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https://issues.apache.org/jira/browse/OAK-5253?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15741338#comment-15741338
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Julian Sedding commented on OAK-5253:
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[~amitjain] In {{BlobStoreBlob#equals}} there is the following comment before
comparing blob ids (and that's the best I could find regarding the guarantees
of blob ids).
{quote}
// theoretically, the data could be the same
// even if the id is different
return b.blobId.equals(blobId);
{quote}
So strictly speaking, just like with {{#getContentIdentity()}}, equal blob ids
guarantee that two blobs are equal, but different blob ids do not guarantee
that two blobs are different.
I don't want to be a pain, and since {{BlobStoreBlob}} already uses the blob
ids to implement equals, I won't object here. However, I would prefer if we
could extend or clarify the contract of {{BlobStore}} or {{Blob}} in order to
accommodate the use-case of determining that two blobs are different without
comparing their bytes.
> Optimize AbstractBlob#equal to not do content equals when possible
> ------------------------------------------------------------------
>
> Key: OAK-5253
> URL: https://issues.apache.org/jira/browse/OAK-5253
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: blob
> Reporter: Amit Jain
> Assignee: Amit Jain
> Fix For: 1.6, 1.5.16, 1.4.11
>
> Attachments: OAK-5253.1.patch
>
>
> AbstractBlob#equals tries to match content when length is equal and content
> identities is not null and different. Matching content triggers an expensive
> download of binaries for S3DataStore.
> Since, right now the content identity is the content hash the check can be
> short -circuited when the content identities is not null and not equal to
> return false.
> This can be revisited if we change the identity to something different.
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