*: refactor table.Table interface, clean up unnecessay methods

[tiancaiamao]

What problem does this PR solve?

The bigger the interface, the weaker the abstraction – Rob Pike

There are so many methods in the Table interface definition, make it less flexible.

What is changed and how it works?

Clean up unnecessary methods from the table.Table interface.

What's Changed:

	// Seek returns the handle greater or equal to h.	
	Seek(ctx sessionctx.Context, h kv.Handle) (handle kv.Handle, found bool, err error)

This one is only used in one place and is in the test code, so remove it.

	// DeletableIndices returns delete-only, write-only and public indices of the table.	
	DeletableIndices() []Index	

This one is not really used.

	// RecordKey returns the key in KV storage for the row.	
	RecordKey(h kv.Handle) kv.Key	

This can be replaced by tablecodec.EncodeRecordKey(RecordPrefix(), h) provide that RecordPrefix() is given.

	// FirstKey returns the first key.	
	FirstKey() kv.Key	

This one is a simple wrap on RecordKey(), it's not necessary to be an interface method.

	// RecordPrefix returns the record key prefix.	
	RecordPrefix() kv.Key	

	// IndexPrefix returns the index key prefix.	
	IndexPrefix() kv.Key	

Those are implementation-related, the interface should be abstract.
We may have temporary table, memory table, partition table, and many more, not all of them have the concept of RecordPrefix

	// RebaseAutoID rebases the auto_increment ID base.		
	// If allocIDs is true, it will allocate some IDs and save to the cache.		
	// If allocIDs is false, it will not allocate IDs.		
	RebaseAutoID(ctx sessionctx.Context, newBase int64, allocIDs bool, tp autoid.AllocatorType) error

We already provide Allocator() method in the Table interface, this one is just a simple wrap on Allocator(), so it's duplicated.

How it Works:

Remove RecordPrefix and IndexPrefix involves a lot of changes, maybe I should do it in another PR.

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• No code

Side effects

• Breaking backward compatibility

API change

Release note

• Code refactor, clean up the table.Table interface

[tiancaiamao]

IterRecords() method is also moved out from the table.Table interface:

t.IterRecords(..) =>  table.IterRecords(t, ...)

[tiancaiamao]

The remained methods for Table now is:

// Table is used to retrieve and modify rows in table.
type Table interface {
	columnAPI

	// Indices returns the indices of the table.
	Indices() []Index

	// RecordPrefix returns the record key prefix.
	RecordPrefix() kv.Key

	// AddRecord inserts a row which should contain only public columns
	AddRecord(ctx sessionctx.Context, r []types.Datum, opts ...AddRecordOption) (recordID kv.Handle, err error)

	// UpdateRecord updates a row which should contain only writable columns.
	UpdateRecord(ctx context.Context, sctx sessionctx.Context, h kv.Handle, currData, newData []types.Datum, touched []bool) error

	// RemoveRecord removes a row in the table.
	RemoveRecord(ctx sessionctx.Context, h kv.Handle, r []types.Datum) error

	// Allocators returns all allocators.
	Allocators(ctx sessionctx.Context) autoid.Allocators

	// RebaseAutoID rebases the auto_increment ID base.
	// If allocIDs is true, it will allocate some IDs and save to the cache.
	// If allocIDs is false, it will not allocate IDs.
	RebaseAutoID(ctx sessionctx.Context, newBase int64, allocIDs bool, tp autoid.AllocatorType) error

	// Meta returns TableInfo.
	Meta() *model.TableInfo

	// Type returns the type of table
	Type() Type
}

RecordPrefix() kv.Key and RebaseAutoID(ctx sessionctx.Context ...) is not really necessary, but I'll keep it here to make the changes friendly for reviews.

[xhebox]

Maybe it is worth to remove writableIndices based on the fact that it is not widely used. A helper method like index.IsWritable would help.

[tiancaiamao]

Now WritableIndices() is also removed. @xhebox

[tiancaiamao]

PTAL @xhebox @tangenta

[xhebox]

Rest LGTM

[xhebox]

/lgtm

[tangenta]

/lgtm

[tangenta]

/lgtm

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[tiancaiamao]

/merge

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

Commit hash: 5781f11

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