Change to a minimal first pre-fetch to avoid latency on the async path. (#4174)

* Change to a minimal first pre-fetch to avoid latency on the async path.

The "async" path is now synchronous, and was causing latency for first page by loading 500 results.
We avoid pre-fetch on the first page, and only pre-fetch after users fetch the second page.

* Fix a nasty bug continuing a pre-fetched search.

* Update hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_2_0/3664-shorten-first-prefetch.yaml

* Patch up tests that assumed 500 pre-fetch first step

hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_2_0/3664-shorten-first-prefetch.yaml

@@ -0,0 +1,4 @@
+---
+type: fix
+issue: 3664
+title: "Initial page loading has been optimized to reduce the number of prefetched resources. This should improve the speed of initial search queries in many cases."

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/SearchCoordinatorSvcImpl.java

@@ -92,7 +92,6 @@ import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
 import static ca.uhn.fhir.jpa.util.QueryParameterUtils.DEFAULT_SYNC_SIZE;
-import static ca.uhn.fhir.jpa.util.SearchParameterMapCalculator.isWantCount;
 import static org.apache.commons.lang3.StringUtils.isBlank;
 import static org.apache.commons.lang3.StringUtils.isNotBlank;
 

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/builder/SearchBuilder.java

@@ -338,7 +338,8 @@ public class SearchBuilder implements ISearchBuilder {
 
 	private void init(SearchParameterMap theParams, String theSearchUuid, RequestPartitionId theRequestPartitionId) {
 		myCriteriaBuilder = myEntityManager.getCriteriaBuilder();
-		myParams = theParams;
+		// we mutate the params.  Make a private copy.
+		myParams = theParams.clone();
 		mySearchUuid = theSearchUuid;
 		myRequestPartitionId = theRequestPartitionId;
 	}

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/builder/tasks/SearchTask.java

@@ -581,7 +581,7 @@ public class SearchTask implements Callable<Void> {
 		int currentlyLoaded = defaultIfNull(mySearch.getNumFound(), 0);
 		int minWanted = 0;
 		if (myParams.getCount() != null) {
-			minWanted = myParams.getCount();
+			minWanted = myParams.getCount() + 1; // Always fetch one past this page, so we know if there is a next page.
 			minWanted = Math.min(minWanted, myPagingProvider.getMaximumPageSize());
 			minWanted += currentlyLoaded;
 		}

hapi-fhir-jpaserver-elastic-test-utilities/src/test/java/ca/uhn/fhir/jpa/provider/r4/ResourceProviderR4ElasticTest.java

@@ -166,7 +166,7 @@ public class ResourceProviderR4ElasticTest extends BaseResourceProviderR4Test {
 			Coding blood_count = new Coding("http://loinc.org", "789-8", "Erythrocytes in Blood by Automated count for code: " + (index + 1));
 			createObservationWithCode(blood_count);
 		});
-		HttpGet countQuery = new HttpGet(BaseResourceProviderR4Test.ourServerBase + "/Observation?code=789-8&_count=5");
+		HttpGet countQuery = new HttpGet(BaseResourceProviderR4Test.ourServerBase + "/Observation?code=789-8&_count=5&_total=accurate");
 		myCaptureQueriesListener.clear();
 		try (CloseableHttpResponse response = BaseResourceProviderR4Test.ourHttpClient.execute(countQuery)) {
 			myCaptureQueriesListener.logSelectQueriesForCurrentThread();

hapi-fhir-jpaserver-test-dstu2/src/test/java/ca/uhn/fhir/jpa/provider/ResourceProviderDstu2Test.java

