[JS] Implement list contains predicate

[asfimport]

As far as I can see there is no way to check if a list contains a specific element.

My code is as follows:

 

var listChild = new arrow.Field('list[Utf8]', new arrow.Utf8())

var all = arrow.Table.new([
 arrow.DateVector.from(dates),
 arrow.Int32Vector.from(flumeseqs),
 arrow.Utf8Vector.from(keys),
 arrow.Vector.from({ values: authors, type: new arrow.Dictionary(new arrow.Utf8(), new arrow.Int32()) }),
 arrow.Int32Vector.from(sequences),
 arrow.Vector.from({ values: types, type: new arrow.Dictionary(new arrow.Utf8(), new arrow.Int32()) }),
 arrow.Vector.from({ values: links, type: new arrow.List(listChild) }),
 ], ["date", "flumeseq", "key", "author", "sequence", "type", "links"])

And I want to get all the items that has a specific element in the links section.

So something like:

 

var q2 = Array.from(
all.filter(
 arrow.predicate.col('links').contains('%GcvjVk+NLsjOB5Vd+vceGXEOeYmHoRA6lgXVJzPuMxw=.sha256')))

 

 

Reporter: Anders Rune Jensen

_{Note: This issue was originally created as ARROW-7738. Please see the migration documentation for further details.}

[asfimport]

Anders Rune Jensen:
For future travelers this can be done using something like:

 

    const link = '%TbiUknx1XfDdxccudfDds54hfzVNCjh2N99KXtLuyVc=.sha256'
    const uLink = new TextEncoder("utf-8").encode(link);
    
    var q2 = Array.from(
      all.filter(
        arrow.predicate.custom(
          (idx) => {
            var l = get_links(idx)
            if (l.length > 0) {
              for (var o = 0; o < l.valueOffsets.length - 1; ++o) {
                var start = l.valueOffsets[o], end = l.valueOffsets[o+1]
                if (end - start != uLink.length) continue                

                var found = true
                for (var i = start; i < end; ++i) {
                  if (l.values[i] != uLink[i-start]) {
                    found = false
                    break
                  }
                }
                if (found) return true
              }
              return false
            } else
              return false
          },
          (batch) => {
            get_links = arrow.predicate.col('links').bind(batch)
          })
      )
    )

[domoritz]

We removed predicate support. Please use something like arquero now.