Add MemGQL v0.6.1 (#1650)

Author: gitbuda

pages/memgraph-zero/memgql/changelog.mdx

@@ -5,6 +5,51 @@ description: MemGQL release notes
 
 # MemGQL Changelog
 
+## MemGQL v0.6.1 - May 31st, 2026
+
+### ✨ New features & Improvements
+
+- **Cross-backend joins (phase 1).** Queries that `USE` two or more
+  different graphs in a single statement now execute as a federated
+  left-deep hash-join chain inside the Bolt server. `LinearQuery`
+  carries `parts: Vec<FocusedPart>`; a multi-`USE` query lowers to a
+  `CrossGraphJoin` chain of per-part `RemoteScan`s.
+  `dispatch_cross_backend` peels `Limit > Sort > Distinct > Project >
+  Filter` into a `FederationPipeline`, dispatches each part via the
+  per-backend `BoltHandler::run_plan`, materializes rows to canonical
+  scalars, and folds via hash-join (SQL 3VL — `NULL` keys dropped) or
+  Cartesian product when there's no equi-predicate. Per-side
+  materialization is capped at 1,000,000 rows.
+  - **Verified end-to-end:** Memgraph, MySQL, PostgreSQL, DuckDB.
+  - **Wired but not yet verified end-to-end:** Neo4j, Oracle, ClickHouse,
+    Iceberg, Pinot — the integration is mechanically identical and
+    awaits a broader live-backend test harness.
+  - Composite (multi-column) equi-joins are supported.
+  - Post-join `Filter` / `Sort` / `Limit` / `Distinct` and a federation
+    expression evaluator run over the joined wide row, including
+    cross-part arithmetic, string functions (`toUpper`, `toLower`,
+    `length`, `size`, `trim`), and residual filters (`STARTS WITH`,
+    comparisons).
+  - Three-backend left-deep chains with skip-level predicates are
+    supported.
+  - Unsupported shapes return a typed error with an actionable
+    headline: whole-node returns across the federation boundary,
+    non-literal `LIMIT`/`SKIP`, unrecognized plan nodes above the
+    join (`Aggregate`, `Union`), unsupported functions, etc.
+
+### 🚧 Known limitations
+
+- Whole-node `RETURN m` across federation is rejected;
+  `CanonicalScalar::Node` modeling is deferred. Reference individual
+  properties instead (`m.name`).
+- Scalar functions reach the GQL parser catch-all today (the
+  evaluator supports them — covered by unit tests — but the e2e path
+  waits on a parser extension; aggregates and `COALESCE` / `NULLIF`
+  go through the normal `FnCall` path).
+- No output-cardinality cap (only per-side input cap of 1,000,000
+  rows). Per-side dispatch is sequential; parallel fan-out is a
+  follow-up.
+
 ## MemGQL v0.6.0 - May 23rd, 2026
 
 ### ⚠️ Breaking changes

pages/memgraph-zero/memgql/complete.mdx

@@ -102,7 +102,7 @@ Save the following as `docker-compose.yml`:
 ```yaml
 services:
   memgql:
-    image: ${MEMGQL_IMAGE:-memgraph/memgql:0.6.0}
+    image: ${MEMGQL_IMAGE:-memgraph/memgql:0.6.1}
     container_name: memgql
     ports:
       - "7688:7688"

pages/memgraph-zero/memgql/use-cases/public-private.mdx

@@ -62,7 +62,7 @@ MemGQL, and a one-shot init container:
 cat > docker-compose.yml << 'EOF'
 services:
   memgql:
-    image: ${MEMGQL_IMAGE:-memgraph/memgql:0.6.0}
+    image: ${MEMGQL_IMAGE:-memgraph/memgql:0.6.1}
     ports:
       - "7688:7688"
     environment: