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

     1  /*
     2  Copyright 2020 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  	"sync"
    22  
    23  	"vitess.io/vitess/go/vt/sqlparser"
    24  	"vitess.io/vitess/go/vt/sysvars"
    25  	"vitess.io/vitess/go/vt/vterrors"
    26  	"vitess.io/vitess/go/vt/vtgate/evalengine"
    27  )
    28  
    29  type sysvarPlanCache struct {
    30  	funcs map[string]planFunc
    31  	once  sync.Once
    32  }
    33  
    34  func (pc *sysvarPlanCache) initForSettings(systemVariables []sysvars.SystemVariable, f func(setting) planFunc) {
    35  	for _, sysvar := range systemVariables {
    36  		if _, alreadyExists := pc.funcs[sysvar.Name]; alreadyExists {
    37  			panic("bug in set plan init - " + sysvar.Name + " already configured")
    38  		}
    39  
    40  		s := setting{
    41  			name:               sysvar.Name,
    42  			boolean:            sysvar.IsBoolean,
    43  			identifierAsString: sysvar.IdentifierAsString,
    44  			supportSetVar:      sysvar.SupportSetVar,
    45  			storageCase:        sysvar.Case,
    46  		}
    47  
    48  		if sysvar.Default != "" {
    49  			s.defaultValue = pc.parseAndBuildDefaultValue(sysvar)
    50  		}
    51  		pc.funcs[sysvar.Name] = f(s)
    52  	}
    53  }
    54  
    55  func (pc *sysvarPlanCache) parseAndBuildDefaultValue(sysvar sysvars.SystemVariable) evalengine.Expr {
    56  	stmt, err := sqlparser.Parse(fmt.Sprintf("select %s", sysvar.Default))
    57  	if err != nil {
    58  		panic(fmt.Sprintf("bug in set plan init - default value for %s not parsable: %s", sysvar.Name, sysvar.Default))
    59  	}
    60  	sel := stmt.(*sqlparser.Select)
    61  	aliasedExpr := sel.SelectExprs[0].(*sqlparser.AliasedExpr)
    62  	def, err := evalengine.Translate(aliasedExpr.Expr, nil)
    63  	if err != nil {
    64  		panic(fmt.Sprintf("bug in set plan init - default value for %s not able to convert to evalengine.Expr: %s", sysvar.Name, sysvar.Default))
    65  	}
    66  	return def
    67  }
    68  
    69  func (pc *sysvarPlanCache) init() {
    70  	pc.once.Do(func() {
    71  		pc.funcs = make(map[string]planFunc)
    72  		pc.initForSettings(sysvars.ReadOnly, buildSetOpReadOnly)
    73  		pc.initForSettings(sysvars.IgnoreThese, buildSetOpIgnore)
    74  		pc.initForSettings(sysvars.UseReservedConn, buildSetOpReservedConn)
    75  		pc.initForSettings(sysvars.CheckAndIgnore, buildSetOpCheckAndIgnore)
    76  		pc.initForSettings(sysvars.NotSupported, buildNotSupported)
    77  		pc.initForSettings(sysvars.VitessAware, buildSetOpVitessAware)
    78  	})
    79  }
    80  
    81  var sysvarPlanningFuncs sysvarPlanCache
    82  
    83  func (pc *sysvarPlanCache) Get(expr *sqlparser.SetExpr) (planFunc, error) {
    84  	pc.init()
    85  	pf, ok := pc.funcs[expr.Var.Name.Lowered()]
    86  	if !ok {
    87  		return nil, vterrors.VT05006(sqlparser.String(expr))
    88  	}
    89  	return pf, nil
    90  }