forked from pingcap/tidb
/
expression.go
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/
expression.go
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// Copyright 2016 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package expression
import (
"bytes"
"encoding/json"
"fmt"
"github.com/juju/errors"
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/terror"
"github.com/pingcap/tidb/util/codec"
"github.com/pingcap/tidb/util/types"
)
// Error instances.
var (
errInvalidOperation = terror.ClassExpression.New(codeInvalidOperation, "invalid operation")
errIncorrectParameterCount = terror.ClassExpression.New(codeIncorrectParameterCount, "Incorrect parameter count in the call to native function '%s'")
errFunctionNotExists = terror.ClassExpression.New(codeFunctionNotExists, "FUNCTION %s does not exist")
)
// Error codes.
const (
codeInvalidOperation terror.ErrCode = 1
codeIncorrectParameterCount = 1582
codeFunctionNotExists = 1305
)
// EvalAstExpr evaluates ast expression directly.
var EvalAstExpr func(expr ast.ExprNode, ctx context.Context) (types.Datum, error)
// Expression represents all scalar expression in SQL.
type Expression interface {
fmt.Stringer
json.Marshaler
// Eval evaluates an expression through a row.
Eval(row []types.Datum) (types.Datum, error)
// EvalInt returns the int64 representation of expression.
EvalInt(row []types.Datum, sc *variable.StatementContext) (val int64, isNull bool, err error)
// EvalReal returns the float64 representation of expression.
EvalReal(row []types.Datum, sc *variable.StatementContext) (val float64, isNull bool, err error)
// EvalString returns the string representation of expression.
EvalString(row []types.Datum, sc *variable.StatementContext) (val string, isNull bool, err error)
// EvalDecimal returns the decimal representation of expression.
EvalDecimal(row []types.Datum, sc *variable.StatementContext) (val *types.MyDecimal, isNull bool, err error)
// GetType gets the type that the expression returns.
GetType() *types.FieldType
// Clone copies an expression totally.
Clone() Expression
// HashCode create the hashcode for expression
HashCode() []byte
// Equal checks whether two expressions are equal.
Equal(e Expression, ctx context.Context) bool
// IsCorrelated checks if this expression has correlated key.
IsCorrelated() bool
// Decorrelate try to decorrelate the expression by schema.
Decorrelate(schema *Schema) Expression
// ResolveIndices resolves indices by the given schema.
ResolveIndices(schema *Schema)
}
// CNFExprs stands for a CNF expression.
type CNFExprs []Expression
// Clone clones itself.
func (e CNFExprs) Clone() CNFExprs {
cnf := make(CNFExprs, 0, len(e))
for _, expr := range e {
cnf = append(cnf, expr.Clone())
}
return cnf
}
// EvalBool evaluates expression list to a boolean value.
func EvalBool(exprList CNFExprs, row []types.Datum, ctx context.Context) (bool, error) {
for _, expr := range exprList {
data, err := expr.Eval(row)
if err != nil {
return false, errors.Trace(err)
}
if data.IsNull() {
return false, nil
}
i, err := data.ToBool(ctx.GetSessionVars().StmtCtx)
if err != nil {
return false, errors.Trace(err)
}
if i == 0 {
return false, nil
}
}
return true, nil
}
// evalExprToInt evaluates `expr` to int type.
func evalExprToInt(expr Expression, row []types.Datum, sc *variable.StatementContext) (res int64, isNull bool, err error) {
val, err := expr.Eval(row)
if val.IsNull() || err != nil {
return 0, val.IsNull(), errors.Trace(err)
}
tc := expr.GetType().ToClass()
if tc == types.ClassInt {
return val.GetInt64(), false, nil
}
res, err = val.ToInt64(sc)
return res, false, errors.Trace(err)
}
// evalExprToReal evaluates `expr` to real type.
func evalExprToReal(expr Expression, row []types.Datum, sc *variable.StatementContext) (res float64, isNull bool, err error) {
val, err := expr.Eval(row)
if val.IsNull() || err != nil {
return 0, val.IsNull(), errors.Trace(err)
}
tc := expr.GetType().ToClass()
if tc == types.ClassReal {
return val.GetFloat64(), false, nil
}
res, err = val.ToFloat64(sc)
return res, false, errors.Trace(err)
}
// evalExprToDecimal evaluates `expr` to decimal type.
func evalExprToDecimal(expr Expression, row []types.Datum, sc *variable.StatementContext) (res *types.MyDecimal, isNull bool, err error) {
val, err := expr.Eval(row)
if val.IsNull() || err != nil {
return nil, val.IsNull(), errors.Trace(err)
}
tc := expr.GetType().ToClass()
if tc == types.ClassDecimal {
return val.GetMysqlDecimal(), false, nil
}
res, err = val.ToDecimal(sc)
return res, false, errors.Trace(err)
}
// evalExprToString evaluates `expr` to string type.
