Improve performance in the "getUrls"-endpoint, and more:

- Optimize the "findAssignmentsQuery" by using an inner limit (larger than the outer).
- Save a ton of time from inserting the assignments into the database, by using a temporal table to hold the new assignments, in order for them to be easily accessible both from the Controller (which processes them and send them to the Worker) and the database itself, in order to "import" them into the "assignment"-table.
- Replace the "Date" with "Timestamp", in order to hold more detailed information.
- Code cleanup.

src/main/java/eu/openaire/urls_controller/controllers/ImpalaController.java

@@ -11,7 +11,6 @@ import org.springframework.web.bind.annotation.RestController;
 
 import java.sql.Connection;
 import java.sql.ResultSet;
-import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -49,15 +48,10 @@ public class ImpalaController {
 
         } catch (Exception e) {
             String errorMsg = "Problem when executing \"getAssignmentsQuery\": " + query;
-            logger.error(errorMsg);
+            logger.error(errorMsg, e);
-            e.printStackTrace();
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
         } finally {
-            try {
+            ImpalaConnector.closeConnection(con);
-                con.close();
-            } catch (SQLException sqle) {
-                logger.error("Could not close the connection with the Impala-database.\n" + sqle);
-            }
         }
     }
 

src/main/java/eu/openaire/urls_controller/controllers/UrlController.java

@@ -16,7 +16,6 @@ import org.springframework.web.bind.annotation.*;
 import javax.servlet.http.HttpServletRequest;
 import java.sql.*;
 
-import java.sql.Date;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -47,8 +46,7 @@ public class UrlController {
             assignmentsLimit = ControllerConstants.ASSIGNMENTS_LIMIT;
         }
 
-
+        String findAssignmentsQuery = "select pubid, url, datasourceid, datasourcetype\n" +
-        String getAssignmentsQuery = "select pubid, url, datasourceid, datasourcetype\n" +
                 "from (select distinct pubid, url, datasourceid, datasourcetype, attempt_count from (\n" +
                 "select  p.id as pubid, pu.url as url, d.id as datasourceid, d.type as datasourcetype, attempts.counts as attempt_count\n" +
                 "from " + ImpalaConnector.databaseName + ".publication p\n" +
@@ -59,25 +57,16 @@ public class UrlController {
                 "  select a.id, a.original_url from " + ImpalaConnector.databaseName + ".assignment a\n" +
                 "  union all\n" +
                 "  select pl.id, pl.original_url from " + ImpalaConnector.databaseName + ".payload pl) as existing on existing.id=p.id and existing.original_url=pu.url\n" +
-                "where d.allow_harvest=true and existing.id is null and coalesce(attempts.counts, 0) <= ? and not exists (select 1 from " + ImpalaConnector.databaseName + ".attempt a where a.id=p.id and a.error_class = 'noRetry')\n" +
+                "where d.allow_harvest=true and existing.id is null and coalesce(attempts.counts, 0) <= " + ControllerConstants.MAX_ATTEMPTS_PER_RECORD + " and not exists (select 1 from " + ImpalaConnector.databaseName + ".attempt a where a.id=p.id and a.error_class = 'noRetry')\n" +
-                ") as non_distinct_results\n" +
+                "limit " + (assignmentsLimit * 10) + ") as non_distinct_results\n" +
                 "order by coalesce(attempt_count, 0), reverse(pubid), url\n" +
-                "limit ?) as getAssignmentsQuery";
+                "limit " + assignmentsLimit + ") as findAssignmentsQuery";
 
         // The "order by" in the end makes sure the older attempted records will be re-attempted after a long time.
 
