forked from src-d/go-mysql-server
/
project.go
138 lines (118 loc) · 3.08 KB
/
project.go
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package plan
import (
"strings"
opentracing "github.com/opentracing/opentracing-go"
"github.com/xsec-lab/go-mysql-server/sql"
)
// Project is a projection of certain expression from the children node.
type Project struct {
UnaryNode
// Expression projected.
Projections []sql.Expression
}
// NewProject creates a new projection.
func NewProject(expressions []sql.Expression, child sql.Node) *Project {
return &Project{
UnaryNode: UnaryNode{child},
Projections: expressions,
}
}
// Schema implements the Node interface.
func (p *Project) Schema() sql.Schema {
var s = make(sql.Schema, len(p.Projections))
for i, e := range p.Projections {
var name string
if n, ok := e.(sql.Nameable); ok {
name = n.Name()
} else {
name = e.String()
}
var table string
if t, ok := e.(sql.Tableable); ok {
table = t.Table()
}
s[i] = &sql.Column{
Name: name,
Type: e.Type(),
Nullable: e.IsNullable(),
Source: table,
}
}
return s
}
// Resolved implements the Resolvable interface.
func (p *Project) Resolved() bool {
return p.UnaryNode.Child.Resolved() &&
expressionsResolved(p.Projections...)
}
// RowIter implements the Node interface.
func (p *Project) RowIter(ctx *sql.Context) (sql.RowIter, error) {
span, ctx := ctx.Span("plan.Project", opentracing.Tag{
Key: "projections",
Value: len(p.Projections),
})
i, err := p.Child.RowIter(ctx)
if err != nil {
span.Finish()
return nil, err
}
return sql.NewSpanIter(span, &iter{p, i, ctx}), nil
}
func (p *Project) String() string {
pr := sql.NewTreePrinter()
var exprs = make([]string, len(p.Projections))
for i, expr := range p.Projections {
exprs[i] = expr.String()
}
_ = pr.WriteNode("Project(%s)", strings.Join(exprs, ", "))
_ = pr.WriteChildren(p.Child.String())
return pr.String()
}
// Expressions implements the Expressioner interface.
func (p *Project) Expressions() []sql.Expression {
return p.Projections
}
// WithChildren implements the Node interface.
func (p *Project) WithChildren(children ...sql.Node) (sql.Node, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(p, len(children), 1)
}
return NewProject(p.Projections, children[0]), nil
}
// WithExpressions implements the Expressioner interface.
func (p *Project) WithExpressions(exprs ...sql.Expression) (sql.Node, error) {
if len(exprs) != len(p.Projections) {
return nil, sql.ErrInvalidChildrenNumber.New(p, len(exprs), len(p.Projections))
}
return NewProject(exprs, p.Child), nil
}
type iter struct {
p *Project
childIter sql.RowIter
ctx *sql.Context
}
func (i *iter) Next() (sql.Row, error) {
childRow, err := i.childIter.Next()
if err != nil {
return nil, err
}
return filterRow(i.ctx, i.p.Projections, childRow)
}
func (i *iter) Close() error {
return i.childIter.Close()
}
func filterRow(
s *sql.Context,
expressions []sql.Expression,
row sql.Row,
) (sql.Row, error) {
var fields []interface{}
for _, expr := range expressions {
f, err := expr.Eval(s, row)
if err != nil {
return nil, err
}
fields = append(fields, f)
}
return sql.NewRow(fields...), nil
}