/
channel_row_source.go
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/
channel_row_source.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 mvdata
import (
"fmt"
"io"
"github.com/dolthub/go-mysql-server/sql"
)
// ChannelRowSource is a sql.Node that wraps a channel as a sql.RowIter.
type ChannelRowSource struct {
schema sql.Schema
rowChannel chan sql.Row
}
// NewChannelRowSource returns a ChannelRowSource object.
func NewChannelRowSource(schema sql.Schema, rowChannel chan sql.Row) *ChannelRowSource {
return &ChannelRowSource{schema: schema, rowChannel: rowChannel}
}
var _ sql.Node = (*ChannelRowSource)(nil)
// Resolved implements the sql.Node interface.
func (c *ChannelRowSource) Resolved() bool {
return true
}
// String implements the sql.Node interface.
func (c *ChannelRowSource) String() string {
return fmt.Sprintf("ChannelRowSource()")
}
// Schema implements the sql.Node interface.
func (c *ChannelRowSource) Schema() sql.Schema {
return c.schema
}
// Children implements the sql.Node interface.
func (c *ChannelRowSource) Children() []sql.Node {
return nil
}
// RowIter implements the sql.Node interface.
func (c *ChannelRowSource) RowIter(ctx *sql.Context, row sql.Row) (sql.RowIter, error) {
return &channelRowIter{
rowChannel: c.rowChannel,
}, nil
}
// WithChildren implements the sql.Node interface.
func (c *ChannelRowSource) WithChildren(children ...sql.Node) (sql.Node, error) {
if len(children) != 0 {
return nil, sql.ErrInvalidChildrenNumber.New(c, len(children), 0)
}
return c, nil
}
// CheckPrivileges implements the sql.Node interface.
func (c *ChannelRowSource) CheckPrivileges(ctx *sql.Context, opChecker sql.PrivilegedOperationChecker) bool {
return true
}
// channelRowIter wraps the channel under the sql.RowIter interface
type channelRowIter struct {
rowChannel chan sql.Row
}
var _ sql.RowIter = (*channelRowIter)(nil)
// Next implements the sql.RowIter interface.
func (c *channelRowIter) Next(ctx *sql.Context) (sql.Row, error) {
for r := range c.rowChannel {
select {
case <-ctx.Done():
return nil, io.EOF
default:
return r, nil
}
}
return nil, io.EOF
}
// Close implements the sql.RowIter interface.
func (c *channelRowIter) Close(context *sql.Context) error {
return nil
}