domoritz commented on code in PR #44247:
URL: https://github.com/apache/arrow/pull/44247#discussion_r1779658502
##########
js/src/table.ts:
##########
@@ -238,17 +238,30 @@ export class Table<T extends TypeMap = any> {
*
* @returns An Array of Table rows.
*/
- public toArray() {
+ public toArray(): Array<Struct<T>['TValue']> {
return [...this];
}
+ /**
+ * Return a JavaScript Array view of the Table rows.
+ *
+ * It is a lightweight read-only proxy that delegates to the table.
Accessing elements has some
+ * overhead compared to the regular array returned by `toArray()` because
of this indirection,
+ * but it avoids potentially large memory allocation.
+ *
+ * @returns An Array proxy to the Table rows.
+ */
+ public toArrayView(): Array<Struct<T>['TValue']> {
+ return new Proxy([] as Array<Struct<T>['TValue']>, new
TableArrayProxyHandler(this));
+ }
+
/**
* Returns a string representation of the Table rows.
*
* @returns A string representation of the Table rows.
*/
public toString() {
- return `[\n ${this.toArray().join(',\n ')}\n]`;
+ return `[\n ${this.toArrayView().join(',\n ')}\n]`;
Review Comment:
I understand the difference but I wonder whether this change introduces a
performance regression since "the proxy adds some overhead to direct array
access."
I'm not against this change but want to make sure we have thought through
the implications.
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