[ARROW-15852] [JS] Table getByteLength and indexOf don't work

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 7.0.0
• Fix Version/s: 8.0.0
• Component/s: JavaScript
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20140
• Assignee: Paul Taylor
• Reporter: Timothy Higinbottom
• Created: 04/Mar/22 18:58
• Updated: 11/Jan/23 11:40
• Resolved: 01/Apr/22 17:39

Description

The functions table.getByteLength() and table.indexOf() don't return the correct values.

They are bound dynamically to the Table class, in a way I don't fully understand, with the following code:

https://github.com/apache/arrow/blob/1b796ec3f9caeb5e86e3348ba940bef8d95915c5/js/src/table.ts#L378-L390

The other functions like that, get(), set(), and isValid() all seem to work.  However, getByteLength() and indexOf() return the placeholder/sentinel values of 0 and -1 respectively that are defined in the no-op code here: https://github.com/apache/arrow/blob/1b796ec3f9caeb5e86e3348ba940bef8d95915c5/js/src/table.ts#L207-L221, which I assume is to generate the right type definitions, and thus documentation.

It's fairly simple for a user to implement the right logic themselves (at least for getByteLength) and it's a quick patch to define the functions normally instead of on the prototype, e.g.:

 

    /**
     * Get the size in bytes of an element by index.
     * @param index The index at which to get the byteLength.
     */
    // @ts-ignore
    public getByteLength(index: number): number { return this.data[index].byteLength; }
    /**
     * Get the size in bytes of a table.
     */
    //@ts-ignore
    public getByteLength(): number { 
        return this.data.map((batch) => batch.byteLength).reduce((sum, newLength) => sum + newLength);
    } 

I'd be happy to send this as a PR if that's an OK alternative to the way it's currently implemented.

Here's a Github repo of a minimal reproduction of the issue in NodeJS:
https://github.com/alexkreidler/apache-arrow-js-small-bug
 
And an observable notebook for in the browser (although I couldn't get ESM working): https://observablehq.com/@08027ecfa2b2f7bb/arrow-7-canary
 
Thanks to all for your work on Arrow!

 

Issue Links

• links to: GitHub Pull Request #12771