tidb/pkg/meta/model/index.go

// Copyright 2024 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package model

import (
	"github.com/pingcap/tidb/pkg/parser/model"
	"github.com/pingcap/tidb/pkg/parser/types"
)

// IndexInfo provides meta data describing a DB index.
// It corresponds to the statement `CREATE INDEX Name ON Table (Column);`
// See https://dev.mysql.com/doc/refman/5.7/en/create-index.html
type IndexInfo struct {
	ID            int64           `json:"id"`
	Name          model.CIStr     `json:"idx_name"` // Index name.
	Table         model.CIStr     `json:"tbl_name"` // Table name.
	Columns       []*IndexColumn  `json:"idx_cols"` // Index columns.
	State         SchemaState     `json:"state"`
	BackfillState BackfillState   `json:"backfill_state"`
	Comment       string          `json:"comment"`      // Comment
	Tp            model.IndexType `json:"index_type"`   // Index type: Btree, Hash or Rtree
	Unique        bool            `json:"is_unique"`    // Whether the index is unique.
	Primary       bool            `json:"is_primary"`   // Whether the index is primary key.
	Invisible     bool            `json:"is_invisible"` // Whether the index is invisible.
	Global        bool            `json:"is_global"`    // Whether the index is global.
	MVIndex       bool            `json:"mv_index"`     // Whether the index is multivalued index.
}

// Clone clones IndexInfo.
func (index *IndexInfo) Clone() *IndexInfo {
	if index == nil {
		return nil
	}
	ni := *index
	ni.Columns = make([]*IndexColumn, len(index.Columns))
	for i := range index.Columns {
		ni.Columns[i] = index.Columns[i].Clone()
	}
	return &ni
}

// HasPrefixIndex returns whether any columns of this index uses prefix length.
func (index *IndexInfo) HasPrefixIndex() bool {
	for _, ic := range index.Columns {
		if ic.Length != types.UnspecifiedLength {
			return true
		}
	}
	return false
}

// HasColumnInIndexColumns checks whether the index contains the column with the specified ID.
func (index *IndexInfo) HasColumnInIndexColumns(tblInfo *TableInfo, colID int64) bool {
	for _, ic := range index.Columns {
		if tblInfo.Columns[ic.Offset].ID == colID {
			return true
		}
	}
	return false
}

// FindColumnByName finds the index column with the specified name.
func (index *IndexInfo) FindColumnByName(nameL string) *IndexColumn {
	_, ret := FindIndexColumnByName(index.Columns, nameL)
	return ret
}

// IsPublic checks if the index state is public
func (index *IndexInfo) IsPublic() bool {
	return index.State == StatePublic
}

// FindIndexByColumns find IndexInfo in indices which is cover the specified columns.
func FindIndexByColumns(tbInfo *TableInfo, indices []*IndexInfo, cols ...model.CIStr) *IndexInfo {
	for _, index := range indices {
		if IsIndexPrefixCovered(tbInfo, index, cols...) {
			return index
		}
	}
	return nil
}

// IsIndexPrefixCovered checks the index's columns beginning with the cols.
func IsIndexPrefixCovered(tbInfo *TableInfo, index *IndexInfo, cols ...model.CIStr) bool {
	if len(index.Columns) < len(cols) {
		return false
	}
	for i := range cols {
		if cols[i].L != index.Columns[i].Name.L ||
			index.Columns[i].Offset >= len(tbInfo.Columns) {
			return false
		}
		colInfo := tbInfo.Columns[index.Columns[i].Offset]
		if index.Columns[i].Length != types.UnspecifiedLength && index.Columns[i].Length < colInfo.GetFlen() {
			return false
		}
	}
	return true
}

// FindIndexInfoByID finds IndexInfo in indices by id.
func FindIndexInfoByID(indices []*IndexInfo, id int64) *IndexInfo {
	for _, idx := range indices {
		if idx.ID == id {
			return idx
		}
	}
	return nil
}

// IndexColumn provides index column info.
type IndexColumn struct {
	Name   model.CIStr `json:"name"`   // Index name
	Offset int         `json:"offset"` // Index offset
	// Length of prefix when using column prefix
	// for indexing;
	// UnspecifedLength if not using prefix indexing
	Length int `json:"length"`
}

// Clone clones IndexColumn.
func (i *IndexColumn) Clone() *IndexColumn {
	ni := *i
	return &ni
}

// FindIndexColumnByName finds IndexColumn by name. When IndexColumn is not found, returns (-1, nil).
func FindIndexColumnByName(indexCols []*IndexColumn, nameL string) (int, *IndexColumn) {
	for i, ic := range indexCols {
		if ic.Name.L == nameL {
			return i, ic
		}
	}
	return -1, nil
}