diff --git a/modules/ROOT/pages/subqueries/subqueries-in-transactions.adoc b/modules/ROOT/pages/subqueries/subqueries-in-transactions.adoc index 9af386cbb..93c2f6153 100644 --- a/modules/ROOT/pages/subqueries/subqueries-in-transactions.adoc +++ b/modules/ROOT/pages/subqueries/subqueries-in-transactions.adoc @@ -956,7 +956,7 @@ CALL (row) { MERGE (y:Year {year: row.year}) MERGE (m)-[r:RELEASED_IN]->(y) } IN 2 CONCURRENT TRANSACTIONS OF 10 ROWS ON ERROR RETRY FOR 3 SECONDS THEN CONTINUE REPORT STATUS AS status -RETURN status.transactionID as transaction, status.committed AS successfulTransaction +RETURN status.transactionId as transaction, status.committed AS successfulTransaction ---- // end::subqueries_in_transactions_deadlock_example[] @@ -1064,6 +1064,31 @@ The result shows that all transactions are now successful: +-------------------------------------------------+ ---- +Deadlock resolution and transaction retries are time-consuming, making deadlock avoidance a preferred strategy. +This can be achieved by dividing a task into two distinct subqueries: a data-independent subquery run in parallel with maximum concurrency, and a data-dependent subquery executed serially (i.e. one transaction at a time) to avoid deadlocks. +In the below example, nodes and properties are created in a concurrent subquery, while the relationships connecting those nodes are created in a serial subquery. +This method benefits from the performance of concurrent transactions while avoiding deadlocks. + +.Avoiding deadlocks by dividing an import task into a data-independent concurrent subquery followed by a data-dependent serial subquery +// tag::subqueries_in_transactions_deadlock_example_2[] +[source, cypher] +---- +LOAD CSV WITH HEADERS FROM 'https://data.neo4j.com/importing-cypher/movies.csv' AS row +CALL (row) { + MERGE (m:Movie {movieId: row.movieId}) + MERGE (y:Year {year: row.year}) + RETURN m, y +} IN CONCURRENT TRANSACTIONS OF 10 ROWS ON ERROR RETRY THEN CONTINUE REPORT STATUS AS nodeStatus +CALL (m, y) { + MERGE (m)-[r:RELEASED_IN]->(y) +} IN TRANSACTIONS OF 10 ROWS ON ERROR RETRY THEN CONTINUE REPORT STATUS AS relationshipStatus +RETURN nodeStatus.transactionId as nodeTransaction, + nodeStatus.committed AS successfulNodeTransaction, + relationshipStatus.transactionId as relationshipTransaction, + relationshipStatus.committed AS successfulRelationshipTransaction +---- +// end::subqueries_in_transactions_deadlock_example_2[] + ===== [[restrictions]]