Reduce metadata mutation overhead via second-byte dispatch

[dlambrig]

applyMetadataMutations() is called for each transaction containing system key mutations. The original implementation calls 23+ check* functions for system key mutation, even though most mutations only match 1-2 prefixes. For a transaction with N system mutations, this creates ~22N wasted function calls and string comparisons.

This PR groups check* functions based on the second byte of system keys and use a switch statement to dispatch to the appropriate subset:

• Second byte '/' (0x2F): Most common - \xff/keyServers/, \xff/serverKeys/, \xff/conf/, etc. (17 functions)
• Second byte '\x02' (0x02): Less common - \xff\x02/feed/, \xff\x02/cacheKeys/ (4 functions)
• Second byte '\xff' (0xFF): Private keys - \xff\xff/cf/, \xff\xff/cc/ (1 function)

This reduces the average function calls per mutation from 23 to 10-17 depending on key pattern.

---

After some tests. The second-byte dispatch adds:

• Switch statement overhead (probably a small branch prediction cost)
• Extra code size (may affect instruction cache)

And saves nothing when there's only 1 mutation since all the check* functions would return quickly anyway on mismatched prefixes.

This seems to be the common case. I do not think the optimization is worth it.

Code-Reviewer Section

The general pull request guidelines can be found here.

Please check each of the following things and check all boxes before accepting a PR.

• The PR has a description, explaining both the problem and the solution.
• The description mentions which forms of testing were done and the testing seems reasonable.
• Every function/class/actor that was touched is reasonably well documented.

For Release-Branches

If this PR is made against a release-branch, please also check the following:

• This change/bugfix is a cherry-pick from the next younger branch (younger release-branch or main if this is the youngest branch)
• There is a good reason why this PR needs to go into a release branch and this reason is documented (either in the description above or in a linked GitHub issue)

[foundationdb-ci]

Result of foundationdb-pr-macos on macOS Ventura 13.x

• Commit ID: d38eb7a
• Duration 0:12:25
• Result: ❌ FAILED
• Error: Error while executing command: ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ${HOME}/.ssh_key ec2-user@${MAC_EC2_HOST} /usr/local/bin/bash --login -c ./build_pr_macos.sh. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux RHEL 9

• Commit ID: d38eb7a
• Duration 0:21:18
• Result: ❌ FAILED
• Error: Error while executing command: ninja -v -C build_output -j ${NPROC} all packages strip_targets. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux RHEL 9

• Commit ID: d38eb7a
• Duration 0:21:18
• Result: ❌ FAILED
• Error: Error while executing command: ninja -v -C build_output -j ${NPROC} all packages strip_targets. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)
• Cluster Test Logs zip file of the test logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux RHEL 9

• Commit ID: d38eb7a
• Duration 0:24:49
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-macos on macOS Ventura 13.x

• Commit ID: abf2458
• Duration 0:11:34
• Result: ❌ FAILED
• Error: Error while executing command: ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ${HOME}/.ssh_key ec2-user@${MAC_EC2_HOST} /usr/local/bin/bash --login -c ./build_pr_macos.sh. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-macos-m1 on macOS Ventura 13.x

• Commit ID: d38eb7a
• Duration 0:39:39
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux RHEL 9

• Commit ID: abf2458
• Duration 0:20:54
• Result: ❌ FAILED
• Error: Error while executing command: ninja -v -C build_output -j ${NPROC} all packages strip_targets. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)
• Cluster Test Logs zip file of the test logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux RHEL 9

• Commit ID: abf2458
• Duration 0:21:26
• Result: ❌ FAILED
• Error: Error while executing command: ninja -v -C build_output -j ${NPROC} all packages strip_targets. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang-arm on Linux CentOS 7

• Commit ID: d38eb7a
• Duration 0:44:53
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux RHEL 9

• Commit ID: abf2458
• Duration 0:24:33
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang on Linux RHEL 9

• Commit ID: d38eb7a
• Duration 0:48:18
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang-arm on Linux CentOS 7

• Commit ID: abf2458
• Duration 0:44:12
• Result: ❌ FAILED
• Error: Error while executing command: ctest -j ${NPROC} --no-compress-output -T test --output-on-failure. Reason: exit status 8
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang on Linux RHEL 9

• Commit ID: abf2458
• Duration 0:45:16
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)