vitess.io/vitess@v0.16.2/go/vt/vtgate/planbuilder/fallback_planner.go (about)

     1  /*
     2  Copyright 2021 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package planbuilder
    18  
    19  import (
    20  	"fmt"
    21  
    22  	"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
    23  
    24  	"vitess.io/vitess/go/vt/sqlparser"
    25  )
    26  
    27  type fallbackPlanner struct {
    28  	primary, fallback stmtPlanner
    29  }
    30  
    31  var _ stmtPlanner = (*fallbackPlanner)(nil).plan
    32  
    33  func (fp *fallbackPlanner) safePrimary(stmt sqlparser.Statement, reservedVars *sqlparser.ReservedVars, vschema plancontext.VSchema) (res *planResult, err error) {
    34  	defer func() {
    35  		// if the primary planner panics, we want to catch it here so we can fall back
    36  		if r := recover(); r != nil {
    37  			err = fmt.Errorf("%v", r) // not using vterror since this will only be used for logging
    38  		}
    39  	}()
    40  	res, err = fp.primary(stmt, reservedVars, vschema)
    41  	return
    42  }
    43  
    44  func (fp *fallbackPlanner) plan(stmt sqlparser.Statement, reservedVars *sqlparser.ReservedVars, vschema plancontext.VSchema) (*planResult, error) {
    45  	res, err := fp.safePrimary(sqlparser.CloneStatement(stmt), reservedVars, vschema)
    46  	if err != nil {
    47  		return fp.fallback(stmt, reservedVars, vschema)
    48  	}
    49  	return res, nil
    50  }