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explain.go
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explain.go
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/*
* NeoDB
*
* Copyright 2018 The Radon Authors.
* Copyright 2021-2030 The NeoDB Authors.
* Code is licensed under the GPLv3.
*
*/
package proxy
import (
"github.com/sealdb/neodb/optimizer"
"github.com/sealdb/mysqlstack/driver"
"github.com/sealdb/mysqlstack/sqldb"
"github.com/sealdb/mysqlstack/sqlparser"
querypb "github.com/sealdb/mysqlstack/sqlparser/depends/query"
"github.com/sealdb/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},
}
explainableStmt := node.(*sqlparser.Explain).Statement
privilegePlug := spanner.plugins.PlugPrivilege()
if err := privilegePlug.Check(database, session.User(), explainableStmt); err != nil {
return nil, err
}
// Explain only supports DML.
// see: https://dev.mysql.com/doc/refman/8.0/en/explain.html
switch explainableStmt.(type) {
case *sqlparser.Union:
case *sqlparser.Select:
case *sqlparser.Delete:
case *sqlparser.Insert:
autoincPlug := spanner.plugins.PlugAutoIncrement()
if err := autoincPlug.Process(database, explainableStmt.(*sqlparser.Insert)); err != nil {
return nil, err
}
case *sqlparser.Update:
default:
return nil, sqldb.NewSQLError(sqldb.ER_SYNTAX_ERROR, "explain only supports SELECT/DELETE/INSERT/UNION")
}
simOptimizer := optimizer.NewSimpleOptimizer(log, database, query, explainableStmt, router)
planTree, err := simOptimizer.BuildPlanTree()
if err != nil {
log.Error("proxy.explain.error:%+v", err)
return nil, err
}
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
}