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/*
Copyright 2017 Google 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 sqlparser
import (
"fmt"
"github.com/xwb1989/sqlparser/dependency/sqltypes"
"github.com/xwb1989/sqlparser/dependency/querypb"
)
// Normalize changes the statement to use bind values, and
// updates the bind vars to those values. The supplied prefix
// is used to generate the bind var names. The function ensures
// that there are no collisions with existing bind vars.
// Within Select constructs, bind vars are deduped. This allows
// us to identify vindex equality. Otherwise, every value is
// treated as distinct.
func Normalize(stmt Statement, bindVars map[string]*querypb.BindVariable, prefix string) {
nz := newNormalizer(stmt, bindVars, prefix)
_ = Walk(nz.WalkStatement, stmt)
}
type normalizer struct {
stmt Statement
bindVars map[string]*querypb.BindVariable
prefix string
reserved map[string]struct{}
counter int
vals map[string]string
}
func newNormalizer(stmt Statement, bindVars map[string]*querypb.BindVariable, prefix string) *normalizer {
return &normalizer{
stmt: stmt,
bindVars: bindVars,
prefix: prefix,
reserved: GetBindvars(stmt),
counter: 1,
vals: make(map[string]string),
}
}
// WalkStatement is the top level walk function.
// If it encounters a Select, it switches to a mode
// where variables are deduped.
func (nz *normalizer) WalkStatement(node SQLNode) (bool, error) {
switch node := node.(type) {
case *Select:
_ = Walk(nz.WalkSelect, node)
// Don't continue
return false, nil
case *SQLVal:
nz.convertSQLVal(node)
case *ComparisonExpr:
nz.convertComparison(node)
}
return true, nil
}
// WalkSelect normalizes the AST in Select mode.
func (nz *normalizer) WalkSelect(node SQLNode) (bool, error) {
switch node := node.(type) {
case *SQLVal:
nz.convertSQLValDedup(node)
case *ComparisonExpr:
nz.convertComparison(node)
}
return true, nil
}
func (nz *normalizer) convertSQLValDedup(node *SQLVal) {
// If value is too long, don't dedup.
// Such values are most likely not for vindexes.
// We save a lot of CPU because we avoid building
// the key for them.
if len(node.Val) > 256 {
nz.convertSQLVal(node)
return
}
// Make the bindvar
bval := nz.sqlToBindvar(node)
if bval == nil {
return
}
// Check if there's a bindvar for that value already.
var key string
if bval.Type == sqltypes.VarBinary {
// Prefixing strings with "'" ensures that a string
// and number that have the same representation don't
// collide.
key = "'" + string(node.Val)
} else {
key = string(node.Val)
}
bvname, ok := nz.vals[key]
if !ok {
// If there's no such bindvar, make a new one.
bvname = nz.newName()
nz.vals[key] = bvname
nz.bindVars[bvname] = bval
}
// Modify the AST node to a bindvar.
node.Type = ValArg
node.Val = append([]byte(":"), bvname...)
}
// convertSQLVal converts an SQLVal without the dedup.
func (nz *normalizer) convertSQLVal(node *SQLVal) {
bval := nz.sqlToBindvar(node)
if bval == nil {
return
}
bvname := nz.newName()
nz.bindVars[bvname] = bval
node.Type = ValArg
node.Val = append([]byte(":"), bvname...)
}
// convertComparison attempts to convert IN clauses to
// use the list bind var construct. If it fails, it returns
// with no change made. The walk function will then continue
// and iterate on converting each individual value into separate
// bind vars.
func (nz *normalizer) convertComparison(node *ComparisonExpr) {
if node.Operator != InStr && node.Operator != NotInStr {
return
}
tupleVals, ok := node.Right.(ValTuple)
if !ok {
return
}
// The RHS is a tuple of values.
// Make a list bindvar.
bvals := &querypb.BindVariable{
Type: querypb.Type_TUPLE,
}
for _, val := range tupleVals {
bval := nz.sqlToBindvar(val)
if bval == nil {
return
}
bvals.Values = append(bvals.Values, &querypb.Value{
Type: bval.Type,
Value: bval.Value,
})
}
bvname := nz.newName()
nz.bindVars[bvname] = bvals
// Modify RHS to be a list bindvar.
node.Right = ListArg(append([]byte("::"), bvname...))
}
func (nz *normalizer) sqlToBindvar(node SQLNode) *querypb.BindVariable {
if node, ok := node.(*SQLVal); ok {
var v sqltypes.Value
var err error
switch node.Type {
case StrVal:
v, err = sqltypes.NewValue(sqltypes.VarBinary, node.Val)
case IntVal:
v, err = sqltypes.NewValue(sqltypes.Int64, node.Val)
case FloatVal:
v, err = sqltypes.NewValue(sqltypes.Float64, node.Val)
default:
return nil
}
if err != nil {
return nil
}
return sqltypes.ValueBindVariable(v)
}
return nil
}
func (nz *normalizer) newName() string {
for {
newName := fmt.Sprintf("%s%d", nz.prefix, nz.counter)
if _, ok := nz.reserved[newName]; !ok {
nz.reserved[newName] = struct{}{}
return newName
}
nz.counter++
}
}
// GetBindvars returns a map of the bind vars referenced in the statement.
// TODO(sougou); This function gets called again from vtgate/planbuilder.
// Ideally, this should be done only once.
func GetBindvars(stmt Statement) map[string]struct{} {
bindvars := make(map[string]struct{})
_ = Walk(func(node SQLNode) (kontinue bool, err error) {
switch node := node.(type) {
case *SQLVal:
if node.Type == ValArg {
bindvars[string(node.Val[1:])] = struct{}{}
}
case ListArg:
bindvars[string(node[2:])] = struct{}{}
}
return true, nil
}, stmt)
return bindvars
}