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explain.go
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explain.go
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/*
* Radon
*
* Copyright 2018 The Radon Authors.
* Code is licensed under the GPLv3.
*
*/
package proxy
import (
"fmt"
"regexp"
"optimizer"
"github.com/pkg/errors"
"github.com/xelabs/go-mysqlstack/driver"
"github.com/xelabs/go-mysqlstack/sqldb"
"github.com/xelabs/go-mysqlstack/sqlparser"
querypb "github.com/xelabs/go-mysqlstack/sqlparser/depends/query"
"github.com/xelabs/go-mysqlstack/sqlparser/depends/sqltypes"
)
// handleExplain used to handle the EXPLAIN command.
func (spanner *Spanner) handleExplain(session *driver.Session, query string, node sqlparser.Statement) (*sqltypes.Result, error) {
log := spanner.log
database := session.Schema()
router := spanner.router
qr := &sqltypes.Result{}
qr.Fields = []*querypb.Field{
{Name: "EXPLAIN", Type: querypb.Type_VARCHAR},
}
pat := `(?i)explain`
reg := regexp.MustCompile(pat)
idx := reg.FindStringIndex(query)
if len(idx) != 2 {
return nil, errors.Errorf("explain.query[%s].syntax.error", query)
}
cutQuery := query[idx[1]:]
subNode, err := sqlparser.Parse(cutQuery)
if err != nil {
msg := fmt.Sprintf("query[%s].parser.error: %v", cutQuery, err)
row := []sqltypes.Value{
sqltypes.MakeTrusted(querypb.Type_VARCHAR, []byte(msg)),
}
qr.Rows = append(qr.Rows, row)
return qr, nil
}
// Explain only supports DML.
// see https://dev.mysql.com/doc/refman/5.7/en/explain.html
switch subNode.(type) {
case *sqlparser.Select:
case *sqlparser.Delete:
case *sqlparser.Insert:
case *sqlparser.Update:
default:
return nil, sqldb.NewSQLError(sqldb.ER_SYNTAX_ERROR, "", "explain only supports SELECT/DELETE/INSERT/UPDATE")
}
simOptimizer := optimizer.NewSimpleOptimizer(log, database, cutQuery, subNode, router)
planTree, err := simOptimizer.BuildPlanTree()
if err != nil {
log.Error("proxy.explain.error:%+v", err)
msg := fmt.Sprintf("unsupported: cannot.explain.the.query:%s", cutQuery)
row := []sqltypes.Value{
sqltypes.MakeTrusted(querypb.Type_VARCHAR, []byte(msg)),
}
qr.Rows = append(qr.Rows, row)
return qr, nil
}
if len(planTree.Plans()) > 0 {
msg := planTree.Plans()[0].JSON()
row := []sqltypes.Value{
sqltypes.MakeTrusted(querypb.Type_VARCHAR, []byte(msg)),
}
qr.Rows = append(qr.Rows, row)
return qr, nil
}
return qr, nil
}