[SOLR-9691] Streaming expressions need to be able to use a metric computed by the facet stream as a field in other streams.

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 6.2.1
• Component/s: Parallel SQL
• Assignee: Unassigned
• Reporter: Timothy Potter
• Created: 25/Oct/16 14:26
• Updated: 08/Jun/19 15:29

Description

Using 6.2.1, I want to use a facet stream to do an intermediate count and then sum up the counts in a rollup stream, i.e. something like:

rollup(
  sort(
    hashJoin(
      search(products,
                  q="*:*",
                  fl="product_id,model_num",
                  sort="product_id asc",
                  qt="/export",
                  partitionKeys="product_id"),
      hashed=facet(transactions, q="*:*", buckets="product_id", bucketSizeLimit=1000000, bucketSorts="product_id asc", count(*)),
      on="product_id"
    ), 
    by="model_num asc"
  ), 
  over="model_num",
  sum(count(*))
)

Basically, I want to get a count of each product_id from the transactions collection (# of transactions per product) and then join that with the products table to generate a projection containing:

{
  "result-set": {
    "docs": [
      {
        "product_id": "1234",
        "count(*)": 4,
        "model_num": "X"
      },
      {
        "product_id": "5678",
        "count(*)": 5,
        "model_num": "Y"
      },
      ...
    ]
  }
}

This works, but the outer rollup doesn't recognize the count as a field. I get this error:

{
  "result-set": {
    "docs": [
      {
        "EXCEPTION": "Invalid expression sum(count(*)) - expected sum(columnName)",
        "EOF": true
      }
    ]
  }
}