修复identity 类型字段数据的跳跃（译）
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转自http://www.chinaunix.net
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内容提要
1、引言
2、dbcc object_atts
3、下载'sp_identity' 存储过程
4、使用sp_identity显示使用identity 类型字段的表
5 使用sp_identity显示当前表的 identity 数字
6、使用sp_identity 修改表的 identity数字
1引言
在sybase 中，有一个使用未公开的dbcc 命令 ，即 dbcc object_atts 快速修复identity 跳跃的方法，因为 dbcc
object_atts 比较难于使用,而存储过程 sp_identity 更容易完成你的问题
警告：本文的方法没有出现在sybase 发布的文档中，并且没有被 sybase 支持，使用与否取决定你自己，如果出现问题，不能从
sybase 技术支持那里得到帮助
2、dbcc object_atts
dbcc object_atts 命令提供了 一个访问 OAM 页的后门，在 OMA 中，保存了表的 identity 计数器。
不幸的是，这个命令在文档中几乎没有任何说明，并且很难使用，其语法如下：
dbcc object_atts (table_name, 0, subcommand, [ new_value ] )
第一个参数 ：表名，第二个参数 0，
第三个参数： get ---显示 保存在 OMA 中的 identity 值
或put ---设置 OMA 中的 identity 值，设置的具体数据为 第四个参数数据
第四个参数 ：新设置的数
主要的问题是 dbcc object_atts 显示的数据为 16字节的 16进制字符，你必须自己解释为10进制，并且，如何解释依赖于
identity 列的长度，同样，设置它也是。在实际环境中，很少作为首选。
幸运的是，有一个存储过程 sp_identity 能够处理编码与解码， 并且给出所有含 identity 列的表的情况
下载 'sp_identity'
sp_identity 只支持 11。0 以后版本，下载文件中包含两个版本，一个用于 ASE 11.9/11.5/11.0 的叫
,sp_identity.119.sql，另外一个用于ASE 12.0及以后版本(sp_identity.120.sql)
4、使用sp_identity显示使用identity 类型字段的表
sp_identity 有几个不同的功能，不带任何参数运行，只显示当前数据库中 包含 identity 列的表，
以及最大可能的 identity 跳跃
1>; sp_identity
2>; go
Tables with an identity column in database '':
Owner.Table.Column datatype Maximum Identity Gap
------------------------------- -------------------------------
dbo.invoices.inv_nr numeric(18) 500000000000000 (burn)
dbo.small_gap_tab.a numeric(30) 10 (identity_gap)
dbo.my_table.n numeric(6) 500 (burn)
(burn) 表示 identity列的 一次取数由系统参数"identity burning set factor" 决定，而
(identity_gap) 表示 该表有自定义的identity_gap 属性
5 使用sp_identity显示当前表的 identity 数字
确定当前特定表的 OAM 页的identity 值，必须按照以下三步过程：
首先 打开跟踪标志 3604 (运行 dbcc traceon(3604) )
运行 指定特定表名运行 sp_identity
1>; sp_identity invoices
2>; go
Table = invoices (id=1804533462)
Identity column = a numeric(18)
Max. Identity Gap = 500000000000000
("identity burning set factor" = 5000 = 0.05%)
Reading identity value from OAM page...
object_atts:get:return value=1
0207E20C: 0001c6bf 52634001 00000000 00000000 ....Rc@.........
0207E21C: .
DBCC execution completed. If DBCC printed error messages,
contact a user with System Administrator (SA) role.
这个 16字节的 16进制字符串是 OAM 中保存的 identity 值 （0001c6bf 52634001 00000000 00000000）
再次运行 sp_identity ,并且 指定这个字符串参数
1>; sp_identity invoices, "0001c6bf 52634001 00000000 0000000"
2>; go
Table = invoices (id=1804533462)
Identity column = a numeric(18)
Max. Identity Gap = 500000000000000
("identity burning set factor" = 5000 = 0.05%)
Decoded identity value on OAM page = 500000000000001
(hex=0001c6bf52634001)
现在，我们得到并解码了 OAM 中的 identity 值，但它意味着什么呢？
首先，如果你用 "with nowait" 停止服务器，这个 identity 列将跳跃多少。而不是表中数据的下一个。
而是保存在 OAM 中的数据加上 identity 种子设顶数(在 ASE 12.0, 为identity_gap 选项)
另外，当你运行 ASE 12.0, 可以通过运行 dbcc listoam看到这个数据
6、使用sp_identity 修改表的 identity数字
使用 sp_identity ， OAM 中identity 的 数字可以被设置为任意数. 这个需要如下步骤：
1、确认你要设置的数据（查看表中identity 的数据应该到多少,比如 10033 ）
2、正常停止服务器
3 重新启动服务器，以单用户模式，或者不让用户访问
4、 运行 sp_identity table_name, null, new_value ;
1>; sp_identity invoices, null, 10032
2>; go
Table = invoices (id=1804533462)
Identity column = a numeric(18)
Max. Identity Gap = 500000000000000
("identity burning set factor" = 5000 = 0.05%)
object_atts:put:return value=1
DBCC execution completed. If DBCC printed error messages,
contact a user with System Administrator (SA) role.