-        // TODO - If we add more limits it could be faster.. Inner queries could have a limit of e.g. < assignmentsLimit ^ 2 >
+        String createAssignmentsQuery = "create table " + ImpalaConnector.databaseName + ".current_assignment as \n" + findAssignmentsQuery;
-        // The LIMIT of < assignmentsLimit > should be kept in the end, as we want 10_000 of distinct results.
+        String computeCurrentAssignmentsStatsQuery = "COMPUTE STATS " + ImpalaConnector.databaseName + ".current_assignment";
-
+        String getAssignmentsQuery = "select * from " + ImpalaConnector.databaseName + ".current_assignment";
-        // This is just for tests without the attempts, payloads and the assignments
-        /*String getAssignmentsQuery = "select * from (select distinct pubid, url, datasourceid, datasourcetype from (\n" +
-                "select  p.id as pubid, pu.url as url, d.id as datasourceid, d.type as datasourcetype\n" +
-                "from " + ImpalaConnector.databaseName + ".publication p\n" +
-                "join " + ImpalaConnector.databaseName + ".publication_urls pu on pu.id=p.id\n" +
-                "join " + ImpalaConnector.databaseName + ".datasource d on d.id=p.datasourceid\n" +
-                "where d.allow_harvest=true " +
-                "order by reverse(p.id), pu.url) as distinct_results\n" +
-                "limit ? ) as getAssignmentsQuery";*/
 
         List<Assignment> assignments = new ArrayList<>(assignmentsLimit);
 
@@ -89,30 +78,51 @@ public class UrlController {
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Problem when connecting with the Impala-database!");
         }
 
+        PreparedStatement createCurrentAssignmentsPreparedStatement = null;
+        try {
+            createCurrentAssignmentsPreparedStatement = con.prepareStatement(createAssignmentsQuery);
+            createCurrentAssignmentsPreparedStatement.execute();
+        } catch (SQLException sqle) {
+            ImpalaConnector.databaseLock.unlock();
+            String errorMsg = ImpalaConnector.handlePreparedStatementException("createAssignmentsQuery", createAssignmentsQuery, "createCurrentAssignmentsPreparedStatement", createCurrentAssignmentsPreparedStatement, con, sqle);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
+        } finally {
+            try {
+                if ( createCurrentAssignmentsPreparedStatement != null )
+                    createCurrentAssignmentsPreparedStatement.close();
+            } catch (SQLException sqle2) {
+                logger.error("Failed to close the \"createCurrentAssignmentsPreparedStatement\"!\n" + sqle2.getMessage());
+            }
+        }
+
+        PreparedStatement computeCurrentAssignmentsStatsPreparedStatement = null;
+        try {
+            computeCurrentAssignmentsStatsPreparedStatement = con.prepareStatement(computeCurrentAssignmentsStatsQuery);
+            computeCurrentAssignmentsStatsPreparedStatement.execute();
+        } catch (SQLException sqle) {
+            ImpalaConnector.databaseLock.unlock();
+            String errorMsg = ImpalaConnector.handlePreparedStatementException("computeCurrentAssignmentsStatsQuery", computeCurrentAssignmentsStatsQuery, "computeCurrentAssignmentsStatsPreparedStatement", computeCurrentAssignmentsStatsPreparedStatement, con, sqle);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
+        } finally {
+            try {
+                if ( computeCurrentAssignmentsStatsPreparedStatement != null )
+                    computeCurrentAssignmentsStatsPreparedStatement.close();
+            } catch (SQLException sqle2) {
+                logger.error("Failed to close the \"computeCurrentAssignmentsStatsPreparedStatement\"!\n" + sqle2.getMessage());
+            }
+        }
+
         PreparedStatement getAssignmentsPreparedStatement = null;
         try {
             getAssignmentsPreparedStatement = con.prepareStatement(getAssignmentsQuery);
-            getAssignmentsPreparedStatement.setInt(1, ControllerConstants.MAX_ATTEMPTS_PER_RECORD);
-            getAssignmentsPreparedStatement.setInt(2, assignmentsLimit);
         } catch (SQLException sqle) {
             ImpalaConnector.databaseLock.unlock();
-            String errorMsg = "Problem when creating the prepared statement for \"getAssignmentsQuery\"!\n";
+            String errorMsg = ImpalaConnector.handlePreparedStatementException("getAssignmentsQuery", getAssignmentsQuery, "getAssignmentsPreparedStatement", getAssignmentsPreparedStatement, con, sqle);
-            logger.error(errorMsg + sqle.getMessage());
+            // The "getAssignmentsPreparedStatement" will always be null here, so we do not close it.
-            try {
-                if ( getAssignmentsPreparedStatement != null )
-                    getAssignmentsPreparedStatement.close();
-            } catch (SQLException sqle2) {
-                logger.error("Could not close the \"getAssignmentsPreparedStatement\".\n" + sqle2.getMessage());
-            }
-            try {
-                con.close();
-            } catch (SQLException sqle2) {
-                logger.error("Could not close the connection with the Impala-database.\n" + sqle2.getMessage());
-            }
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
         }
 
