Golang Schema.GetIndex方法代碼示例

func makeUsedList(usedCols []*expression.Column, schema expression.Schema) []bool {
	used := make([]bool, len(schema))
	for _, col := range usedCols {
		idx := schema.GetIndex(col)
		used[idx] = true
	}
	return used
}

func initColumnIndexInExpr(expr expression.Expression, schema expression.Schema) {
	switch assign := expr; assign.(type) {
	case (*expression.Column):
		assign.(*expression.Column).Index = schema.GetIndex(assign.(*expression.Column))
	case (*expression.ScalarFunction):
		for i, args := 0, assign.(*expression.ScalarFunction).Args; i < len(args); i++ {
			initColumnIndexInExpr(args[i], schema)
		}
	}
}

func getUsedList(usedCols []*expression.Column, schema expression.Schema) []bool {
	used := make([]bool, len(schema))
	for _, col := range usedCols {
		idx := schema.GetIndex(col)
		if idx == -1 {
			log.Errorf("Can't find column %s from schema %s.", col, schema)
		}
		used[idx] = true
	}
	return used
}

// columnSubstitute substitutes the columns in filter to expressions in select fields.
// e.g. select * from (select b as a from t) k where a < 10 => select * from (select b as a from t where b < 10) k.
func columnSubstitute(expr expression.Expression, schema expression.Schema, newExprs []expression.Expression) expression.Expression {
	switch v := expr.(type) {
	case *expression.Column:
		id := schema.GetIndex(v)
		return newExprs[id]
	case *expression.ScalarFunction:
		for i, arg := range v.Args {
			v.Args[i] = columnSubstitute(arg, schema, newExprs)
		}
	}
	return expr
}

// columnSubstitute substitutes the columns in filter to expressions in select fields.
// e.g. select * from (select b as a from t) k where a < 10 => select * from (select b as a from t where b < 10) k.
func columnSubstitute(expr expression.Expression, schema expression.Schema, newExprs []expression.Expression) expression.Expression {
	switch v := expr.(type) {
	case *expression.Column:
		id := schema.GetIndex(v)
		if id == -1 {
			log.Errorf("Can't find columns %s in schema %s", v.ToString(), schema.ToString())
		}
		return newExprs[id]
	case *expression.ScalarFunction:
		for i, arg := range v.Args {
			v.Args[i] = columnSubstitute(arg, schema, newExprs)
		}
	}
	return expr
}

// replaceColsInPropBySchema replaces the columns in original prop with the columns in schema.
func replaceColsInPropBySchema(prop *requiredProperty, schema expression.Schema) *requiredProperty {
	newProps := make([]*columnProp, 0, len(prop.props))
	for _, p := range prop.props {
		idx := schema.GetIndex(p.col)
		if idx == -1 {
			log.Errorf("Can't find column %s in schema", p.col)
		}
		newProps = append(newProps, &columnProp{col: schema[idx], desc: p.desc})
	}
	return &requiredProperty{
		props:      newProps,
		sortKeyLen: prop.sortKeyLen,
		limit:      prop.limit,
	}
}

// getAggFuncChildIdx gets which children it belongs to, 0 stands for left, 1 stands for right, -1 stands for both.
func (a *aggPushDownSolver) getAggFuncChildIdx(aggFunc expression.AggregationFunction, schema expression.Schema) int {
	fromLeft, fromRight := false, false
	var cols []*expression.Column
	for _, arg := range aggFunc.GetArgs() {
		cols = append(cols, expression.ExtractColumns(arg)...)
	}
	for _, col := range cols {
		if schema.GetIndex(col) != -1 {
			fromLeft = true
		} else {
			fromRight = true
		}
	}
	if fromLeft && fromRight {
		return -1
	} else if fromLeft {
		return 0
	}
	return 1
}

// calculateResultOfExpression set inner table columns in a expression as null and calculate the finally result of the scalar function.
func calculateResultOfExpression(schema expression.Schema, expr expression.Expression) (expression.Expression, error) {
	switch x := expr.(type) {
	case *expression.ScalarFunction:
		var err error
		args := make([]expression.Expression, len(x.Args))
		for i, arg := range x.Args {
			args[i], err = calculateResultOfExpression(schema, arg)
		}
		if err != nil {
			return nil, errors.Trace(err)
		}
		return expression.NewFunction(x.FuncName.L, types.NewFieldType(mysql.TypeTiny), args...)
	case *expression.Column:
		if schema.GetIndex(x) == -1 {
			return x, nil
		}
		constant := &expression.Constant{Value: types.Datum{}}
		constant.Value.SetNull()
		return constant, nil
	default:
		return x.DeepCopy(), nil
	}
}