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// Copyright 2017 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 (
"github.com/pingcap/parser/ast"
)
// UnCacheableFunctions stores functions which can not be cached to plan cache.
var UnCacheableFunctions = map[string]struct{}{
ast.Database: {},
ast.CurrentUser: {},
ast.CurrentRole: {},
ast.User: {},
ast.ConnectionID: {},
ast.LastInsertId: {},
ast.Version: {},
ast.Like: {},
}
// unFoldableFunctions stores functions which can not be folded duration constant folding stage.
var unFoldableFunctions = map[string]struct{}{
ast.Sysdate: {},
ast.FoundRows: {},
ast.Rand: {},
ast.UUID: {},
ast.Sleep: {},
ast.RowFunc: {},
ast.Values: {},
ast.SetVar: {},
ast.GetVar: {},
ast.GetParam: {},
ast.Benchmark: {},
ast.DayName: {},
}
// DisableFoldFunctions stores functions which prevent child scope functions from being constant folded.
// Typically, these functions shall also exist in unFoldableFunctions, to stop from being folded when they themselves
// are in child scope of an outer function, and the outer function is recursively folding its children.
var DisableFoldFunctions = map[string]struct{}{
ast.Benchmark: {},
}
// IllegalFunctions4GeneratedColumns stores functions that is illegal for generated columns.
// See https://github.com/mysql/mysql-server/blob/5.7/mysql-test/suite/gcol/inc/gcol_blocked_sql_funcs_main.inc for details
var IllegalFunctions4GeneratedColumns = map[string]struct{}{
ast.ConnectionID: {},
ast.LoadFile: {},
ast.LastInsertId: {},
ast.Rand: {},
ast.UUID: {},
ast.UUIDShort: {},
ast.Curdate: {},
ast.CurrentDate: {},
ast.Curtime: {},
ast.CurrentTime: {},
ast.CurrentTimestamp: {},
ast.LocalTime: {},
ast.LocalTimestamp: {},
ast.Now: {},
ast.UnixTimestamp: {},
ast.UTCDate: {},
ast.UTCTime: {},
ast.UTCTimestamp: {},
ast.Benchmark: {},
ast.CurrentUser: {},
ast.Database: {},
ast.FoundRows: {},
ast.GetLock: {},
ast.IsFreeLock: {},
ast.IsUsedLock: {},
ast.MasterPosWait: {},
ast.NameConst: {},
ast.ReleaseLock: {},
ast.RowCount: {},
ast.Schema: {},
ast.SessionUser: {},
ast.Sleep: {},
ast.Sysdate: {},
ast.SystemUser: {},
ast.User: {},
ast.Values: {},
ast.Encrypt: {},
ast.Version: {},
ast.JSONMerge: {},
ast.SetVar: {},
ast.GetVar: {},
ast.ReleaseAllLocks: {},
}
// DeferredFunctions stores non-deterministic functions, which can be deferred only when the plan cache is enabled.
var DeferredFunctions = map[string]struct{}{
ast.Now: {},
ast.CurrentTimestamp: {},
ast.UTCTime: {},
ast.Curtime: {},
ast.CurrentTime: {},
ast.UTCTimestamp: {},
ast.UnixTimestamp: {},
ast.Sysdate: {},
ast.Curdate: {},
ast.CurrentDate: {},
ast.UTCDate: {},
ast.Rand: {},
ast.UUID: {},
}
// inequalFunctions stores functions which cannot be propagated from column equal condition.
var inequalFunctions = map[string]struct{}{
ast.IsNull: {},
}
// mutableEffectsFunctions stores functions which are mutable or have side effects, specifically,
// we cannot remove them from filter even if they have duplicates.
var mutableEffectsFunctions = map[string]struct{}{
// Time related functions in MySQL have various behaviors when executed multiple times in a single SQL,
// for example:
// mysql> select current_timestamp(), sleep(5), current_timestamp();
// +---------------------+----------+---------------------+
// | current_timestamp() | sleep(5) | current_timestamp() |
// +---------------------+----------+---------------------+
// | 2018-12-18 17:55:39 | 0 | 2018-12-18 17:55:39 |
// +---------------------+----------+---------------------+
// while:
// mysql> select sysdate(), sleep(5), sysdate();
// +---------------------+----------+---------------------+
// | sysdate() | sleep(5) | sysdate() |
// +---------------------+----------+---------------------+
// | 2018-12-18 17:57:38 | 0 | 2018-12-18 17:57:43 |
// +---------------------+----------+---------------------+
// for safety consideration, treat them all as mutable.
ast.Now: {},
ast.CurrentTimestamp: {},
ast.UTCTime: {},
ast.Curtime: {},
ast.CurrentTime: {},
ast.UTCTimestamp: {},
ast.UnixTimestamp: {},
ast.Sysdate: {},
ast.Curdate: {},
ast.CurrentDate: {},
ast.UTCDate: {},
ast.Rand: {},
ast.RandomBytes: {},
ast.UUID: {},
ast.UUIDShort: {},
ast.Sleep: {},
ast.SetVar: {},
ast.GetVar: {},
ast.AnyValue: {},
}
// some functions like "get_lock" and "release_lock" currently do NOT have
// right implementations, but may have noop ones(like with any inputs, always return 1)
// if apps really need these "funcs" to run, we offer sys var(tidb_enable_noop_functions) to enable noop usage
var noopFuncs = map[string]struct{}{
ast.GetLock: {},
ast.ReleaseLock: {},
}
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