-        Date date = new Date(System.currentTimeMillis()); // Store it here, in order to have the same for all current records.
+        Timestamp timestamp = new Timestamp(System.currentTimeMillis()); // Store it here, in order to have the same for all current records.
 
         try ( ResultSet resultSet = getAssignmentsPreparedStatement.executeQuery() ) {
             // Unfortunately, we cannot use the following as the used version of the Impala-driver does not support it.
@@ -128,7 +138,7 @@ public class UrlController {
                 // The following few lines, cannot be outside the "while" loop, since the same record is returned, despite that we update the inner-values.
                 Assignment assignment = new Assignment();
                 assignment.setWorkerId(workerId);
-                assignment.setDate(date);
+                assignment.setTimestamp(timestamp);
                 Datasource datasource = new Datasource();
                 try {   // For each of the 4 columns returned. The indexing starts from  1
                     assignment.setId(resultSet.getString(1));
@@ -159,7 +169,7 @@ public class UrlController {
         int assignmentsSize = assignments.size();
         if ( assignmentsSize == 0 ) {
             ImpalaConnector.databaseLock.unlock();
-            String errorMsg = "No results retrieved from the \"getAssignmentsQuery\" for worker with id: " + workerId;
+            String errorMsg = "No results retrieved from the \"findAssignmentsQuery\" for worker with id: " + workerId;
             logger.error(errorMsg);
             ImpalaConnector.closeConnection(con);
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
@@ -167,68 +177,45 @@ public class UrlController {
 
         logger.debug("Finished gathering " + assignmentsSize + " assignments for worker with id \"" + workerId + "\". Going to insert them into the \"assignment\" table and then return them to the worker.");
 
-        // The following is a test of inserting multiple rows with a singme insert-query. If applied with a preparedStatement, then the JDBC fails with "OutOfMemory"-Error.
-        /*String testInsert = "INSERT INTO assignment (id,original_url,workerid,`date`) VALUES  ( 'doiboost____::4e8b1f12ac3ba5a9d8fbff9872000000', 'http://dx.doi.org/10.17267/2596-3368dentistry.v6i2.586', 'worker_1', CAST('2021-10-01' AS TIMESTAMP) ) , ( 'doiboost____::4e8b1f12ac3ba5a9d8fbff9872000000', 'https://academic.microsoft.com/#/detail/2887540302', 'worker_1', CAST('2021-10-01' AS TIMESTAMP) );";
-        try (Statement insertStatement = con.createStatement()) {
-            insertStatement.execute(testInsert);
-        } catch (SQLException sqle) {
-            ImpalaConnector.databaseLock.unlock();
-            String mergeErrorMsg = "Problem when executing the testInsert statement for \"" + testInsert + "\"";
-            logger.error(mergeErrorMsg + sqle.getMessage());
-            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(mergeErrorMsg);
-        }*/
 
-        // Write the Assignment details to the database and then send it to the worker.
+        // Write the Assignment details to the assignment-table.
-        String insertIntoAssignmentBaseQuery = "INSERT INTO " + ImpalaConnector.databaseName + ".assignment (id, original_url, workerid, date) VALUES (?, ?, ?, ?)";
 
