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generate.go
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generate.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 plan
import (
"fmt"
"io"
"github.com/Sndav/go-mysql-server/sql"
"github.com/Sndav/go-mysql-server/sql/expression"
)
// Generate will explode rows using a generator.
type Generate struct {
UnaryNode
Column *expression.GetField
}
// NewGenerate creates a new generate node.
func NewGenerate(child sql.Node, col *expression.GetField) *Generate {
return &Generate{UnaryNode{child}, col}
}
// Schema implements the sql.Node interface.
func (g *Generate) Schema() sql.Schema {
s := g.Child.Schema()
col := s[g.Column.Index()]
s[g.Column.Index()] = &sql.Column{
Name: g.Column.Name(),
Type: sql.UnderlyingType(col.Type),
Nullable: col.Nullable,
}
return s
}
// RowIter implements the sql.Node interface.
func (g *Generate) RowIter(ctx *sql.Context, row sql.Row) (sql.RowIter, error) {
span, ctx := ctx.Span("plan.Generate")
childIter, err := g.Child.RowIter(ctx, nil)
if err != nil {
return nil, err
}
return sql.NewSpanIter(span, &generateIter{
child: childIter,
idx: g.Column.Index(),
}), nil
}
// Expressions implements the Expressioner interface.
func (g *Generate) Expressions() []sql.Expression { return []sql.Expression{g.Column} }
// WithChildren implements the Node interface.
func (g *Generate) WithChildren(children ...sql.Node) (sql.Node, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(g, len(children), 1)
}
return NewGenerate(children[0], g.Column), nil
}
// WithExpressions implements the Expressioner interface.
func (g *Generate) WithExpressions(exprs ...sql.Expression) (sql.Node, error) {
if len(exprs) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(g, len(exprs), 1)
}
gf, ok := exprs[0].(*expression.GetField)
if !ok {
return nil, fmt.Errorf("Generate expects child to be expression.GetField, but is %T", exprs[0])
}
return NewGenerate(g.Child, gf), nil
}
func (g *Generate) String() string {
tp := sql.NewTreePrinter()
_ = tp.WriteNode("Generate(%s)", g.Column)
_ = tp.WriteChildren(g.Child.String())
return tp.String()
}
type generateIter struct {
child sql.RowIter
idx int
gen sql.Generator
row sql.Row
}
func (i *generateIter) Next() (sql.Row, error) {
for {
if i.gen == nil {
var err error
i.row, err = i.child.Next()
if err != nil {
return nil, err
}
i.gen, err = sql.ToGenerator(i.row[i.idx])
if err != nil {
return nil, err
}
}
val, err := i.gen.Next()
if err != nil {
if err == io.EOF {
if err := i.gen.Close(); err != nil {
return nil, err
}
i.gen = nil
continue
}
return nil, err
}
var row = make(sql.Row, len(i.row))
copy(row, i.row)
row[i.idx] = val
return row, nil
}
}
func (i *generateIter) Close(ctx *sql.Context) error {
if i.gen != nil {
if err := i.gen.Close(); err != nil {
_ = i.child.Close(ctx)
return err
}
}
return i.child.Close(ctx)
}