/
project.go
176 lines (153 loc) · 4.85 KB
/
project.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
// 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 (
"strings"
opentracing "github.com/opentracing/opentracing-go"
"github.com/Ciyfly/FakerMysql/sql"
"github.com/Ciyfly/FakerMysql/sql/expression"
)
// 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 {
s[i] = expression.ExpressionToColumn(e)
}
return s
}
// Resolved implements the Resolvable interface.
func (p *Project) Resolved() bool {
return p.UnaryNode.Child.Resolved() &&
expression.ExpressionsResolved(p.Projections...)
}
// RowIter implements the Node interface.
func (p *Project) RowIter(ctx *sql.Context, row sql.Row) (sql.RowIter, error) {
span, ctx := ctx.Span("plan.Project", opentracing.Tag{
Key: "projections",
Value: len(p.Projections),
})
i, err := p.Child.RowIter(ctx, row)
if err != nil {
span.Finish()
return nil, err
}
return sql.NewSpanIter(span, &iter{
p: p,
childIter: i,
ctx: ctx,
row: row,
}), 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()
}
func (p *Project) DebugString() string {
pr := sql.NewTreePrinter()
var exprs = make([]string, len(p.Projections))
for i, expr := range p.Projections {
exprs[i] = sql.DebugString(expr)
}
_ = pr.WriteNode("Project(%s)", strings.Join(exprs, ", "))
_ = pr.WriteChildren(sql.DebugString(p.Child))
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
row sql.Row
ctx *sql.Context
}
func (i *iter) Next() (sql.Row, error) {
childRow, err := i.childIter.Next()
if err != nil {
return nil, err
}
return ProjectRow(i.ctx, i.p.Projections, childRow)
}
func (i *iter) Close(ctx *sql.Context) error {
return i.childIter.Close(ctx)
}
// ProjectRow evaluates a set of projections.
func ProjectRow(
s *sql.Context,
projections []sql.Expression,
row sql.Row,
) (sql.Row, error) {
var err error
var secondPass []int
var fields sql.Row
for i, expr := range projections {
// Default values that are expressions may reference other fields, thus they must evaluate after all other exprs.
// Also default expressions may not refer to other columns that come after them if they also have a default expr.
// This ensures that all columns referenced by expressions will have already been evaluated.
// Since literals do not reference other columns, they're evaluated on the first pass.
if defaultVal, ok := expr.(*sql.ColumnDefaultValue); ok {
if !defaultVal.IsLiteral() {
fields = append(fields, nil)
secondPass = append(secondPass, i)
continue
}
}
f, err := expr.Eval(s, row)
if err != nil {
return nil, err
}
fields = append(fields, f)
}
for _, index := range secondPass {
fields[index], err = projections[index].Eval(s, fields)
if err != nil {
return nil, err
}
}
return sql.NewRow(fields...), nil
}