fix(table cache) block cache logic for table with no compression

[hugy718]

Problem

Fixes #2021.

The problem is in the block() function in table.go. blk.data takes a slice of the t.Data. If there is no decryption or decompression, it will hold this slice and added to the cache, which means it will always hold a reference of t.Data. That will also preventing GC of the mmap file buffer, so long as a block of it is in cache.

Solution

Make a copy of the block data, when no decryption nor compression.

[netlify[bot]]

✅ Deploy Preview for badger-docs ready!

Name	Link
🔨 Latest commit	d01e622973593d0a2abdcbe177a6770ce063984b
🔍 Latest deploy log	https://app.netlify.com/sites/badger-docs/deploys/652e5431236ac00008d3dbc0
😎 Deploy Preview	https://deploy-preview-2022--badger-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[github-actions[bot]]

This PR has been stale for 60 days and will be closed automatically in 7 days. Comment to keep it open.