-        PreparedStatement preparedInsertAssignmentStatement;
+        String insertAssignmentsQuery = "insert into " + ImpalaConnector.databaseName + ".assignment \n select pub_data.pubid, pub_data.url, '" + workerId + "', cast('" + timestamp + "' as timestamp)\n"
-        try {   // We use a "PreparedStatement" to do insertions, for security and performance reasons.
+                                        + "from (\n select pubid, url from " + ImpalaConnector.databaseName + ".current_assignment) as pub_data";
-            preparedInsertAssignmentStatement = con.prepareStatement(insertIntoAssignmentBaseQuery);
+
-        } catch (SQLException sqle) {
+        PreparedStatement insertAssignmentsPreparedStatement = null;
-            ImpalaConnector.databaseLock.unlock();
-            String errorMsg = "Problem when creating the prepared statement for \"insertIntoAssignmentBaseQuery\"!\n";
-            logger.error(errorMsg + sqle.getMessage());
         try {
-                con.close();
+            insertAssignmentsPreparedStatement = con.prepareStatement(insertAssignmentsQuery);
+            insertAssignmentsPreparedStatement.execute();
+        } catch (SQLException sqle) {
+            ImpalaConnector.databaseLock.unlock();
+            String errorMsg = ImpalaConnector.handlePreparedStatementException("insertAssignmentsQuery", insertAssignmentsQuery, "insertAssignmentsPreparedStatement", insertAssignmentsPreparedStatement, con, sqle);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
+        } finally {
+            try {
+                if ( insertAssignmentsPreparedStatement != null )
+                    insertAssignmentsPreparedStatement.close();
             } catch (SQLException sqle2) {
-                logger.error("Could not close the connection with the Impala-database.\n" + sqle2.getMessage());
+                logger.error("Failed to close the \"insertAssignmentsPreparedStatement\"!\n" + sqle2.getMessage());
             }
-            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
         }
 
-        // Before, we wanted to execute the getAssignmentQuery and take the assignments immediately, but now it's more efficient to commit all the inserts in the end.
+        String dropCurrentAssignmentsQuery = "DROP TABLE " + ImpalaConnector.databaseName + ".current_assignment PURGE";
+        PreparedStatement dropCurrentAssignmentsPreparedStatement = null;
         try {
-            con.setAutoCommit(false);
+            dropCurrentAssignmentsPreparedStatement = con.prepareStatement(dropCurrentAssignmentsQuery);
-        } catch (SQLException sqle) {   // There is a database-error. The latter actions will probably fail as well.
+            dropCurrentAssignmentsPreparedStatement.execute();
-            ImpalaConnector.databaseLock.unlock();
-            String errorMsg = "Problem when setting Connection.AutoCommit to \"false\"!";
-            logger.error(errorMsg + "\n" + sqle.getMessage());
-            closePreparedStatements(preparedInsertAssignmentStatement, null, con);
-            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
-        }
-
-        String tempFullQueryString = null;
-        for ( Assignment assignment : assignments ) {
-            try {
-                preparedInsertAssignmentStatement.setString(1, assignment.getId());
-                preparedInsertAssignmentStatement.setString(2, assignment.getOriginalUrl());
-                preparedInsertAssignmentStatement.setString(3, workerId);
-                preparedInsertAssignmentStatement.setDate(4, date);
-                tempFullQueryString = getAssignmentsPreparedStatement.toString();
-                preparedInsertAssignmentStatement.executeUpdate();
-            } catch (SQLException sqle) {
-                logger.error("Problem when executing the \"insertIntoAssignmentQuery\":\n" + tempFullQueryString + "\n" + sqle.getMessage() + "\n\n");
-            }
-        }//end for-loop
-
-        try {
-            con.commit();   // Send all the insert-queries to the database.
         } catch (SQLException sqle) {
             ImpalaConnector.databaseLock.unlock();
-            String errorMsg = "Problem when committing changes to the database!";
+            String errorMsg = ImpalaConnector.handlePreparedStatementException("dropCurrentAssignmentsQuery", dropCurrentAssignmentsQuery, "dropCurrentAssignmentsPreparedStatement", dropCurrentAssignmentsPreparedStatement, con, sqle);
-            logger.error(errorMsg + "\n" + sqle.getMessage());
-            closePreparedStatements(preparedInsertAssignmentStatement, null, con);
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
+        } finally {
+            try {
+                if ( dropCurrentAssignmentsPreparedStatement != null )
+                    dropCurrentAssignmentsPreparedStatement.close();
+            } catch (SQLException sqle2) {
+                logger.error("Failed to close the \"dropCurrentAssignmentsPreparedStatement\"!\n" + sqle2.getMessage());
+            }
         }
 
         logger.debug("Finished inserting " + assignmentsSize + " assignments into the \"assignment\"-table. Going to merge the parquet files for this table.");
@@ -236,21 +223,12 @@ public class UrlController {
         String mergeErrorMsg = FileUtils.mergeParquetFiles("assignment", con);
         if ( mergeErrorMsg != null ) {
             ImpalaConnector.databaseLock.unlock();
-            closePreparedStatements(preparedInsertAssignmentStatement, null, con);
+            ImpalaConnector.closeConnection(con);
             return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(mergeErrorMsg);
         }
 
