Class ExportWriter

java.lang.Object
org.apache.solr.handler.export.ExportWriter
All Implemented Interfaces:
Closeable, AutoCloseable, SolrCore.RawWriter

public class ExportWriter extends Object implements SolrCore.RawWriter, Closeable
Prepares and writes the documents requested by /export requests

ExportWriter gathers and sorts the documents for a core using "stream sorting".

Stream sorting works by repeatedly processing and modifying a bitmap of matching documents. Each pass over the bitmap identifies the smallest docs (default is DEFAULT_BATCH_SIZE) that haven't been sent yet and stores them in a Priority Queue. They are then exported (written across the wire) and marked as sent (unset in the bitmap). This process repeats until all matching documents have been sent.