lightning: fix routes panic for csv data load (#45405)

[ti-chi-bot]

This is an automated cherry-pick of #45405

What problem does this PR solve?

Issue Number: close #43284

Problem Summary:

Routes does not work for standard csv data.

tidb/br/pkg/lightning/mydump/loader.go

Lines 512 to 527 in c0e7057

	knownDBNames := make(map[string]*dbInfo)
	for _, info := range s.dbSchemas {
	knownDBNames[info.TableName.Schema] = &dbInfo{
	fileMeta: info.FileMeta,
	count: 1,
	}
	}
	for _, info := range s.tableSchemas {
	knownDBNames[info.TableName.Schema].count++
	}
	for _, info := range s.viewSchemas {
	knownDBNames[info.TableName.Schema].count++
	}
	for _, info := range s.tableDatas {
	knownDBNames[info.TableName.Schema].count++
	}

It does map initialization for s.dbSchemas, then operate on s.tableSchemas, s.viewSchemas, and s.tableDatas. However, the scope of s.tableSchemas does not cover the latter three ones, resulting in accessing invalid memory address or nil pointer dereference.

What is changed and how it works?

For s.tableSchemas, s.viewSchemas, and s.tableDatas, initialize for each of them respectively, instead of initializing for s.dbSchemas.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[lyzx2001]

/cc @lance6716

[lyzx2001]

/cc @lance6716

[lyzx2001]

/cc @lance6716

ignore it, mistakenly request review again

[lyzx2001]

/cc @GMHDBJD

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, lance6716

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-07-25 10:06:49.476179446 +0000 UTC m=+262552.070710423: ☑️ agreed by lance6716.
• 2023-07-25 12:30:51.411886539 +0000 UTC m=+271194.006417524: ☑️ agreed by GMHDBJD.