.replace 盘区.replace extents

• 08/18/2020
• • o
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此命令在特定数据库的上下文中运行。This command runs in the context of a specific database. 它将指定的区从其源表移至目标表，然后从目标表中删除指定的区。It moves the specified extents from their source tables to the destination table, and then drops the specified extents from the destination table. 所有删除和移动操作都在单个事务中完成。All of the drop and move operations are done in a single transaction.

需要源表和目标表的表管理员权限。Requires Table admin permission for the source and destination tables.

语法Syntax

.replace [async] extents in table DestinationTableName <| {查询要从表中删除的盘区},{查询要移动到表中的盘区}.replace [async] extents in table DestinationTableName <| {query for extents to be dropped from table},{query for extents to be moved to table}

• async（可选）：以异步方式执行该命令。async (optional): Execute the command asynchronously.
  • 返回操作 ID (Guid)。An Operation ID (Guid) is returned.
  • 可以监视操作的状态。The operation's status can be monitored. 请使用 .show operations 命令。Use the .show operations command.
  • 可以检索成功执行的结果。The results of a successful execution can be retrieved. 请使用 .show operation details 命令。Use the .show operation details command.

若要指定应该删除或移动哪些区，请使用以下两个查询之一。To specify which extents should be dropped or moved, use one of two queries.

• 查询要从表中删除的区：此查询的结果指定应从目标表中删除的区 ID。query for extents to be dropped from table: The results of this query specify the extent IDs that should be dropped from the destination table.
• 查询要移动到表的区：此查询的结果指定源表中应移至目标表的区 ID。query for extents to be moved to table: The results of this query specify the extent IDs in the source tables that should be moved to the destination table.

这两个查询都应返回一个包含名为“ExtentId”的列的记录集。Both queries should return a recordset with a column called "ExtentId".

限制Restrictions

• 源表和目标表都必须位于上下文数据库中。Both source and destination tables must be in the context database.
• 对要从表中删除的盘区的查询所指定的所有盘区应属于目标表。All extents specified by the query for extents to be dropped from table are expected to belong to the destination table.
• 源表中的所有列均应以相同的名称和数据类型存在于目标表中。All columns in the source tables are expected to exist in the destination table with the same name and data type.

返回输出（对于同步执行）Return output (for sync execution)

示例Examples

移动两个表中所有的区Move all extents from two tables

从两个特定表（MyTable1、MyTable2）中将所有区移至表 MyOtherTable，并删除 MyOtherTable 中标有 drop-by:MyTag 的所有区：Move all extents from two specific tables (MyTable1, MyTable2) to table MyOtherTable, and drop all extents in MyOtherTable tagged with drop-by:MyTag:

.replace extents in table MyOtherTable <|
    {
        .show table MyOtherTable extents where tags has 'drop-by:MyTag'
    },
    {
        .show tables (MyTable1,MyTable2) extents
    }

示例输出Sample output

将一个表中所有的区移至另一个表，删除特定区Move all extents from one table to another, drop specific extent

从一个特定表 (MyTable1) 中将所有区移至表 MyOtherTable，并删除 MyOtherTable 中的特定区（按其 ID）：Move all extents from one specific tavle (MyTable1) to table MyOtherTable, and drop a specific extent in MyOtherTable, by its ID:

.replace extents in table MyOtherTable <|
    {
        print ExtentId = "2cca5844-8f0d-454e-bdad-299e978be5df"
    },
    {
        .show table MyTable1 extents 
    }

.replace extents in table MyOtherTable  <|
    {
        .show table MyOtherTable extents
        | where ExtentId == guid(2cca5844-8f0d-454e-bdad-299e978be5df) 
    },
    {
        .show table MyTable1 extents 
    }

实现幂等逻辑Implement an idempotent logic

实现幂等逻辑，以便 Kusto 仅在有区要从表 t_source 移至表 t_dest 的情况下才从表 t_dest 中删除区：Implement an idempotent logic so that Kusto drops extents from table t_dest only if there are extents to move from table t_source to table t_dest:

.replace async extents in table t_dest <|
{
    let any_extents_to_move = toscalar( 
        t_source
        | where extent_tags() has 'drop-by:blue'
        | summarize count() > 0
    );
    let extents_to_drop =
        t_dest
        | where any_extents_to_move and extent_tags() has 'drop-by:blue'
        | summarize by ExtentId = extent_id()
    ;
    extents_to_drop
},
{
    let extents_to_move = 
        t_source
        | where extent_tags() has 'drop-by:blue'
        | summarize by ExtentId = extent_id()
    ;
    extents_to_move
}