[SOLR-12572] Reuse fieldvalues computed while sorting at writing in ExportWriter

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 7.5, 8.0
• Component/s: streaming expressions
• Assignee: Varun Thacker
• Reporter: Amrit Sarkar
• Created: 20/Jul/18 15:28
• Updated: 21/Nov/19 00:41
• Resolved: 24/Aug/18 08:03

Description

While exporting result through "/export" handler,

http://localhost:8983/solr/core_name/export?q=my-query&sort=severity+desc,timestamp+desc&fl=severity,timestamp,msg

Doc-values are sought for all the sort fields defined (in this example 'severity, 'timestamp'). When we stream out docs we again make doc-value seeks against the fl fields ('severity','timestamp','msg') .

In most common use-cases we have fl = sort fields, or atleast the sort fields are subset of fl fields, so if we can pre-collect the values while sorting it, we can reduce the doc-value seeks potentially bringing speed improvement.