Add documentation and README for memoryUsage and sizeInBytes for graph.list

Author: DarthMax

doc/modules/ROOT/pages/graph-list.adoc

@@ -53,8 +53,8 @@ CALL gds.graph.list(
 | density                | Float    | Density of the graph.
 | creationTime           | Datetime | Time when the graph was projected.
 | modificationTime       | Datetime | Time when the graph was last modified.
-| sizeInBytes            | Integer  | Number of bytes used in the Java heap to store the graph.
-| memoryUsage            | String   | Human readable description of `sizeInBytes`.
+| sizeInBytes            | Integer  | Number of bytes used in the Java heap to store the graph. This feature is not supported on all JDKs and might return -1 instead.
+| memoryUsage            | String   | Human readable description of `sizeInBytes`. This feature is not supported on all JDKs and might return null instead.
 |===
 --
 

proc/catalog/src/main/java/org/neo4j/gds/catalog/GraphInfo.java

@@ -86,7 +86,10 @@ static GraphInfo withMemoryUsage(
         GraphStore graphStore
     ) {
         var sizeInBytes = MemoryUsage.sizeOf(graphStore);
-        var memoryUsage = MemoryUsage.humanReadable(sizeInBytes);
+
+        var memoryUsage = sizeInBytes >= 0
+            ? MemoryUsage.humanReadable(sizeInBytes)
+            : null;
 
         return create(
             graphProjectConfig,