179289f0bf
### What changes were proposed in this pull request?
This PR intends to clean up the SQL documents in `doc/sql-ref*`.
Main changes are as follows;
- Fixes wrong syntaxes and capitalize sub-titles
- Adds some DDL queries in `Examples` so that users can run examples there
- Makes query output in `Examples` follows the `Dataset.showString` (right-aligned) format
- Adds/Removes spaces, Indents, or blank lines to follow the format below;
```
---
license...
---
### Description
Writes what's the syntax is.
### Syntax
{% highlight sql %}
SELECT...
WHERE... // 4 indents after the second line
...
{% endhighlight %}
### Parameters
<dl>
<dt><code><em>Param Name</em></code></dt>
<dd>
Param Description
</dd>
...
</dl>
### Examples
{% highlight sql %}
-- It is better that users are able to execute example queries here.
-- So, we prepare test data in the first section if possible.
CREATE TABLE t (key STRING, value DOUBLE);
INSERT INTO t VALUES
('a', 1.0), ('a', 2.0), ('b', 3.0), ('c', 4.0);
-- query output has 2 indents and it follows the `Dataset.showString`
-- format (right-aligned).
SELECT * FROM t;
+---+-----+
|key|value|
+---+-----+
| a| 1.0|
| a| 2.0|
| b| 3.0|
| c| 4.0|
+---+-----+
-- Query statements after the second line have 4 indents.
SELECT key, SUM(value)
FROM t
GROUP BY key;
+---+----------+
|key|sum(value)|
+---+----------+
| c| 4.0|
| b| 3.0|
| a| 3.0|
+---+----------+
...
{% endhighlight %}
### Related Statements
* [XXX](xxx.html)
* ...
```
### Why are the changes needed?
The most changes of this PR are pretty minor, but I think the consistent formats/rules to write documents are important for long-term maintenance in our community
### Does this PR introduce any user-facing change?
Yes.
### How was this patch tested?
Manually checked.
Closes #28151 from maropu/MakeRightAligned.
Authored-by: Takeshi Yamamuro <yamamuro@apache.org>
Signed-off-by: Sean Owen <srowen@gmail.com>
5 KiB
| layout | title | displayTitle | license |
|---|---|---|---|
| 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_identifier [ partition_spec ] COMPUTE STATISTICS [ NOSCAN | FOR COLUMNS col [ , ... ] | FOR ALL COLUMNS ] {% endhighlight %}
Parameters
table_identifier-
Specifies a table name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] table_name
partition_spec-
An optional parameter that specifies a comma separated list of key and value pairs
for partitions. When specified, partition statistics is returned.
Syntax:PARTITION ( partition_col_name [ = partition_col_val ] [ , ... ] )
[ NOSCAN | FOR COLUMNS col [ , ... ] | FOR ALL COLUMNS ]-
- If no analyze option is specified,
ANALYZE TABLEcollects 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 %} CREATE TABLE students (name STRING, student_id INT) PARTITIONED BY (student_id); INSERT INTO students PARTITION (student_id = 111111) VALUES ('Mark'); INSERT INTO students PARTITION (student_id = 222222) VALUES ('John');
ANALYZE TABLE students COMPUTE STATISTICS NOSCAN;
DESC EXTENDED students; +--------------------+--------------------+-------+ | col_name| data_type|comment| +--------------------+--------------------+-------+ | name| string| null| | student_id| int| null| | ...| ...| ...| | Statistics| 864 bytes| | | ...| ...| ...| | Partition Provider| Catalog| | +--------------------+--------------------+-------+
ANALYZE TABLE students COMPUTE STATISTICS;
DESC EXTENDED students; +--------------------+--------------------+-------+ | col_name| data_type|comment| +--------------------+--------------------+-------+ | name| string| null| | student_id| int| null| | ...| ...| ...| | Statistics| 864 bytes, 2 rows| | | ...| ...| ...| | Partition Provider| Catalog| | +--------------------+--------------------+-------+
ANALYZE TABLE students PARTITION (student_id = 111111) COMPUTE STATISTICS;
DESC EXTENDED students PARTITION (student_id = 111111); +--------------------+--------------------+-------+ | col_name| data_type|comment| +--------------------+--------------------+-------+ | name| string| null| | student_id| int| null| | ...| ...| ...| |Partition Statistics| 432 bytes, 1 rows| | | ...| ...| ...| | OutputFormat|org.apache.hadoop...| | +--------------------+--------------------+-------+
ANALYZE TABLE students COMPUTE STATISTICS FOR COLUMNS name;
DESC EXTENDED students name; +--------------+----------+ | info_name|info_value| +--------------+----------+ | col_name| name| | data_type| string| | comment| NULL| | min| NULL| | max| NULL| | num_nulls| 0| |distinct_count| 2| | avg_col_len| 4| | max_col_len| 4| | histogram| NULL| +--------------+----------+ {% endhighlight %}