CYPHER_UPDATE_BRANCH_HEAD = '\nMATCH (
t:Thread {thread_id: $thread_id, checkpoint_ns: $checkpoint_ns})\n -[:ACTIVE_BRANCH]->(b:Branch)\nOPTIONAL MATCH (b)-[old:HEAD]->()\nDELETE old\nWITH b\nMATCH (c:Checkpoint {checkpoint_id: $checkpoint_id})\nCREATE (b)-[:HEAD]->(c)\nMERGE (c)-[:ON_BRANCH]->(b
)\nRETURN b.branch_id as branch_id\n'