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https://issues.apache.org/jira/browse/TAJO-95?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13728573#comment-13728573
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Hyunsik Choi commented on TAJO-95:
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Henry,
As I mentioned in the above comment, this bug blocks the progress of TAJO-83.
If you don't start this issue, I would like to resolve this issue as soon as
possible.
> Eliminate the lazy copy approach from the classes wrapping protobuf-generated
> classes.
> --------------------------------------------------------------------------------------
>
> Key: TAJO-95
> URL: https://issues.apache.org/jira/browse/TAJO-95
> Project: Tajo
> Issue Type: Improvement
> Reporter: Hyunsik Choi
> Assignee: Henry Saputra
> Priority: Blocker
>
> We have used two (de)serialization methods, such as JSON and Protocol Buffer.
> In a (de) serializable object, each attribute can be placed on the
> corresponding member variable or the member variable of the protocol buffer
> object.
> For reducing the frequency of data copies, we have used the laze copy
> approach that delays copying values from the contents of PB object to member
> variables or vice versa. It is similar to copy-on-wrote (COW).
> In many cases, however, this mechanism is actually burden rather than the
> performance benefit like the below code. Especially, this problem becomes
> more complicated if the wrapper class can be (de)serialized via both JSON and
> protocol buffer.
> {code:title=a getter method based on the lazy copy approach}
> protected TableDescProto proto = TableDescProto.getDefaultInstance();
> protected TableDescProto.Builder builder = null;
> protected boolean viaProto = false;
>
> @Expose protected String tableId;
> @Expose protected Path uri;
> @Expose protected TableMeta meta;
>
> .
> .
> public String getId() { // <- even a simple getter becomes very complicated.
> TableDescProtoOrBuilder p = viaProto ? proto : builder;
>
> if (tableId != null) {
> return this.tableId;
> }
> if (!p.hasId()) {
> return null;
> }
> this.tableId = p.getId();
>
> return this.tableId;
> }
> {code}
> Therefore, I would like to propose the simplification of wrapper classes by
> eliminating the laze copy approach. My proposal is as follows:
> * A wrapper class only keeps values in member variables when it is created.
> * A wrapper class only builds the corresponding protobuf object when
> getProto() is called.
> I think that the performance benefit has been very low. We should remove the
> lazy copy approach for more robust system.
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