make previous tx id accessible to triggers

One piece of information that could be useful for triggers to have access to is the previous transactions's id. This allows for guaranteed in-order processing, even if TxData is received out of order.
graphfoundation · Feb 13, 2020 · 70be072 · 70be072
1 parent 7d91e9e
commit 70be072
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diff --git a/src/main/java/apoc/trigger/Trigger.java b/src/main/java/apoc/trigger/Trigger.java
@@ -10,13 +10,15 @@
 import org.neo4j.graphdb.event.TransactionData;
 import org.neo4j.graphdb.event.TransactionEventHandler;
 import org.neo4j.helpers.collection.Iterators;
+import org.neo4j.kernel.api.KernelTransaction;
 import org.neo4j.kernel.impl.core.GraphProperties;
 import org.neo4j.kernel.impl.core.NodeManager;
 import org.neo4j.kernel.internal.GraphDatabaseAPI;
 //import org.neo4j.procedure.Mode;
 import org.neo4j.logging.Log;
 import org.neo4j.procedure.*;
 
+import java.lang.reflect.Field;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Stream;
@@ -225,6 +227,19 @@ private void executeTriggers(TransactionData txData, String phase) {
                     if (phase.equals( "after" ))
                     {
                         params.putAll( txDataCollector( txData, phase, (Map<String,Object>) data.get( "config" ) ) );
+
+                        try
+                        {
+                            Field f = txData.getClass().getDeclaredField( "transaction" );
+                            f.setAccessible( true );
+                            KernelTransaction kernelTransaction = (KernelTransaction) f.get( txData );
+                            params.put( "lastTxId", kernelTransaction.lastTransactionIdWhenStarted() );
+                            f.setAccessible( false );
+                        }
+                        catch ( NoSuchFieldException | IllegalAccessException e )
+                        {
+                            log.error( "Failed to get last transaction id: " + e.getMessage() );
+                        }
                     }
                     if( ( (Map<String,Object>) data.get( "config" )).get( "params" ) != null)
                     {

diff --git a/src/test/java/apoc/trigger/TriggerDataTest.java b/src/test/java/apoc/trigger/TriggerDataTest.java
@@ -57,6 +57,16 @@ public void testTriggerData_TransactionId() throws Exception {
         });
     }
 
+    @Test
+    public void testTriggerData_lastTxId() {
+        db.execute("CALL apoc.trigger.add('test','WITH {createdNodes} AS createdNodes, {lastTxId} AS lastTxId UNWIND {createdNodes} AS n SET n.testProp = lastTxId',{phase: 'after'}, { uidKeys: ['uid'], params: {}})").close();
+        db.execute("CREATE (f:Foo {name:'Michael'})").close();
+        TestUtil.testCall(db, "MATCH (f:Foo) RETURN f", (row) -> {
+            assertEquals(true, ((Node)row.get("f")).hasProperty("testProp"));
+            assertNotEquals( "``:``:`0`", ((Node)row.get("f")).getProperty( "testProp") );
+        });
+    }
+
     @Test
     public void testTriggerData_CommitTime() throws Exception {
         db.execute("CALL apoc.trigger.add('test','WITH {createdNodes} AS createdNodes, {txData} AS txData UNWIND {createdNodes} AS n SET n.testProp = txData." + COMMIT_TIME + "',{phase: 'after'}, { uidKeys: ['uid'], params: {}})").close();