@@ -58,6 +58,7 @@ import ca.uhn.fhir.model.primitive.UriDt;
 import ca.uhn.fhir.parser.IParser;
 import ca.uhn.fhir.rest.api.Constants;
 import ca.uhn.fhir.rest.api.MethodOutcome;
+import ca.uhn.fhir.rest.api.SearchTotalModeEnum;
 import ca.uhn.fhir.rest.api.SummaryEnum;
 import ca.uhn.fhir.rest.client.api.IGenericClient;
 import ca.uhn.fhir.rest.gclient.NumberClientParam;
@@ -325,6 +326,7 @@ public class ResourceProviderDstu2Test extends BaseResourceProviderDstu2Test {
 			.forResource(Organization.class)
 			.where(Organization.NAME.matches().value("rpdstu2_testCountParam_01"))
 			.count(10)
+			.totalMode(SearchTotalModeEnum.ACCURATE)
 			.returnBundle(Bundle.class)
 			.execute();
 		assertEquals(100, found.getTotalElement().getValue().intValue());
@@ -334,10 +336,9 @@ public class ResourceProviderDstu2Test extends BaseResourceProviderDstu2Test {
 			.search()
 			.forResource(Organization.class)
 			.where(Organization.NAME.matches().value("rpdstu2_testCountParam_01"))
-			.count(999)
+			.count(50)
 			.returnBundle(Bundle.class)
 			.execute();
-		assertEquals(100, found.getTotalElement().getValue().intValue());
 		assertEquals(50, found.getEntry().size());
 
 	}

hapi-fhir-jpaserver-test-dstu3/src/test/java/ca/uhn/fhir/jpa/provider/dstu3/ResourceProviderDstu3Test.java

@@ -15,6 +15,7 @@ import ca.uhn.fhir.parser.StrictErrorHandler;
 import ca.uhn.fhir.rest.api.CacheControlDirective;
 import ca.uhn.fhir.rest.api.Constants;
 import ca.uhn.fhir.rest.api.MethodOutcome;
+import ca.uhn.fhir.rest.api.SearchTotalModeEnum;
 import ca.uhn.fhir.rest.api.SummaryEnum;
 import ca.uhn.fhir.rest.api.server.IBundleProvider;
 import ca.uhn.fhir.rest.client.api.IClientInterceptor;
@@ -649,12 +650,14 @@ public class ResourceProviderDstu3Test extends BaseResourceProviderDstu3Test {
 		}
 		ourClient.transaction().withResources(resources).prettyPrint().encodedXml().execute();
 
-		Bundle found = ourClient.search().forResource(Organization.class).where(Organization.NAME.matches().value("rpdstu2_testCountParam_01")).count(10).returnBundle(Bundle.class).execute();
+		Bundle found = ourClient.search().forResource(Organization.class)
+			.where(Organization.NAME.matches().value("rpdstu2_testCountParam_01"))
+			.totalMode(SearchTotalModeEnum.ACCURATE)
+			.count(10).returnBundle(Bundle.class).execute();
 		assertEquals(100, found.getTotal());
 		assertEquals(10, found.getEntry().size());
 
-		found = ourClient.search().forResource(Organization.class).where(Organization.NAME.matches().value("rpdstu2_testCountParam_01")).count(999).returnBundle(Bundle.class).execute();
+		found = ourClient.search().forResource(Organization.class).where(Organization.NAME.matches().value("rpdstu2_testCountParam_01")).count(50).returnBundle(Bundle.class).execute();
-		assertEquals(100, found.getTotal());
 		assertEquals(50, found.getEntry().size());
 
 	}

hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/dao/r4/FhirResourceDaoR4SearchOptimizedTest.java

@@ -1162,7 +1162,7 @@ public class FhirResourceDaoR4SearchOptimizedTest extends BaseJpaR4Test {
 		myCaptureQueriesListener.clear();
 
 		ourLog.info("** About to perform search");
-		IBundleProvider search = myPatientDao.search(new SearchParameterMap().setLoadSynchronous(false));
+		IBundleProvider search = myPatientDao.search(new SearchParameterMap().setCount(50).setLoadSynchronous(false));
 		ourLog.info("** About to retrieve resources");
 		search.getResources(0, 20);
 		ourLog.info("** Done retrieving resources");
@@ -1171,13 +1171,13 @@ public class FhirResourceDaoR4SearchOptimizedTest extends BaseJpaR4Test {
 
 		myCaptureQueriesListener.logSelectQueriesForCurrentThread();
 		assertEquals(4, myCaptureQueriesListener.countSelectQueries());
-		// Batches of 30 are written for each query - so 9 inserts total
+		// first prefetch is 50+1
-		assertEquals(221, myCaptureQueriesListener.logInsertQueries());
+		assertEquals(51, myCaptureQueriesListener.logInsertQueries());
 		assertEquals(1, myCaptureQueriesListener.countUpdateQueries());
 		assertEquals(0, myCaptureQueriesListener.countDeleteQueries());
 
 		assertEquals(4, myCaptureQueriesListener.countSelectQueriesForCurrentThread());
-		assertEquals(9, myCaptureQueriesListener.countInsertQueriesForCurrentThread());
+		assertEquals(3, myCaptureQueriesListener.countInsertQueriesForCurrentThread());
 		assertEquals(1, myCaptureQueriesListener.countUpdateQueriesForCurrentThread());
 		assertEquals(0, myCaptureQueriesListener.countDeleteQueriesForCurrentThread());
 

hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/provider/r4/SystemProviderR4Test.java

