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tablealias.go
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tablealias.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 (
"reflect"
opentracing "github.com/opentracing/opentracing-go"
"github.com/Sndav/go-mysql-server/sql"
)
// TableAlias is a node that acts as a table with a given name.
type TableAlias struct {
*UnaryNode
name string
}
// NewTableAlias returns a new Table alias node.
func NewTableAlias(name string, node sql.Node) *TableAlias {
return &TableAlias{UnaryNode: &UnaryNode{Child: node}, name: name}
}
// Name implements the Nameable interface.
func (t *TableAlias) Name() string {
return t.name
}
// Schema implements the Node interface. TableAlias alters the schema of its child element to rename the source of
// columns to the alias.
func (t *TableAlias) Schema() sql.Schema {
childSchema := t.Child.Schema()
copy := make(sql.Schema, len(childSchema))
for i, col := range childSchema {
colCopy := *col
colCopy.Source = t.name
copy[i] = &colCopy
}
return copy
}
// WithChildren implements the Node interface.
func (t *TableAlias) WithChildren(children ...sql.Node) (sql.Node, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(t, len(children), 1)
}
return NewTableAlias(t.name, children[0]), nil
}
// RowIter implements the Node interface.
func (t *TableAlias) RowIter(ctx *sql.Context, row sql.Row) (sql.RowIter, error) {
var table string
if tbl, ok := t.Child.(sql.Nameable); ok {
table = tbl.Name()
} else {
table = reflect.TypeOf(t.Child).String()
}
span, ctx := ctx.Span("sql.TableAlias", opentracing.Tag{Key: "table", Value: table})
iter, err := t.Child.RowIter(ctx, row)
if err != nil {
span.Finish()
return nil, err
}
return sql.NewSpanIter(span, iter), nil
}
func (t TableAlias) String() string {
pr := sql.NewTreePrinter()
_ = pr.WriteNode("TableAlias(%s)", t.name)
_ = pr.WriteChildren(t.Child.String())
return pr.String()
}
func (t TableAlias) DebugString() string {
pr := sql.NewTreePrinter()
_ = pr.WriteNode("TableAlias(%s)", t.name)
_ = pr.WriteChildren(sql.DebugString(t.Child))
return pr.String()
}
func (t TableAlias) WithName(name string) *TableAlias {
t.name = name
return &t
}