# Support \`@threads\` for a lazy object

**URL:** <https://discourse.julialang.org/t/support-threads-for-a-lazy-object/64458>\
**Category:** Performance\
**Tags:** question\
**Created:** [July 11, 2021, 11:39am UTC](https://discourse.julialang.org/t/support-threads-for-a-lazy-object/64458 "2021-07-11T11:39:01Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [July 11, 2021, 11:39am UTC](https://discourse.julialang.org/t/support-threads-for-a-lazy-object/64458/1 "2021-07-11T11:39:01Z")

</div>

Say I have a big `LazyArray` with size `10^5` and the underlying structure is that every `5000` entries are in a “chunk” and one has to read and decompress a chunk together.

I have implemented `getindex()` for `LazyArray` and it caches the “chunk” that contains my entry such that when you iterate over it, it only does slow I/O once per chunk. In fact this works so well I can even wrap multiple array into a dataframe-like lazy object with `TypedTables.Table` and have super fast type-stable loop.

But I now run into problem with `@threads for ... in LazyTable`, it tries to materialize the table ahead of the for loop (by design of threads macro I guess?). My question is 1) is there a way to support `@threads`? if not, how can I error and tell user to use `@spawn` inside a normal for loop