### What changes were proposed in this pull request? Document ANALYZE TABLE statement in SQL Reference ### Why are the changes needed? To complete SQL reference ### Does this PR introduce any user-facing change? Yes ***Before***: There was no documentation for this. ***After***: ![image](https://user-images.githubusercontent.com/13592258/64046883-f8339480-cb21-11e9-85da-6617d5c96412.png) ![image](https://user-images.githubusercontent.com/13592258/64209526-9a6eb780-ce55-11e9-9004-53c5c5d24567.png) ![image](https://user-images.githubusercontent.com/13592258/64209542-a2c6f280-ce55-11e9-8624-e7349204ec8e.png) ### How was this patch tested? Tested using jykyll build --serve Closes #25524 from huaxingao/spark-28788. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Xiao Li <gatorsmile@gmail.com>
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layout | title | displayTitle | license |
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global | ANALYZE TABLE | ANALYZE TABLE | Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You 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, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. |
Description
The ANALYZE TABLE
statement collects statistics about the table to be used by the query optimizer to find a better query execution plan.
Syntax
{% highlight sql %} ANALYZE TABLE table_name [ PARTITION ( partition_col_name [ = partition_col_val ] [ , ... ] ) ] COMPUTE STATISTICS [ NOSCAN | FOR COLUMNS col [ , ... ] | FOR ALL COLUMNS ]
{% endhighlight %}
Parameters
table_name
- The name of an existing table.
PARTITION ( partition_col_name [ = partition_col_val ] [ , ... ] )
- Specifies one or more partition column and value pairs. The partition value is optional.
[ NOSCAN | FOR COLUMNS col [ , ... ] | FOR ALL COLUMNS ]
-
- If no analyze option is specified,
ANALYZE TABLE
collects the table's number of rows and size in bytes. - NOSCAN
Collect only the table's size in bytes ( which does not require scanning the entire table ). - FOR COLUMNS col [ , ... ]
|
FOR ALL COLUMNS
Collect column statistics for each column specified, or alternatively for every column, as well as table statistics.
- If no analyze option is specified,
Examples
{% highlight sql %} ANALYZE TABLE students COMPUTE STATISTICS NOSCAN;
DESC EXTENDED students; ...... Statistics 2820 bytes ......
ANALYZE TABLE students COMPUTE STATISTICS;
DESC EXTENDED students; ...... Statistics 2820 bytes, 3 rows ......
ANALYZE TABLE students PARTITION (student_id = 111111) COMPUTE STATISTICS;
DESC EXTENDED students PARTITION (student_id = 111111); ...... Partition Statistics 919 bytes, 1 rows ......
ANALYZE TABLE students COMPUTE STATISTICS FOR COLUMNS name;
DESC EXTENDED students name; =default tbl=students col_name name data_type string comment NULL min NULL max NULL num_nulls 0 distinct_count 3 avg_col_len 11 max_col_len 13 histogram NULL
{% endhighlight %}