@@ -24,6 +24,7 @@ import ca.uhn.fhir.rest.api.CacheControlDirective;
 import ca.uhn.fhir.rest.api.Constants;
 import ca.uhn.fhir.rest.api.EncodingEnum;
 import ca.uhn.fhir.rest.api.MethodOutcome;
+import ca.uhn.fhir.rest.api.SearchTotalModeEnum;
 import ca.uhn.fhir.rest.api.server.IBundleProvider;
 import ca.uhn.fhir.rest.api.server.RequestDetails;
 import ca.uhn.fhir.rest.client.apache.ResourceEntity;
@@ -1001,7 +1002,10 @@ public class SystemProviderR4Test extends BaseJpaR4Test {
 	}
 
 	private Bundle getAllResourcesOfType(String theResourceName) {
-		return myClient.search().forResource(theResourceName).cacheControl(new CacheControlDirective().setNoCache(true)).returnBundle(Bundle.class).execute();
+		return myClient.search().forResource(theResourceName)
+			.totalMode(SearchTotalModeEnum.ACCURATE)
+			.cacheControl(new CacheControlDirective().setNoCache(true))
+			.returnBundle(Bundle.class).execute();
 	}
 
 	@AfterAll

hapi-fhir-jpaserver-test-utilities/src/main/java/ca/uhn/fhir/jpa/test/BaseJpaTest.java

@@ -535,32 +535,11 @@ public abstract class BaseJpaTest extends BaseTest {
 	protected List<IIdType> toUnqualifiedVersionlessIds(IBundleProvider theProvider) {
 
 		List<IIdType> retVal = new ArrayList<>();
-		Integer size = theProvider.size();
-		StopWatch sw = new StopWatch();
-		while (size == null) {
-			int timeout = 20000;
-			if (sw.getMillis() > timeout) {
-				String message = "Waited over " + timeout + "ms for search " + theProvider.getUuid();
-				ourLog.info(message);
-				fail(message);
-			}
-			try {
-				Thread.sleep(100);
-			} catch (InterruptedException theE) {
-				//ignore
-			}
 
-			if (theProvider instanceof PersistedJpaBundleProvider) {
+		Integer size = theProvider.size();
-				PersistedJpaBundleProvider provider = (PersistedJpaBundleProvider) theProvider;
-				provider.clearCachedDataForUnitTest();
-			}
-			size = theProvider.size();
-		}
 
 		ourLog.info("Found {} results", size);
-		List<IBaseResource> resources = theProvider instanceof PersistedJpaBundleProvider ?
+		List<IBaseResource> resources = theProvider.getResources(0, Integer.MAX_VALUE/4);
-			theProvider.getResources(0, size) :
-			theProvider.getResources(0, Integer.MAX_VALUE);
 		for (IBaseResource next : resources) {
 			retVal.add(next.getIdElement().toUnqualifiedVersionless());
 		}

hapi-fhir-storage/src/main/java/ca/uhn/fhir/jpa/api/config/DaoConfig.java

@@ -183,7 +183,11 @@ public class DaoConfig {
 	private int myExpungeThreadCount;
 	private Set<String> myBundleTypesAllowedForStorage;
 	private boolean myValidateSearchParameterExpressionsOnSave = true;
-	private List<Integer> mySearchPreFetchThresholds = Arrays.asList(500, 2000, -1);
+
+	// start with a tiny number so our first page always loads quickly.
+	// If they fetch the second page, fetch more.
+	// Use prime sizes to avoid empty next links.
+	private List<Integer> mySearchPreFetchThresholds = Arrays.asList(13, 503, 2003, -1);
 	private List<WarmCacheEntry> myWarmCacheEntries = new ArrayList<>();
 	private boolean myDisableHashBasedSearches;
 	private boolean myEnableInMemorySubscriptionMatching = true;