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derivations: Don't invoke the substituter when an item is already in store.

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Fixes <http://bugs.gnu.org/20188>.
Reported by Mark H Weaver <mhw@netris.org>.

* guix/derivations.scm (substitution-oracle): Add 'valid?' procedure.
  Remove 'valid?' items from PATHS.
This commit is contained in:
Ludovic Courtès 2015-03-24 22:47:25 +01:00
parent b655b2154c
commit c7d1d88f6c
1 changed files with 13 additions and 7 deletions
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20
guix/derivations.scm
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@ -225,22 +225,28 @@ download with a fixed hash (aka. `fetchurl')."
(define* (substitution-oracle store drv)
"Return a one-argument procedure that, when passed a store file name,
returns #t if it's substitutable and #f otherwise. The returned procedure
knows about all substitutes for all the derivations listed in DRV and their
prerequisites.
knows about all substitutes for all the derivations listed in DRV; it also
knows about their prerequisites, unless they are themselves substitutable.
Creating a single oracle (thus making a single 'substitutable-paths' call) and
reusing it is much more efficient than calling 'has-substitutes?' or similar
repeatedly, because it avoids the costs associated with launching the
substituter many times."
(define valid?
(cut valid-path? store <>))
(let* ((paths (delete-duplicates
(fold (lambda (drv result)
(let ((self (match (derivation->output-paths drv)
(((names . paths) ...)
paths)))
(deps (append-map derivation-input-output-paths
(derivation-prerequisites
drv))))
(append self deps result)))
paths))))
(if (every valid? self)
result
(let ((deps
(append-map derivation-input-output-paths
(derivation-prerequisites drv))))
(append (remove valid? (append self deps))
result)))))
'()
drv)))
(subst (list->set (substitutable-paths store paths))))