Ks 20211202 fix major reindex bug (#3211)

* begin with failing test

* fix bug

* change log

* change log

hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_7_0/3211-reindex-performance.yaml

@@ -0,0 +1,4 @@
+---
+type: fix
+jira: SMILE-3472
+title: "Fixed a serious performance issue with the `$reindex` operation."

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/reindex/job/ReindexWriter.java

@@ -56,7 +56,7 @@ public class ReindexWriter implements ItemWriter<List<Long>> {
 
 		// Note that since our chunk size is 1, there will always be exactly one list
 		for (List<Long> pidList : thePidLists) {
-			partitionRunner.runInPartitionedThreads(new SliceImpl<>(pidList), pids -> reindexPids(pidList));
+			partitionRunner.runInPartitionedThreads(new SliceImpl<>(pidList), pids -> reindexPids(pids));
 		}
 	}
 

hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/reindex/job/ReindexWriterTest.java

@@ -0,0 +1,51 @@
+package ca.uhn.fhir.jpa.reindex.job;
+
+import ca.uhn.fhir.jpa.api.config.DaoConfig;
+import ca.uhn.fhir.jpa.search.reindex.ResourceReindexer;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.transaction.PlatformTransactionManager;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+public class ReindexWriterTest {
+
+	@Mock
+	private DaoConfig myDaoConfig;
+	@Mock
+	private PlatformTransactionManager myPlatformTransactionManager;
+	@Mock
+	ResourceReindexer myResourceReindexer;
+
+	@InjectMocks
+	private ReindexWriter myReindexWriter;
+
+	@Test
+	public void testReindexSplitsPidList() throws Exception {
+		when(myDaoConfig.getReindexBatchSize()).thenReturn(5);
+		when(myDaoConfig.getReindexThreadCount()).thenReturn(4);
+
+		List<Long> pidList = new ArrayList<>();
+		int count = 20;
+		for (long i = 0; i < count; ++i) {
+			pidList.add(i);
+		}
+		List<List<Long>> pidListList = new ArrayList<>();
+		pidListList.add(pidList);
+		myReindexWriter.write(pidListList);
+
+		verify(myResourceReindexer, times(count)).readAndReindexResourceByPid(anyLong());
+		verifyNoMoreInteractions(myResourceReindexer);
+	}
+}