/
st_dimension.go
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/
st_dimension.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package spatial
import (
"fmt"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/expression"
"github.com/dolthub/go-mysql-server/sql/types"
)
// Dimension is a function that converts a spatial type into WKT format (alias for AsText)
type Dimension struct {
expression.UnaryExpression
}
var _ sql.FunctionExpression = (*Dimension)(nil)
var _ sql.CollationCoercible = (*Dimension)(nil)
// NewDimension creates a new point expression.
func NewDimension(e sql.Expression) sql.Expression {
return &Dimension{expression.UnaryExpression{Child: e}}
}
// FunctionName implements sql.FunctionExpression
func (p *Dimension) FunctionName() string {
return "st_dimension"
}
// Description implements sql.FunctionExpression
func (p *Dimension) Description() string {
return "returns the dimension of the geometry given."
}
// IsNullable implements the sql.Expression interface.
func (p *Dimension) IsNullable() bool {
return p.Child.IsNullable()
}
// Type implements the sql.Expression interface.
func (p *Dimension) Type() sql.Type {
return types.Int32
}
// CollationCoercibility implements the interface sql.CollationCoercible.
func (*Dimension) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
return sql.Collation_binary, 5
}
func (p *Dimension) String() string {
return fmt.Sprintf("%s(%s)", p.FunctionName(), p.Child.String())
}
// WithChildren implements the Expression interface.
func (p *Dimension) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(p, len(children), 1)
}
return NewDimension(children[0]), nil
}
func FindDimension(g types.GeometryValue) interface{} {
switch v := g.(type) {
case types.Point, types.MultiPoint:
return 0
case types.LineString, types.MultiLineString:
return 1
case types.Polygon, types.MultiPolygon:
return 2
case types.GeomColl:
if len(v.Geoms) == 0 {
return nil
}
maxDim := 0
for _, geom := range v.Geoms {
dim := FindDimension(geom)
if dim == nil {
return nil
}
if dim.(int) > maxDim {
maxDim = dim.(int)
}
}
return maxDim
default:
return nil
}
}
// Eval implements the sql.Expression interface.
func (p *Dimension) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
// Evaluate child
val, err := p.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
// Return nil if geometry is nil
if val == nil {
return nil, nil
}
// Expect one of the geometry types
switch v := val.(type) {
case types.GeometryValue:
return FindDimension(v), nil
default:
return nil, sql.ErrInvalidGISData.New("ST_DIMENSION")
}
}