Given a main module with no user defined functions, is it considered better
practice to use `declare variable` as opposed to `let`, the reason I ask is
twofold:
1) I have started on a large code-base that seems to eschew `let` in favour of
using `declare variable`. This seems somewhat strange to me.
2) We have seen different evaluation strategies, whereby a function which
returns an empty-sequence which is bound in a declare variable clause, is never
executed. Yet when we re-write that as a let binding, the code is executed. I
think perhaps the query optimiser in ML is being too aggressive here?
For example -
declare variable $content-type as xs:string :=
slib:validated-bulk-load-content-type();
and then a few lines later we have -
slib:normal-bulk-load-response ($etag-map, fn:count
($etag-map/store:etag-entry), $content-type)
Subsequently the `slib:normal-bulk-load-response` calls
xdmp:set-response-content-type($content-type). However the
`slib:validated-bulk-content-type()` function is never evaluated, we are
certain of this because it eventually calls `fn:error`, yet the error never
occurs!
If we switch the `declare variable $content-type` for a `let $content-type`
then we do see the error occurring!
Cheers Adam.
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