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Fix rebalance bug #539
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Fix rebalance bug #539
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This commit fixes a rare issue where a page can become accessible when it has already been freed. This occurs when the first two child pages of a parent both have deletions and the first page has 1 remaining children and the second page has 2 remaining children. During rebalancing the first page pulls an element from the second page and then the second page pulls the same element back from the first. The child page was not being freed properly. I resolved this issue by removing this part of the rebalancing. I made this choice for two reasons: 1. Moving a single item between pages has negligible benefit. The page will eventually be cleaned up when it reaches zero elements. 2. This is an infrequently executed branch of code which increases the likelihood of bugs occurring and it makes it more difficult to test properly. Fixes boltdb#348
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+1 for removing code. Though it's not my project, I do prefer the philosophy of correctness over optimization. Given sufficient testing, you can have both, but time is valuable and sometimes it's not worth the effort. |
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@DavidVorick Agreed! There are few things in this world that I enjoy more than |
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LGTM. Can we do a release after this fix? |
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@xiang90 Yep. I'll tag it as |
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@xiang90 Tagged & shipped: https://github.com/boltdb/bolt/releases/tag/v1.2.0 |
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@benbjohnson Awesome! Thank you so much. |
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Overview
This commit fixes a rare issue where a page can become accessible when it has already been freed. This occurs when the first two child pages of a parent both have deletions and the first page
has 1 remaining children and the second page has 2 remaining children. During rebalancing the first page pulls an element from the second page and then the second page pulls the same element back from the first. The child page was not being freed properly.
I resolved this issue by removing this part of the rebalancing.
I made this choice for two reasons:
Fixes #348