func evalExprToString(expr Expression, row []types.Datum, _ *variable.StatementContext) (res string, isNull bool, err error) {
val, err := expr.Eval(row)
if val.IsNull() || err != nil {
return "", val.IsNull(), errors.Trace(err)
}
tc := expr.GetType().ToClass()
if tc == types.ClassString {
return val.GetString(), false, nil
}
res, err = val.ToString()
return res, false, errors.Trace(err)
}
// One stands for a number 1.
var One = &Constant{
Value: types.NewDatum(1),
RetType: types.NewFieldType(mysql.TypeTiny),
}
// Zero stands for a number 0.
var Zero = &Constant{
Value: types.NewDatum(0),
RetType: types.NewFieldType(mysql.TypeTiny),
}
// Null stands for null constant.
var Null = &Constant{
Value: types.NewDatum(nil),
RetType: types.NewFieldType(mysql.TypeTiny),
}
// Constant stands for a constant value.
type Constant struct {
Value types.Datum
RetType *types.FieldType
}
// String implements fmt.Stringer interface.
func (c *Constant) String() string {
return fmt.Sprintf("%v", c.Value.GetValue())
}
// MarshalJSON implements json.Marshaler interface.
func (c *Constant) MarshalJSON() ([]byte, error) {
buffer := bytes.NewBufferString(fmt.Sprintf("\"%s\"", c))
return buffer.Bytes(), nil
}
// Clone implements Expression interface.
func (c *Constant) Clone() Expression {
con := *c
return &con
}
// GetType implements Expression interface.
func (c *Constant) GetType() *types.FieldType {
return c.RetType
}
// Eval implements Expression interface.
func (c *Constant) Eval(_ []types.Datum) (types.Datum, error) {
return c.Value, nil
}
// EvalInt returns int representation of Constant.
func (c *Constant) EvalInt(_ []types.Datum, sc *variable.StatementContext) (int64, bool, error) {
val, isNull, err := evalExprToInt(c, nil, sc)
return val, isNull, errors.Trace(err)
}
// EvalReal returns real representation of Constant.
func (c *Constant) EvalReal(_ []types.Datum, sc *variable.StatementContext) (float64, bool, error) {
val, isNull, err := evalExprToReal(c, nil, sc)
return val, isNull, errors.Trace(err)
}
// EvalString returns string representation of Constant.
func (c *Constant) EvalString(_ []types.Datum, sc *variable.StatementContext) (string, bool, error) {
val, isNull, err := evalExprToString(c, nil, sc)
return val, isNull, errors.Trace(err)
}
// EvalDecimal returns decimal representation of Constant.
func (c *Constant) EvalDecimal(_ []types.Datum, sc *variable.StatementContext) (*types.MyDecimal, bool, error) {
val, isNull, err := evalExprToDecimal(c, nil, sc)
return val, isNull, errors.Trace(err)
}
// Equal implements Expression interface.
func (c *Constant) Equal(b Expression, ctx context.Context) bool {
y, ok := b.(*Constant)
if !ok {
return false
}
con, err := c.Value.CompareDatum(ctx.GetSessionVars().StmtCtx, y.Value)
if err != nil || con != 0 {
return false
}
return true
}
// IsCorrelated implements Expression interface.
func (c *Constant) IsCorrelated() bool {
return false
}
// Decorrelate implements Expression interface.
func (c *Constant) Decorrelate(_ *Schema) Expression {
return c
}
// HashCode implements Expression interface.
func (c *Constant) HashCode() []byte {
var bytes []byte
bytes, _ = codec.EncodeValue(bytes, c.Value)
return bytes
}
// ResolveIndices implements Expression interface.
func (c *Constant) ResolveIndices(_ *Schema) {
}
// composeConditionWithBinaryOp composes condition with binary operator into a balance deep tree, which benefits a lot for pb decoder/encoder.
func composeConditionWithBinaryOp(ctx context.Context, conditions []Expression, funcName string) Expression {
length := len(conditions)
if length == 0 {
return nil
}
if length == 1 {
return conditions[0]
}
expr, _ := NewFunction(ctx, funcName,
types.NewFieldType(mysql.TypeTiny),
composeConditionWithBinaryOp(ctx, conditions[:length/2], funcName),
composeConditionWithBinaryOp(ctx, conditions[length/2:], funcName))
return expr
}
// ComposeCNFCondition composes CNF items into a balance deep CNF tree, which benefits a lot for pb decoder/encoder.
func ComposeCNFCondition(ctx context.Context, conditions ...Expression) Expression {
return composeConditionWithBinaryOp(ctx, conditions, ast.AndAnd)
}
// ComposeDNFCondition composes DNF items into a balance deep DNF tree.
func ComposeDNFCondition(ctx context.Context, conditions ...Expression) Expression {
return composeConditionWithBinaryOp(ctx, conditions, ast.OrOr)
}
// Assignment represents a set assignment in Update, such as
// Update t set c1 = hex(12), c2 = c3 where c2 = 1
type Assignment struct {
Col *Column
Expr Expression
}
// VarAssignment represents a variable assignment in Set, such as set global a = 1.
type VarAssignment struct {
Name string
Expr Expression
IsDefault bool
IsGlobal bool
IsSystem bool
ExtendValue *Constant
}
// splitNormalFormItems split CNF(conjunctive normal form) like "a and b and c", or DNF(disjunctive normal form) like "a or b or c"
func splitNormalFormItems(onExpr Expression, funcName string) []Expression {
switch v := onExpr.(type) {
case *ScalarFunction:
if v.FuncName.L == funcName {
var ret []Expression
for _, arg := range v.GetArgs() {
ret = append(ret, splitNormalFormItems(arg, funcName)...)