-        try {
+        ImpalaConnector.closeConnection(con);
-            con.commit();   // Apply the merge.
-            con.setAutoCommit(true);    // Restore the "auto-commit" value for this connection of the pool.
-        } catch (SQLException sqle) {
-            String errorMsg = "Problem when committing changes to the database!";
-            logger.error(errorMsg , sqle);//+ "\n" + sqle.getMessage());
-            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(errorMsg);
-        } finally {
         ImpalaConnector.databaseLock.unlock();
-            closePreparedStatements(preparedInsertAssignmentStatement, null, con);
-        }
 
         logger.info("Sending batch-assignments_" + assignmentsBatchCounter.incrementAndGet() + " with " + assignmentsSize + " assignments to worker with ID: " + workerId + ".");
         return ResponseEntity.status(HttpStatus.OK).body(new AssignmentsResponse(assignmentsBatchCounter.get(), assignments));
@@ -331,7 +309,7 @@ public class UrlController {
                 preparedInsertPayloadStatement.setString(1, payload.getId());
                 preparedInsertPayloadStatement.setString(2, payload.getOriginal_url());
                 preparedInsertPayloadStatement.setString(3, payload.getActual_url());
-                preparedInsertPayloadStatement.setDate(4, payload.getDate_acquired());
+                preparedInsertPayloadStatement.setTimestamp(4, payload.getTimestamp_acquired());
                 preparedInsertPayloadStatement.setString(5, payload.getMime_type());
 
                 // The column "size" in the table is of type "String" so we cast the Long to String. The Parquet-format in the database does not work well with integers.
@@ -359,7 +337,7 @@ public class UrlController {
             try {   // We use a "PreparedStatement" to do insertions, for security reasons.
                 preparedInsertAttemptStatement.setString(1, payload.getId());
                 preparedInsertAttemptStatement.setString(2, payload.getOriginal_url());
-                preparedInsertAttemptStatement.setDate(3, payload.getDate_acquired());
+                preparedInsertAttemptStatement.setTimestamp(3, payload.getTimestamp_acquired());
                 preparedInsertAttemptStatement.setString(4, urlReport.getStatus().toString());
                 preparedInsertAttemptStatement.setString(5, String.valueOf(error.getType()));    // This covers the case of "null".
                 preparedInsertAttemptStatement.setString(6, error.getMessage());
@@ -476,7 +454,7 @@ public class UrlController {
         HashMultimap<String, String> loadedIdUrlPairs;
         boolean isFirstRun = true;
         boolean assignmentsLimitReached = false;
-        Date date = new Date(System.currentTimeMillis()); // Store it here, in order to have the same for all current records.
+        Timestamp timestamp = new Timestamp(System.currentTimeMillis()); // Store it here, in order to have the same for all current records.
 
         // Start loading urls.
         while ( true ) {
@@ -497,7 +475,7 @@ public class UrlController {
                 }
 
                 int randomNum = GenericUtils.getRandomNumber(1, 5);
-                assignments.add(new Assignment(pair.getKey(), pair.getValue(), new Datasource("ID_" + randomNum, "NAME_" + randomNum), workerId, date));
+                assignments.add(new Assignment(pair.getKey(), pair.getValue(), new Datasource("ID_" + randomNum, "NAME_" + randomNum), workerId, timestamp));
             }// end pairs-for-loop
 
             if ( assignmentsLimitReached ) {

src/main/java/eu/openaire/urls_controller/models/Assignment.java

@@ -4,7 +4,7 @@ import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
-import java.util.Date;
+import java.sql.Timestamp;
 
