thread's associated actual a virtual connection, the current thread's associated actual
connection is used to execute the query. If there is no actual connection is used to execute the query. If there is no actual