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sql-ref-syntax-aux-analyze-table.md

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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 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.

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 %}