77 lines
1.9 KiB
Go
77 lines
1.9 KiB
Go
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// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package evaluator
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import (
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/util/types"
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)
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// See https://dev.mysql.com/doc/refman/5.7/en/control-flow-functions.html#function_if
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func builtinIf(args []interface{}, _ context.Context) (interface{}, error) {
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// if(expr1, expr2, expr3)
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// if expr1 is true, return expr2, otherwise, return expr3
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v1 := args[0]
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v2 := args[1]
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v3 := args[2]
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if v1 == nil {
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return v3, nil
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}
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b, err := types.ToBool(v1)
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if err != nil {
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return nil, err
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}
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// TODO: check return type, must be numeric or string
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if b == 1 {
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return v2, nil
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}
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return v3, nil
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}
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// See https://dev.mysql.com/doc/refman/5.7/en/control-flow-functions.html#function_ifnull
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func builtinIfNull(args []interface{}, _ context.Context) (interface{}, error) {
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// ifnull(expr1, expr2)
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// if expr1 is not null, return expr1, otherwise, return expr2
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v1 := args[0]
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v2 := args[1]
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if v1 != nil {
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return v1, nil
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}
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return v2, nil
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}
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// See https://dev.mysql.com/doc/refman/5.7/en/control-flow-functions.html#function_nullif
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func builtinNullIf(args []interface{}, _ context.Context) (interface{}, error) {
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// nullif(expr1, expr2)
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// returns null if expr1 = expr2 is true, otherwise returns expr1
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v1 := args[0]
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v2 := args[1]
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if v1 == nil || v2 == nil {
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return v1, nil
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}
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if n, err := types.Compare(v1, v2); err != nil || n == 0 {
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return nil, err
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}
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return v1, nil
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}
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