github.com/dolthub/go-mysql-server@v0.18.0/sql/external_stored_procedure_registry.go (about)

     1  // Copyright 2022 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package sql
    16  
    17  import (
    18  	"math"
    19  	"reflect"
    20  	"strings"
    21  )
    22  
    23  // ExternalStoredProcedureRegistry manages a collection of ExternalStoredProcedures and encapsulates
    24  // the logic for looking up external stored procedures based on name and number of arguments.
    25  type ExternalStoredProcedureRegistry struct {
    26  	procedures map[string]map[int]ExternalStoredProcedureDetails
    27  }
    28  
    29  // NewExternalStoredProcedureRegistry creates a new, empty instance of ExternalStoredProcedureRegistry.
    30  func NewExternalStoredProcedureRegistry() ExternalStoredProcedureRegistry {
    31  	return ExternalStoredProcedureRegistry{
    32  		procedures: make(map[string]map[int]ExternalStoredProcedureDetails),
    33  	}
    34  }
    35  
    36  // Register adds an external stored procedure to this registry.
    37  func (epd *ExternalStoredProcedureRegistry) Register(procedureDetails ExternalStoredProcedureDetails) {
    38  	numOfParams := epd.countNumberOfParams(procedureDetails)
    39  
    40  	if _, ok := epd.procedures[procedureDetails.Name]; !ok {
    41  		epd.procedures[procedureDetails.Name] = make(map[int]ExternalStoredProcedureDetails)
    42  	}
    43  	epd.procedures[procedureDetails.Name][numOfParams] = procedureDetails
    44  }
    45  
    46  // LookupByName returns all stored procedure variants registered with the specified name, no matter
    47  // how many parameters they require. If no external stored procedures are registered with the specified
    48  // name, nil is returned, with no error. If an unexpected error occurs, it is returned as the error
    49  // parameter.
    50  func (epd *ExternalStoredProcedureRegistry) LookupByName(name string) ([]ExternalStoredProcedureDetails, error) {
    51  	procedureVariants, ok := epd.procedures[strings.ToLower(name)]
    52  	if !ok {
    53  		return nil, nil
    54  	}
    55  
    56  	procedures := make([]ExternalStoredProcedureDetails, 0, len(procedureVariants))
    57  	for _, procedure := range procedureVariants {
    58  		procedures = append(procedures, procedure)
    59  	}
    60  	return procedures, nil
    61  }
    62  
    63  // LookupByNameAndParamCount returns the external stored procedure registered with the specified name
    64  // and able to accept the specified number of parameters. If no external stored procedures are
    65  // registered with the specified name and able to accept the specified number of parameters, nil
    66  // is returned with no error. If an unexpected error occurs, it is returned as the error param.
    67  func (epd *ExternalStoredProcedureRegistry) LookupByNameAndParamCount(name string, numOfParams int) (*ExternalStoredProcedureDetails, error) {
    68  	procedureVariants, ok := epd.procedures[strings.ToLower(name)]
    69  	if !ok {
    70  		return nil, nil
    71  	}
    72  
    73  	// If we find an exact match on param count, return that stored procedure
    74  	procedure, ok := procedureVariants[numOfParams]
    75  	if ok {
    76  		return &procedure, nil
    77  	}
    78  
    79  	// Otherwise, find the largest param length and return that stored procedure
    80  	var largestParamLen int
    81  	var largestParamProc ExternalStoredProcedureDetails
    82  	for paramLen, procedure := range procedureVariants {
    83  		if largestParamLen < paramLen {
    84  			largestParamProc = procedure
    85  			largestParamLen = paramLen
    86  		}
    87  	}
    88  	return &largestParamProc, nil
    89  }
    90  
    91  // countNumberOfParams returns the number of parameters accepted by the specified external stored
    92  // procedure, including allowing variadic return types to expand to accept at most MaxInt parameters.
    93  func (epd *ExternalStoredProcedureRegistry) countNumberOfParams(externalProcedure ExternalStoredProcedureDetails) int {
    94  	funcVal := reflect.ValueOf(externalProcedure.Function)
    95  	funcType := funcVal.Type()
    96  
    97  	// Return MaxInt for variadic types, since they can accommodate any number of params
    98  	if funcVal.Type().IsVariadic() {
    99  		return math.MaxInt
   100  	}
   101  
   102  	// We subtract one because ctx is required to always be the first parameter to a function, but
   103  	// customers won't actually pass that in to the stored procedure.
   104  	return funcType.NumIn() - 1
   105  }