Avoid uneccessary copies in generated VisitorTransforms

Previously, the generated VisitorTransform classes *always* made a deep copy of the input tree. With this commit, only those nodes which are actually changed will be copied. In the transform*() functions of the VisitorTransform super classes, we now check to see if all of the new child nodes are the same instance as the original child nodes. If so, there is no need to copy the original node. Note that this does not apply to cross-domain visitor transforms since the type of the nodes is changing, it is still neccessary to perform the deep copy.
partiql · May 30, 2021 · 3c09dd9 · 3c09dd9
1 parent 7e9ae0f
commit 3c09dd9
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diff --git a/pig-runtime/src/org/partiql/pig/runtime/DomainVisitorTransformBase.kt b/pig-runtime/src/org/partiql/pig/runtime/DomainVisitorTransformBase.kt
@@ -26,23 +26,39 @@ import com.amazon.ionelement.api.MetaContainer
 abstract class DomainVisitorTransformBase {
     open fun transformMetas(metas: MetaContainer) = metas
 
-    open fun transformAnyElement(node: AnyElement): AnyElement =
-        // TODO:  remove .asAnyElement() below when https://github.com/amzn/ion-element-kotlin/issues/36 is fixed.
-        node.copy(metas = transformMetas(node.metas)).asAnyElement()
+    open fun transformAnyElement(node: AnyElement): AnyElement {
+        val newMetas = transformMetas(node.metas)
+        return if(node.metas !== newMetas) {
+            // TODO:  remove .asAnyElement() below when https://github.com/amzn/ion-element-kotlin/issues/36 is fixed.
+            node.copy(metas = newMetas).asAnyElement()
+        } else {
+            node
+        }
+    }
 
-    open fun transformSymbolPrimitive(sym: SymbolPrimitive) =
-        SymbolPrimitive(
-            transformSymbolPrimitiveText(sym),
-            transformSymbolPrimitiveMetas(sym))
+    open fun transformSymbolPrimitive(sym: SymbolPrimitive): SymbolPrimitive {
+        val newText = transformSymbolPrimitiveText(sym)
+        val newMetas = transformSymbolPrimitiveMetas(sym)
+        return if(sym.text != newText || sym.metas !== newMetas) {
+            SymbolPrimitive(newText, newMetas)
+        } else {
+            sym
+        }
+    }
 
     open fun transformSymbolPrimitiveText(sym: SymbolPrimitive) = sym.text
 
     open fun transformSymbolPrimitiveMetas(sym: SymbolPrimitive) = transformMetas(sym.metas)
 
-    open fun transformLongPrimitive(lng: LongPrimitive) =
-        LongPrimitive(
-            transformLongPrimitiveValue(lng),
-            transformLongPrimitiveMetas(lng))
+    open fun transformLongPrimitive(lng: LongPrimitive): LongPrimitive {
+        val newValue = transformLongPrimitiveValue(lng)
+        val newMetas = transformLongPrimitiveMetas(lng)
+        return if(lng.value != newValue || lng.metas !== newMetas) {
+            LongPrimitive(newValue, newMetas)
+        } else {
+            lng
+        }
+    }
 
     open fun transformLongPrimitiveValue(sym: LongPrimitive): Long = sym.value