Identity value on OAM page has been set to 10032
(hex=0x00000000000027300000000000000000)
You should now do a 'shutdown with nowait' immediately.
After restarting the server, the value assigned to the
next row inserted into 'invoices' will be 10033.
5 然后立即运行 'shutdown with nowait' ，这样 表的下一个 identity 数字是 10033
6 重新正常启动sybase 服务
[color=red][b]说明：如果你应用了 identity 数据类型，并且要求identity 列保持连续，并且数据量很大，那么，用这个方法需要的时间可能比较短
否则不推荐使用。[/b][/color]
下面是SP_IDENTITY.120.SQL，用于 12.0 以后版本
set nocount on
go
set flushmessage on
go
use sybsystemprocs
go
-- we need to be at ASE 12.0 or later; if not, abort this script
if isnull(object_id("master.dbo.sysqueryplans"),99) >;= 99
begin
print ""
print ""
print "********************************************"
print "********************************************"
print " This script is for ASE 12.0 or later."
print " Please install SP_IDENTITY.119.SQL instead."
print "********************************************"
print "********************************************"
print " "
print " "
print ""
set background on -- terminate this script now
end
go
print ""
print "Installing 'sp_identity'..."
print ""
go
if object_id("sp_identity_help") <>; NULL
begin
drop proc sp_identity_help
end
go
create proc sp_identity_help
as
begin
print " "
print " Usage: sp_identity table_name, ""hex-string-from-OAM-page"", new-identity-value "
print " Notes: "
print " - specifying only parameter 1 retrieves the current identity value for"
print " that table from the OAM page as a hexadecimal string."
print " - specifying this hexadecimal string as the second parameter (in quotes)"
print " will decode the hex value to a numeric value."
print " - specifying a numeric value for the third parameter will set that"
print " value as the new identity value for this table."
print " - parameters 2 and 3 cannot be specified together: one of them must be NULL."
print " - ""dbcc traceon(3604)"" must be run before using option 2 or 3"
print " "
print " Copyright (c) 2000-2002 Rob Verschoor/Sypron B.V."
print " See http://www.sypron.nl/idfix.html for background information & updates."
print " "
end
go
grant execute on sp_identity_help to public
dump tran sybsystemprocs with truncate_only
go
if object_id("sp_identity") <>; NULL
begin
drop proc sp_identity
end
go
create proc sp_identity
@p0 varchar(50) = NULL, -- table name
@p1 varchar(50) = NULL, -- hex value to decode
@p2 numeric(38) = NULL -- new value to set
as
begin
set nocount on
declare @n numeric(38), @j numeric(38), @n256 numeric(3), @n10 numeric(38)
declare @i int, @max int, @idlen int, @idlenb int, @ib int, @len int
declare @p0_id int, @b int, @b1 binary(1), @lsb int
declare @idgap int, @idburn int, @maxidgap numeric(38), @max1 int, @max2 int
declare @idburnpct numeric(5,2), @v int, @ntab int
declare @c2 char(2), @doampg int, @indid int, @dbname varchar(32)
declare @vc50 varchar(50), @colname varchar(32), @vb16 varbinary(16)
select @dbname = db_name()
-- check version
select @v = 0
if exists (select * from sysobjects
where name = "sysqueryplans" and type = "S")
begin
select @v = 12
end
if @p0 = '?'