 
 @JsonInclude(JsonInclude.Include.NON_NULL)
@@ -13,7 +13,7 @@ import java.util.Date;
         "original_url",
         "datasource",
         "workerId",
-        "date"
+        "timestamp"
 })
 public class Assignment {
 
@@ -29,19 +29,18 @@ public class Assignment {
     @JsonProperty("workerid")
     private String workerId;
 
-    @JsonProperty("date")
+    @JsonProperty("timestamp")
-    private Date date;
+    private Timestamp timestamp;
 
 
     public Assignment() {}
 
-
+    public Assignment(String id, String originalUrl, Datasource datasource, String workerId, Timestamp timestamp) {
-    public Assignment(String id, String originalUrl, Datasource datasource, String workerId, Date date) {
         this.id = id;
         this.originalUrl = originalUrl;
         this.datasource = datasource;
         this.workerId = workerId;
-        this.date = date;
+        this.timestamp = timestamp;
     }
 
 
@@ -77,12 +76,12 @@ public class Assignment {
         this.workerId = workerId;
     }
 
-    public Date getDate() {
+    public Timestamp getTimestamp() {
-        return date;
+        return timestamp;
     }
 
-    public void setDate(Date date) {
+    public void setTimestamp(Timestamp timestamp) {
-        this.date = date;
+        this.timestamp = timestamp;
     }
 
     @Override
@@ -92,7 +91,7 @@ public class Assignment {
                 ", originalUrl='" + originalUrl + '\'' +
                 ", datasource=" + datasource +
                 ", workerId='" + workerId + '\'' +
-                ", date=" + date +
+                ", timestamp=" + timestamp +
                 '}';
     }
 }

src/main/java/eu/openaire/urls_controller/models/Payload.java

@@ -4,7 +4,7 @@ import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
-import java.sql.Date;
+import java.sql.Timestamp;
 
 
 @JsonInclude(JsonInclude.Include.NON_NULL)
@@ -12,7 +12,7 @@ import java.sql.Date;
         "id",
         "original_url",
         "actual_url",
-        "date",
+        "timestamp_acquired",
         "mime_type",
         "size",
         "hash",
@@ -30,8 +30,8 @@ public class Payload {
     @JsonProperty("actual_url")
     private String actual_url;
 
-    @JsonProperty("date")
+    @JsonProperty("timestamp_acquired")
-    private Date date_acquired;
+    private Timestamp timestamp_acquired;
 
     @JsonProperty("mime_type")
     private String mime_type;
@@ -50,11 +50,11 @@ public class Payload {
 
     public Payload() {}
 
-    public Payload(String id, String original_url, String actual_url, Date date_acquired, String mime_type, Long size, String hash, String location, String provenance) {
+    public Payload(String id, String original_url, String actual_url, Timestamp timestamp_acquired, String mime_type, Long size, String hash, String location, String provenance) {
         this.id = id;
         this.original_url = original_url;
         this.actual_url = actual_url;
-        this.date_acquired = date_acquired;
+        this.timestamp_acquired = timestamp_acquired;
         this.mime_type = mime_type;
         this.size = size;
         this.hash = hash;
@@ -86,12 +86,12 @@ public class Payload {
         this.actual_url = actual_url;
     }
 
-    public Date getDate_acquired() {
+    public Timestamp getTimestamp_acquired() {
-        return date_acquired;
+        return timestamp_acquired;
     }
 
-    public void setDate_acquired(Date date_acquired) {
+    public void setTimestamp_acquired(Timestamp timestamp_acquired) {
-        this.date_acquired = date_acquired;
+        this.timestamp_acquired = timestamp_acquired;
     }
 
     public String getMime_type() {
@@ -140,7 +140,7 @@ public class Payload {
                 "id='" + id + '\'' +
                 ", original_url='" + original_url + '\'' +
                 ", actual_url='" + actual_url + '\'' +
-                ", date_acquired='" + date_acquired + '\'' +
+                ", timestamp_acquired='" + timestamp_acquired + '\'' +
                 ", mime_type='" + mime_type + '\'' +
                 ", size='" + size + '\'' +
                 ", md5='" + hash + '\'' +