}
return ret
}
}
return []Expression{onExpr}
}
// SplitCNFItems splits CNF items.
// CNF means conjunctive normal form, e.g. "a and b and c".
func SplitCNFItems(onExpr Expression) []Expression {
return splitNormalFormItems(onExpr, ast.AndAnd)
}
// SplitDNFItems splits DNF items.
// DNF means disjunctive normal form, e.g. "a or b or c".
func SplitDNFItems(onExpr Expression) []Expression {
return splitNormalFormItems(onExpr, ast.OrOr)
}
// EvaluateExprWithNull sets columns in schema as null and calculate the final result of the scalar function.
// If the Expression is a non-constant value, it means the result is unknown.
func EvaluateExprWithNull(ctx context.Context, schema *Schema, expr Expression) (Expression, error) {
switch x := expr.(type) {
case *ScalarFunction:
var err error
args := make([]Expression, len(x.GetArgs()))
for i, arg := range x.GetArgs() {
args[i], err = EvaluateExprWithNull(ctx, schema, arg)
if err != nil {
return nil, errors.Trace(err)
}
}
newFunc, err := NewFunction(ctx, x.FuncName.L, types.NewFieldType(mysql.TypeTiny), args...)
if err != nil {
return nil, errors.Trace(err)
}
return FoldConstant(newFunc), nil
case *Column:
if !schema.Contains(x) {
return x, nil
}
constant := &Constant{Value: types.Datum{}, RetType: types.NewFieldType(mysql.TypeNull)}
return constant, nil
default:
return x.Clone(), nil
}
}
// TableInfo2Schema converts table info to schema.
func TableInfo2Schema(tbl *model.TableInfo) *Schema {
cols := ColumnInfos2Columns(tbl.Name, tbl.Columns)
keys := make([]KeyInfo, 0, len(tbl.Indices)+1)
for _, idx := range tbl.Indices {
if !idx.Unique || idx.State != model.StatePublic {
continue
}
ok := true
newKey := make([]*Column, 0, len(idx.Columns))
for _, idxCol := range idx.Columns {
find := false
for i, col := range tbl.Columns {
if idxCol.Name.L == col.Name.L {
if !mysql.HasNotNullFlag(col.Flag) {
break
}
newKey = append(newKey, cols[i])
find = true
break
}
}
if !find {
ok = false
break
}
}
if ok {
keys = append(keys, newKey)
}
}
if tbl.PKIsHandle {
for i, col := range tbl.Columns {
if mysql.HasPriKeyFlag(col.Flag) {
keys = append(keys, KeyInfo{cols[i]})
break
}
}
}
schema := NewSchema(cols...)
schema.SetUniqueKeys(keys)
return schema
}
// ColumnInfos2Columns converts a slice of ColumnInfo to a slice of Column.
func ColumnInfos2Columns(tblName model.CIStr, colInfos []*model.ColumnInfo) []*Column {
columns := make([]*Column, 0, len(colInfos))
for i, col := range colInfos {
newCol := &Column{
ColName: col.Name,
TblName: tblName,
RetType: &col.FieldType,
Position: i,
}
columns = append(columns, newCol)
}
return columns
}
// NewCastFunc creates a new cast function.
func NewCastFunc(tp *types.FieldType, arg Expression, ctx context.Context) *ScalarFunction {
bt := &builtinCastSig{newBaseBuiltinFunc([]Expression{arg}, ctx), tp}
return &ScalarFunction{
FuncName: model.NewCIStr(ast.Cast),
RetType: tp,
Function: bt,
}
}
// NewValuesFunc creates a new values function.
func NewValuesFunc(offset int, retTp *types.FieldType, ctx context.Context) *ScalarFunction {
fc := &valuesFunctionClass{baseFunctionClass{ast.Values, 0, 0}, offset}
bt, _ := fc.getFunction(nil, ctx)
return &ScalarFunction{
FuncName: model.NewCIStr(ast.Values),
RetType: retTp,
Function: bt,
}
}
func init() {
expressionMySQLErrCodes := map[terror.ErrCode]uint16{
codeIncorrectParameterCount: mysql.ErrWrongParamcountToNativeFct,
codeFunctionNotExists: mysql.ErrSpDoesNotExist,
}
terror.ErrClassToMySQLCodes[terror.ClassExpression] = expressionMySQLErrCodes
}