stevedlawrence commented on a change in pull request #331: Fix deep stack sizes
when serializing some schemas
URL: https://github.com/apache/incubator-daffodil/pull/331#discussion_r389774383
##########
File path:
daffodil-runtime1/src/main/scala/org/apache/daffodil/dsom/CompiledExpression1.scala
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@@ -212,7 +212,48 @@ class DPathCompileInfo(
extends ImplementsThrowsSDE with PreSerialization
with HasSchemaFileLocation {
+
+ /**
+ * This "parents" val is a backpointer to all DPathCompileInfo's that
+ * reference this DPathCompileInfo. The problem with this is that when
+ * elements are shared, these backpointers create a highly connected graph
+ * that requires a large stack to serialize using the default java
+ * serialization as it jumps around parents and children. To avoid this large
+ * stack requirement, we make the parents backpointer transient. This
+ * prevents jumping back up to parents during serialization and results in
+ * only needing a stack depth relative to the schema depth. Once all that
+ * serialization is completed and all the DPathCompileInfo's are serialized,
+ * we then manually traverse all the DPathCompileInfo's again and serialize
+ * the parent sequences (via the serailizeParents method). Because all the
+ * DPathCompileInfo's are already serialized, this just serializes the
+ * Sequence objects and the stack depth is again relative to the schema
+ * depth.
+ */
+ @transient
lazy val parents = parentsArg
Review comment:
Correct. Will fix.
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