[jira] [Commented] (ARROW-15651) [JavaScript] Structs incorrectly initialise null values

["Dominik Moritz (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-15651?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17523971#comment-17523971 ] 

Dominik Moritz commented on ARROW-15651:
----------------------------------------

Since https://issues.apache.org/jira/browse/ARROW-15705 if fixed, can we close this? 

> [JavaScript] Structs incorrectly initialise null values
> -------------------------------------------------------
>
>                 Key: ARROW-15651
>                 URL: https://issues.apache.org/jira/browse/ARROW-15651
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: JavaScript
>    Affects Versions: 7.0.0
>            Reporter: Alfred Mountfield
>            Priority: Major
>
> Nullable StructArrays created with FixedSizeList fields seem to incorrectly initialise.
> I've tried to create them using both the `Builder` and `makeVector` methods and I believe it breaks the specification.
> I believe that the underlying arrays for the fields of a struct should be the length of the struct array.
> However the `nullCount`s, `numChildren`s, and other methods all return different numbers. (And this is causing a problem when we try to read the same memory within Rust as the lengths and offsets differ)
> Specifically this:
> {code:javascript}
> let list_field = new Field('n1', new FixedSizeList(2, Float64), true);
> let struct_field = new Field('foo', new Struct([list_field]), true);
> let builder = new Builder({
> type:struct_field.type,
> nullValues: [null, undefined],
> });
> builder.append(null);
> console.log('Builder:' + JSON.stringify(builder));
> console.log('numChildren: ' + builder.numChildren);
> console.log('nullCount: ' + builder.nullCount);
> console.log('length: ' + builder.length);
> let vec1 = builder.toVector();
> console.log('Vector from Builder:' + vec1);
> console.log('numChildren: ' + vec1.numChildren);
> console.log('nullCount: ' + vec1.nullCount);
> console.log('length: ' + vec1.length);
> let vec2 = makeVector({
> data: [null],
> type:struct_field.type,
> nullable:true,
> });
> console.log('Vector from makeVector:' + JSON.stringify(vec2));
> console.log('numChildren: ' + vec2.numChildren);
> console.log('nullCount: ' + vec2.nullCount);
> console.log('length: ' + vec2.length);
> {code}
> Results in (I've removed some fields for brevity)
> {code:javascript}
> Builder: \{"length":1,"finished":false,"type":{"children":[{"name":"n1","type":{"listSize":2,"children":[null]},"nullable":true,"metadata":{}}]},"children":[],"nullValues":[null,null],"stride":1,"_nulls":\{"buffer": ... ,"stride":0.125,"BYTES_PER_ELEMENT":1,"length":1,"numValid":0}}
> numChildren: 0
> nullCount: 1
> length: 1
> Vector from Builder:[]
> numChildren: 1
> nullCount: 1
> length: 1
> Vector from makeVector:[]
> numChildren: 1
> nullCount: 0
> length: 0{code}
> I tried to test this within stackblitz, the Project source code [should be available here|https://stackblitz.com/edit/node-kpgovc?file=index.js]



--
This message was sent by Atlassian Jira
(v8.20.1#820001)