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database.go
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database.go
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package mysql_flashback
import (
"database/sql"
"fmt"
_ "github.com/go-sql-driver/mysql"
"github.com/juju/errors"
"strings"
)
func LinkDB(uri string) (*DBMap, error) {
db, err := sql.Open("mysql", uri)
if err != nil {
return nil, errors.Trace(err)
}
if err := db.Ping(); err != nil {
return nil, errors.Trace(err)
}
return NewDBMap(db), nil
}
type TableMetadata struct {
Schema string
Table string
Fields map[int]string // map[idx]columnName (idx: field在table中的idx)
}
type DBMap struct {
tableMetadataMap map[uint64]*TableMetadata
fieldsCache map[string]map[int]string // map[schema_table]Fields
db *sql.DB
}
func NewDBMap(db *sql.DB) *DBMap {
return &DBMap{
db: db,
tableMetadataMap: make(map[uint64]*TableMetadata),
fieldsCache: make(map[string]map[int]string),
}
}
func (m *DBMap) LookupTableMetadata(id uint64) (*TableMetadata, bool) {
val, ok := m.tableMetadataMap[id]
return val, ok
}
func (m *DBMap) Add(id uint64, schema, table string) error {
fields, err := m.getFields(schema, table)
if err != nil {
return errors.Trace(err)
}
m.tableMetadataMap[id] = &TableMetadata{schema, table, fields}
return nil
}
func (m *DBMap) getFields(schema, table string) (map[int]string, error) {
cacheKey := fmt.Sprintf("%s_%s", schema, table)
if cachedFields, ok := m.fieldsCache[cacheKey]; ok {
return cachedFields, nil
}
fields, err := getFieldsFromDb(m.db, schema, table)
m.fieldsCache[cacheKey] = fields
if err != nil {
return nil, errors.Trace(err)
}
return fields, nil
}
// map[idx]columnName
func getFieldsFromDb(db *sql.DB, schema string, table string) (map[int]string, error) {
sql := "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ? ORDER BY ORDINAL_POSITION"
rows, err := db.Query(sql, schema, table)
if err != nil {
return nil, errors.Trace(err)
}
defer rows.Close()
fields := make(map[int]string)
i := 0
var columnName string
for rows.Next() {
if err := rows.Scan(&columnName); err != nil {
return nil, errors.Trace(err)
}
fields[i] = columnName
i++
}
return fields, nil
}
type BinlogInfo struct {
name string
size uint32
path string
startPos uint32
}
func getBinlogFromDb(db *sql.DB) ([]*BinlogInfo, error) {
sql := "SHOW MASTER LOGS;"
rows, err := db.Query(sql)
if err != nil {
return nil, errors.Trace(err)
}
defer rows.Close()
var result []*BinlogInfo
var fileName string
var fileSize uint32
for rows.Next() {
if err := rows.Scan(&fileName, &fileSize); err != nil {
return nil, errors.Trace(err)
}
result = append(result, &BinlogInfo{
name: fileName,
size: fileSize,
startPos: 0,
})
}
return result, nil
}
func getGitdModeFromDb(db *sql.DB) (ok bool, err error) {
sql := "SELECT @@GLOBAL.GTID_MODE;"
rows, err := db.Query(sql)
if err != nil {
return false, errors.Trace(err)
}
defer rows.Close()
var status string
for rows.Next() {
if err := rows.Scan(&status); err != nil {
return false, errors.Trace(err)
}
}
return strings.ToUpper(status) == "ON", nil
}
func getBinlogDirFromDb(db *sql.DB) (dirname string, err error) {
sql := `SHOW variables WHERE Variable_name = "log_bin_basename";`
rows, err := db.Query(sql)
if err != nil {
return "", errors.Trace(err)
}
defer rows.Close()
for rows.Next() {
if err = rows.Scan(&dirname); err != nil {
return "", errors.Trace(err)
}
}
return
}