begin
exec sp_identity_help
return 0
end
-- numeric values
select @n256 = 256
select @n10 = 10
-- id burning set factor
select @idburn = value from master.dbo.syscurconfigs where config=141
select @idburnpct = convert(numeric(5,2), @idburn * 0.00001)
-- figure out msb/lsb
select @lsb = 0
if substring(convert(binary(4), 1), 1 ,1) = 0x01 select @lsb = 1
if substring(convert(binary(4), 1), 2 ,1) = 0x01 select @lsb = 2
if substring(convert(binary(4), 1), 3 ,1) = 0x01 select @lsb = 3
if substring(convert(binary(4), 1), 4 ,1) = 0x01 select @lsb = 4
-- get all tables containing identity columns in this database
select id = so.id, owner = su.name, uid = so.uid, so.name, si.doampg, si.indid, idgap =
isnull(si.identitygap,0),
colname = sc.name, sc.prec, maxgap = convert(numeric(38), ceiling((@idburn * 0.0000001) *
power(@n10,prec)))
into #id
from sysindexes si, syscolumns sc, sysobjects so, sysusers su
where si.indid < 2
and so.type = "U"
and sc.status & 128 = 128
and so.id = sc.id
and so.id = si.id
and so.uid = su.uid
select @ntab = @@rowcount
set arithabort numeric_truncation off
if @p0 = null
begin
-- display all tables with identity columns in the current DB
if @ntab = 0
begin
print " There are no tables with an identity column in database '%1!'", @dbname
return 0
end
print " Tables with an identity column in database '%1!':", @dbname
print " "
select @max1 = max(char_length(owner + "." + name + "." + colname)) + 12 from #id
select @max2 = max(char_length(convert(varchar(38), maxgap))) + 7 from #id
if @max1 <= 52 and @max2 <= 24
begin
select convert(varchar(52), owner + "." + name + "." + colname + " numeric(" +
convert(varchar(2),prec) + ")") "Owner.Table.Column datatype",
convert(varchar(24), case when idgap = 0 then convert(varchar(38),maxgap) + "
(burn)"
else convert(varchar, idgap) + " (identity_gap)"
end) "Maximum Identity Gap"
from #id
order by name
end
else
if @max1 <= 32 and @max2 <= 44
begin
select convert(varchar(32), owner + "." + name + "." + colname + " numeric(" +
convert(varchar(2),prec) + ")") "Owner.Table.Column datatype",
convert(varchar(44), case when idgap = 0 then convert(varchar(38),maxgap) + "
(burn)"
else convert(varchar, idgap) + " (identity_gap)"
end) "Maximum Identity Gap"
from #id
order by name
end
else
begin
select convert(varchar(78), owner + "." + name + "." + colname + " numeric(" +
convert(varchar(2),prec) + ")") "Owner.Table.Column datatype",
convert(varchar(50), case when idgap = 0 then convert(varchar(38),maxgap) + "
(burn)"
else convert(varchar, idgap) + " (identity_gap)"
end) "Maximum Identity Gap"
from #id
order by name
end
print " "
print " Legend:"
print " (burn) : gap size is determined by ""identity burning set factor"" "
if @v = 12
begin
print " (identity_gap) : gap size is determined by the ""identity_gap"" setting"
end
print " "
print " Current value for ""identity burning set factor"" = %1! (=%2!%%)", @idburn, @idburnpct
return 0
end
if charindex("sa_role", show_role()) = 0
begin
print "You must have 'sa_role' to run this procedure."
return -1
end
if charindex("sybase_ts_role", show_role()) = 0
begin
print "You must have 'sybase_ts_role' to run this procedure."
return -1
end
-- get some info on the object
select @p0_id = object_id(@p0)
if @p0_id = NULL
begin
print " Error: '%1!' is not a user table.", @p0
return -1
end
if @p0 not like "%.%"
begin
select @ntab = count(*) from sysobjects where name = @p0 and type = "U"
if @ntab >; 1
begin
print " %1! tables named '%2!' exist in this database:", @ntab, @p0
print " "
select owner + "." + name "owner.table_name"
from #id where name = @p0 order by uid
print " "
print " Specify 'owner.table_name' to identify the table."
return -1
end
end
select @doampg = doampg, @indid = indid, @idgap = idgap
from #id where id = @p0_id
if not exists (select 1 from syscolumns where id = @p0_id and status & 128 = 128)
begin
print " Error: Table '%1!' does not have an identity column", @p0
return -1
end
-- retrieve the length of the numeric identity column as declared when the
-- table was created
select @len = prec, @colname = name
from syscolumns where id = @p0_id and status & 128 = 128
if @@rowcount = 0
begin
print " Error: Could not retrieve length of identity column for table '%1!'", @p0
return -1
end
select @idlen = @len -- column precision (positions)
select @idlenb = (@idlen+1-((@idlen+5)/12)-(@idlen/12))/2 -- column length (bytes)
print " "
print " Table = %1! (id=%2!)", @p0, @p0_id
print " Identity column = %1! numeric(%2!)", @colname, @len
--print " OAM page = %1!", @doampg
--print " Bytes on OAM page = %1!", @idlenb
if @idgap >; 0
begin
print " Max. Identity Gap = %1! (""identity_gap"" = %2!)", @idgap, @idgap
end
else
begin
set arithabort numeric_truncation off
select @maxidgap = ceiling((convert(numeric(38),@idburn) * 0.0000001) * power(@n10,@len))
print " Max. Identity Gap = %1!", @maxidgap
print " (""identity burning set factor"" = %1! = %2!%%)", @idburn, @idburnpct
if @v = 12
begin
print " (Note: ""identity_gap"" has not been set for this table !)"
end
end
print " "
if @p1 = NULL and @p2 = NULL -- retrieve current ID value
begin
print " "
print " Reading identity value from OAM page... (traceflag 3604 should be enabled !)"
