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正确答案:D
Oracle 11g新特性之统计信息收集
在以前的数据库版本中，当收集到新的优化器统计信息时会自动发布。在11g中，这仍然是默认的动作，但你多了一个选择，
你可以将最新的统计信息挂起，直到人为地发布它们。DBMS_STATS.GET_PREFS函数运行你检查“PUBLISH”属性，查看统计信息
是否已经自动发布。默认返回的值为TRUE，意味着已经自动发布了，而FALSE表示它还处于挂起状态，等待发布。
检查当前数据库的PUBLISH”属性:
gyj@OCM> col get_prefs for a50
gyj@OCM> SELECT DBMS_STATS.get_prefs(\'PUBLISH\',\'SH\',\'CUSTOMERS\') get_prefs FROM dual;
GET_PREFS
--------------------------------------------------
TRUE
使用存储过程DBMS_STATS.SET_TABLE_PREFS可以重新设置“PUBLISH”属性,设为FALSE表示它还处于挂起状态，等待发布:
gyj@OCM> BEGIN
2 DBMS_STATS.SET_TABLE_PREFS(\'SH\', \'CUSTOMERS\', \'PUBLISH\', \'false\');
3 END;
4 /
PL/SQL procedure successfully completed.
gyj@OCM> SELECT DBMS_STATS.get_prefs(\'PUBLISH\',\'SH\',\'CUSTOMERS\') get_prefs FROM dual;
GET_PREFS
--------------------------------------------------
FALSE
参考官方文档:
SET_TABLE_PREFS Procedure
This procedure isused to set the statistics preferences of the specified table in the specifiedschema.
Syntax
DBMS_STATS.SET_TABLE_PREFS (
ownname IN VARCHAR2,
tabname IN VARCHAR2,
pname IN VARCHAR2,
pvalue IN VARCHAR2);
Parameters
Table 141-93SET_TABLE_PREFS Procedure Parameters
|
Parameter
|
Description
|
|
ownname
|
Owner name
|
|
tabname
|
Table name
|
|
pname
|
Preference name. The default value for following preferences can be set:
· CASCADE
· DEGREE
· ESTIMATE_PERCENT
· METHOD_OPT
· NO_INVALIDATE
· GRANULARITY
· PUBLISH
· INCREMENTAL
· STALE_PERCENT
|
|
.
|
CASCADE - Determines whether or not index statistics are collected as part of gathering table statistics.
|
|
.
|
DEGREE - Determines degree of parallelism used for gathering statistics.
|
|
.
|
ESTIMATE_PERCENT - Determines the percentage of rows to estimate. The valid range is [0.000001,100]. Use the constantDBMS_STATS.AUTO_SAMPLE_SIZE to have Oracle determine the appropriate sample size for good statistics.
This is the default.
|
|
.
|
METHOD_OPT - Controls column statistics collection and histogram creation. It accepts either of the following options, or both in combination:
· FOR ALL [INDEXED | HIDDEN] COLUMNS [size_clause]
· FOR COLUMNS [size clause] column [size_clause] [,column [size_clause]...]
size_clause is defined as size_clause := SIZE {integer | REPEAT | AUTO | SKEWONLY}
column is defined as column := column_name | extension name | extension
- integer : Number of histogram buckets. Must be in the range [1,254].
- REPEAT : Collects histograms only on the columns that already have histograms
- AUTO : Oracle determines the columns to collect histograms based on data distribution and the workload of the columns.
- SKEWONLY : Oracle determines the columns to collect histograms based on the data distribution of the columns.
- column_name : Name of a column
- extension : Can be either a column group in the format of (column_name, colume_name [, ...]) or an expression
The default is FOR ALL COLUMNS SIZE AUTO.
|
|
.
|
NO_INVALIDATE - The value controls the invalidation of dependent cursors of the tables for which statistics are being gathered. Does not invalidate the dependent cursors if set to TRUE. The procedure invalidates the dependent cursors
immediately if set to FALSE. Use DBMS_STATS.AUTO_INVALIDATE to have Oracle decide when to invalidate dependent cursors. This is the default.
|
|
.
|
GRANULARITY - Determines granularity of statistics to collect (only pertinent if the table is partitioned).
\'ALL\' - Gathers all (subpartition, partition, and global) statistics
\'AUTO\'- Determines the granularity based on the partitioning type. This is the default value.
\'DEFAULT\' - Gathers global and partition-level statistics. This option is obsolete, and while currently supported, it is included in the documentation for legacy reasons only. You should use the \'GLOBAL AND PARTITION\' for this functionality.
Note that the default value is now \'AUTO\'.
\'GLOBAL\' - Gathers global statistics
\'GLOBAL AND PARTITION\' - Gathers the global and partition level statistics. No subpartition level statistics are gathered even if it is a composite partitioned object.
\'PARTITION \'- Gathers partition-level statistics
\'SUBPARTITION\' - Gathers subpartition-level statistics.
|
|
.
|
PUBLISH - Determines whether or not newly gathered statistics will be published once the gather job has completed. Prior to Oracle Database 11g, Release 1 (11.1), once a statistic gathering job completed the new statistics were automatically
published into the dictionary tables. The user now has the ability to gather statistics but not publish them immediately. This allows the DBA to test the new statistics before publishing them.
|
|
.
|
INCREMENTAL - Determines whether or not the global statistics of a partitioned table will be maintained without doing a full table scan. With partitioned tables it is very common to load new data into a new partition. As new partitions are added
and data loaded, the global table statistics need to be kept up to date. Oracle will update the global table statistics by scanning only the partitions that have been changed instead of the entire table if the following conditions hold:
· INCREMENTAL value for the partitioned table is set to TRUE;
· PUBLISH value for the partitioned table is set to TRUE;
· User specifies AUTO_SAMPLE_SIZE for ESTIMATE_PERCENT and AUTO for GRANULARITY when gathering statistics on the table.
If the INCREMENTAL value for the partitioned table was set to FALSE (default value), a full table scan is used to maintain the global statistics which is a much more resource intensive and time-consuming operation for large tables.
|
|
.
|
STALE_PERCENT - Determines the percentage of rows in a table that have to change before the statistics on that table are deemed stale and should be regathered. The default value is 10%.
|
|
pvalue
|
Preference value. If NULL is specified, it will set the Oracle default value.
|
Exceptions
: Object doesnot exist or insufficient privileges
: Invalid orillegal input values
Usage Notes
· To run this procedure, you need to connect as owner of the tableor should have the ANALYZE ANY systemprivilege.
· All arguments are of type VARCHAR2 and values are enclosed in quotes, even when they representnumbers.
Examples
DBMS_STATS.SET_TABLE_PREFS(\'SH\', \'SALES\', \'CASCADE\', \'DBMS_STATS.AUTO_CASCADE\');
DBMS_STATS.SET_TABLE_PREFS(\'SH\', \'SALES\',\'ESTIMATE_PERCENT\',\'9\');
DBMS_STATS.SET_TABLE_PREFS(\'SH\', \'SALES\', \'DEGREE\',\'99\');
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