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with.go
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with.go
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package exclause
import (
"gorm.io/gorm"
"gorm.io/gorm/clause"
)
// With with clause
//
// // examples
// // WITH `cte` AS (SELECT * FROM `users`) SELECT * FROM `cte`
// db.Clauses(exclause.With{CTEs: []exclause.CTE{{Name: "cte", Subquery: clause.Expr{SQL: "SELECT * FROM `users`"}}}}).Table("cte").Scan(&users)
//
// // WITH `cte` AS (SELECT * FROM `users`) SELECT * FROM `cte`
// db.Clauses(exclause.With{CTEs: []exclause.CTE{{Name: "cte", Subquery: exclause.Subquery{DB: db.Table("users")}}}}).Table("cte").Scan(&users)
//
// // WITH `cte` (`id`,`name`) AS (SELECT * FROM `users`) SELECT * FROM `cte`
// db.Clauses(exclause.With{CTEs: []exclause.CTE{{Name: "cte", Columns: []string{"id", "name"}, Subquery: exclause.Subquery{DB: db.Table("users")}}}}).Table("cte").Scan(&users)
//
// // WITH RECURSIVE `cte` AS (SELECT * FROM `users`) SELECT * FROM `cte`
// db.Clauses(exclause.With{Recursive: true, CTEs: []exclause.CTE{{Name: "cte", Subquery: exclause.Subquery{DB: db.Table("users")}}}}).Table("cte").Scan(&users)
type With struct {
Recursive bool
CTEs []CTE
}
// CTE common table expressions
type CTE struct {
Name string
Columns []string
Subquery clause.Expression
}
// Name with clause name
func (with With) Name() string {
return "WITH"
}
// Build build with clause
func (with With) Build(builder clause.Builder) {
if with.Recursive {
builder.WriteString("RECURSIVE ")
}
for index, cte := range with.CTEs {
if index > 0 {
builder.WriteByte(',')
}
cte.Build(builder)
}
}
// Build build CTE
func (cte CTE) Build(builder clause.Builder) {
builder.WriteQuoted(cte.Name)
if len(cte.Columns) > 0 {
builder.WriteString(" (")
for index, column := range cte.Columns {
if index > 0 {
builder.WriteByte(',')
}
builder.WriteQuoted(column)
}
builder.WriteByte(')')
}
builder.WriteString(" AS ")
builder.WriteByte('(')
cte.Subquery.Build(builder)
builder.WriteByte(')')
}
// MergeClause merge With clauses
func (with With) MergeClause(clause *clause.Clause) {
if w, ok := clause.Expression.(With); ok {
if w.Recursive {
with.Recursive = true
}
ctes := make([]CTE, len(w.CTEs)+len(with.CTEs))
copy(ctes, w.CTEs)
copy(ctes[len(w.CTEs):], with.CTEs)
with.CTEs = ctes
}
clause.Expression = with
}
// NewWith is easy to create new With
//
// // examples
// // WITH `cte` AS (SELECT * FROM `users`) SELECT * FROM `cte`
// db.Clauses(exclause.NewWith("cte", "SELECT * FROM `users`")).Table("cte").Scan(&users)
//
// // WITH `cte` AS (SELECT * FROM `users` WHERE `name` = 'WinterYukky') SELECT * FROM `cte`
// db.Clauses(exclause.NewWith("cte", "SELECT * FROM `users` WHERE `name` = ?", "WinterYukky")).Table("cte").Scan(&users)
//
// // WITH `cte` AS (SELECT * FROM `users` WHERE `name` = 'WinterYukky') SELECT * FROM `cte`
// db.Clauses(exclause.NewWith("cte", db.Table("users").Where("`name` = ?", "WinterYukky"))).Table("cte").Scan(&users)
//
// If you need more advanced WITH clause, you can see With struct.
func NewWith(name string, subquery interface{}, args ...interface{}) With {
switch v := subquery.(type) {
case *gorm.DB:
return With{
CTEs: []CTE{
{
Name: name,
Subquery: Subquery{DB: v},
},
},
}
case string:
return With{
CTEs: []CTE{
{
Name: name,
Subquery: clause.Expr{SQL: v, Vars: args},
},
},
}
}
return With{}
}