github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/spatial/st_srid.go (about)

     1  // Copyright 2020-2021 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 spatial
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  
    21  	"github.com/dolthub/go-mysql-server/sql"
    22  	"github.com/dolthub/go-mysql-server/sql/expression"
    23  	"github.com/dolthub/go-mysql-server/sql/types"
    24  )
    25  
    26  // SRID is a function that returns SRID of Geometry object or returns a new object with altered SRID.
    27  type SRID struct {
    28  	expression.NaryExpression
    29  }
    30  
    31  var _ sql.FunctionExpression = (*SRID)(nil)
    32  var _ sql.CollationCoercible = (*SRID)(nil)
    33  
    34  // NewSRID creates a new STX expression.
    35  func NewSRID(args ...sql.Expression) (sql.Expression, error) {
    36  	if len(args) != 1 && len(args) != 2 {
    37  		return nil, sql.ErrInvalidArgumentNumber.New("ST_SRID", "1 or 2", len(args))
    38  	}
    39  	return &SRID{expression.NaryExpression{ChildExpressions: args}}, nil
    40  }
    41  
    42  // FunctionName implements sql.FunctionExpression
    43  func (s *SRID) FunctionName() string {
    44  	return "st_srid"
    45  }
    46  
    47  // Description implements sql.FunctionExpression
    48  func (s *SRID) Description() string {
    49  	return "returns the SRID value of given geometry object. If given a second argument, returns a new geometry object with second argument as SRID value."
    50  }
    51  
    52  // Type implements the sql.Expression interface.
    53  func (s *SRID) Type() sql.Type {
    54  	if len(s.ChildExpressions) == 1 {
    55  		return types.Int32
    56  	} else {
    57  		return s.ChildExpressions[0].Type()
    58  	}
    59  }
    60  
    61  // CollationCoercibility implements the interface sql.CollationCoercible.
    62  func (*SRID) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    63  	return sql.Collation_binary, 5
    64  }
    65  
    66  func (s *SRID) String() string {
    67  	var args = make([]string, len(s.ChildExpressions))
    68  	for i, arg := range s.ChildExpressions {
    69  		args[i] = arg.String()
    70  	}
    71  	return fmt.Sprintf("ST_SRID(%s)", strings.Join(args, ","))
    72  }
    73  
    74  // WithChildren implements the Expression interface.
    75  func (s *SRID) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    76  	return NewSRID(children...)
    77  }
    78  
    79  // Eval implements the sql.Expression interface.
    80  func (s *SRID) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    81  	g, err := s.ChildExpressions[0].Eval(ctx, row)
    82  	if err != nil {
    83  		return nil, err
    84  	}
    85  
    86  	if g == nil {
    87  		return nil, nil
    88  	}
    89  
    90  	// If just one argument, return SRID
    91  	if len(s.ChildExpressions) == 1 {
    92  		switch g := g.(type) {
    93  		case types.GeometryValue:
    94  			return g.GetSRID(), nil
    95  		default:
    96  			return nil, sql.ErrIllegalGISValue.New(g)
    97  		}
    98  	}
    99  
   100  	v, err := s.ChildExpressions[1].Eval(ctx, row)
   101  	if err != nil {
   102  		return nil, err
   103  	}
   104  
   105  	if v == nil {
   106  		return nil, nil
   107  	}
   108  
   109  	val, _, err := types.Int64.Convert(v)
   110  	if err != nil {
   111  		return nil, err
   112  	}
   113  
   114  	if err = types.ValidateSRID(int(val.(int64)), s.FunctionName()); err != nil {
   115  		return nil, err
   116  	}
   117  	srid := uint32(val.(int64))
   118  
   119  	// Create new geometry object with matching SRID
   120  	switch g := g.(type) {
   121  	case types.GeometryValue:
   122  		return g.SetSRID(srid), nil
   123  	default:
   124  		return nil, sql.ErrIllegalGISValue.New(g)
   125  	}
   126  }