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query_gen.go
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query_gen.go
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// Copyright 2014, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package planbuilder
import (
"fmt"
"github.com/youtube/vitess/go/vt/schema"
"github.com/youtube/vitess/go/vt/sqlparser"
)
// GenerateFullQuery generates the full query from the ast.
func GenerateFullQuery(statement sqlparser.Statement) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
statement.Format(buf)
return buf.ParsedQuery()
}
// GenerateFieldQuery generates a query to just fetch the field info
// by adding impossible where clauses as needed.
func GenerateFieldQuery(statement sqlparser.Statement) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(FormatImpossible)
buf.Myprintf("%v", statement)
if buf.HasBindVars() {
return nil
}
return buf.ParsedQuery()
}
// FormatImpossible is a callback function used by TrackedBuffer
// to generate a modified version of the query where all selects
// have impossible where clauses. It overrides a few node types
// and passes the rest down to the default FormatNode.
func FormatImpossible(buf *sqlparser.TrackedBuffer, node sqlparser.SQLNode) {
switch node := node.(type) {
case *sqlparser.Select:
buf.Myprintf("select %v from %v where 1 != 1", node.SelectExprs, node.From)
case *sqlparser.JoinTableExpr:
if node.Join == sqlparser.AST_LEFT_JOIN || node.Join == sqlparser.AST_RIGHT_JOIN {
// ON clause is requried
buf.Myprintf("%v %s %v on 1 != 1", node.LeftExpr, node.Join, node.RightExpr)
} else {
buf.Myprintf("%v %s %v", node.LeftExpr, node.Join, node.RightExpr)
}
default:
node.Format(buf)
}
}
// GenerateSelectLimitQuery generates a select query with a limit clause.
func GenerateSelectLimitQuery(selStmt sqlparser.SelectStatement) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
sel, ok := selStmt.(*sqlparser.Select)
if ok {
limit := sel.Limit
if limit == nil {
sel.Limit = execLimit
defer func() {
sel.Limit = nil
}()
}
}
buf.Myprintf("%v", selStmt)
return buf.ParsedQuery()
}
// GenerateSelectOuterQuery generates the outer query for dmls.
func GenerateSelectOuterQuery(sel *sqlparser.Select, tableInfo *schema.Table) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
fmt.Fprintf(buf, "select ")
writeColumnList(buf, tableInfo.Columns)
buf.Myprintf(" from %v where %a", sel.From, ":#pk")
return buf.ParsedQuery()
}
// GenerateInsertOuterQuery generates the outer query for inserts.
func GenerateInsertOuterQuery(ins *sqlparser.Insert) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
buf.Myprintf("insert %v%sinto %v%v values %a",
ins.Comments,
ins.Ignore,
ins.Table,
ins.Columns,
":#values",
)
return buf.ParsedQuery()
}
// GenerateUpdateOuterQuery generates the outer query for updates.
func GenerateUpdateOuterQuery(upd *sqlparser.Update) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
buf.Myprintf("update %v%v set %v where %a", upd.Comments, upd.Table, upd.Exprs, ":#pk")
return buf.ParsedQuery()
}
// GenerateDeleteOuterQuery generates the outer query for deletes.
func GenerateDeleteOuterQuery(del *sqlparser.Delete) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
buf.Myprintf("delete %vfrom %v where %a", del.Comments, del.Table, ":#pk")
return buf.ParsedQuery()
}
// GenerateSelectSubquery generates the subquery for selects.
func GenerateSelectSubquery(sel *sqlparser.Select, tableInfo *schema.Table, index string) *sqlparser.ParsedQuery {
hint := &sqlparser.IndexHints{Type: sqlparser.AST_USE, Indexes: []sqlparser.SQLName{sqlparser.SQLName(index)}}
tableExpr := sel.From[0].(*sqlparser.AliasedTableExpr)
savedHint := tableExpr.Hints
tableExpr.Hints = hint
defer func() {
tableExpr.Hints = savedHint
}()
return GenerateSubquery(
tableInfo.Indexes[0].Columns,
tableExpr,
sel.Where,
sel.OrderBy,
sel.Limit,
false,
)
}
// GenerateUpdateSubquery generates the subquery for updats.
func GenerateUpdateSubquery(upd *sqlparser.Update, tableInfo *schema.Table) *sqlparser.ParsedQuery {
return GenerateSubquery(
tableInfo.Indexes[0].Columns,
&sqlparser.AliasedTableExpr{Expr: upd.Table},
upd.Where,
upd.OrderBy,
upd.Limit,
true,
)
}
// GenerateDeleteSubquery generates the subquery for deletes.
func GenerateDeleteSubquery(del *sqlparser.Delete, tableInfo *schema.Table) *sqlparser.ParsedQuery {
return GenerateSubquery(
tableInfo.Indexes[0].Columns,
&sqlparser.AliasedTableExpr{Expr: del.Table},
del.Where,
del.OrderBy,
del.Limit,
true,
)
}
// GenerateSubquery generates a subquery based on the input parameters.
func GenerateSubquery(columns []string, table *sqlparser.AliasedTableExpr, where *sqlparser.Where, order sqlparser.OrderBy, limit *sqlparser.Limit, forUpdate bool) *sqlparser.ParsedQuery {
buf := sqlparser.NewTrackedBuffer(nil)
if limit == nil {
limit = execLimit
}
fmt.Fprintf(buf, "select ")
i := 0
for i = 0; i < len(columns)-1; i++ {
fmt.Fprintf(buf, "%s, ", columns[i])
}
fmt.Fprintf(buf, "%s", columns[i])
buf.Myprintf(" from %v%v%v%v", table, where, order, limit)
if forUpdate {
buf.Myprintf(sqlparser.AST_FOR_UPDATE)
}
return buf.ParsedQuery()
}
func writeColumnList(buf *sqlparser.TrackedBuffer, columns []schema.TableColumn) {
i := 0
for i = 0; i < len(columns)-1; i++ {
fmt.Fprintf(buf, "%s, ", columns[i].Name)
}
fmt.Fprintf(buf, "%s", columns[i].Name)
}