print " "
dbcc object_atts (@p0, 0, get)
print " "
print " To decode this hexadecimal value, re-run 'sp_identity' with the hexadecimal"
print " string as a quoted 2nd parameter (you can leave the spaces in). "
print " Example: sp_identity %1!, ""the-hex-string-from-the-above-output"" ", @p0
print " "
--
-- only for 12.0+, dbcc listoam will display the values in the OAM and the DES
--
--dbcc listoam(@dbname, @p0_id, @indid)
--
return 0
end
if upper(@p1) like "[ 0-9A-F]%" -- entered a hex string, decode it
begin
if @p2 != NULL
begin
print " Error: When decoding a hex value from the OAM page, parameter 3"
print " (the new identity value) must be NULL."
exec sp_identity_help
return -1
end
select @ib = @idlenb -- counts bytes
select @i = char_length(@p1) -- counts string
select @n = 0 -- holds result
while 1 = 1
begin
select @c2 = substring(@p1, (char_length(@p1)[email protected])+1, 2)
--print "Step %1!, [%2!]", @ib, @c2
if upper(substring(@c2,1,1)) = " " -- ignore single space pasted in by user
begin
select @i = @i - 1
continue
end
if (upper(@c2) not like "[0-9A-F][0-9A-F]")
begin
print " Error: Invalid characters (%1!) in hex string", @c2
break
end
-- add this byte to the result
select @vc50 = @vc50 + @c2
select @j = power(@n256, (@ib-1))
select @n = @n + @j * hextoint("0x" + @c2)
--print "Step %1!, exp= %2!, result = %3!", @ib, @j, @n
-- next byte
select @ib = @ib - 1
if @ib = 0 break -- ready
-- next 2 chars
select @i = @i - 2
if @i = 0
begin
-- we shouldn't have got here, error
print " Error: ID column length and specified hex string do not match !"
break
end
end
if @ib = 0
begin
print " Decoded identity value on OAM page = %1!", @n
print " (hex= %1!)", @vc50
print " "
return 0
end
else
begin
print " Error: Aborted due to error."
return -1
end
end
if @p2 != NULL -- entered a new ID value, set it
begin
if @p1 != NULL
begin
print " Error: When setting a new identity value, parameter 2"
print " (the hex string from the OAM page) must be NULL."
exec sp_identity_help
return -1
end
-- set the new ID value
if @p2 <= 0
begin
print " Error: The new identity value must be >;= 0."
print " "
exec sp_identity_help
return -1
end
if char_length(convert(varchar, @p2)) >; @idlen
begin
select @vc50 = replicate("9", @idlen)
print " Error: New identity value (%1!) is too large", @p2
print " for this identity column. The maximum possible value", @p2
print " is %1! (%2! positions).", @vc50, @idlen
return -1
end
if @lsb = 0
begin
print " "
print "Internal error in 'sp_identity':"
print "Cannot figure out byte order on this platform."
print "Please send a note to '[email protected]' with the text of this"
print "error and your @@version string."
return -1
end
-- convert the numeric value to hex
select @ib = @idlenb -- counts bytes
select @i = 15
select @vc50 = NULL -- holds result
select @vb16 = NULL -- holds result
select @n256 = 256
select @n = @p2
set arithabort numeric_truncation off
while 1 = 1
begin
select @j = power(@n256, @i)
select @b = @n / @j
select @n = @n - (@b * @j)
select @c2 = right(inttohex(@b),2)
select @b1 = substring(convert(binary(4), @b), @lsb,1)
select @vb16 = @vb16 + @b1
--print "Step %1!, @b=%2!, hex(c2)=%3!, hex(b1)=%5!, result=%4!", @i, @b, @c2, @vb16, @b1
select @i = @i - 1
if @i < 0 break -- ready
end
if @i < 0
begin
select @vb16 = substring(@vb16, 16 - (@idlenb) + 1, (@idlenb) ) + substring(@vb16, 1, 16 -
(@idlenb) )
-- set the new ID value
dbcc object_atts(@p0, 0, "put", @vb16)
print " "
print " Identity value on OAM page has been set to %1!", @p2
print " (hex= %1!)", @vb16
print " "
select @p2 = @p2 + 1
print " You should now do a 'shutdown with nowait' immediately."
print " After restarting the server, the value assigned to the next row "
print " inserted into '%1!' will be %2!.", @p0, @p2
print " "
return 0
end
else
begin
print " Error: Aborted due to error."
return -1
end
end
-- we should never get here
print "Internal error in 'sp_identity': Reached invalid end of procedure."
return -1
end
go
grant execute on sp_identity to public
dump tran sybsystemprocs with truncate_only
go
print "Ready. For usage information, run 'sp_identity ""?"" '."
print ""
go
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