Index Reorganize 和 Rebuild 的区别

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对Index 进行 Reorganize 和 Rebuild 是有区别的。

1，语义区别

Rebuild 是重新创建，将Index之前占用的空间释放，重新申请空间来创建index。Rebuilding an index means that a whole new set of pages is allocated for it。

Reorganize 是重新组织，作用于 index leaf level pages。Reorganizing an index compacts the leaf-level pages back to their original specified fillfactor ant then rearrages the pages at the leaf level pages to correct the logical fragmentation, using the same pages that the index originally occupied.No new pages are allocated.

2, Different Syntax

ALTER INDEX index_name
    ON <object>
{ 
    REBUILD 
        [ [PARTITION = ALL] [ WITH ( <rebuild_index_option> [ ,...n ] ) ] 
          | [ PARTITION = partition_number [ WITH ( <single_partition_rebuild_index_option> [ ,...n ] )] ]
        ]
    | REORGANIZE 
        [ PARTITION = partition_number ]
        [ WITH ( LOB_COMPACTION = { ON | OFF } ) ]
}
[ ; ]

<rebuild_index_option > ::=
{
    PAD_INDEX = { ON | OFF }
  | FILLFACTOR = fillfactor 
  | SORT_IN_TEMPDB = { ON | OFF }
  | IGNORE_DUP_KEY = { ON | OFF }
  | STATISTICS_NORECOMPUTE = { ON | OFF }
  | ONLINE = { ON | OFF } 
  | ALLOW_ROW_LOCKS = { ON | OFF }
  | ALLOW_PAGE_LOCKS = { ON | OFF }
  | MAXDOP = max_degree_of_parallelism
  | DATA_COMPRESSION = { NONE | ROW | PAGE } 
     [ ON PARTITIONS ( { <partition_number_expression> | <range> } 
     [ , ...n ] ) ]
}

<range> ::= 
<partition_number_expression> TO <partition_number_expression>

<single_partition_rebuild_index_option> ::=
{
    SORT_IN_TEMPDB = { ON | OFF }
  | MAXDOP = max_degree_of_parallelism
  | DATA_COMPRESSION = { NONE | ROW | PAGE } }
}

REBUILD [ WITH (<rebuild_index_option> [ ,... n]) ]               

Specifies the index will be rebuilt using the same columns, index type, uniqueness attribute, and sort order. This clause is equivalent to DBCC DBREINDEX. REBUILD enables a disabled index. Rebuilding a clustered index does not rebuild associated nonclustered indexes unless the keyword ALL is specified.

If index options are not specified, the existing index option values stored in sys.indexes are applied. For any index option whose value is not stored in sys.indexes, the default indicated in the argument definition of the option applies.

在sys.indexes 视图中，共存储5个index option，分别是 ignore_dup_key,fill_factor,is_padded,allow_row_locks,allow_page_locks，其他5个Index Option的Default value都是“否定的”，分别是

SORT_IN_TEMPDB :            Default OFF
STATISTICS_NORECOMPUTE :    Default OFF
DROP_EXISTING:              Default OFF
ONLINE:                     Default OFF
DATA_COMPRESSION :          Default NONE
MAXDOP:                     0

详细信息，查看CREATE INDEX (Transact-SQL)

If ALL is specified and the underlying table is a heap, the rebuild operation has no effect on the table. Any nonclustered indexes associated with the table are rebuilt.

The rebuild operation can be minimally logged if the database recovery model is set to either bulk-logged or simple.

REORGANIZE               

Specifies the index leaf level will be reorganized. ALTER INDEX REORGANIZE statement is always performed online. This means long-term blocking table locks are not held and queries or updates to the underlying table can continue during the ALTER INDEX REORGANIZE transaction. REORGANIZE cannot be specified for a disabled index or an index with ALLOW_PAGE_LOCKS set to OFF.

3, sys.indexes 存储的Index option

select i.object_id,i.name as IndexName,i.index_id,i.type,i.type_desc,
    i.data_space_id,i.is_disabled,

    --Unique Property
    i.is_unique,
    
    --Constraint
    i.is_primary_key,
    i.is_unique_constraint,

    --Filter Index
    i.has_filter,
    i.filter_definition,

    --Index Options
    i.ignore_dup_key,
    i.fill_factor,
    i.is_padded,
    i.allow_row_locks,
    i.allow_page_locks
from sys.indexes i

4，Alter Index Remarks

ALTER INDEX cannot be used to repartition an index or move it to a different filegroup. This statement cannot be used to modify the index definition, such as adding or deleting columns or changing the column order. Use CREATE INDEX with the DROP_EXISTING clause to perform these operations.

When an option is not explicitly specified, the current setting is applied. For example, if a FILLFACTOR setting is not specified in the REBUILD clause, the fill factor value stored in the system catalog will be used during the rebuild process. To view the current index option settings, use sys.indexes.

Note
The values for ONLINE, MAXDOP, and SORT_IN_TEMPDB are not stored in the system catalog. Unless specified in the index statement, the default value for the option is used.

On multiprocessor computers, just like other queries do, ALTER INDEX REBUILD automatically uses more processors to perform the scan and sort operations that are associated with modifying the index. When you run ALTER INDEX REORGANIZE, with or without LOB_COMPACTION, the max degree of parallelism value is a single threaded operation. For more information, see Configure Parallel Index Operations.

An index cannot be reorganized or rebuilt if the filegroup in which it is located is offline or set to read-only. When the keyword ALL is specified and one or more indexes are in an offline or read-only filegroup, the statement fails.

Rebuilding Indexes

Reorganizing Indexes

参考文档：

https://msdn.microsoft.com/en-us/library/ms188783(v=sql.110).aspx

https://msdn.microsoft.com/en-us/library/ms189858(v=sql.110).aspx

https://msdn.microsoft.com/en-us/library/ms188388(v=sql.110).aspx

Index Reorganize 和 Rebuild 的区别

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原文地址：http://www.cnblogs.com/ljhdo/p/5136024.html