github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/spatial/st_dimension.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  
    20  	"github.com/dolthub/go-mysql-server/sql"
    21  	"github.com/dolthub/go-mysql-server/sql/expression"
    22  	"github.com/dolthub/go-mysql-server/sql/types"
    23  )
    24  
    25  // Dimension is a function that converts a spatial type into WKT format (alias for AsText)
    26  type Dimension struct {
    27  	expression.UnaryExpression
    28  }
    29  
    30  var _ sql.FunctionExpression = (*Dimension)(nil)
    31  var _ sql.CollationCoercible = (*Dimension)(nil)
    32  
    33  // NewDimension creates a new point expression.
    34  func NewDimension(e sql.Expression) sql.Expression {
    35  	return &Dimension{expression.UnaryExpression{Child: e}}
    36  }
    37  
    38  // FunctionName implements sql.FunctionExpression
    39  func (p *Dimension) FunctionName() string {
    40  	return "st_dimension"
    41  }
    42  
    43  // Description implements sql.FunctionExpression
    44  func (p *Dimension) Description() string {
    45  	return "returns the dimension of the geometry given."
    46  }
    47  
    48  // IsNullable implements the sql.Expression interface.
    49  func (p *Dimension) IsNullable() bool {
    50  	return p.Child.IsNullable()
    51  }
    52  
    53  // Type implements the sql.Expression interface.
    54  func (p *Dimension) Type() sql.Type {
    55  	return types.Int32
    56  }
    57  
    58  // CollationCoercibility implements the interface sql.CollationCoercible.
    59  func (*Dimension) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
    60  	return sql.Collation_binary, 5
    61  }
    62  
    63  func (p *Dimension) String() string {
    64  	return fmt.Sprintf("%s(%s)", p.FunctionName(), p.Child.String())
    65  }
    66  
    67  // WithChildren implements the Expression interface.
    68  func (p *Dimension) WithChildren(children ...sql.Expression) (sql.Expression, error) {
    69  	if len(children) != 1 {
    70  		return nil, sql.ErrInvalidChildrenNumber.New(p, len(children), 1)
    71  	}
    72  	return NewDimension(children[0]), nil
    73  }
    74  
    75  func FindDimension(g types.GeometryValue) interface{} {
    76  	switch v := g.(type) {
    77  	case types.Point, types.MultiPoint:
    78  		return 0
    79  	case types.LineString, types.MultiLineString:
    80  		return 1
    81  	case types.Polygon, types.MultiPolygon:
    82  		return 2
    83  	case types.GeomColl:
    84  		if len(v.Geoms) == 0 {
    85  			return nil
    86  		}
    87  		maxDim := 0
    88  		for _, geom := range v.Geoms {
    89  			dim := FindDimension(geom)
    90  			if dim == nil {
    91  				return nil
    92  			}
    93  			if dim.(int) > maxDim {
    94  				maxDim = dim.(int)
    95  			}
    96  		}
    97  		return maxDim
    98  	default:
    99  		return nil
   100  	}
   101  }
   102  
   103  // Eval implements the sql.Expression interface.
   104  func (p *Dimension) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
   105  	// Evaluate child
   106  	val, err := p.Child.Eval(ctx, row)
   107  	if err != nil {
   108  		return nil, err
   109  	}
   110  
   111  	// Return nil if geometry is nil
   112  	if val == nil {
   113  		return nil, nil
   114  	}
   115  
   116  	// Expect one of the geometry types
   117  	switch v := val.(type) {
   118  	case types.GeometryValue:
   119  		return FindDimension(v), nil
   120  	default:
   121  		return nil, sql.ErrInvalidGISData.New("ST_DIMENSION")
   122  	}
   123  }