[elephant-devel] function calls as keyforms for btree-indexes

[Sean Ross]

Hi all,

I would like to propose the following adjustment to the way that
key-forms for btree indexes are
 converted into functions. Currently this is done by looking up the
fdefinition of the symbol provided
 or calling compile nil on the form. I would like to amend this to
also allow function forms
 eg.  '(create-indexer "foo")

Keyform lookup would then work as follows.

a) (and (symbolp key) (fboundp key)) => (fdefintiion key)
b) (and (consp key) (eql (first key) 'lambda)) => (compile nil key)
c) (consp key) =>  (apply (first key) (rest key))
d) error 'invalid-keyform

and is used something like the following.

  (defun create-indexer (tag)
    (lambda (idx k v)
      (declare (ignore idx k))
      (values (find tag (tags-of v))
                 (tags-of v))))

and indexes using this can be created by using (list 'create-indexer
name)  as the key-form.

While the functionality of this can be accomplished using (compile nil
...) it seems a
bit lispier to invoke a function which subsequently returns a function
(and also offers
a performance advantage).

I've attached a patch which implements this on the shared-initalize
:after method for btree-index.

cheers,
 sean.
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