pkg/lightning: fix incorrect table counter (#996)

[ti-srebot]

cherry-pick #996 to release-5.0
You can switch your code base to this Pull Request by using git-extras:

# In br repo:
git pr https://github.com/pingcap/br/pull/1005

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/br.git pr/1005:release-5.0-d5e5cdc7676e

---

What problem does this PR solve?

Fix the wrong table count in the progress log like following:

[2021/04/12 14:26:43.837 +08:00] [INFO] [restore.go:1026] [progress] [total=0.0%] [tables="0/2 (0.0%)"] [chunks="0/99 (0.0%)"] [engines="0/2 (0.0%)"] [speed(MiB/s)=145.03058180393646] [state=preparing] []

There is only one table data in the source files but the pending tables count is 2.

What is changed and how it works?

Calculate pending table count based on the tables in dbMetas instead of tables fetched from TiDB.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release Note

• Fix the bug that the table count in the progress log is wrong

[glorv]

/run-all-tests

[3pointer]

/lgtm

[overvenus]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3pointer
• overvenus

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[glorv]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 32cfdbf

[glorv]

/run-all-tests

[glorv]

/run-all-tests