castable as performance

[Matthias Brantner]

The "castable as" expression has a big performance bottleneck because its implementation uses cast as followed by catching a potential exception. Constructing the exception (including the parameter substitution for the error message) takes a lot of time and it's not needed.

A query to reproduce this is as follows:

jsoniq version "1.0";

for $value in
  (
    "true", "false", ((1 to 1000) ! ($$ cast as string))
  )
return
  if ($value castable as boolean)
  then $value cast as boolean
  else if ($value castable as double)
  then $value cast as double
  else if ($value castable as decimal)
  then $value cast as decimal
  else if ($value castable as integer)
  then $value cast as integer
  else $value

The attached screenshot shows the relevant part of a callgrind profile.

[Paul J. Lucas (paul-lucas)]

Can you give a specific example of such a query?

[Matthias Brantner (matthias-brantner)]

callgrind profile

[Paul J. Lucas (paul-lucas)]

Try out this branch.