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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"

"vitess.io/vitess/go/sqltypes"

querypb "vitess.io/vitess/go/vt/proto/query"

)

// 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

}