Optimize read-only modsnap transactions #4999
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Coding style check: Error. ⚠.
Smoke testing: Success ✓.
Cbuild submission: Success ✓.
Regression testing: 0/0 tests failed ⚠.
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Signed-off-by: Morgan Douglas <[email protected]>
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The changes in #4902 forced all modsnap transactions to open shadow btrees. It did this because the table version cache, which is necessary for all snapshot transactions, was coupled to the shadow code; therefore, even though some read-only modsnap transactions don't require shadow btrees, they still needed to open them just to use the table version cache.
The changes in this PR decouple the table version cache from shadow code so that eligible read-only modsnap transactions can skip opening shadows, which can be expensive.