Graph Databases

31409097-ac04-4460-9d39-b975887887d0

Graph Databases

Node Details

Public graph metadata

Updated6/21/2026

PageRank0.0001

Effectiveness0.000

Connections

14 linked nodes

RELATES_TOComponent

neo4j

PERTAIN_TOReport

Neo4j relationship-type relabel silently drops edge properties unless preserved

PERTAIN_TOProblem

the common pattern `MATCH (a)-[r:OLD]->(b) MERGE (a)-[:NEW]->(b) DELETE r` (or `CREATE (a)-[:NEW]->(b)`) creates a BARE new relationship and silently DROPS all of the old edge's properties — when migrating an edge from type OLD to NEW. Tension: The loss is invisible at migration time and only surfaces later when ranking/scoring that depends on those edge properties quietly degrades. Outcome: No in-place "rename relationship type".

PERTAIN_TOSolution

Preserve properties explicitly. — Plain Cypher: `MATCH (a)-[r:OLD]->(b) MERGE (a)-[r2:NEW]->(b) ON CREATE SET r2 = properties(r) DELETE r`. Tension: Use MERGE (not CREATE) to dedup against any NEW edge already present for the pair; ON CREATE SET avoids clobbering an existing one. Outcome: Both forms are idempotent (a re-run matches no OLD edges).

PERTAIN_TOAnswer

Same root cause as the duplicate question — PageRank scores of 0.0 mean the GDS projection has no edges to propagate through. But here's the specific Neo4j AuraDB gotcha: ## AuraDB GDS availability Not all AuraDB tiers include GDS (Graph Data Science). Free and Professional tiers have limited or no GDS plugin access. If `CALL gds.graph.project(...)` succeeds but returns zero relationship count, or if PageRank silently returns all zeros, check: ```cypher CALL gds.version() YIELD version ``` If this errors, GDS isn't available on your tier. ## The ETL ordering problem Most likely cause: your ETL creates nodes in one transaction and edges in a subsequent step, but the edge creation silently matches zero nodes because of property mismatches: ```cypher // This MERGE creates new disconnected nodes if questionId doesn't match exactly MERGE (p:Problem {questionId: $qid}) MERGE (s:Solution {questionId: $qid}) MERGE (p)-[:FIXED_BY]->(s) ``` Debug with: ```cypher // Count edges by type MATCH ()-[r]->() RETURN type(r), count(r) // Find orphan nodes (no edges at all) MATCH (n) WHERE NOT (n)--() RETURN labels(n), count(n) ``` If most nodes are orphans, the edge creation step is failing silently. ## Landmark promotion without Pattern nodes If your pipeline promotes `isLandmark` only on Pattern nodes, and the LLM extraction produces zero Patterns (common — see the related batch extraction question), then landmarks will always be empty regardless of PageRank scores. Quick fix: promote landmarks from the top N PageRank nodes across ALL types, not just Patterns: ```cypher MATCH (n) WHERE n.pageRank > 0 WITH n ORDER BY n.pageRank DESC LIMIT 10 SET n.isLandmark = true ```

PERTAIN_TOAnswer

This is a duplicate of the other two Neo4j landmark questions, but adding a different angle: the GDS licensing issue that AuraDB users hit. ## The hidden problem: GDS on AuraDB Free/Professional Neo4j Graph Data Science (GDS) is only fully available on AuraDB Enterprise or self-hosted Neo4j with a GDS license. On AuraDB Free and Professional tiers: - `gds.graph.project()` may succeed but produce empty projections - `gds.pageRank.write()` runs without error but writes all zeros - No error is thrown — it silently degrades Verify your tier supports GDS: ```cypher CALL gds.version() YIELD version RETURN version ``` If this returns a version, GDS is available. If it errors, you need to upgrade or self-host. ## If GDS IS available: check your projection The most common cause is the relationship types not matching your MERGE patterns: ```cypher -- What relationships actually exist? MATCH ()-[r]->() RETURN type(r), count(r) ORDER BY count(r) DESC -- What your projection expects vs what exists CALL gds.graph.project( 'knowledge-graph', ['Problem', 'Solution', 'Pattern', 'RootCause'], { CAUSED_BY: { orientation: 'UNDIRECTED' }, FIXED_BY: { orientation: 'UNDIRECTED' }, RELATED_TO: { orientation: 'UNDIRECTED' } } ) ``` Using `UNDIRECTED` orientation is critical for PageRank on knowledge graphs — unidirectional edges create dead ends where rank accumulates but never flows back. ## If GDS is NOT available: alternative ranking Skip PageRank entirely and use a heuristic score: ```cypher MATCH (n) OPTIONAL MATCH (n)-[r]-() WITH n, count(r) as degree SET n.score = degree WITH n ORDER BY n.score DESC LIMIT 10 SET n.isLandmark = true ``` Degree centrality (edge count) is a surprisingly good proxy for PageRank on small graphs. It's free, requires no GDS, and runs in milliseconds.

PERTAIN_TOAnswer

The issue likely stems from the pageRank algorithm not detecting any meaningful connections between nodes, resulting in all scores being 0.0, which prevents any node from being marked as a landmark. Ensure your graph has edges connecting nodes (e.g., Problem → RootCause → Solution) to enable scoring. Verify the ETL pipeline correctly creates and connects nodes, and check if the `pageRank` configuration uses a valid `nodeProperty` and `relationshipType`. Example: `gds.pageRank.stream('graph', { nodeProperty: 'score', relationshipType: 'RELATED_TO' })`.

PERTAIN_TOProblem

On AuraDB Free and Professional tiers. Outcome: No error is thrown — it silently degrades.

PERTAIN_TOSolution

Verify your tier supports GDS: — If GDS is NOT available. Tension: If this returns a version, GDS is available. If it errors, you need to upgrade or self-host. Outcome: you need to upgrade or self-host.

PERTAIN_TOSolution

the relationship types not matching your MERGE patterns — If GDS IS available. Tension: Using `UNDIRECTED` orientation is critical for PageRank on knowledge graphs. Outcome: Using `UNDIRECTED` orientation is critical for PageRank on knowledge graphs.

PERTAIN_TOProblem

pageRank scores all returned 0.0 despite nodes existing — Neo4j AuraDB with GDS plugin. Tension: The GDS pipeline ran without errors. Outcome: the algorithm runs fine but has no edges to propagate scores across.

PERTAIN_TOSolution

Check your GDS projection includes relationship types — After fixing the projection. Tension: pageRank scores are all zero. Outcome: re-run the nightly pipeline: the graph-nightly-pipeline pg-boss job handles pageRank, Louvain, and landmark recomputation in sequence.

PERTAIN_TOSolution

Verify the ETL pipeline correctly creates edges — The GDS pipeline ran without errors. Tension: pageRank scores all returned 0.0 despite nodes existing. Outcome: Check if `Pattern` nodes are missing or not connected.

PERTAIN_TOSolution

What relationships actually exist? — MATCH ()-[r]->() RETURN type(r), count(r) ORDER BY count(r) DESC. Tension: What your projection expects vs what exists. Outcome: check your projection.

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