[New cypher engine] UNWIND + Params : Relations are not created

[ExtReMLapin]

Hello,

While the ingestion of my data in my RAG app "succeeds" with no error, there are clearly missing relations in the database. I end up with "isolated" vertexes/nodes, which should not really happen.

Version : using latest commit build (HEAD on main).

long story short, I have a querythat creates relations by batch :

UNWIND $batch as row
MATCH (a),(b) WHERE ID(a) = row.source_id and ID(b) = row.target_id 
MERGE (a)-[r:in]->(b) RETURN a, b, r

params : {"batch": [{"source_id": "#1:0", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:1", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:2", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:3", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:2048", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:2049", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:2050", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:2051", "target_id": "#4:0", "features": {}, "relation_type": "in"}, {"source_id": "#1:4", "target_id": "#4:0", "features": {}, "relation_type": "in"}]}

Database dump (right BEFORE trying to execute this query) :

MIAOUUU-backup-20260115-065309854.zip

Reading the query, we would expect to create a relation between #1:0 and #4:0

Check before executing the query from above :

(please note that in studio the relation/edge even if not requested is still displayed between returned nodes)

match (a), (b) WHERE ID(a) = "#1:0" AND ID(b) = "#4:0" return a, b

Check after executing the query from above :

Execution of query (the one with params) returned nothing, even with the RETURN a, b, r

---

• Tried to replace MERGE with CREATE, still not working

[lvca]

Ok, the CypherExecutionPlan.buildExecutionSteps() processes clauses in a fixed order (MATCH first, then UNWIND), but in your query UNWIND ... MATCH ..., UNWIND should execute first. Working to a fix.

[lvca]

Fixed!

[ExtReMLapin]

Hooray